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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Water resources management 12 (1998), S. 409-432 
    ISSN: 1573-1650
    Keywords: diffusion ; dispersion ; fracture network ; percolation theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Dispersion and transport of mass in a fracture network is a percolation process. Macro-scale dispersion is related to travel time, distance, mass distribution and fracture geometry. This article presents a stochastic, discrete fracture model in conjunction with percolation theory to investigate the dispersion phenomenon and the power law relationship between mean square travel paths displacement 〈 r2 〉 and particle travel time t. For imposed boundary conditions, particle dispersion is simulated to observe percolation thresholds and dispersion trends in different network structures. Simulation results demonstrate that the critical exponent values of t in the percolated networks are extremely close to the theoretical value of 1.27 and occur at certain percolation factors. Below these percolation factors, the exponents of t increase with decreasing percolation factors, above these percolation factors, exponents decrease with increasing percolation factors. In our simulated cases, the proportionality between 〈 r2 〉 and time t is given by t raised to a power between 1.27 and 1.66, depending on the fracture pattern. The coefficient of anisotropic dispersion tensor increases with increasing distance. The percolation process is related to travel time and distance, and cannot be interpreted as a Fickian diffusive process.
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  • 2
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    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 1-26 
    ISSN: 1082-5010
    Keywords: anisotropy ; failure criterion ; schist ; sedimentary rock ; rock joints ; laboratory testing ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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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  • 3
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 89-103 
    ISSN: 1082-5010
    Keywords: transversely isotropic material ; elliptic paraboloid failure surface ; strength differential effect ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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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  • 4
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 27-39 
    ISSN: 1082-5010
    Keywords: creep ; effective spring concept ; Kelvin chain model ; load bearing volume ; micromechanical model ; relaxation ; softening spring ; solidification ; tension softening ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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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  • 5
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 41-63 
    ISSN: 1082-5010
    Keywords: elastoplasticity ; damage ; bonded geomaterials ; triaxial testing ; intact and remoulded specimen ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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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  • 6
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    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 65-87 
    ISSN: 1082-5010
    Keywords: elastoplasticity ; sand ; constitutive modelling ; controllability ; instability ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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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  • 7
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 105-125 
    ISSN: 1082-5010
    Keywords: localization ; non-local damage ; Perzyna viscoplasticity ; mesh adaptivity ; Arbitrary Lagrangian-Eulerian technique ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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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  • 8
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 127-153 
    ISSN: 1082-5010
    Keywords: constitutive equations ; post-localization behaviour ; large strain ; interface model ; bifurcation ; shear band ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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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  • 9
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 155-180 
    ISSN: 1082-5010
    Keywords: reinforced concrete ; bond model ; plasticity ; interface ; yield surface ; modelling ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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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  • 10
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    New York, NY [u.a.] : Wiley-Blackwell
    Mechanics of Cohesive-frictional Materials 3 (1998), S. 181-205 
    ISSN: 1082-5010
    Keywords: cemented ; carbide ; finite ; element ; compaction ; sintering ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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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  • 11
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 229-256 
    ISSN: 1082-5010
    Keywords: finite element method ; viscous constitutive equations ; time-discrete scheme ; stability ; superstability ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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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  • 12
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 257-276 
    ISSN: 1082-5010
    Keywords: impacts ; structural damage ; discrete element method ; dynamic loading ; scabbing ; perforation ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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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  • 13
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 207-228 
    ISSN: 1082-5010
    Keywords: jointed rock masses ; stability ; failure ; yield design ; homogenization ; strength anisotropy ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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.
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  • 14
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 277-290 
    ISSN: 1082-5010
    Keywords: experimental analysis ; slabs on soil ; reinforced concrete ; steel fibres ; fracture energy ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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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  • 15
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 291-303 
    ISSN: 1082-5010
    Keywords: poroelasticity ; isotropic damage ; brittle geomaterials ; enhanced consolidation ; saturated geomaterials ; computational modelling ; indentation of geomaterials ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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.
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  • 16
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 305-322 
    ISSN: 1082-5010
    Keywords: strain localization ; finite element ; mesh sensitivity ; regularization ; gradient plasticity ; multilayered concrete beams ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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.
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  • 17
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 365-365 
    ISSN: 1082-5010
    Keywords: Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 18
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 323-342 
    ISSN: 1082-5010
    Keywords: concrete fracture ; computational modelling ; continuum damage mechanics ; localization ; regularization ; gradient enhancement ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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.
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  • 19
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    Mechanics of Cohesive-frictional Materials 3 (1998), S. 343-364 
    ISSN: 1082-5010
    Keywords: concrete modelling ; microplane model ; anisotropic damage ; consistent linearization ; localization analysis ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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.
