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  • Civil and Mechanical Engineering
  • photoluminescence
  • Wiley-Blackwell  (162)
  • American Meteorological Society
  • PANGAEA
  • 1995-1999  (162)
Sammlung
Schlagwörter
Verlag/Herausgeber
  • Wiley-Blackwell  (162)
  • American Meteorological Society
  • PANGAEA
  • Springer  (22)
Erscheinungszeitraum
  • 1995-1999  (162)
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    Polysilane spherulites and their high photoluminescence quantum yields (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 427-430 
    Details
    ISSN: 0887-624X
    Schlagwort(e): polysilane ; spherulite ; photoluminescence ; quantum yield ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Large polysilane spherulites have been observed. The spherulites were prepared by controlling the removal rate of solvents from poly(n-butyl-n-pentylsilane) under a xylene atmosphere. The diameter of the spherulites was greater than 0.1 mm. The structure of the spherulites was compared with that of the polysilane powder by polarized microscopy, SEM, DSC, and x-ray diffractometry. A high photoluminescence quantum yield of 0.3 was obtained for the spherulites. © 1997 John Wiley & Sons, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Dimensional reduction in II-VI materials: A2Cd3Q4 (A = K, Q = S, Se, Te; A = Rb, Q = S, Se), novel ternary low-dimensional cadmium chalcogenides produced by incorporation of A2Q in CdQ (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 656-666 
    Details
    ISSN: 0947-6539
    Schlagwort(e): cadmium compounds ; chalcogen compounds ; crystal structure ; dimensionality ; photoluminescence ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The synthesis of the isomorphous, layered chalcogenides K2Cd3S4 (I), Rb2Cd3S4 (II), K2Cd3Se4 (III), Rb2Cd3Se4 (IV), and K2Cd3Te4 (V) in molten A2Qx fluxes in reported (A = K, Rb; Q = S, Se, Te; x = 2 to 3). The compounds form as (Cd3Q4)n2n- layers interspersed with A + cations; the layers are composed of Cd3Q2-4 units shaped as truncated cubes. The compounds have room-temperature band gaps of 2.75, 2.92, 2.36, 2.37, and 2.26 eV for I, II, III, IV, and V, respectively, and also display strong photoluminescence. The thermal analysis data for all compounds are reported. The properties of these compounds are compared with those of the three-dimensional compounds CdS, CdSe, and CdTe, as well as those of the nanometer-sized CdQ clusters. A conceptual context is presented to connect all these different types of compounds.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chem.1460020607
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  • 3
    Digitale Medien
    Digitale Medien
    Optical investigations of strained InGaAs quantum wells (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 7 (1997), S. 307-310 
    Details
    ISSN: 1057-9257
    Schlagwort(e): photoreflectance ; photoluminescence ; InGaAs/GaAs quantum well ; type I and II excitonic transition ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: InGaAs/GaAs MOCVD-grown quantum wells have been investigated. Photoluminescence (PL) measurements have shown heavy-hole-related excitonic transitions within the temperature range from 10 to 100 K for all samples. In room-temperature photoreflectance (PR), sharp heavy- and light-hole excitonic transitions in the quantum wells have been observed. The transition energies obtained have been compared with values derived from theoretical considerations using the envelope function model including lattice-mismatch-related stress. The heavy- and light-hole transitions have been identified as excitonic transitions of types I and II respectively. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Some new synthetic low-dimensional semiconductors based on inorganic units (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 263-267 
    Details
    ISSN: 1057-9257
    Schlagwort(e): semiconductors ; low-dimensional systems ; crystal structure ; optical properties ; photoluminescence ; Raman spectra ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: The structural, optical and related properties (i.e. photoluminescence and resonance Raman spectra) of some synthetic (i.e. unconventional) low-dimensional semiconductor systems such as K2Cd3S4, [CH3SC(NH2)=NH2]3PbI5 and [H3N(CH2)6NH3]BiI5 are reported. They are compared with the properties of the corresponding higher-dimensionality systems. A blue shift of the excitonic bands and an enhancement of their binding energy and intensity were observed by decreasing the dimensionality or the size of the materials active part. The results are similar to those obtained from conventional semiconductors by decreasing the dimensionality or the size and are attributed to quantum confinement of excitons. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Photoexcitations in linear trans-quinacridone (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 7 (1997), S. 83-86 
    Details
    ISSN: 1057-9257
    Schlagwort(e): photoluminescence ; time-resolved fast spectrocopy ; photoinduced absorption spectroscopy ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: We have studied the photophysics of linear trans-quinacridone films by applying a variety of transient and continuous wave photomodulation techniques. Our experimental results demonstrate the ultrafast formation of excimer species which are responsible for the emission. The excimer decay kinetics seems to suggest a predominantly charge transfer character of these emitting species. This is consistent with the long-lived states which we detected on the millisecond time scale. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Photoexcitations in linear trans-quinacridone (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 7 (1997), S. 35-38 
    Details
    ISSN: 1057-9257
    Schlagwort(e): photoluminescence ; time-resolved fast spectrocopy ; photoinduced absorption spectroscopy ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: We have studied the photophysics of linear trans-quinacridone films by applying a variety of transient and continuous wave photomodulation techniques. Our experimental results demonstrate the ultrafast formation of excimer species which are responsible for the emission. The excimer decay kinetics seems to suggest a predominantly charge transfer character of these emitting species. This is consistent with the long-lived states which we detected on the millisecond time scale. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Photoluminescence measurements of GaAs grown by liquid phase epitaxy from Ga-Bi solution (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 9-12 
    Details
    ISSN: 1057-9257
    Schlagwort(e): LPE growth ; Ga-Bi solution ; ‘purification effect’ ; photoluminescence ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Thick, intentionally undoped GaAs epitaxial layers grown by LPE from Ga-Bi solution with different contents of Bi in liquid solvent (from 0 to 82 at.%Bi) were studied by photoluminescence (PL) at temperature &helvbi;T&helvbd;=2 K. The dependence of the photoluminescence spectrum on the content of Bi in solution was analysed. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Morphological evolution, Raman and photoluminescence spectra in optically transparent cubic silicon carbide (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 7 (1997), S. 195-206 
    Details
    ISSN: 1057-9257
    Schlagwort(e): cubic silicon carbide ; morphology ; photoluminescence ; micro-Raman ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Optically transparent cubic SiC crystals were grown via atmospheric-pressure chemical vapour deposition (APCVD) on graphite substrates from methyltrichlorosilane (MTS) in hydrogen in a cold-wall RF induction furnace at temperatures from 1500 to 2000°C. The morphology of the crystals was correlated to substrate temperature, H2/MTS ratio and hydrogen flow. Low-temperature photoluminescence (PL) spectra exhibited a zero-phonon line (2.3787 eV) attributable to an exciton bound to a neutral nitrogen donor, in addition to TA, LA, TO, and LO phonon replicas. The observed broadening and splitting of the PL spectral lines were associated with the morphological habit and internal strain of individual crystallites.Above about 1600°C preferential 〈110〉 growth directions were identified for the majority of the crystals. At intermediate deposition temperatures (1600-1700°C) the dominant morphology consisted of yellow prismatic crystals heavily twinned along {111} and {111¯}. At temperatures of about 1750°C hexagonally shaped {111}-oriented 3C-SiC platelets were formed with alternating {001}/{101} edges. A layer-by-layer growth model was used to rationalise the transition in preferred growth direction from 〈111〉 to 〈101〉 with increasing substrate temperature. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Three-dimensional yield strength properties of jointed rock mass as a homogenized medium (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 1-24 
    Details
    ISSN: 1082-5010
    Schlagwort(e): jointed rocks ; strength criterion ; homogenization method ; yield design ; anisotropy ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: A comprehensive three-dimensional formulation for the strength criterion of regular jointed rocks is derived in this paper. The approach is based upon the implementation of the homogenization method of periodic media within the framework of the yield design theory. A rigorous explicit expression of the macroscopic criterion is given as a function of the strength properties of the intact rock and of the joints modelled as interfaces. Attention is focused on the particular case of an infinitely resistance intact rock. It is shown in particular how the relevant velocity jumps for the homogenized medium can be characterized from the introduction of the set of admissible stress vectors acting upon an elementary surface. The results make it possible to perform the static and kinematic approaches in order to address the stability analysis of rock masses cut by sets of regular joints, even for the three-dimensional geometries.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Time dependent mechanical behaviour of loose sands (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 45-73 
    Details
    ISSN: 1082-5010
    Schlagwort(e): loose sand ; load controlled triaxial tests ; creep tests ; time dependency delayed mechanical response ; elasto viscoplasticity ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The time dependency of loose sands mechanical behaviour has been experimentally analysed and theoretically interpreted. A series of load controlled triaxial tests, by imposing finite load increments, has been performed. The single load increments are followed by variable time periods, in order to carry out many classical creep tests.According to the authors, the considered time dependency is due to the internal fabric rearrangement of the granular assembly, i.e. to the plastic strain development with time.This mechanical peculiarity is theoretically interpreted by means of an elastoviscoplastic constitutive model. This is a very simple extension of a previous incremental elastoplastic constitutive model and appears to be capable to reproduce experimental data quite well.Finally, the importance of the considered time dependency is underlined, both by considering numerical solutions and in analysing unstable natural and experimental phenomena.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Plane shear waves and loss of stability in a saturated granular body (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 25-44 
    Details
    ISSN: 1082-5010
    Schlagwort(e): shear waves ; spontaneous liquefaction ; stability ; hypoplasticity ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: A theoretical study of plane shear waves in a fully saturated granular medium is presented using a hypoplastic constitutive relation for the solid constituent. Dynamic equations for small disturbances about an initial state are derived and analysed with constitutive parameters for Karlsruhe sand. Permanent changes in stresses during the propagation of waves are shown to result in the liquefaction of the material. As follows from the equations, in the general case the propagation is characterized by two different wave speeds, corresponding to the plus or minus sign of the velocity gradient, i.e. to different directions of an instantaneous shear. The values of the wave speeds depend on the initial state (stresses and void ratio) as well as on the orientation of the wave with respect to the principal stresses of the initial stress tensor. If the granular material is loose enough and the initial stress state differs from the hydrostatic one, it is possible that one of the wave speeds becomes imaginary, i.e. physically does not exist. This case means a loss of stability of the body in the sense that a small boundary disturbance results in a flow of the whole mass which cannot be prevented by a boundary control. Such a solution can be viewed as a model of spontaneous liquefaction. The condition obtained for stability is compared with the one derived from the analysis of the second-order work.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Computational aspects of a softening plasticity model for plain concrete (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 75-94 
    Details
    ISSN: 1082-5010
    Schlagwort(e): concrete modelling ; softening plasticity ; fracture energy models ; stress return ; five parameter model ; improved predictors ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: Several computational aspects of the fracture energy based softening plasticity model for plain concrete are considered. A need for a more robust stress return strategy is identified, as the basic closest point projection algorithm leads to regions of nonconvergence, associated with zones of high curvature near the compressive meridian close to the apex. The use of an intermediate stress return to an auxiliary surface to establish an improved predictor is proposed, in conjunction with a controlled scaling of stress return increments, ensuring convergence and providing an efficient and robust stress return strategy.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Editorial (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. iii 
    Details
    ISSN: 1082-5010
    Schlagwort(e): Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cfm.1600010101
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  • 14
    Digitale Medien
    Digitale Medien
    A multiphase medium model for localisation and postlocalisation simulation in geomaterials (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 95-114 
    Details
    ISSN: 1082-5010
    Schlagwort(e): multiphase material ; strain localisation ; averaging theories ; pore pressure ; cavitation ; finite element method ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: It is recalled that negative water pressures are of importance in localisation phenomena of fully saturated, undrained samples of dilatant geomaterials. A model to simulate cavitation phenomena connected with such pore water tractions is developed and implemented in a simplified form in a dynamics code for partially saturated porous media. A case of localisation is studied from the onset of the instability up to the full developed shear band. The weak mesh dependence of the maximum effective plastic strain, due to the employed physical model, is also shown.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Experimental investigation of concrete fracture under uniaxial compression (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 115-127 
    Details
    ISSN: 1082-5010
    Schlagwort(e): concrete ; fracture ; uniaxial compression tests ; boundary restraint ; slenderness ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: Localization of deformations has been investigated in a series of displacement controlled uniaxial compression experiments. Of main interest are the effects of specimen slenderness and friction between loading platen and specimen. Both effects have a direct influence on the development of localized fracture zones in the specimen. The results indicate that the use of a double layer of teflon with an intermediate layer of grease yields size-independent results as far as the pre-peak stress-strain behaviour and the peak strength are concerned. However, in terms of stress and strain, a significant influence of both the specimen slenderness and the amount of boundary restraint has been observed in the post-peak regime. It is found that the post-peak curves become almost completely identical when they are plotted in terms of nominal stress and post-peak displacement. For any type of loading platen used, the post-peak relative stress-displacement curves are found to be independent of the specimen height. Furthermore, since during post-peak localization relative sliding and movements of larger parts of the specimen are observed, the definition of a unique Poisson's ratio is virtually impossible.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Damage and localisation in elastic materials with voids (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 129-144 