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  • 20
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 29-48 
    ISSN: 0363-9061
    Keywords: hydraulic behaviour ; joint ; mechanics of joint ; joint degradation ; joint elements ; interface mechanics ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: 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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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 229-238 
    ISSN: 0363-9061
    Keywords: inclined shaft ; stress distribution ; field stress ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: 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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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 197-227 
    ISSN: 0363-9061
    Keywords: elastoplasticity ; constitutive equation ; subloading surface model ; cyclic plasticity ; soil ; rotational hardening ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: 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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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 303-322 
    ISSN: 0363-9061
    Keywords: pile driving ; open-ended piles ; plugging mechanism ; one-dimensional modelling ; stress wave propagation ; finite element analysis ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: 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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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 425-447 
    ISSN: 0363-9061
    Keywords: closed-form solution ; transversely isotropic half-space ; Fourier transform ; Hankel transform ; rock anisotropy ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: 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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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 575-595 
    ISSN: 0363-9061
    Keywords: contaminant transport ; variable density flow ; fractures ; leakage ; dispersion ; diffusion ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: 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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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 671-687 
    ISSN: 0363-9061
    Keywords: recurrent neural network ; residual soil ; shear behaviour ; simulation ; prediction ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: 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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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 749-769 
    ISSN: 0363-9061
    Keywords: wellbore stability ; sand erosion ; sand production ; sand prediction ; radial flow ; poroelasticity ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: 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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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 867-901 
    ISSN: 0363-9061
    Keywords: finite elements ; hydromechanical coupling ; fractured rock masses ; viscoplasticity ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: 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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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 1021-1033 
    ISSN: 0363-9061
    Keywords: retaining wall ; interface ; finite element ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: 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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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 1-27 
    ISSN: 0363-9061
    Keywords: expansive clay ; hydromechanics ; unsaturated soils ; nuclear waste ; in situ test ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: BACCHUS2 in situ isothermal wetting experiment has been analysed by means of a coupled flow-deformation approach. Backfill material, a mixture of Boom clay powder and high density pellets, has been extensively tested in the laboratory in order to determine its hydraulic and mechanical properties. Parameters of constitutive equations were derived from this experimental data base. Two mechanical constitutive models have been used in the simulation of the ‘in situ’ experiment: a state surface approach and an elastoplastic model. Calculations have shown several features of the hydration process which help to understand the behaviour of expansive clay barriers. Predictions using both models have been compared with each other and with actual measurement records. This has allowed a discussion of the comparative mertis of both approaches and the identification of some critical parameters of backfill behaviour. Overall agreement between calculations and field measurements is encouraging and shows the potential of the methods developed to model the behaviour of engineered clay barriers in the context of nuclear waste disposal. © 1998 by John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 75-95 
    ISSN: 0363-9061
    Keywords: three-dimensional ; heat ; moisture ; air ; transfer ; unsaturated ; soil ; Engineering ; Civil and Mechanical Engineering
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    Notes: A new three-dimensional numerical model of coupled heat, moisture and air transfer in unsaturated soil is presented. In particular, the model accommodates moisture transfer in the form of liquid and vapour flow and heat transfer arising from conduction, convection and latent heat of vaporization. The bulk flow of dry air and the movement of air in a dissolved state are also included. The theoretical basis of the model, the finite element solution of the spatial terms and finite difference solution of the temporal terms are briefly presented. Attention is focused on the verification of the new numerical solution. This is achieved via comparisons with independent solutions of heat, moisture and air transfer in an unsaturated soil. The physical problem considered includes the highly non-linear hydraulic properties of sand. Thermal conductivity is also included as a function of soil moisture content. Excellent correlation of results is shown thus providing confidence in the new model.The new model is also applied to a number of test cases which illustrate the need for the development of a model which can fully include three-dimensional behaviour. In particular, three applications are presented each increasing in complexity. The first application illustrates three-dimensional heat transfer. This particular application is verified against existing commercial finite element software. Subsequent applications serve to illustrate how the coupled processes of heat moisture and air transfer combine to yield three-dimensional problems even within a simple geometric domain. Visualization of three-dimensional results is also addressed. © 1998 by John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 175-196 