    Details
    ISSN: 1082-5010
    Schlagwort(e): damage ; void growth ; softening ; localisation ; bifurcation ; rupture ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: An extension of the theory of elastic material with voids to the case where the material undergoes an irreversible void growth is presented. The particularity of this theory is that the continuum is described by two kinematic variables: the displacements and the variation of the volume fraction of material in the porous continuum. Motion is controlled by two governing equations, the classical one involving the displacement or stresses and another one that involves the other kinematic variable, similar to the governing equation in heat conduction problems. The degradation of the elastic moduli is described in the model by a damage scalar variable. A simplified model where the damage variable is proportional to the irreversible variation of volume fraction of material is discussed. From the governing equations, it is deduced that the equation which governs the growth of damage involves the second gradient of damage and a material parameter which plays the role of an internal length according to the analysis of strain localisation. The finite element implementation of the theory is briefly presented. The two variables are discretised separately and the form of the equations to be solved is similar to those obtained in coupled thermoelasticity. One dimensional finite element results of strain localisation show that a proper convergence upon mesh refinement is obtained. The equation which governs the irreversible variation of volume fraction (or the damage growth) acts as a localisation limiter.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Failure criterion, flow rule and dissipation function derived from hypoplasticity (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 145-163 
    Details
    ISSN: 1082-5010
    Schlagwort(e): constitutive model ; hypoplasticity ; failure criterion ; flow rule ; dissipation function ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: Failure criterion, flow rule and dissipation function derived from a class of incrementally non-linear, so-called hypoplastic, constitutive equations are presented. Although the hypoplastic model is developed without recourse to some concepts pertinent to pasticity theory, such as failure surface, plastic potential, flow rule and decomposition of deformation into elastic and plastic parts, it is shown how these concepts may be obtained as natural outcomes of the constitutive model. A connection of the hypoplastic model to Truesdell's hypoelasticity theory and of the derived failure criterion and flow rule to their hypoelastic counterparts is made. By defining the plastic strain rate properly, the dissipation surface is obtained based on the principle of maximum entropy production. Furthermore, the plastic potential is constructed with reference to the direction of plastic strain rate. Finally, the failure surface, flow rule and dissipation surface obtained with a specific hypoplastic constitutive equation are presented and compared with experimental results in the literature.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Homogenization for Granular Materials: non reversible behaviour (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 199-218 
    Details
    ISSN: 1082-5010
    Schlagwort(e): homogenization ; granular material ; yield surface ; elasticity ; plasticity ; modelling ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: Using a homogenization framework, this paper proposes a description of the non-reversible behaviour of granular materials. First the basic equations are reviewed and some general elasticity results are presented with a comparison to DEM simulations. The global non-reversible behaviour is introduced by the definition of local conditions of contact stability: loss of contact and sliding. The first consequence is the possible definition of global yield surfaces and thus failure surfaces. These surfaces are compared to the usual plastic criteria. The influence of the different homogenization parameters introduced by the definition of localization and averaging operators is also studied. In the last section, a simulation of non-reversible behaviour is presented. Comparisons to experimental data are made in the case of simple loading paths (isotropic compression, triaxial test) as well as in complex loading histories.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Masthead (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996) 
    Details
    ISSN: 1082-5010
    Schlagwort(e): Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cfm.1600010201
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  • 20
    Digitale Medien
    Digitale Medien
    Validity and Limits of the Effective Stress Concept in Geomechanics (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 219-234 
    Details
    ISSN: 1082-5010
    Schlagwort(e): effective stress ; theory of mixture ; compressibility ; pore-water pressure ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The effective stress concept in geomechanics advocated by Terzaghi is historically reviewed and the mechanical interpretation of this concept is clarified based on the theory of mixtures. In the interpretation of the effective stress concept, both the compressibility of the constituents and the balance of force are taken into consideration. The effectiveness of the effective stress comes from the fact that the descriptions of the effective stress in undrained and unjacketed conditions are approximately equal, although the role of the pore-water pressure under different test conditions is not the same. It is shown that the effective stress concept is also applicable to soft rock. Finally, classical interpretations and various definitions of the effective stresses are critically examined.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Creep, damage and failure around large rectangular-like caverns and galleries (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 165-197 
    Details
    ISSN: 1082-5010
    Schlagwort(e): creep ; dilatancy ; damage ; stability ; failure ; galleries ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: An analysis of stability of rectangular-like galleries or caverns is developed from the point of view of creep, creep failure and short-time failure. The initial stress distribution around the cavern just after excavation is obtained with an exact elastic solution. Further this solution is used in conjunction with an elastic/viscoplastic non-associated constitutive equation to determine first the domains around the excavation where the rock becomes dilatant, where compressible, and where a short-time failure is expected. This constitutive equation is further used to determine the creep of the rock around the opening, and where and when a creep failure is to be expected due to excessive dilatancy. It is shown that the location of the incipient creep failure depends on the stress concentration due to the presence of the ‘corners’, on the possible elongated shape of the cavern, and also to the stress concentration induced by the far field stresses. This location also depends on the internal pressure and on depth, and it can be determined quite accurately. Thus the location of incipient creep damage depends on a variety of parameters and the determination of this exact location is very important, and is described in this paper. It is shown that the evolutive damage is spreading mainly in the direction of minimum far field stresses or in the direction of greater elongation of the cross-section. The same constitutive equation allows us to determine the creep convergence (or divergence) of the walls, where this creep is quite fast and when for the first time the incipient creep failure due to dilatancy is to be expected. This timing depends primarily on the magnitude of octahedral shear stress. The time up to creep failure is shorter if this stress is larger (close to the short-term failure value), but tends towards infinity if the stress is relatively small (close but still above the compressibility/dilatancy boundary). Once the various failure modes are well understood the orientation and magnitude of far field stresses can be determined by this analysis if not known a priori. Also, once the location of losing the stability and that of the volume of rock involved in fast creep and creep failure are determined, one can suggest the optimal design of a support. The way in which the stress variation is influencing the above mentioned problem will be discussed in forthcoming papers. While the authors recognize the importance of the pre-existing rock discontinuities in the overall cavern stability, it was thought that a better understanding of this stability starts from analyzing a rock without such pre-existing discontinuities. The examples are given for rock salt.
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  • 22
    Digitale Medien
    Digitale Medien
    Announcement (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. i 
    Details
    ISSN: 1082-5010
    Schlagwort(e): Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cfm.1600010202
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  • 23
    Digitale Medien
    Digitale Medien
    Book Review: Computational Mechanics of Reinforced Concrete Structures, Günter Hofstetter and Herbert A. Mang. Vieweg, Weisbaden, Germany, 1995. 366pp. (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 357-357 
    Details
    ISSN: 1082-5010
    Schlagwort(e): Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Materialart: Digitale Medien
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  • 24
    Digitale Medien
    Digitale Medien
    On shear band localization phenomena of liquid-saturated granular elastoplastic porous solid materials accounting for fluid viscosity and micropolar solid rotations (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 301-320 
    Details
    ISSN: 1082-5010
    Schlagwort(e): theory of porous media ; micropolar grain rotations ; liquid-saturated cohesive-frictional granular elastoplastic skeleton materials ; single-surface yield function ; non-associated flow ; shear band localization ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: Elastoplastic deformations of cohesive-frictional liquid-saturated granular solid materials can be described by use of a macroscopic continuum mechanical approach within the well-founded framework of the theory of porous media (TPM). In the present contribution, the TPM formulation of the skeleton material is extended by micropolar degrees of freedom in the sense of the Cosserat brothers. Proceeding from two basic assumptions, material incompressibility of both constituents (skeleton material and pore liquid) and geometrically linear solid deformations, the non-symmetric effective skeleton stress and the couple stress tensor are determined by linear elasticity laws. In the framework of the ideal plasticity concept, the plastic yield limit is governed by a smooth and closed single-surface yield function together with non-associated flow rules for both the plastic strain rate and the plastic rate of curvature tensor. Fluid viscosity is taken into account by the drag force.The inclusion of micropolar degrees of freedom, in contrast to the usual continuum mechanical approach to the TPM, allows, on the one hand, for the determination of the local average grain rotations and, on the other hand, additionally yields a regularization effect on the solution of the strongly coupled system of governing equations when shear banding occurs. However, in the framework of the original TPM formulation of fluid-saturated porous materials, the inclusion of the fluid viscosity alone also yields a certain regularization on shear band computations. The numerical examples are solved by use of finite element discretization techniques, where, in particular, the computation of shear band localization phenomena is carried out by the example of the well-known base failure problem of geotechnical engineering. © 1997 John Wiley & Sons, Ltd.
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  • 25
    Digitale Medien
    Digitale Medien
    Closed-form solution on the thermoplastic behaviour of a deep tunnel in a thermal-softening material (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 321-337 
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    ISSN: 1082-5010
    Schlagwort(e): thermal-softening behaviour ; transient evolution ; corner flow ; analytical solution ; convergence-confinement concept ; thermomechanical interaction ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: A closed-form solution of deep tunnel subject to an internal pressure and to an axisymmetrical time-dependent temperature field is presented. The material is supposed to have a thermal-softening behaviour, the cohesion decreasing with the temperature. The thermal expansion generates plastic zones with face flow and corner flow, which can coexist and interact. The explicit character of the solution allows rigorous demonstrations of the evolution of such plastic zones, as well as other interesting and fundamental properties of the thermoplastic behaviour of deep tunnels. On the other hand, the causal relationship between the thermomechanical loading and the structural response (convergence, extension of rupture zones) is rendered transparent, thanks to the simplicity of the analytical solution. The consequence of thermal-softening is clearly shown by comparison with the analytical solution for a constant cohesion previously established. Quantitatively, its importance is illustrated by a restricted parametric study, to which the analytical solution is ideally suited. © 1997 John Wiley & Sons, Ltd.
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  • 26
    Digitale Medien
    Digitale Medien
    Modelling the strengths of engineering materials in three dimensions (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 339-356 
    Details
    ISSN: 1082-5010
    Schlagwort(e): biaxial tests ; combined stresses ; compressive strength ; engineering materials ; failure ; failure surfaces ; mathematical models ; tensile strength ; triaxial tests ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: A general, three-dimensional failure criterion is presented. This criterion is formulated in terms of the first and third stress invariants of the stress tensor, and it involves only three independent material parameters. Although these parameters interact with one another, each parameter corresponds to one of three failure characteristics of material behaviour. These material parameters may be determined from any type of strength test, including the simplest possible, such as uniaxial compression and tension tests or biaxial tests for materials with cohesion and tensile strength, and by triaxial compression tests for materials without tensile strength. The procedure for determination of the three material parameters is demonstrated and comparisons between the failure criterion and experimental results are presented for different types of engineering materials. © 1997 John Wiley & Sons, Ltd.
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  • 27
    Digitale Medien
    Digitale Medien
    Assessment of some failure criteria for strongly anisotropic geomaterials (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 1-26 
    Details
    ISSN: 1082-5010
    Schlagwort(e): anisotropy ; failure criterion ; schist ; sedimentary rock ; rock joints ; laboratory testing ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: This paper is devoted to the assessment of some representative failure criteria in the framework of modelling the failure behaviour of strongly anisotropic geomaterials. Experimental data concerning the failure behaviour of a typical strongly anisotropic rock; the schist of Angers are first presented. Nine widely used failure criteria are then selected and classified into three groups, the mathematical continuous models, the empirical continuous models and the discontinuous weakness planes based models. This classification is made up according to the main assumptions and techniques used in each criterion to describe the strength anisotropy. The calibration of each one is carried out with respect to the laboratory data of Angers schist. Qualitative and quantitative comparisons between the selected criteria and with the experimental data are provided. © 1998 John Wiley & Sons, Ltd.
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  • 28
    Digitale Medien
    Digitale Medien
    A new anisotropic failure criterion for transversely isotropic solids (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 89-103 
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    ISSN: 1082-5010
    Schlagwort(e): transversely isotropic material ; elliptic paraboloid failure surface ; strength differential effect ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: A coordinate-free formulation of a failure criterion for transversely isotropic solids is proposed. In the three-dimensional stress space the criterion is represented by an elliptic paraboloid. The anisotropic form of the proposed criterion is based on generalization of the second invariant of the deviatoric stress and of the mean stress obtained through the introduction of a unique fourth-order tensor. For isotropic conditions, the criterion reduces to the Mises-Schleicher failure condition. It is shown that the criterion satisfactorily predicts the strength anisotropy of transversely isotropic rocks subjected to an axisymmetric stress state. The procedure for the identification of the parameters of the criterion from a few simple laboratory tests is outlined. © 1998 John Wiley & Sons, Ltd.
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  • 29
    Digitale Medien
    Digitale Medien
    A model for ageing visco-elastic tension softening materials (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 27-39 
    Details
    ISSN: 1082-5010
    Schlagwort(e): creep ; effective spring concept ; Kelvin chain model ; load bearing volume ; micromechanical model ; relaxation ; softening spring ; solidification ; tension softening ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: An analytical constitutive model similar to the Kelvin chain rheological model associated with solidification theory, is developed for time-dependent tension softening of ageing materials like concrete. The stiffness of spring elements is allowed to vary with time via a function of load bearing volume fraction as in the solidification theory. The development of cracks reduces the load bearing volume fraction with time, so that the overall behaviour of springs is a softening type. A reduction in the load bearing volume with time ensures a gradual reduction in the spring stiffness without violating prescribed retardation times. In some circumstances, depending on the boundary conditions, the stress in a structure can remain unchanged over a period of time. During this period, any cracks in the structure will continue to experience an increased opening due to creep. In other parts of the structure, again depending on the boundary conditions, the crack opening displacements may remain unchanged over a period of time, so that the stress will relax over these parts of the structure. In a large concrete structure, creep and relaxation may be taking place simultaneously in different parts or in the same part but at different times. There is thus a need for a visco-elastic tension softening model for ageing concrete that will cater for both creep and relaxation. © 1998 John Wiley & Sons, Ltd.
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  • 30
    Digitale Medien
    Digitale Medien
    A constitutive model coupling elastoplasticity and damage for cohesive-frictional materials (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 41-63 
    Details
    ISSN: 1082-5010
    Schlagwort(e): elastoplasticity ; damage ; bonded geomaterials ; triaxial testing ; intact and remoulded specimen ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: In order to model the various phenomena which govern the mechanical response of bonded geomaterials under monotonic loadings, an elastoplastic model coupled with an elastic model with damage was developed, taking into account both the frictional and cohesive aspects of these materials. First, the principles at the base of the model are presented, as well as the physical meaning of the parameters which were used in the elastic model with damage. In order to illustrate the capabilities of the model to reproduce the mechanical behaviour of bonded geomaterials, we simulated triaxial tests on various materials: a deep cemented clay, whose heterogeneity from one specimen to another appeared mainly due to the calcium carbonate content; an assembly of sintered glass balls; and an artificially cemented sand. In this last example, various initial mean stresses allowed us to enlighten the brittle-ductile transition which was modelled by introducing the mean confining pressure in the damage evolution law. We demonstrated that the parameters of each part of the model could be adapted to reproduce the observed general trends. For weak bonds, the elastoplastic part played the predominant role, whereas for strong bonds, the elastic part with damage governed the mechanical behaviour. © 1998 John Wiley & Sons, Ltd.
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  • 31
    Digitale Medien
    Digitale Medien
    An investigation on the uniqueness of the incremental response of elastoplastic models for virgin sand (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 65-87 
    Details
    ISSN: 1082-5010
    Schlagwort(e): elastoplasticity ; sand ; constitutive modelling ; controllability ; instability ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The paper investigates the possibility of the occurrence of a multiplicity of homogeneous responses of soil specimens under the same incremental loading, and the associated non-controllability of the imposed loading path.It is shown that for non-associated elastoplastic strain-hardening constitutive laws, such a possibility exists even in the hardening regime. Only when the stiffness matrix is positive-definite is the incremental solution unique for any loading programme.A particular constitutive model is chosen and the shape of the loci of non-uniqueness is calculated for various loading programmes. It is shown that the conditions for the occurrence of a shear band and of a peak of the deviator stress in a triaxial undrained test can be seen as special cases of the theory presented. Accordingly, the so-called ‘instability line’ concept in undrained conditions is generalized. © 1998 by John Wiley & Sons, Ltd.
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  • 32
    Digitale Medien
    Digitale Medien
    ALE analyses of localization in wave propagation problems (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 105-125 
    Details
    ISSN: 1082-5010
    Schlagwort(e): localization ; non-local damage ; Perzyna viscoplasticity ; mesh adaptivity ; Arbitrary Lagrangian-Eulerian technique ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The computational modelling of localization of deformation in cohesive-frictional materials must be carried out in a proper, accurate and efficient manner. A proper solution can be obtained by using an enriched material description such as a non-local damage model or Perzyna's viscoplasticity model. However, still a large number of finite elements is needed for an accurate description of the localization zone. To improve efficiency, mesh adaption is applied here by means of the Arbitrary Lagrangian-Eulerian (ALE) technique. The ALE technique must typically be applied in combination with an enriched material model. Otherwise, the use of a standard model gives a zero-width solution of the localization zone and therefore remeshing results in a continuing decrease of finite element size. Implementation of this method requires the addition of convective forces in the equations of motion, transport of the state variables and the formulation of a remeshing strategy. The remeshing strategy heavily determines the success of the ALE method. Three examples of wave propagation have been treated and it is shown that a suitable remeshing strategy in combination with an enriched material model leads to proper, accurate and efficient analyses of the localization process. © 1998 John Wiley & Sons. Ltd.
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  • 33
    Digitale Medien
    Digitale Medien
    Daphnis: a new model for the description of post-localization behaviour: application to sands (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 127-153 
    Details
    ISSN: 1082-5010
    Schlagwort(e): constitutive equations ; post-localization behaviour ; large strain ; interface model ; bifurcation ; shear band ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: This paper addresses developments on a constitutive model able to describe the post-localized behaviour of structures composed by geomaterials. The behaviour of the shear band is defined by means of a specific non-linear constitutive equation in the framework of large strain. Concept of ‘consistency’ of this model with the CLoE model from which it is derived at the onset of localization is discussed. During the post-localization regime this model evolves in a specific way by introducing the concept of critical void ratio. After some recalls about the CLoE framework and about a Rice bifurcation analysis involving CLoE models, the basic concepts of the Daphnis model are introduced. The last part of this paper is devoted to numerical results on an initially homogeneous frictionless biaxial test. The behaviour of the sample is modelled by means of a plane Mohr Coulomb model defined in the CLoE framework and its associated Daphnis model is used to characterize the specific behaviour of the shear band in the post-localization regime. © 1998 John Wiley & Sons, Ltd.
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  • 34
    Digitale Medien
    Digitale Medien
    Development of a plasticity bond model for steel reinforcement (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 155-180 
    Details
    ISSN: 1082-5010
    Schlagwort(e): reinforced concrete ; bond model ; plasticity ; interface ; yield surface ; modelling ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The development of an interface, non-associative, plasticity model for bond between ribbed, steel bars and concrete is discussed. The model relates average local slip and radial dilation to average bond shear stress and radial confinement stress. The model partially accounts for the response of the damaged, finite-thickness region around the bar - the bond zone. The model is developed for standard steel bars that are initially unstrained. With simplifying assumptions, data for the components of a plasticity law are extracted from a key set of experimental results. In this paper, we emphasize the development of an expression for the yield surface for monotonic loading. While the forms of the model's components are empirically derived, they qualitatively reflect the mechanics of the mechanical interaction of ribbed bars with the adjacent concrete. A characteristic length, related to the rib pattern, helps quantify this interaction. The mechanics of the bond are difficult to characterize in a simple form, but the calibrated model only requires four physical properties and reproduces with acceptable accuracy experimental results with various levels of radial confinement stress. Model refinements are suggested for future work. © 1998 John Wiley & Sons, Ltd.
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  • 35
    Digitale Medien
    Digitale Medien
    FE-Simulation of compaction and solid-state sintering of cemented carbides (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 181-205 
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    ISSN: 1082-5010
    Schlagwort(e): cemented ; carbide ; finite ; element ; compaction ; sintering ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: We have developed a tool for simulating the press cycle and the sintering cycle of cemented carbides. A constitutive model for compaction and tensile fracture has been implemented in the explicit FE programme LS-DYNA2D, and it has been tuned to experiments of hydrostatic compression, uniaxial strain and conventional triaxial compression. The programme simulates the complete compaction cycle in a robust manner. Friction against the tooling is properly taken into account. We have further developed a constitutive model for the stress-free solid-state sintering to also account for a mechanical stress field. The sintering model is based on physical concepts, diffusion parameters, free surface energy, dimensions of carbide grains, etc. of the constituents, and was tuned to successfully simulate the unloaded and loaded sintering of simple specimens. The models of compaction and sintering have a common set of state variables, such that after the compaction cycle, and at raising the temperature the sintering starts out with proper account of the residual stress field. Finally, the potential of the model is demonstrated by simulating the production cycle of a simple WC-Co tool piece until sintering to 75% of full density. The final geometrical shape of the specimen is compared to experimental data. © 1998 John Wiley & Sons, Ltd.
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  • 36
    Digitale Medien
    Digitale Medien
    A superstable time-discrete scheme for the numerical integration of viscous constitutive equations (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 229-256 
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    ISSN: 1082-5010
    Schlagwort(e): finite element method ; viscous constitutive equations ; time-discrete scheme ; stability ; superstability ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The general framework of the paper deals with the finite element modelling of mechanical problems involving viscous materials such as bitumen or bituminous concrete. Its aim is to present a second-order-accurate discrete scheme which remains unconditionally superstable when used for the time discretization of the linear and non-linear viscoelastic constitutive equations considered. After stating the space- and time-continuous mechanical problem we focus on the time discretization of these equations, considering three different schemes. For both of them sufficiently small values of the time step are required in order to ensure the superstability, whereas the third remains unconditionally superstable. Eventually, some numerical results are presented. © 1998 John Wiley & Sons, Ltd.
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  • 37
    Digitale Medien
    Digitale Medien
    Numerical simulations of impacts using a discrete element method (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 257-276 
    Details
    ISSN: 1082-5010
    Schlagwort(e): impacts ; structural damage ; discrete element method ; dynamic loading ; scabbing ; perforation ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: Impacts of rigid spherical nose shaped missiles on concrete beams are simulated with a discrete element method. The history of the structural damage of the beam is followed from the very first crushing and fracturing processes to the ultimate fragmentation step. Spalling, scabbing, penetration and perforation events are characterized and compared with real test cases of the civil engineering industry. It is found that these phenomena depend not only on the kinetic energy of the missile as predicted by some recent empirical laws but also on its momentum. This means that the dynamic impact loading time is determinant in the scabbing and perforation thicknesses. When the numerical data is plotted against the empirical rules determined from experimental data, the fit is good although the model is two dimensional. © 1998 John Wiley & Sons, Ltd.