    ISSN: 0363-9061
    Keywords: shear crack ; singular integral equation ; excavation ; discontinuities ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The problem of the equilibrium of a plane with a circular hole and a shear crack is considered to model failure of an excavation (borehole or circular opening) in rocks weakened by discontinuities (planes of weakness). It is assumed that sliding occurs in a part of the plane of weakness when the Mohr-Coulomb friction criterion is satisfied due to the stress redistribution caused by the excavation. The method of singular integral equations is employed to solve the boundary value problem. Geomechanical problems concerning borehole breakout and rockburst caused by fault-opening interaction are discussed. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 277-301 
    ISSN: 0363-9061
    Keywords: seepage ; flow rate ; drain ; tunnel ; optimization ; Engineering ; Civil and Mechanical Engineering
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    Notes: The known formulae of Freeze and Cherry, Polubarinova-Kochina, Vedernikov for flow rate during 2-D seepage into horizontal drains and axisymmetric flow into cavities are examined and generalized. The case of an empty drain under ponded soil surface is studied and existence of drain depth providing minimal seepage rate is presented. The depth is found exhibiting maximal difference in rate between a filled and an empty drain. 3-D flow to an empty semi-spherical cavity on an impervious bottom is analysed and the difference in rate as compared with a completely filled cavity is established. Rate values for slot drains in a two-layer aquifer are ‘inverted’ using the Schulgasser theorem from the Polubarinova-Kochina expressions for corresponding flow rates under a dam. Flow to a point sink modelling a semi-circular drain in a layered aquifer is treated by the Fourier transform method. For unsaturated flow the catchment area of a single drain is established in terms of the quasi-linear model assuming the isobaric boundary condition along the drain contour. Optimal shape design problems for irrigation cavities are addressed in the class of arbitrary contours with seepage rate as a criterion and cavity cross-sectional area as an isoperimetric restriction. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 351-391 
    ISSN: 0363-9061
    Keywords: cone penetration testing ; sand ; Engineering ; Civil and Mechanical Engineering
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    Notes: The cone penetration test (CPT) is widely used, and although initially developed as a stratigraphic logging tool its excellent repeatability and accuracy offers a benchmark quantitative test for sand in particular. A continuing difficulty, however, is that the CPT does not measure any soil property directly, so that parameters of interest must be recovered from solution of an inverse boundary value problem, which is difficult. To date most CPT interpretations in sand have been based on very limited calibration testing carried out in large chambers on a few sands from which mappings are developed. But there are differences in the CPT response from one sand to another leaving the interpretation imprecise (and arguably even speculative) because these differences remain poorly understood. In this paper we use the familiar spherical cavity expansion analogy to the CPT including large strains and a good, critical-state-based, soil model to develop a pattern of behaviour which we then compare to some of the reference chamber test data. We find that one of the issues of dispute in the empirical interpretation methods, the so-called stress-level effect, is caused by neglect of elasticity and that there are several additional parameters of first-order significance to cavity expansion in sands. More generally, we show that the difference in CPT response between various chamber sands in predicted. Our results are cast in dimensionless form and the inversion illustrates that extreme care is required in interpreting CPT data if the in situ sand state is to be determined with precision approaching that suggested as achievable by the repeatability of the CPT data itself. Aspects requiring particular care in interpreting CPT data in sand are discussed. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 449-475 
    ISSN: 0363-9061
    Keywords: consolidation ; heat transfer ; poroelasticity ; pore pressure ; coupled fields ; Laplace transform ; Engineering ; Civil and Mechanical Engineering
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    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: This paper presents a theoretical approach to analyse coupled, linear thermoporoelastic fields in a saturated porous medium under radial and spherical symmetry. The governing equations account for compressibility and thermal expansion of constituents, heat sink due to thermal dilatation of water and thermal expansion of the medium, and thermodynamically coupled heat-water flow. It has been reported in the literature that thermodynamically coupled heat-water flows known as thermo-osmosis and thermal filtration have the potential to significantly alter the flow fields in clay-rich barriers in the near field of a underground waste containment scheme. This study presents a mathematical model and examines the effects of thermo-osmosis and thermal-filtration on coupled consolidation fields in a porous medium with a cavity. Analytical solutions of the governing equations are presented in the Laplace transform space. A numerical inversion scheme is used to obtain the time-domain solutions for a cylindrical cavity in a homogeneous or a non-homogeneous medium. A closed form time-domain solution is presented for a spherical cavity in a homogeneous medium. Selected numerical solutions for homogeneous and non-homogeneous media show a significant increase in pore pressure and displacements due to the presence of thermodynamically coupled flows and a negligible influence on temperature. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 421-423 
    ISSN: 0363-9061
    Keywords: Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 603-619 
    ISSN: 0363-9061
    Keywords: earthquakes ; stress-strain response ; downhole arrays ; Engineering ; Civil and Mechanical Engineering
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    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Recordings from downhole accelerometer arrays offer unique insight into soil behavior and ground response during earthquakes. In this paper we present a scheme for interpolating displacement and acceleration measurements to provide approximations for subsurface shear strain and stress as continuous functions of time. Our suggested interpolating functions are constructed in such a way that the free surface boundary condition will always be satisfied and the interpolated displacement and acceleration remain finite for all depths. We also show how the functions can be adapted to represent layered soil profiles. Depending on the number of instruments in the downhole array, a truncated series of functions can be derived so that each represents a modal shape for the layered soil profile. The resulting approximations for strain and stress are considered more accurate and robust than previous approximations. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 621-653 
    ISSN: 0363-9061
    Keywords: state parameter ; stress-state relation ; constitutive modelling ; plasticity ; critical state ; sand and clay ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The purpose of this paper is to present a simple, unified critical state constitutive model for both clay and sand. The model, called CASM (Clay And Sand Model), is formulated in terms of the state parameter that is defined as the vertical distance between current state (v, p′) and the critical state line in v-ln p′ space. The paper first shows that the standard Cam-clay models (i.e. the original and modified Cam-clay models) can be reformulated in terms of the state parameter. Although the standard Cam-clay models prove to be successful in modelling normally consolidated clays, it is well known that they cannot predict many important features of the behavior of sands and overconsolidated clays. By adopting a general stress ratio-state parameter relation to describe the state boundary surface of soils, it is shown that a simple, unified constitutive model (CASM) can be developed for both clay and sand. It is also demonstrated that the standard Cam-clay yield surfaces can be either recovered or approximated as special cases of the yield locus assumed in CASM.The main feature of the proposed model is that a single set of yield and plastic potential functions has been used to model the behaviour of clay and sand under both drained and undrained loading conditions. In addition, it is shown that the behaviour of overconsolidated clays can also be satisfactorily modelled. Simplicity is a major advantage of the present state parameter model, as only two new material constants need to be introduced when compared with the standard Cam-clay models. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 855-865 
    ISSN: 0363-9061
    Keywords: anchor ; trapdoor ; limit load ; cohesionless ; associative ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: A methodology for determining the plane strain limit load acting on an anchor or trapdoor buried within a purely associative Coulomb soil is presented. True lower bounds derived from a family of limiting stress fields appropriate to shallow horizontal trapdoors and anchors are shown to correlate to within less than 1 percent of upper bounds available in the literature, permitting the true limit load to be almost exactly defined. The solution form alters for deeply buried anchors and trapdoors resulting in poorer correlations. Methods by which the work may be extended to cover the more practical instances of non-associative Coulomb soils are indicated but are beyond the scope of the current paper. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 903-919 
    ISSN: 0363-9061
    Keywords: hollow cylinders ; diffuse mode bifurcations ; geomaterials ; non-normality ; pressure-sensitivity ; Engineering ; Civil and Mechanical Engineering
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    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: This paper derives analytically the condition for the onset of diffuse mode bifurcations in thick-walled hollow cylinders with internal radius a, external radius b and length L under axial compression and confining pressure. The thick-walled cylindrical specimens are made of geomaterial characterized by Rudnicki's constitutive model, and the method of solution for the governing equations is the velocity potential approach employed by Chau. Numerical results show that thick-walled cylinders are stronger than thin-walled cylinders against diffuse mode bifurcations, including both buckling, axisymmetric and non-axisymmetric deformations. In contrast to the conclusion for solid cylinders (Chau), no buckling solution is found for γ = mπa / L smaller than about 0·7 under compression for a fixed and finite value of a / b (i.e. no buckling for long and slender hollow cylinders with small a / L and fixed b / a). When 0·7 〈 γ 〈 0·9, buckling is the expected first bifurcation; whereas, when γ 〉 0·9, bulging or barrelling is anticipated. The exact value of γ that excludes buckling and separates the buckling and barrelling phenomena depends on the current values of the constitutive parameters of the solid. Hollow cylinders with higher degree of anisotropy, disobeying normality flow rule, and subjected to confining pressure are more conducive to bifurcations than cylinders made of materials with isotropy, obeying normality, and subjected to no confining pressure. In addition, diffuse mode bifurcations are found possible in the pre-peak regime of the stress-strain curve. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 983-1000 
    ISSN: 0363-9061
    Keywords: geomechanics ; indirect boundary element method (BEM) ; three-dimensional (3-D) elastostatics ; iterative methods ; approximate solution ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The research herein primarily addresses to geomechanical problems of underground constructions in Mining and Civil Engineering. The problems are solved using the Indirect Boundary Element Method (IBEM). Although the geometry of the constructions themselves is usually very complicated, it will become much more complicated if we were to draw the existing joints. The computational problem therefore is how to deal with huge amount of equations and find out efficient methods of their formation and solution keeping in mind restraints of the computer memory and calculation time. Several approaches are used to enhance the performance of the Indirect Boundary Element Method. One of them deals with application of efficient equation solvers. It is shown that Krylov-type methods like CGS and GMRES with simple Jacoby preconditioning appear to be efficient and robust. In addition, adaptive integration on the boundary elements, together with diagonal dominance of equationsmake it possible to accelerate convergence of the iterative procedure. Some of the problems discussed allow a substantial reduction of matrix entries that leads to a very cheap iterative solution keeping reasonable accuracy of the results. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 97-132 