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  • 38
    Digitale Medien
    Digitale Medien
    Failure design of jointed rock structures by means of a homogenization approach (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 207-228 
    Details
    ISSN: 1082-5010
    Schlagwort(e): jointed rock masses ; stability ; failure ; yield design ; homogenization ; strength anisotropy ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: Conceived as a potential alternative to the methods usually employed for evaluating the stability of jointed rock masses, the homogenization approach developed in this paper stems from the intuitive idea that, from a macroscopic point of view, a rock mass intersected by a regular network of joint surfaces may be perceived as a homogeneous continuum. The failure criterion of such an equivalent medium is theoretically determined from the knowledge of the failure conditions of the individual constituents, namely the intact rock matrix and joint interfaces. Owing to the existence of privileged material directions associated with the joint orientation distribution, this criterion turns out to be of the anisotropic frictional type, as shown by the closed-form expression obtained in the particular case of two mutually orthogonal joint sets. This criterion is then applied to the investigation of two illustrative engineering problems: the calculation of the load-bearing capacity of a shallow foundation on a jointed rock half-space and the stability analysis of an excavation. Both problems are handled by means of the kinematic method of yield design, making use of the previously determined macroscopic failure condition. The upper bound estimates thus derived appear to be significantly better than those obtained from a direct analysis in which the intact rock matrix and joints are considered separately. In spite of some limitations regarding its range of applicability, which are underlined throughout the paper, the homogenization approach may constitute an appropriate general framework for the design of densely jointed rock structures. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 14 Ill.
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  • 39
    Digitale Medien
    Digitale Medien
    Experimental behaviour of fibre concrete slabs on soil (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 277-290 
    Details
    ISSN: 1082-5010
    Schlagwort(e): experimental analysis ; slabs on soil ; reinforced concrete ; steel fibres ; fracture energy ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The cracking control of plain concrete slabs on soil foundation requires the execution of joints with mechanisms of load transfer between adjacent panels. These joints increase the construction costs and, often, are the source of local damage and loss of service performance. Slabs reinforced with steel wire mesh have been used in order to increase the load-carrying capacity and to enhance the cracking control. However, the use of this conventional reinforcement increases the costs, mainly due to labour time spent on the arrangement and positioning of the reinforcement.Fibre-reinforced concrete is a recent material well fitted for applications in industrial floors on soil foundation. The cost of fibres is compensated by a faster construction process and a reduction in the number of expansion joints. The fatigue, impact and flexural strength are significantly improved when steel fibres are added to the concrete mix.The work developed aims to contribute to the on going research effort to clarify the behaviour of fibre-reinforced concrete slabs on soil foundation. For this purpose, an experimental and numerical investigation were carried out. The present article deals basically with the experimental work developed, describing the tests performed and discussing the main results obtained. © 1998 John Wiley & Sons, Ltd.
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  • 40
    Digitale Medien
    Digitale Medien
    Enhanced consolidation in brittle geomaterials susceptible to damage (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 291-303 
    Details
    ISSN: 1082-5010
    Schlagwort(e): poroelasticity ; isotropic damage ; brittle geomaterials ; enhanced consolidation ; saturated geomaterials ; computational modelling ; indentation of geomaterials ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: This paper examines consolidation behaviour of saturated geomaterials with a matrix component which is susceptible to damage. Finite-element-based computational model accounts for the alteration in both the deformability and permeability characteristics of the porous material due to damage evolution. The isotropic damage criteria governing the evolution of elastic stiffness and hydraulic conductivity parameters are characterized by the dependency of the damage variable on the distortional strain invariant. The computational procedure is utilized to evaluate the extent to which the time-dependent axisymmetric indentation behaviour of a rigid circular punch on a poroelastic half-space can be influenced by the damage evolution in the porous skeleton. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 8 Ill.
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  • 41
    Digitale Medien
    Digitale Medien
    A multilayered mixed beam element in gradient plasticity for the analysis of localized failure modes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 305-322 
    Details
    ISSN: 1082-5010
    Schlagwort(e): strain localization ; finite element ; mesh sensitivity ; regularization ; gradient plasticity ; multilayered concrete beams ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: A gradient-dependent plasticity theory is applied to finite element solutions of static strain localization problems. Assuming weak satisfaction of constitutive equations, a multilayered beam finite element with a mixed character is developed. The plastic strain field is discretized in addition of the displacement field. A consistent Newton-Raphson algorithm for this approach is presented. Some examples are carried out in order to illustrate the approach and verify the performances of the element. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 13 Ill.
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  • 42
    Digitale Medien
    Digitale Medien
    Sliding friction, Physical Principles and Applications by Bo N. J. Persson, Springer, Berlin, 1998 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 365-365 
    Details
    ISSN: 1082-5010
    Schlagwort(e): Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: No Abstract
    Materialart: Digitale Medien
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  • 43
    Digitale Medien
    Digitale Medien
    Gradient-enhanced damage modelling of concrete fracture (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 323-342 
    Details
    ISSN: 1082-5010
    Schlagwort(e): concrete fracture ; computational modelling ; continuum damage mechanics ; localization ; regularization ; gradient enhancement ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: Classical continuum damage theory for quasi-brittle fracture exhibits an extreme sensitivity to the fineness and orientation of the spatial discretization in finite element simulations. This sensitivity is caused by the fact that the mathematical description becomes ill-posed at a certain level of accumulated damage. The ill-posedness can be removed by the use of a gradient-enhanced damage model. In this model, higher-order deformation gradients give rise to a non-local effect, which regularizes the localization of deformation and thus renders numerical analyses mesh-objective.The mesh objectivity of the gradient-enhanced damage approach is demonstrated by the application to two concrete fracture experiments: a double-edge notched bar subjected to a uniaxial, tensile load and a single-edge notched beam under anti-symmetric four-point loading. Both the initiation and the propagation of damage can be simulated. Particularly the latter aspect calls for an appropriate definition of the strain measure which governs the evolution of damage. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 18 Ill.
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  • 44
    Digitale Medien
    Digitale Medien
    On the linearization of the microplane model (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 343-364 
    Details
    ISSN: 1082-5010
    Schlagwort(e): concrete modelling ; microplane model ; anisotropic damage ; consistent linearization ; localization analysis ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The paper addresses the microplane model in the context of localization analysis. Capable of reproducing experimental results of concrete specimens, the microplane model includes anisotropic damage in a natural and conceptually simple and explicit way. However, the efficiency of former microplane implementations suffers from the expense of the solution procedure being based on the secant stiffness method. Within this paper, the macroscopic constitutive equation derived by kinematically constraining the microplane strains to the macroscopic strain tensor is consistently linearized resulting in quadratic convergence of the Newton-Raphson iteration for the equilibrium equations. A fully three-dimensional model will be presented and linearized incorporating the two-dimensional case in a natural fashion. Furthermore, the localization criterion is analysed, indicating locally the onset of localization in terms of the acoustic tensor. Several examples demonstrate the features of the microplane model in predicting the material behaviour of concrete in tension and compression as well as in shear. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
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  • 45
    Digitale Medien
    Digitale Medien
    Boundary element analysis of the pullout behaviour of an anchor bolt embedded in concrete (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 235-249 
    Details
    ISSN: 1082-5010
    Schlagwort(e): boundary element method ; concrete ; fracture mechanics ; fictitious crack model ; crack growth ; contact mechanics ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: A boundary element formulation for the analysis of pullout behaviour of an anchor bolt embedded in concrete is presented. The pullout analysis involves modelling two different bodies (i.e. anchor head and concrete) which are in contact over a certain region. The fracture of concrete is represented by the fictitious crack model (FCM) in which the fracture zone is replaced by applying closing forces on both crack surface. The FCM in conjunction with the boundary element method (BEM) allows the simulation of crack growth in concrete in a straight forward manner without remeshing. The crack path need not be known in advance as it is calculated during the iteration process. The numerical results obtained are compared with the round-robin analysis of pullout test proposed by RILEM TC 90-FMA.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 46
    Digitale Medien
    Digitale Medien
    A hypoplastic relation for granular materials with a predefined limit state surface (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 251-271 
    Details
    ISSN: 1082-5010
    Schlagwort(e): constitutive law ; plasticity ; hypoplasticity ; asymptotic state ; limit surface ; sand ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: A hypoplastic theory for granular materials developed by Gudehus and Bauer is discussed. The description of asymptotic states is of particular interest. Three forms of asymptotic states are defined. Useful criteria to describe the tensorial part of the constitutive relation is developed for one of them, namely for the critical states. The terms proposed by Wu are correlated to the well-known formulations of elastic plastic theory: the Drucker/Prager model and the yield condition by Matsuoka/Nakai. The suitability of the Matsuoka/Nakai criterion for critical states is discussed.Specification of tensorial functions follows in two steps. First the hypoplastic Drucker/Prager model is developed, and then the limit condition by Matsuoka/Nakai is implemented. The resulting tensorial functions require the critical friction angle as the only material constant. The limit condition in critical states obtained from the hypoplastic law coincide with the one by Matsuoka/Nakai. A more comprehensive hypoplastic constitutive relation based on these new tensorial functions is discussed and applied to simulations of element tests. These numerical results are compared with experimental results for sand.
    Zusätzliches Material: 15 Ill.
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  • 47
    Digitale Medien
    Digitale Medien
    Masthead (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996) 
    Details
    ISSN: 1082-5010
    Schlagwort(e): Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cfm.1600010301
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  • 48
    Digitale Medien
    Digitale Medien
    A matrix formulation for the elastoplastic homogenisation of layered materials (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 273-294 
    Details
    ISSN: 1082-5010
    Schlagwort(e): homogenisation ; layered media ; non-linear analysis ; plasticity ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: In this article attention is given to the homogenisation of periodic layered materials. Based on the assumption of a homogeneous state of stress and strain in each layer, a novel matrix formulation capable of representing the elastic behaviour of the composite material is established. The matrix formulation yields a much clearer implementation of linear elastic homogenisation algorithms and a relatively straightforward extension to inelastic behaviour. The theory of plasticity, which is adopted to describe the inelastic behaviour, follows modern concepts, including a unconditionally stable implicit Euler backward return mapping, a local Newton-Raphson method and a consistent tangent stiffness matrix. A comparison between the homogenised continuum and the standard continuum with an exact discretisa tion of the geometry of the composite shows excellent agreement, both in the presence of elastic and inelastic material behaviour.
    Zusätzliches Material: 18 Ill.
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  • 49
    Digitale Medien
    Digitale Medien
    Time-dependent tension softening (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 295-304 
    Details
    ISSN: 1082-5010
    Schlagwort(e): creep ; effective spring concept ; micromechanical model ; relaxation ; rheological model ; softening-type spring ; tension softening ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: A methodology that combines a rheological model for viscoelastic behaviour with a micromechanical model for tension softening through the effective spring concept is developed for materials exhibiting both tension softening and time-dependent behaviour. Spring elements with softening characteristics and dashpot with varying viscosity are used for this purpose. The characteristics of the spring elements and dashpot are obtained from a micromechanical model which relates the microstructure of the material to its tension softening response. The softening-type springs ensure gradual reduction in stiffness, whereas the dashpot with varying viscosity ensures that the retardation and relaxation times equal prescribed values. In this way, both the stress and crack opening are allowed to vary with time to reflect the real behaviour of a time-dependent tension softening material. The methodology is illustrated on the simple Poynting- Thompson rheological model, without restricting its application to more sophisticated models.
    Zusätzliches Material: 7 Ill.
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  • 50
    Digitale Medien
    Digitale Medien
    Numerical analysis of concrete structures subjected to alkali-aggregate reaction (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 305-319 
    Details
    ISSN: 1082-5010
    Schlagwort(e): concrete structures ; alkali-aggregate reaction ; plasticity ; finite elements ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: In this paper a simple continuum theory, as recently proposed by Pietruszczak (Int. J. Computers Struct., 58, 1093-1099 (1996)), is applied to describe the mechanical effects of the alkali-aggregate reaction in concrete structures. The formation of alkali- silica gel leads to a progressive expansion of the material. The progress in the reaction is assumed to be coupled with the degradation of mechanical properties, the latter described within the framework of elastoplasticity. The paper discusses the details of the numerical implementation of the constitutive model, including an implicit integration scheme and the computation of an updated tangent operator. Numerical examples are provided to assess the performance of the proposed algorithm. The formulation is then used to analyse the junction between the right-wing dam and the water intake structure of the Beauharnois powerhouse situated in Quebec (Canada). A non-linear 3D finite element analysis is performed simulating the time history of the deformation due to continuing reaction.
    Zusätzliches Material: 9 Ill.
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  • 51
    Digitale Medien
    Digitale Medien
    A unilateral damage model for masonry based on a homogenisation procedure (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 349-366 
    Details
    ISSN: 1082-5010
    Schlagwort(e): damage ; fracture energy ; homogenisation ; masonry ; mesh dependence ; unilateral effect ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: By considering masonry as a composite material, its mechanical properties are obtained by taking into account the properties of the components (bricks and mortar) through a homogenisation technique. To describe the behaviour of the material components a unilateral damage model is proposed. This model, based on the introduction of three damage variables, describes the behaviour of brittle materials subjected to alternating tensile-compressive cyclic loads. The model is applied to the simulation of tests on masonry panels and miniaturised walls; numerical results are discussed and successfully compared with experimental data.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 52
    Digitale Medien
    Digitale Medien
    Crush-crack': a non-local damage model for concrete (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 321-347 
    Details
    ISSN: 1082-5010
    Schlagwort(e): damage ; dilatancy ; failure-modes ; fractures ; localization ; shear ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: A model is presented based on the non-local damage theory. It sets out to describe the behavior of concrete under free-variable loads, which are constant in sign. Its purpose is to analyze shear behavior and high strain-gradient localized problems, and it takes Mazar's model as a starting point with reference to the basic idea of a scalar isotropic non-local damage controlled by principal tensile strains. In addition, the other two main features are an internal variable denoted to the control or reversible volumetric expansion in compression, and irreversible strains aimed at modelling crushing in compression and cracks both in tension and compression. As a consequence, induced-anisotropy, dilatancy and path-dep endency can be reproduced. In particular, the modelling of micro- and macrocracks makes it possible to capture mixed-mode cracking as well as aggregate interlock, which requires a residual stiffness to guarantee the transmission of transversal and normal stresses for assigned slips. The model requires the knowledge of the material response in uniaxial tension and compression, and biaxial compression tests which can be introduced directly by adopting experimental curves, or by means of a reduced number of parameters. The effectiveness of the model is shown through comparisons with several sets of experimental tests on both small specimens, assumed to be homogeneous, and boundary value problems.
    Zusätzliches Material: 18 Ill.
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  • 53
    Digitale Medien
    Digitale Medien
    Implicit integration and consistent linearization for yield criteria of the Mohr-Coulomb type (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 367-383 
    Details
    ISSN: 1082-5010
    Schlagwort(e): plasticitity ; isotropy ; Mohr-Coulomb ; consistent linearization ; algorithmic tangent stiffness ; multisurface plasticity ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: In this paper, we discuss the efficient treatment of yield criteria that are of the Mohr-Coulomb type for elastic and plastic isotropy. On the basis of the fully implicit method, we derive the explicit expression for the integrated stress along with a flow rule that represents volumetric non-associativity. The integration algorithm covers all the possible cases of regular, corner and apex solutions including the suitable indicator for each case. We also establish the consequent consistently linearized tangent stiffness modulus tensor, which is shown to appear in the form of an additive modification of the continuum tangent stiffness tensor. The convergence properties of the consistent tangent stiffness tensor are compared with its feasible approximations. The results indicate the strongly sensitivity to the proper treatment of the corner conditions at the establishment of the ATS-tensor.
    Zusätzliches Material: 5 Ill.
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  • 54
    Digitale Medien
    Digitale Medien
    Masthead (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996) 
    Details
    ISSN: 1082-5010
    Schlagwort(e): Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cfm.1600010401
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  • 55
    Digitale Medien
    Digitale Medien
    Examination of the possibility of a fluid-mechanics treatment of dense granular flows (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 1 (1996), S. 385-403 
    Details
    ISSN: 1082-5010
    Schlagwort(e): granular flow ; constitutive equation ; simple fluid ; friction ; collision ; microstructural model ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The aim of this paper is to examine the possibility of a simple fluid-mechanics treatment of rapid dense granular flows. In other words, we examine whether the constitutive equation can be sought in a simple relationship between the strain-rate and stress tensors. With this aim, we first show that an inclined channel is an appropriate device for providing rheological data. Here we provide a complete rheometrical treatment, which allows to infer the shear-stress/shear-rate curve (for simple shear flows) from the flow-depth/mass-flow-rate curve. Experi-ments performed with glass beads and sand grains revealed an apparent decrease in the shear stress with increasing shear rate. We then demonstrate that this result, although paradoxical, is not unphysical. Moreover, more detailed theoretical analysis shows that the main issues raised by our experiments may be overcome by ‘microstructural’ models. We finally give two examples of models including a single microstructural parameter, which are able to qualitatively account for the main features of our experiments.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 56
    Digitale Medien
    Digitale Medien
    A continuum model for periodic two-dimensional block structures (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 31-46 
    Details
    ISSN: 1082-5010
    Schlagwort(e): block structure ; elasticity ; homogenization ; Cosserat continuum ; dynamics ; large deformation ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: A continuum model for regular block structures is derived by replacing the difference quotients of the discrete equations by corresponding differential quotients. The homogenization procedure leads to an anisotropic Cosserat Continuum. For elastic block interactions the dispersion relations of the discrete and the continuous models are derived and compared. Yield criteria for block tilting and sliding are formulated. An extension of the theory for large deformation is proposed. © 1997 by John Wiley & Sons, Ltd.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 57
    Digitale Medien
    Digitale Medien
    Implicit integration of elastoplastic constitutive models for frictional materials with highly non-linear hardening functions (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 1-29 
    Details
    ISSN: 1082-5010
    Schlagwort(e): numerical integration ; constitutive modelling ; frictional materials ; highly non-linear hardening functions ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: Constitutive relations in elastoplasticity may be formulated in a variety of ways, and different update algorithms may be employed to solve the resulting equations. Several implicit integration schemes, although some not widely used, have been suggested in the last years. Among them, the closest point projection method (CPPM) has proven to be an effective and robust integration scheme. In order to gain maximum control of the stress projection, a two-level CPPM iteration scheme is proposed. The hardening variables are fixed during the stress projection onto consequently fixed yield surfaces, and after the stress projection, new values of the hardening variables are calculated defining new yield surfaces. The update of the hardening parameters which, in general, may be highly nonlinear functions, may be determined by a combination of a Picard Iteration (PI) on the hardening variables and an adaptative order inverse interpolation (AOII) on the difference of subsequent iterations of the hardening variables.The integration scheme has been implemented in a general constitutive driver which has been formulated independent of the selected constitutive model and easily linked to finite element codes. A third stress invariant dependent, cone-cap elastoplastic constitutive model, referred to as the MRS-Lade, with a highly non-linear hardening function has been used to show the applicability of the proposed iteration scheme. Error analyses and accuracy assessment are presented along with some representative test results. © 1997 by John Wiley & Sons, Ltd
    Zusätzliches Material: 20 Ill.
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  • 58
    Digitale Medien
    Digitale Medien
    Undrained instability of very loose Hostun sand in triaxial compression and extension. Part 2: theoretical analysis using an elastoplasticity model (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 71-92 
    Details
    ISSN: 1082-5010
    Schlagwort(e): undrained instability ; static liquefaction ; non-associated plasticity ; loss of uniqueness ; model validations ; very loose sand ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The characteristics of the loss of stability associated with the initiation of the static liquefaction phenomenon is obtained using the CJS model within the elastoplasticity framework. This model is based on the characteristic line concept. The determining factors involved in the prediction of this phenomenon and in the modelling process are identified. The importance of the elastic components is highlighted, in particular its non-linearity. The possibilities and the limits of the proposed model to describe the undrained behaviour of very loose sand are examined, taking into consideration the effects of the more or less complex stress history. Finally, the conditions leading to the appearance of the uniqueness domain are indicated. The findings of this theoretical study rely entirely on the experimental data presented in a companion paper, with emphasis on the triaxial tests on anisotropically consolidated samples. © 1997 by John Wiley & Sons, Ltd.
    Zusätzliches Material: 17 Ill.
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  • 59
    Digitale Medien
    Digitale Medien
    Experimental analysis and theoretical interpretation of triaxial load controlled loose sand specimen collapses (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 93-120 
    Details
    ISSN: 1082-5010
    Schlagwort(e): loose sands ; load-controlled triaxial tests ; creep tests ; instability ; theoretical interpretation ; strain-rate sensitivity ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: A series of triaxial load-controlled tests is performed.Finite load increments are imposed. The single load-steps are followed by a time period during which the axial load is kept constant.At low stress levels the mechanical response is stable and characterized by a continuous decrease in strain rate with time. At higher stress levels, the mechanical response changes and, subsequently, the collapse takes place.The collapse is unexpected and occurs at a stress level less than that associated with the steady state, experimentally observed by performing strain triaxial controlled tests.In order to interpret such a behaviour, a theoretical discussion is introduced. This is based on a dynamical reinterpretation of the micromechani cal fabric rearrangement of granular assembly.In particular, the role played by the kinetic energy of the system, as well as that played by the anisotropy of the microstructure, have been analysed. © 1997 by John Wiley & Sons, Ltd. Mech. cohesive-frictional mater. 2, 93-120 (1997)
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    Digitale Medien
    Undrained instability of very loose Hostun sand in triaxial compression and extension. Part 1: experimental observations (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 47-70 
    Details
    ISSN: 1082-5010
    Schlagwort(e): instability ; liquefaction ; laboratory tests ; undrained ; triaxial ; loose sand ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The undrained behavior of very loose Hostun RF sand in triaxial compression and extension tests is described. The samples are consolidated isotropically or anisotropically along constant effective stress ratio paths. Very loose sand exhibits partial liquefaction, deviator peak stress at relatively low to very low axial strain, gradual post-peak stress reduction to a small residual value at large strains, sharp loss of effective mean pressure due to generation of large pore pressure and overall volume reduction. The instability line of Lade is examined in the case of extension tests and extended for anisotropic samples. It is shown that monotonic and anisotropic consolidation strongly influences the instability concept. A higher positive anisotropic consolidation level produces a greater slope of the instability line in compression and a reverse trend can occur in extension. Complex stress history can develop a fossilized instability line depending on the amount of axial strain attained. Effective strain ratio increment at peak has an asymptotic stabilization effect. © 1997 by John Wiley & Sons, Ltd.
    Zusätzliches Material: 14 Ill.
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    Digitale Medien
    Experimental micromechanical analysis of a 2D granular material: relation between structure evolution and loading path (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 121-163 
    Details
    ISSN: 1082-5010
    Schlagwort(e): granular materials ; micromechanics ; biaxial tests ; complex loading paths ; micro-macro relations ; fabric anisotropy ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: This paper is concerned with micromechanics of Schneebeli material specimens composed of wooden roller stacks. Several laboratory tests are carried out to analyse the material behaviour under complex loading conditions, involving loading-unloading cycles and principal axes rotations. In order to characterize micromechanical deformation features and structure evolution, a series of pictures is taken during loading. Pictures are then digitized using a stereo device, obtaining the position of each roller. Starting from these data a number of computer programs, conceived for the purpose, allow us to measure micromechanical variables and to analyse their evolution.In the following, after the description of the devices employed in this research, macromechanical results are analysed to evaluate the reliability of the laboratory model. Then, local variables are introduced and the use of continuum mechanics to describe granular materials behaviour is discussed. Finally, the evolution of local kinematic variables is described, focusing interest on the evolution of specimen anisotropy. © 1997 by John Wiley & Sons, Ltd. Mech. cohesive-frictional mater. 2, 121-163 (1997)
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    Digitale Medien
    Implicit integrations in elastoplastic geotechnics (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 165-183 
    Details
    ISSN: 1082-5010
    Schlagwort(e): elastoplasticity ; pressure sensitive materials ; constitutive modelling ; dilatancy ; implicit integrations ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: The paper presents the derivation of a fully implicit Newton algorithm for direct integration of constitutive equations, in extended stress-internal variable space, involving hardening or softening of a general dilatant isotropic elastoplastic geomaterial. All relevant derivatives are provided in tensor notation, thus facilitating implementation. The consistent, algorithmic tangent stiffness tensor is derived. The relative accuracy of a template algorithm is assessed on a number of examples by means of iso-error maps. We present a rather simple, one-increment example concerning convergence properties of the Newton iterative scheme at the global, finite element level, associated with the consistent tangent stiffness tensor for integrating the weak form of the equilibrium equations. © 1997 by John Wiley & Sons, Ltd. Mech. Cohesive-frictional mater. 2, 165-183 (1977)
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    Enhanced finite element formulation for geometrically linear fluid-saturated porous media (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 185-203 
    Details
    ISSN: 1082-5010
    Schlagwort(e): fluid-saturated porous media ; enhanced element technology ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: This contribution is concerned with a new mixed finite element formulation for geometrically linear Terzaghi-Biot type fluid-saturated porous media. To this end, an extended Hu-Washizu type mixed variational principle is presented for fluid-saturated porous continua. Then, a suitable discretization and its implementation are discussed, resulting in an improved element behaviour especially in numerical localization analyses. The intriguing element performance is firstly demonstrated for the case of localization within an elastoplastic compression problem. Finally, an elastoplastic slope stability problem is examined, whereby the new element formulation proves to render more pronounced failure modes as compared with a standard element expansion. © 1997 John Wiley & Sons, Ltd.