    ISSN: 0363-9061
    Keywords: constitutive model ; rate-independent type ; strain response envelope ; granular material ; uniqueness ; Engineering ; Civil and Mechanical Engineering
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    Notes: This paper reviews some incrementally non-linear constitutive equations of interpolation type, and proposes a new approach to illustrate the discrepancies between different interpolation models. This approach uses the strain response envelopes, based on experimental data when restricted to triaxial plane, and the Jacobian of the constitutive equations to examine the loss of uniqueness. A new family of interpolation functions is proposed to meet the three requirements: C1-continuity of strain response envelope, correct description of experimental data, and respect of the one-to-one property. © 1998 by John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 153-174 
    ISSN: 0363-9061
    Keywords: finite-element ; sea ice pack ; rheology ; viscous-plastic ; viscous fluid ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: In this paper the effects of four different rheologies on the evolution of a large-scale sea ice pack are determined and compared. Two rheologies are of viscous-plastic form, and two are viscous fluid relations. The initial pack domain is rectangular, and the motion is driven by wind stress and resisted by ocean drag. Two adjacent edges are rigid shore boundaries, and the other two are free boundaries at open water which move during the pack motion, so that the pack domain changes in time. Two different forms of boundary conditions at the rigid shore edges are considered, which also influence the evolution. The governing equations are solved numerically using a finite-element method, and, unlike previous numerical treatments, no artificial viscosity is incorporated to stabilise the algorithm near interfaces between converging and diverging flow. Instability arises when any tensile stress is abruptly cut-off when diverging flow is initiated, and an alternative view is offered. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 263-275 
    ISSN: 0363-9061
    Keywords: non-ideal interface ; crack scattering ; domain decomposition ; collocation methods ; Engineering ; Civil and Mechanical Engineering
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    Notes: This work presents a numerical algorithm for solving crack scattering in a transversely isotropic medium whose symmetry axis is perpendicular to the crack surface. The crack is modelled as boundary discontinuities in the displacement u and the particle velocity v, of the stresses [κu+ζv], where the brackets denote discontinuities across the interface. The specific stiffness κ introduces frequency-dependence and phase changes in the interface response and the specific viscosity ζ is related to the energy loss.The numerical method is based on a domain decomposition technique that assignes a different mesh to each side of the interface, that includes the crack plane. As stated above, the effects of the crack on wave propagation are modelled through the boundary conditions, that require a special boundary treatment based on characteristic variables. The algorithm solves the particle velocity-stress wave equations and two additional first-order differential equations (two-dimensional case) in the displacement discontinuity. For each mesh, the spatial derivatives normal to the interface are solved by the Chebyshev method, and the spatial derivatives parallel to the interface are computed with the Fourier method. They allow a highly accurate implementation of the boundary conditions and computation of the spatial derivatives, and an optimal discretization of the model space. Moreover, the algorithm allows general material variability. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 327-350 
    ISSN: 0363-9061
    Keywords: finite element analysis ; large strain ; remeshing ; integration ; penetration ; bearing capacity ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: A practical method is presented for numerical analysis of problems in solid (in particular soil) mechanics which involve large strains or deformations. The method is similar to what is referred to as ‘arbitrary Lagrangian-Eulerian’, with simple infinitesimal strain incremental analysis combined with regular updating of co-ordinates, remeshing of the domain and interpolation of material and stress parameters. The technique thus differs from the Lagrangian or Eulerian methods more commonly used. Remeshing is accomplished using a fully automatic remeshing technique based on normal offsetting, Delaunay triangulation and Laplacian smoothing. This technique is efficient and robust. It ensures good quality shape and distribution of elements for boundary regions of irregular shape, and is very quick computationally. With remeshing and interpolation, small fluctuations appeared initially in the load-deformation results. In order to minimize these, different increment sizes and remeshing frequencies were explored. Also, various planar linear interpolation techniques were compared, and the unique element method found to work best.Application of the technique is focused on the widespread problem of penetration of surface foundations into soft soil, including deep penetration of foundations where soil flows back over the upper surface of the foundation. Numerical results are presented for a plane strain footing and an axisymmetric jack-up (spudcan) foundation, penetrating deeply into soil which has been modelled as a simple Tresca or Von Mises material, but allowing for increase of the soil strength with depth. The computed results are compared with plasticity solutions for bearing capacity. The numerical method is shown to work extremely well, with potential application to a wide range of soil-structure interaction problems. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 495-508 
    ISSN: 0363-9061
    Keywords: consolidation ; cohesive soil ; clay ; axial strain ; true triaxial ; finite difference method ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: This paper presents a simplified approach for the analysis of axial strain induced by three-dimensional consolidation of cohesive soils. The axial strain is divided into a constant volume component and a consolidation component. A relevant undrained stress-strain relationship is required to determine the constant volume component. A theoretical formulation is developed for the evaluation of the consolidation component. Predictions of the axial strain accompanying true triaxial laboratory tests for a variety of stress patterns correlate sufficiently well with the measured data. The proposed method is potentially applicable in conjunction with a finite difference scheme to analyze the time-dependent response of pile groups subjected to static vertical loading. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 549-574 