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    Modelling of pollutant migration in porous media with interfacial transfer: local equilibrium/non-equilibrium (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 205-221 
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    ISSN: 1082-5010
    Schlagwort(e): pollutant diffusion ; advection ; porous media ; surface transfer resistance ; physical modelling ; homogenization ; model classification ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: In the paper, an attempt to model local equilibrium and local non-equilibrium in pollutant migration in porous media is presented. Diffusion is assumed to occur in the pores as well as in the solid porous matrix. The macroscopic models are developed using the homogenization method (asymptotic expansion technique). The resulting macroscopic equations show either a one-concentration field or two-concentration fields or memory effects. The domains of validity of all the presented models are also determined. Local cell problems are provided to compute the effective diffusion tensors. The conditions for the local mass equilibrium assumption to be valid are derived in terms of the dimensionless characteristic parameters. The effect of pollutant source distributions is also investigated. © 1997 John Wiley & Son, Ltd.
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    Digitale Medien
    Coherent vortex structures in deforming granular materials (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 223-236 
    Details
    ISSN: 1082-5010
    Schlagwort(e): granular materials ; vortices ; discrete element method ; coherent structures ; proper orthogonal decomposition ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: Discrete element models are used to investigate the formation of coherent structures within a deforming granular material. The numerical models predict the formation of coherent vortex-like structures, even when the boundary deformations introduce zero vorticity. We name these structures circulation cells because the particles instantaneously translate and rotate as a rigid body about a common centre. They occur for all the particle shapes and material properties tested. The size of these coherent structures range from approximately 20 to 600 particles, with the largest structures being limited by the test boundaries. Circulation cells are seen to play an important role in granular deformations including the formation of shear bands. © 1997 John Wiley & Sons, Ltd.
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    Digitale Medien
    Dilation characteristics of confined concrete (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 237-249 
    Details
    ISSN: 1082-5010
    Schlagwort(e): concrete ; confinement ; dilation ; fibres ; plastics ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: Confinement of concrete enhances it strength and ductility by restraining lateral dilation. The accuracy of a confinement model depends on how well it captures the dilation tendency of concrete. In recent years, external confinement of concrete by fibre composites has become increasingly popular for civil infrastructure applications. This includes fibre-wrapping of existing columns or encasement of concrete in a fibre reinforced plastics (FRP) shell. A total of 54-concrete-filled FRP tubes were tested in uniaxial compression under displacement control mode. Full instrumentation of the specimens has allowed the variation of tangent Poisson's ratio for concrete to be captured. The dilation trend of confined concrete is shown to be a function of jacket stiffness. In steel-encased members, once steel yields, confining pressure becomes constant and the jacket renders itself ineffective in containing the dilation of concrete. On the other hand, for linear-elastic materials such as fibre composites, a strain reversal occurs that results in containment of dilation. A method for predicting the dilation is developed that can be easily adopted in any active confinement model. Moreover, a new confinement model for FRP-encased concrete is discussed. © 1997 John Wiley & Sons, Ltd.
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    Digitale Medien
    Hypoplastic model for cohesionless soils with elastic strain range (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 279-299 
    Details
    ISSN: 1082-5010
    Schlagwort(e): constitutive model ; hypoplasticity ; plasticity ; grain contacts ; intergranular strain ; strain-space plasticity ; recent history ; small strain ; ratcheting ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: In order to eliminate ratcheting a so-called intergranular strain has been added to a hypoplastic constitutive model. This additional state variable represents the deformation of the interface layer between the grains. The new concept is outlined and comparisons with and without intergranular strain are presented. Some comments on numerical implementation and determination of material constants are made. A discussion on the uniqueness of the solution and objectivity of the rate of intergranular strain is added. © 1997 John Wiley & Sons, Ltd.
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    Digitale Medien
    An experimental and theoretical study of a partially saturated collapsible rock (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 2 (1997), S. 251-278 
    Details
    ISSN: 1082-5010
    Schlagwort(e): Pietra Leccesse chalk ; laboratory tests ; constitutive modelling ; capillary forces ; partial saturation ; collapsible rocks ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Maschinenbau
    Notizen: Experiments on Pietra Leccese chalk revealed that many of the material parameters describing its mechanical behaviour, such as the Young's modulus, the uniaxial compressive strength and the plastic yield stress, depend strongly on the water saturation and the ensuing capillary suction. The experimental results show that Bishop's generalized effective stress is not by itself adequate to explain the observed behaviour and in particular the spontaneous collapse which may occur upon water injection under stress. An elastoplastic constitutive model for partially-saturated collapsible rocks is proposed where the capillary suction is assumed to affect primarily the material properties related to the intergranular cohesion, such as the elastic stiffness, the plastic tension cut-off and pressure cap parameters. The model builds upon the well- established Mohr-Coulomb theory of elastoplasticity by including a pressure cap and considering the water saturation as an internal variable. In low levels of water saturation, as is often the case in oil reservoir formations, the experimental and theoretical results demonstrate the potential significance of capillary effects on the response of reservoir rocks, a mechanism that has been largely underestimated in the petroleum industry. © 1997 John Wiley & Sons, Ltd.
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  • 69
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    Digitale Medien
    CHEMO-PLASTICITY OF CLAYS SUBJECTED TO STRESS AND FLOW OF A SINGLE CONTAMINANT (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 43-72 
    Details
    ISSN: 0363-9061
    Schlagwort(e): plasticity ; contaminated clays ; organic contaminants ; chemical consolidation ; chemical swelling ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: Isothermal chemo-elasto-plasticity of clays is discussed, to describe strains induced in clay by permeation of it with a low dielectric constant organic contaminant, in the presence of stress. The strain is crucial in controlling permeability changes in chemically affected clay barriers of landfills and impoundments. The theory encompasses chemical softening or yield surface reduction, coefficient of chemical reversible expansion or contraction due to mass concentration increase, as well as chemical sensitivity of bulk plastic modulus. The experiments on chemistry and stress dependent permeability of Sarnia clay performed by Fernandez and Quigley (1985, 1991) are interpreted using this model. The numerical representations of the chemo-plastic softening function and the chemo-elastic strain function, as well as plastic bulk modulus sensitivity to concentration are evaluated for dioxane and ethanol. Specific requirements for the tests for chemo-plastic behavior of clays are discussed. © 1997 by John Wiley & Sons, Ltd.
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    THERMOPOROELASTIC COUPLING WITH APPLICATION TO CONSOLIDATION (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 121-132 
    Details
    ISSN: 0363-9061
    Schlagwort(e): thermoporoelasticity ; coupling ; decoupling ; consolidation ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: Based on a fully coupled thermoporoelastic formulation, this paper discusses the general conditions where the coupling should be maintained, and where a partial or full decoupling technique may be applied. This exercise is aimed at providing practical solutions for the coupled thermoporoelastic analyses where excessive manipulations and unreasonable simplifications are minimized. The necessity for full coupling and the justification for decoupling are illustrated in a thermoporoelastic application of a one-dimensional consolidation scenario. © 1997 by John Wiley & Sons, Ltd.
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    Digitale Medien
    BEYOND FAILURE IN GRANULAR MATERIALS (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 153-174 
    Details
    ISSN: 0363-9061
    Schlagwort(e): constitutive model ; hypoplasticity ; failure ; stability ; granular material ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: Recent investigations on the hypoplastic constitutive model for granular materials show that the failure surface can be surpassed by some stress paths. This is contradictory to the conventional definition of failure surface in plasticity, according to which the stress is allowed to move on the failure surface but never across it. In the present paper, the interrelations among the different constitutive models are discussed with special reference to failure and stability. For the hypoplastic constitutive equation, the accessible stress states and the stable stress states are found to be enclosed by a bound surface and a stability surface in the stress space, respectively. Theoretical findings about the bound surface and the stability surface are verified qualitatively by presenting results of triaxial tests on dry sand. © 1997 by John Wiley & Sons, Ltd.
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    ANALYSIS OF ROCKBOLT REINFORCEMENT USING BEAM-COLUMN THEORY (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 241-253 
    Details
    ISSN: 0363-9061
    Schlagwort(e): rockbolt ; Euler-Bernoulli ; beam-column ; roof-reinforcement ; stability ; pull-out ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: A simple analytical procedure that applies classical beam-column theory for evaluating passive rockbolt roof reinforcement is presented in this paper. The analytical model is derived from first principles and is capable of modelling any number of reinforcing bolts. Each rockbolt is modelled as a linear spring and the model allows for non-uniform bolt spacing. In this study the rock beam is assumed to be isotropic and linearly elastic for the sake of simplicity. However, the analytical model can be extended to include anisotropic rockmass as well as inelastic material behaviour. The solution to the coupled set of governing equations is obtained by using a simple numerical solution procedure. The results from the analytical model indicate that the critical buckling load of a rock beam is strongly influenced by the ambient rock modulus. For salt-rock excavations the rock modulus typically declines with time due to various phenomena, and a diminished modulus could seriously compromise roof stability. The other main conclusion of this study is that rockbolts loose their effectiveness in restraining a roof beam once its critical buckling load is approached. In such a situation, increasing bolt stiffness does not improve its reinforcing action on a roof beam but it enhances the possibility of bolt failure due to anchor pull-out. © 1997 by John Wiley & Sons, Ltd. Int. J. Numer. Anal. Meth. Geomech., vol. 21, 241-253 (1997)
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    A PACKING GENERATION SCHEME FOR THE GRANULAR ASSEMBLIES WITH PLANAR ELLIPTICAL PARTICLES (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 347-358 
    Details
    ISSN: 0363-9061
    Schlagwort(e): packing ; elliptical ; particle ; assemblies ; simulation ; micromechanics ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: In this paper, a new generator algorithm and a computer program PG2D is introduced for 2D numerical simulation of packing configuration in a granular material composed of elliptical particles of different a/b aspect ratios. Each elliptical particle is approximated by four connected arcs. The centre co-ordinates and radius of each arc and co-ordinates of connecting points can be determined from the formulae derived by entering the major axis length, 2a, and the eccentricity. The domain to be filled with particles can be a polygon of any shape. Given the size of the packing domain, geometrical information and numbers of particles to be generated, the packing location of each particle and the co-ordinates of contact points along with contact normal rose diagram can be generated as outputs.Simulation results show that this new algorithm can provide quite a reasonable packing model in accordance with the initial input required for the analysis of the mechanics of granular material. This generation scheme has the potential to cover packing generation and behaviour analysis of 3D sphere or ellipsoidal shaped granular materials. © 1997 by John Wiley & Sons, Ltd.
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    MODELLING HEAT AND MOISTURE TRANSFER IN UNSATURATED SOIL USING A FINITE DIFFERENCE SELF-IMPLICIT METHOD ON PARALLEL COMPUTERS (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 409-419 
    Details
    ISSN: 0363-9061
    Schlagwort(e): parallel numerical finite difference model ; heat and moisture transfer ; parallel computing ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: A parallel numerical finite difference model, employing the self-implicit method, for coupled heat and moisture transfer in unsaturated soil is presented. The model is programmed in Occam and executed on a parallel computing network of transputers. An assessment of the model was achieved via the simulation of a laboratory experiment. A very good correlation between experimental and numerical results was obtained. Comparison of results with those obtained from a parallel explicit method is also illustrated showing no significant difference. The computational time employing the new method was, however, found to be half of that obtained using the explicit method. The computational efficiency of the approach was also found to be very high. © 1997 John Wiley & Sons, Ltd.