    ISSN: 0363-9061
    Keywords: carbonatic clays ; thermo-plasticity ; nuclear waste disposal ; thermo-mechanical tests ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Argillaceous masses considered for potential nuclear waste repositories may exhibit significant space variability in their carbonate content. This may affect mechanical clay properties, such as strength or maximum apparent preconsolidation stress known to strongly depend on carbonate content. This paper investigates experimentally the dependence of thermo-hydro-mechanical behaviour of clays on carbonate content. The properties investigated are thermal strains, thermally induced over-consolidation, strength changes, destructuration, and thermally developed water pressure in undrained conditions. The experimental data are analysed in terms of a thermo-elasto-plasticity theory for clays, being an extension of Cam-clay model, modified to include the variability of the carbonatic content. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 695-720 
    ISSN: 0363-9061
    Keywords: wave propagation ; compaction ; pore pressure generation ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The propagation of a plane load-unload pulse through a compacting sand is analysed and illustrated for both dry sand and liquid saturated sand in undrained conditions. A major feature is the interaction between the initial loading wave and the faster following unloading wave. Free draining and undrained conditions exhibit distinct qualitative and quantitative results, and the pore liquid pressure generation is a significant physical feature. Illustrations show the effects of different applied surface pulse shapes. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 777-790 
    ISSN: 0363-9061
    Keywords: piles ; rafts ; finite elements ; preconditioning ; conjugate gradients ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Analysis of piled raft foundations, taking account of their full three-dimensional complexity, can be accomplished by modern finite element analysis techniques. The characteristics of the (preconditioned conjugate gradient) numerical method applied to this problem are analysed, and then the method isused in a field problem of a raft subjected to very rapidly varying loading patterns. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 791-818 
    ISSN: 0363-9061
    Keywords: Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: An analytical model to simulate the penetration of the piezocone penetrometer in cohesive soils is presented here. The elasto-plastic coupled field equations of the saturated cohesive soils (given by Voyiadjis and Abu-Farsakh) is used in this analysis. The numerical simulation of the piezocone penetration is implemented into a finite element program. The analytical model is used to analyze the miniature piezocone penetration tests (PCPT) conducted at LSU calibration chambers. Simulation of the piezocone penetration is done for two cases. In the first case, the soil-penetrometer interface friction is neglected, while in the second case, the soil-penetrometer interface friction is taken into consideration. The constraint approach is used to model the soil-piezocone interface friction in which the Mohr-Coulomb frictional model is used to define the sliding potential. Analysis is done for three different soil specimens with different stress histories. The results of the numerical simulations are compared with the experimental measurements of the miniature piezocone penetration tests (PCPT) in cohesive soil specimens conducted in LSU calibration chambers. The resulting excess pore pressure distribution and its dissipation using the numerical model are compared with some available prediction methods. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 1001-1020 
    ISSN: 0363-9061
    Keywords: stone-column reinforcement ; homogenisation technique ; elastoplastic analysis ; sub-iteration scheme ; Engineering ; Civil and Mechanical Engineering
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    Notes: A numerical model is proposed to analyse elastic as well as elastoplastic behaviour of stone-column reinforced foundations. The stone-columns are assumed to be dispersed within the in situ soil and a homogenization technique is invoked to establish equivalent material properties for in situ soil and stone-column composite. The difficulties encountered in carrying out elastoplastic analyses of composite materials are overcome by adopting a separate yield function for each of the constituent materials and a sub-iteration procedure within an implicit backward Euler stress integration scheme. In the proposed procedure, equilibrium as well as kinematic conditions implied in the homogenization procedure are satisfied for both elastic as well as elastoplastic stress states.The proposed model is implemented in an axi-symmetric finite element code and numerical prediction is made for the behaviour of model circular footings resting on stone-column reinforced foundations. This prediction indicates good agreement with experimental observation. Finally, a new scheme in which the length of stone-column is variable is proposed and its behaviour is examined through a numerical example. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 969-981 
    ISSN: 0363-9061
    Keywords: heat and moisture flow ; analytical solution ; transient analysis ; spherical heat source ; coupled analysis ; Green's function method ; Engineering ; Civil and Mechanical Engineering
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    Notes: The present paper develops an analytical approach to the problem of heat-induced moisture movement in the vicinity of a spherical heat source embedded in an undeformable, moist porous solid of infinite extent. A transient-state distribution of temperature within the infinite medium is assumed to induce the moisture transport process. The numerical results, presented in the paper, illustrate the influence of the moisture transport characteristics on the time-dependent distribution of moisture within the porous medium. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 49-71 
    ISSN: 0363-9061
    Keywords: unsaturated soil ; heat transfer ; moisture transfer and stress-strain behaviour ; model and validation ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper focuses attention on the development of a numerical model of the hydro/thermo/mechanical behaviour of unsaturated clay and its consequent verification and validation. The work presented describes on-going collaboration between the Cardiff School of Engineering and Atomic Energy of Canada. The model development, which was carried out at Cardiff, can be described as being based on a mechanistic approach to coupled heat, moisture and air flow. This is then linked to a deformation analysis of the material within a ‘consolidation’ type of model. The whole is solved via the finite element method to yield a computer software code named COMPASS (COde for Modelling PArtly Saturated Soil). Some aspects of verification and validation of the model have been addressed in-house. However, the purpose of current AECL work is to provide an independent, rigorous, structured programme of validation and the paper will also explore the further validation of COMPASS within this context. © 1998 by John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 133-149 
    ISSN: 0363-9061
    Keywords: thermoporoelasticity ; thermoporoplasticity ; Laplace transform ; Stehfest algorithm ; finite element method ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Solutions are presented for the behaviour of a layered porous space which contains a decaying heat source. Such a problem arises when high-level nuclear waste is placed in deep underground depositories in deep clayey formations of sedimentary basins. The geometry of the problem is one dimensional and the porous space is constituted by two layers: a deep low permeability layer which contains the nuclear waste disposal and a superficial layer. The solution is used to examine the effects of contrasts of permeability, thermal conductivity and specific heat capacities between the two layers on the large-scale behaviour of the porous space. Results are presented, using realistic data, for the pore pressure and temperature evolution at the heat source centre, and for the vertical displacement of the ground level. The superficial layer has no significant effects on pore pressure, temperature and stress evolution near the heat source centre. The vertical displacement of the ground level is mainly due to the thermal dilatation of the pore water, so it decreases with an increasing of permeability of the superficial layer. The solution of the time-dependent problem is carried out by applying Laplace transforms to the field variables, obtaining solutions and then using numerical methods to invert the transformed solutions. Comparisons with numerical simulations taking into account the non-linear and non-reversible behaviour of the rock mass are presented. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 245-261 
    ISSN: 0363-9061
    Keywords: Cosserat continuum model ; equivalent continuum medium ; layered rock mass ; finite element method ; non-associative plasticity ; Engineering ; Civil and Mechanical Engineering
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    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Layered rock masses can be modelled either as standard, orthotropic continua if the layer bending can be neglected or as Cosserat continua if the influence of layer bending is essential. This paper presents a finite element smeared joint model based on the Cosserat theory. The layers are assumed to be elastic with equal thickness and equal mechanical properties. All the cosserat parameters are expressed through the elastic properties of layers, layer thickness and joint stiffness. Plastic-slip as well as tensile-opening of layer interface (joint) are accounted for in a manner similar to the conventional non-associative plasticity theory.As an application, the behaviour of an excavation in a layered rock mass is examined. The displacement and stress fields given by smeared joint models based on the Cosserat continuum and the conventional anisotropic continuum approaches are compared with those obtained from the discrete joint model. The conventional anisotropic continuum model is found to break-down completely when the effective shear modulus in the direction parallel to layering is low in comparison to the shear modulus of the intact layer, whereas the Cosserat model is found to be capable of accurately reproducing complex load-deflection patterns irrespective of the differences in shear moduli. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 393-416 
    ISSN: 0363-9061
    Keywords: fabric ; porosity ; tensor ; yield ; stress ; strain ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The porosity of soils is considered to be a directional measure and its distribution is characterized by a functional form. This form has been used to extend the critical state soil mechanics framework to include the effects of structure in soils. A new internal plastic energy dissipation formulation has been proposed to account for fabric arrangement. New expressions for the yield locus, and the plastic stress-strain response of structural soils have been derived. The applicability of the concepts to model the plastic stress-strain behaviour of a number of soils is illustrated. The advantage of the new model is very well identified in modelling the stress-strain behaviour of K0 consolidated and natural clays. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 477-493 
    ISSN: 0363-9061
    Keywords: foundation ; pile ; raft ; analysis ; case history ; Engineering ; Civil and Mechanical Engineering
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    Notes: An approximate numerical method for the analysis of piled raft foundations is presented. The raft is modelled as a thin plate and the piles as interacting non-linear springs. Both the raft and the piles are interacting with the soil which is modelled as an elastic layer. Two sources of non-linearity are accounted for: (i) the unilateral contact at the raft-soil interface and (ii) the non-linear load-settlement relationship of the piles. Both theoretical solutions and experimental results are used to verify that, despite the approximations involved, the proposed method of analysis can provide satisfactory solutions in both linear and non-linear range. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 515-548 
    ISSN: 0363-9061
    Keywords: coupled analysis ; expansive clay ; granite ; radioactive waste ; thermo-hydro-mechanical analysis ; unsaturated soils ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Coupled thermo-hydro-mechanical (THM) analyses have been used to examine the interacting phenomena associated with the simultaneous heating and hydration of an engineered bentonite barrier placed in a drift excavated in granite. The specific problem studied is an in situ test being carried out in the underground laboratory at Grimsel (Switzerland). After describing the test and the theoretical formulation, the results of a coupled THM analysis using the best parameter estimation currently available are presented and discussed. The effect of various features of analysis are explored by means of additional analyses in which each of those features are varied, one at the time. Finally, sensitivity analyses have been carried out to examine some critical aspects of the in situ test design. Performance of coupled THM analyses has led to a better understanding of the various inter-related phenomena occurring during heating and hydration of the engineered clay barrier. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 655-669 