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    PERFORMANCE OF TRENCH DRAINS WITH TIME USING FINITE ELEMENTS (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 485-494 
    Details
    ISSN: 0363-9061
    Schlagwort(e): finite element method ; ground water ; phreatic surface ; transient flow ; unconfined seepage ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: Peformance of rectangular trench drains penetrating fully in a layer of homogeneous and isotropic soil mass down to an underlying impervious base with time has been assessed using the finite element method. Non-dimensional charts have been developed comprehensively to establish the successive positions of a phreatic surface with the passage of time for any given values of permeability of soil and its specific yield. The effect of spacing to depth ratios of drains on their performance has been examined in detail. The rate of downward movements of the phreatic surface decreases with time as well as with increases in the spacing of drains. The spacing affects considerably the magnitudes of drawdown at distant locations from the drains, whereas close to the drains, its effect becomes insignificant. © 1997 John Wiley & Sons, Ltd.
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    CS2: A PIECEWISE-LINEAR MODEL FOR LARGE STRAIN CONSOLIDATION (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 453-475 
    Details
    ISSN: 0363-9061
    Schlagwort(e): consolidation ; settlement ; large strain ; numerical modelling ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: This paper presents a piecewise-linear finite-difference model for one-dimensional large strain consolidation called CS2. CS2 is developed using a fixed Eulerian co-ordinate system and constitutive relationships which are defined by discrete data points. The model is dimensionless such that solutions are independent of the initial height of the compressible layer and the absolute magnitude of the hydraulic conductivity of the soil. The capability of CS2 is illustrated using four example problems involving small strain, large strain, self-weight, and non-linear constitutive relationships. In each case, the performance of the model is comparable to other available analytical and numerical solutions. Using CS2, correction factors are developed for the conventional Terzaghi theory which account for the effect of vertical strain on computed values by elapsed time and maximum excess pore pressure during consolidation. © 1997 John Wiley & Sons, Ltd.
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    Equivalent properties of rock strata: static and dynamic analysis (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 569-579 
    Details
    ISSN: 0363-9061
    Schlagwort(e): layered rock ; heterogeneity ; method of averaging ; variation-difference method ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: The main purpose of this investigation is to study the state of stress of layered rocks forming slopes of deep river valleys. For this purpose averaging technique and a variant of the Variation-Difference Method are used. Because of the averaging method, equivalent homogeneous properties of layered elastic medium are determined. The paper has two parts. The first one is devoted to the analysis of a static stress-strain state of the slopes under gravity. The rock mass in the second part is subjected to dynamic loading caused by an earthquake. As a result of the numerical solution of the raised problems, the stress distribution in slopes and at the base of a deep canyon-like river valley was obtained. © 1997 John Wiley & Sons, Ltd.
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    Three-dimensional FE analysis of a nailed soil wall curved in plan (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 583-597 
    Details
    ISSN: 0363-9061
    Schlagwort(e): finite elements ; soil nailing ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: A nailed soil wall curved in plan was modelled in three-dimensions by the finite element method for construction, service and ultimate loading conditions. The behaviour of the nailed soil wall, the soil-nail interaction, the role of the reinforcement, and the overall and internal failure mechanisms were investigated. © 1997 by John Wiley & Sons, Ltd.
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    A variational approach for vertical deformation analysis of pile group (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 741-752 
    Details
    ISSN: 0363-9061
    Schlagwort(e): vertical deformation analysis ; pile group ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: A variational approach for the analysis of vertical deformation of pile groups is presented. The method assumes that the deformation of piles can be represented by a finite series. The method applies the principle of minimum potential energy to determine the deformation of piles. Using this method, an analytical solution for pile groups in soil modelled by the theoretical load-transfer curves can be obtained rigorously. Analysis of field tests indicates that the method can predict the performance of pile groups reasonably well.
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    A model for coupled mechanical and hydraulic behaviour of a rock joint (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 29-48 
    Details
    ISSN: 0363-9061
    Schlagwort(e): hydraulic behaviour ; joint ; mechanics of joint ; joint degradation ; joint elements ; interface mechanics ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: Constitutive laws for rock joints should be able to reproduce the fundamental mechanical behaviour of real joints, such as dilation under shear and strain softening due to surface asperity degradation. In this work, we extend the model of Plesha to include hydraulic behaviour. During shearing, the joint can experience dilation, leading to an initial increase in its permeability. Experiments have shown that the rate of increase of the permeability slows down as shearing proceeds, and, at later stages, the permeability could decrease again. The above behaviour is attributed to gouge production. The stress-strain relationship of the joint is formulated by appeal to classical theories of interface plasticity. It is shown that the parameters of the model can be estimated from the Barton-Bandis empirical coefficients; the Joint Roughness Coefficient (JRC) and the Joint Compresive strength (JSC). We further assume that gouge production is also related to the plastic work of the shear stresses, which enables the derivation of a relationship between the permeability of the joint and its mechanical aperture. The model is implemented in a finite element code (FRACON) developed by the authors for the simulation of the coupled thermal-hydraulic-mechanical behaviour of jointed rock masses. Typical laboratory experiments are simulated with the FRACON code in order to illustrate the trends predicted in the proposed model. © 1998 by John Wiley & Sons. Ltd.
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    Field stresses around an inclined shaft (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 229-238 
    Details
    ISSN: 0363-9061
    Schlagwort(e): inclined shaft ; stress distribution ; field stress ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: In this study, the vertical overburden pressure in the vicinity of an inclined circular underground opening is defined by relation to the geometry of the medium. The stresses around the opening consisting of six components are induced by geostatic field stress. In this regard, the inclined circular opening i.e. shaft changes the original stress condition and an interrupted region develops beneath it. Three zones are defined on a plane which is perpendicular to the axis of shaft. The mathematical expressions of vertical overburden stresses at these three zones are established, respectively. The example given in appendix demonstrates the variation of radial and tangential stresses around the inclined shaft. It is seen that the stress distributions in the third zone, which includes the interrupted region, beneith the shaft display different configurations than that of those obtained by undisturbed field stresses. In the interrupted region the stresses around the shaft linearly grow up due to increasing overburden pressure by radial distance from the periphery of the shaft. At the boundary of interrupted region stresses jump to the original values induced by field stresses. © 1998 John Wiley & Sons, Ltd.
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    Elastoplastic constitutive equation of soils with the subloading surface and the rotational hardening (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 197-227 
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    ISSN: 0363-9061
    Schlagwort(e): elastoplasticity ; constitutive equation ; subloading surface model ; cyclic plasticity ; soil ; rotational hardening ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: The subloading surface model fulfills the mechanical requirements for constitutive equations, i.e. the continuity condition, the smoothness condition and the work rate stiffness relaxation and describes pertinently the Masing effect. The constitutive equation of soils is formulated by introducing the subloading surface model and formulating the evolutional rule of rotational hardening for the description of anisotropy. The applicability of the constitutive equation to the prediction of real soil deformation behaviour is verified by predicting monotonic and cyclic loading behaviour of sands under drained and undrained conditions and comparing them with test data. © 1998 John Wiley & Sons, Ltd.
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    Numerical analysis of soil plug behaviour inside open-ended piles during driving (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 303-322 
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    ISSN: 0363-9061
    Schlagwort(e): pile driving ; open-ended piles ; plugging mechanism ; one-dimensional modelling ; stress wave propagation ; finite element analysis ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: The plugging mechanism of infinitely-long open-ended piles is examined using numerical simulation of the wave propagation inside the soil plug and pile. It is shown that the key parameters for the plugging mechanism are the pile radius, the shape of the impact load, the shear wave velocity of the soil inside the pile, and the friction at the pile-soil interface. Consequently, the tendency of the pile to plug during driving can be assessed prior to the driving process by consideration of these key parameters. Existing one-dimensional models for the shaft response of open-ended piles are discussed and an improved model is presented. The differences between using one-dimensional models and finite element models to simulate the plugging process are examined. The differences are found to vary with the key parameters. Pile-in-pile and lumped-mass one-dimensional models are found to give satisfactory performance for some parameter combinations, while for others an axisymmetric finite element model must be used. © 1998 John Wiley & Sons, Ltd.
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    Elastic solutions for a transversely isotropic half-space subjected to a point load (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 425-447 
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    ISSN: 0363-9061
    Schlagwort(e): closed-form solution ; transversely isotropic half-space ; Fourier transform ; Hankel transform ; rock anisotropy ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: We rederive and present the complete closed-form solutions of the displacements and stresses subjected to a point load in a transversely isotropic elastic half-space. The half-space is bounded by a horizontal surface, and the plane of transverse isotropy of the medium is parallel to the horizontal surface. The solutions are obtained by superposing the solutions of two infinite spaces, one acting a point load in its interior and the other being free loading. The Fourier and Hankel transforms in a cylindrical co-ordinate system are employed for deriving the analytical solutions. These solutions are identical with the Mindlin and Boussinesq solutions if the half-space is homogeneous, linear elastic, and isotropic. Also, the Lekhnitskii solution for a transversely isotropic half-space subjected to a vertical point load on its horizontal surface is one of these solutions. Furthermore, an illustrative example is given to show the effect of degree of rock anisotropy on the vertical surface displacement and vertical stress that are induced by a single vertical concentrated force acting on the surface. The results indicate that the displacement and stress accounted for rock anisotropy are quite different for the displacement and stress calculated from isotropic solutions. © 1998 John Wiley & Sons, Ltd.
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    Contaminant transport under variable density flow in fractured porous media (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 575-595 
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    ISSN: 0363-9061
    Schlagwort(e): contaminant transport ; variable density flow ; fractures ; leakage ; dispersion ; diffusion ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: A numerical model for simulating flow and transport of contaminants with variable density in fractured porous media is presented. The non-linearities arising from the density variation and the velocty-dependent dispersion terms have been handled by Picard method. It is shown that the contaminant transport in a fractured porous medium is initially dominated by fractures. However, with time increasing, the contaminant concentration in porous blocks increases, due to the leakage of contaminant from the fracture network to the porous blocks. It is also shown that the high density of contaminant has a greater effect on its transport in the fracture network than in the porous blocks. © 1998 John Wiley & Sons, Ltd.
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    Modelling of shearing behaviour of a residual soil with Recurrent Neural Network (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 671-687 
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    ISSN: 0363-9061
    Schlagwort(e): recurrent neural network ; residual soil ; shear behaviour ; simulation ; prediction ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: Modelling of shear behaviour of residual soils is difficult in that there is a significant variability in constituents and structures of the soil. A Recurrent Neural Network (RNN) is developed for modelling shear behaviour of the residual soil. The RNN model appears very effective in modelling complex soil shear behaviour, due to its feedback connections from an hidden layer to an input layer. Two architectures of the RNN model are designed for training different sets of experimental data which include strain-controlled undrained tests and stress-controlled drained tests performed on a residual Hawaiian volcanic soil. A dynamic gradient descent learning algorithm is used to train the network. By training only part of the experimental data the network establishes neural connections between stress and strain relations. Although the soil exhibited significant variations in terms of shearing behaviour, the RNN model displays a strong capability in capturing these variabilities. Both softening and hardening characteristics of the soil are well represented by the RNN model. Isotropic and anisotropic consolidation conditions are precisely reflected by the RNN model. In undrained tests, pore water pressure responses at various loading stages are simultaneously simulated. With a RNN model designed for a special drained test, the network is able to capture abrupt changes in axial and volumetric strains during shearing courses. These good agreements between the measured data and the modelling results demonstrate the desired capability of the RNN model in representing a soil behaviour. © 1998 John Wiley & Sons, Ltd.
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    Coupled wellbore erosion and stability analysis (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 749-769 
    Details
    ISSN: 0363-9061
    Schlagwort(e): wellbore stability ; sand erosion ; sand production ; sand prediction ; radial flow ; poroelasticity ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: This paper extends earlier work on sand erosion and presents an attempt to couple sand erosion to mechanical damage of rock around a wellbore. Porosity which evolves in time and space as surface erosion progresses, is chosen as the coupling parameter. Both rock elasticity and strength (cohesion) are assumed to depend on porosity in such a way that the material becomes weaker with increasing porosity. The mathematical model, consists of erosion equations, mixture flow equations and stress equilibrium equations, is solved numerically by Galerkin finite element method. Numerical results suggest that erosion, resulting in sand production, is high close to the free surface. Erosion is accompained by changes in porosity and a significant permeability increase. Erosion in the vicinity of the wellbore induces alterations in the mechanical behaviour of the medium. Weakening of rock stiffness leads to severe alteration of both effective stresses and pore pressure near the cavity. Since cohesion decreases with increasing porosity, one can also identify the time instant at which rock mechanical failure starts. © 1998 John Wiley & Sons, Ltd.
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    A numerical procedure for the analysis of the hydromechanical coupling in fractured rock masses (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 867-901 
    Details
    ISSN: 0363-9061
    Schlagwort(e): finite elements ; hydromechanical coupling ; fractured rock masses ; viscoplasticity ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: This work presents a finite element implementation to treat the Hydromechanical Coupling (HM) in fractured rock masses under the framework of the so-called ‘equivalent continuum’ approach. The multilaminar concept, introduced by Zienkiewicz and Pande, is used to simulate the mechanical behaviour of both the intact rock and the families of fractures. In that concept, the non-linearities in the constitutive relations are dealt by means of fictitious viscoplasticity. In the present implementation, the mechanical behaviour of the fractures is modelled by means of Barton-Bandis model. The shear stress/shear displacement/dilatancy relationship is modelled as viscoplastic and the normal stress/normal displacement as non-linear viscoelastic. Flow along fractures is considered to occur as a sequence of permanent states. The permeability tensor of the equivalent continuum is determined from the hydraulic apertures, in accordance of Barton et al. From the numerical point of view, the basic aim of the work is the implementation of an efficient scheme to solve the above described problem. This is done by designing a self-adaptive time step control, transparent to the user, which determines the highest possible time step while assuming the conditions of precision, stability and convergence. The paper presents the numerical details of such scheme together with validation/comparative examples and the results obtained on the analysis of the fractured rock foundation of a hypothetical dam. © 1998 John Wiley & Sons, Ltd.
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    The effect of interface properties on retaining wall behaviour (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 1021-1033 
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    ISSN: 0363-9061
    Schlagwort(e): retaining wall ; interface ; finite element ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: A series of finite element analyses have been undertaken to investigate the effects of interface properties on the behaviour of a vertical retaining wall and the deformation of the ground around it. The boundary between a rigid embedded wall and the soil is modelled with zero thickness interface elements. Uniform translation of the wall has been studied. The analyses show the predicted limiting active and passive pressure on the wall are dependent on the maximum wall friction angle and are in reasonable agreement with accepted approximate analytical solutions. The limiting pressure is independent of the stiffness and dilation properties of the interface elements. The dilation properties of the interface have a significant effect on the ground surface deformation around the wall. © 1998 John Wiley & Sons, Ltd.
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    BOOK REVIEWS INTERNATIONAL OFFSHORE ENGINEERING F. L. L. Carneiro, A. J. Ferrante, R. C. Batista and N. F. F. Ebecken (Editors), Wiley, New York, 1995. Number of Pages: 617 (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 73-73 
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    ISSN: 0363-9061
    Schlagwort(e): Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: No Abstract
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    TWO-PHASE OIL MIGRATION IN COMPACTING SEDIMENTARY BASINS MODELLED BY THE FINITE ELEMENT METHOD (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 91-120 
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    ISSN: 0363-9061
    Schlagwort(e): finite elements ; oil migration ; immiscible two-phase flow ; compaction ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: The upstream-weighted finite element method with lumped mass matrix is applied to the modelling of oil migration in compacting sedimentary basins. An implicit formulation is made in Lagrangian co-ordinates of a pressure, saturation and a temperature equation, which is based on immiscible two-phase flow of oil and water. The formulation accounts for the compaction of the sediments, the generation of oil from solid organic material (kerogen), the eventual pore space generated by kerogen breakdown, and the density variations of the fluids which may set up thermal convection. The model is validated by comparison with results from a one-dimensional (1D) fractional flow-based migration model. A 2D case example showing oil expulsion from source rocks, and the filling of a trap is presented. The mass balance of the model is easily checked because all oil in the basin originates from breakdown of kerogen. Compared with other alternatives, the simple upstream-weighted finite element method is suggested as a possible first choice for a numerical method for the modelling of oil migration in compacting sedimentary basins. It easily deals with the complex geometry of a basin, it yields reasonably good results, is simple to implement, and the same implementation applies to all spatial dimensions. © 1997 by John Wiley & Sons, Ltd.
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    A FORMULATION OF FULLY COUPLED THERMAL-HYDRAULIC-MECHANICAL BEHAVIOUR OF SATURATED POROUS MEDIA - NUMERICAL APPROACH (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 199-225 
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    ISSN: 0363-9061
    Schlagwort(e): nuclear waste disposed ; numerical analysis ; finite element method ; thermohydromechanics ; saturated porous media ; temperature effect ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: The theoretical aspects of fully coupled thermohydromechanical behaviour of saturated porous media are presented. The non-linear behaviour of soil skeleton is assumed. A new concept called ‘thermal void ratio state surface’ is introduced to include thermal effects, and the stress state level influence on volume changes. The fluid phase flows according to Darcy's law and energy transport is assumed to follow Fourier's law classically. Variation of water permeability, water and solid unit weight due to thermal effects and pore pressure changes are included. A finite element package is developed based on final matrix form obtained from discretization of integral form of field equations by finite element method and integration in time. A very good agreement between the theoretical predictions and the experimental results was obtained for the several simple problems proposed by other authors. © 1997 by John Wiley & Sons, Ltd.
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    IDENTIFICATION OF DEFECTS IN PILES THROUGH DYNAMIC TESTING (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 277-291 
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    ISSN: 0363-9061
    Schlagwort(e): defects in piles ; dynamic testing ; non-destructive impact-response method ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: The objective of this work was to evaluate the theoretical capabilities of the non-destructive impact-response method in detecting the existence of a single defect in a pile, its location and its length. The cross-section of the pile is assumed to be circular and the defects are assumed to be axisymmetric in geometry. As mentioned in the companion paper, special codes utilizing one-dimensional (1-D) and three-dimensional (3-D) axisymmetric finite element models were developed to simulate the responses of defective piles to an impact load. Extensive parametric studies were then performed. In each study, the results from the direct use of time histories of displacements or velocities and the mechanical admittance (or mobility) function were compared in order to assess their capabilities. The effects of the length and the width of a defect were also investigated using these methods. © 1997 by John Wiley & Sons, Ltd. Int. J. Numer. Anal. Meth. Geomech., vol. 21, 277-291 (1997)
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    SURFACE DISPLACEMENTS OF A NON-HOMOGENEOUS ELASTIC HALF-SPACE SUBJECTED TO UNIFORM SURFACE TRACTIONS. PART I: LOADING ON ARBITRARILY SHAPED AREAS (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 361-378 
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    ISSN: 0363-9061
    Schlagwort(e): elastic half-space ; homogeneous ; non-homogeneous ; contour integral approach ; surface displacement ; arbitrarily shaped loading area ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: A numerical technique is presented for the analysis of surface displacements of a non-homogeneous elastic half-space subjected to vertical and/or horizontal surface loads uniformly distributed over an arbitrarily shaped area. The non-homogeneity considered is a particular form of power variation of Young's modulus with depth. Since the exponent which determines the degree of non-homogeneity may vary from zero to unity, both the homogeneous half-space and the Gibson soil may be included as limiting cases in a single numerical scheme. In order to account for the arbitrary shape of the loading, the boundary of the loaded area is linearized piecemeal. This enables the modeling of any load pattern according to the desired degree of accuracy. Special attention is focused on the integration scheme, since the singularity associated with the Green's function becomes progressively more pronounced the greater the non-homogeneity parameter gets. The performance of the numerical procedure is studied using analytical solutions for rectangular shaped areas. Further comparisons with well-known solutions based on integral transform techniques for a uniformly distributed load acting on a circular area of the non-homogeneous soil mass show excellent agreement as well. © 1997 John Wiley & Sons, Ltd.
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    UPPER BOUND SOLUTION FOR PULLOUT CAPACITY OF ANCHORS ON SANDY SLOPES (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 477-484 
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    ISSN: 0363-9061
    Schlagwort(e): anchors ; failure surface ; foundations ; limit analysis ; sand ; slopes ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: By making use of limit analysis, an upper bound solution in a closed form for determining the ultimate pullout capacity of plate anchors buried in sandy slopes has been established. The anchor plate orientation has been considered either horizontal or parallel to the slope, with the pullout force applied perpendicular to the plate. It has been found that the pullout capacity for horizontal anchors, even on slopes, remains the same as that on horizontal ground surface as long as the average embedment ratio is kept constant. Whereas for anchors which are aligned parallel to the slope the collapse load decreases continuously with the increase in the inclination of slope. © 1997 John Wiley & Sons, Ltd.
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    OPTIMIZATION OF SEEPAGE RATE THROUGH A TRIANGULAR CORE (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 443-451 
    Details
    ISSN: 0363-9061
    Schlagwort(e): seepage ; dam core ; hodograph method ; minimization ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: Seepage through a triangular dam core is studied by the hodograph method. Core slope providing minimal seepage rate at prescribed head value and core cross-sectional area is found. A simple flow pattern involving seepage face, constant head, and non-flow boundaries is assumed. Seepage through a cake of low permeable sediments deposited along the bottom of a channel is treated analogously. © 1997 John Wiley & Sons, Ltd.
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    Digitale Medien
    Digitale Medien
    Behavior of cemented sands - II. Modelling (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 549-568 
    Details
    ISSN: 0363-9061
    Schlagwort(e): cemented sand ; constitutive model ; multiphase material ; strength ; dilatancy ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: This is the companion paper to a study the triaxial testing of cemented sands. The focus here is turned to the constitutive modelling of cemented sands. A novel micromechanical approach that considers the multi-phase nature of cemented sands, is presented in which the clean sand, the cementing bond and the pore water pressure are modelled independently. The model is verified using a series of triaxial compression experiments on 2, 4 and 6 per cent cemented specimens, that were the subject of the companion paper. © 1997 John Wiley & Sons, Ltd.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    Digitale Medien
    Digitale Medien
    Analysis of settlement and lateral deformation of soft clay foundation beneath two full-scale embankments (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 599-618 
    Details
    ISSN: 0363-9061
    Schlagwort(e): embankments ; finite element method ; ground improvement ; settlements ; soft clay ; vertical drains ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: In 1986, the Malaysian Highway Authority constructed a series of trial embankments on the Muar Plain (soft marine clay) with the aim of evaluating the effectiveness of various ground improvement techniques. This study investigates the effect of two such ground improvement schemes: (a) preloading of foundation with surface geogrids and synthetic vertical drains and (b) sand compaction piles. The paper is focused on the finite element analysis of settlements and lateral displacements of the soft foundation. In scheme (a), the numerical predictions are compared with the field measurements. In scheme (b), only the numerical analysis is presented and discussed in the absence of reliable measurements due to the malfunctioning of the electronic extensometer and inclinometer system during embankment construction. The current analysis employs critical state soil mechanics, and the deformations are predicted on the basis of the fully coupled (Biot) consolidation model. The vertical drain pattern is converted to equivalent drain walls to enable plane strain modelling, and the geogrids are simulated by linear interface slip elements. The effect of sand compaction piles is investigated considering both ideal drains and non-ideal drains, as well as varying the pile stiffness. © 1997 by John Wiley & Sons, Ltd.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
  • 99
    Digitale Medien
    Digitale Medien
    APPLICATION OF A SPLITTING FRACTURE MODEL TO THE SIMULATION OF ROCK INDENTATION SUBSURFACE FRACTURES (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 1-13 
    Details
    ISSN: 0363-9061
    Schlagwort(e): rock ; indentation ; fracture modelling ; splitting fracture ; damage ; Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: A two-dimensional fracture model based on micro-fracture mechanics is applied to the Hertzian indentation stress field to simulate subsurface fractures in an axi-symmetrical plane. The simulation of fracture development reveals quantitatively the effects of loading force, mechanical properties of the rocks, and original micro cracks on the formation of subsurface fractures. The distribution patterns of the subsurface fractures are determined by the magnitudes and trajectories of the indentation stresses. Lateral confinement prohibits the fracture development. Simulations of the subsurface fractures in granite and marble are in good agreement with the indentation experiments. © 1997 by John Wiley & Sons, Ltd.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
  • 100
    Digitale Medien
    Digitale Medien
    FIRST INTERNATIONAL CONFERENCE ON EARTHQUAKE GEOTECHNICAL ENGINEERING, Vols. 1 and 2, Kenji Ishihara (Editor), A. A. Balkema/Rotterdam/Brookfield, 1995. (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 74-74 
    Details
    ISSN: 0363-9061
    Schlagwort(e): Engineering ; Civil and Mechanical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie
    Notizen: No Abstract
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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