    ISSN: 0363-9061
    Keywords: elastic nonhomogeneity ; soil deformation ; soil stresses ; surface loading ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The response of a compressible continuously non-homogeneous elastic soil to a static vertical point load on its surface is analytically investigated by using classical integral transform techniques and the extended power series method for obtaining the solution in the transform domain. The non-homogeneity is described by means of a depth-function which is non-zero at the surface and bounded at infinity and is capable in modelling both increasing and decreasing soil stiffness with depth. The influence of non-homogeneity on the displacements and stresses at the surface and in the interior is examined over a wide range on the governing parameters. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 721-748 
    ISSN: 0363-9061
    Keywords: cyclic behaviour ; saturated sands ; disturbed state concept ; liquefaction ; post liquefaction ; threshold transitions ; laboratory tests ; validations ; mathematical analysis ; computer implementation ; application ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: A fundamental procedure is proposed for the identification of liquefaction in saturated soils based on the instability in the material's microstructure. The disturbed state concept (DSC) provides a unified constitutive model for the characterization of entire stress-strain behaviour under cyclic loading, and the values of disturbance at threshold states in the deforming microstructure provides the basis for the identification of liquefaction. The procedure is verified with respect to laboratory behaviour of two sands, saturated Ottawa and Reid Bedford. A mathematical analysis of the DSC constitutive matrix is also performed. Procedures for the application of the DSC for simplified analysis and design, and in finite element procedures are presented. It is believed that the proposed model can provide a fundamental yet simplified procedure for liquefaction analysis, and as a result, it is considered to be an improvement over the available empirical and energy-based procedures. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 819-850 
    ISSN: 0363-9061
    Keywords: stochastic ; finite element ; seismic ; response ; random ; variability ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Some of the available stochastic finite element methods are adapted and evaluated for the analyses of response of soils with uncertain properties subjected to earthquake induced random ground motion. In this study, the dynamic response of a soil mass, with finite element discretization, is formulated in the frequency domain. The spectral density function of the response variables are obtained from which the evaluation of the root-mean-squared and the most probable extreme values of the response are made. The material non-linearities are incorporated by using strain compatible moduli and damping of soils using an equivalent linear model for stress-strain behaviour of soils and an iterative solution of the response. The spatial variability of the shear modulus is described through a random field model and the earthquake included motion is treated as a stochastic process. The available formulations of direct Monte-Carlo simulation, first-order perturbation method, a spectral decomposition method with Neumann expansion and a spectral decomposition method with Polynomial Chaos are used to develop stochastic finite element analyses of the seismic response of soils. The numerical results from these approaches are compared with respect to their accuracy and computational efficiency. © 1998 John Wiley & Sons Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 921-940 
    ISSN: 0363-9061
    Keywords: anisotropic sand ; constitutive model ; non-linear tensorial junctions ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The paper presents a constitutive model for the three-dimensional deformation-strength behaviour of inherently anisotropic sand. Based on non-linear tensorial functions, the model is developed without recourse to the concepts in plasticity theory such as yield surface and plastic potential. Benefited from the fact that no decomposition of strain into elastic and plastic parts is assumed, a unified treatment of anisotropic behaviour of deformation and strength is achieved. Anisotropy is characterized by a vector normal to the bedding plane. The extension of the constitutive model is furnished by incorporating the vector under consideration of the principle of objectivity and the condition of material symmetry. Distinct features of the model are its elegant formulation and its simple structure involving few material parameters. Model performance and comparison with experiments show that the model is capable of capturing the salient behaviour of anisotropic sand. © 1998 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 947-968 
    ISSN: 0363-9061
    Keywords: boundary element method ; complex hypersingular integrals ; Engineering ; Civil and Mechanical Engineering
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    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The definitions of complex integrals of Cauchy and Hadamard with the singular point coinciding with the end point of the integration curve are proposed. It is shown that the new integrals satisfy most of the properties of the regular ones, including the change of variables. It is also shown that the Cauchy principal value (CPV) and Hadamard finite-part (HFP) integrals can be considered as a sum of the new type integrals. The application to numerical solution by the boundary element method (BEM) and the complex hypersingular integral equation (CHSIE) for the multiregions of interacting elastic bodies and bodies with cracks and holes is discussed. The different ways to place the collocation points are considered. The numerical results for the problems of circular hole and circular elastic inclusion in infinite plate indicated that the appropriate choice of the approximating functions leads to a high accuracy of the calculation. Applications of the new technique to geomechanics problems are discussed. © 1998 John Wiley & Sons, Ltd.
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