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Bifurcation and Degradation of Geomaterials with Engineering Applications : Proceedings of the 11th International Workshop on Bifurcation and Degradation in Geomaterials dedicated to Hans Muhlhaus, Limassol, Cyprus, 21-25 May 2017 (2017)

Papamichos, Euripides [HerausgeberIn] ; Papanastasiou, Panos [HerausgeberIn] ; Pasternak, Elena [HerausgeberIn] ; [et al.]

Cham : Springer International Publishing - Springer

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Call number: IASS 17.91203

Description / Table of Contents: Part I. Experimental Modeling of Instabilities Localization and Degradation -- Part II. Constitutive modeling and multi-physical coupling for localization, Instabilities and Degradation of Geomaterials -- Part III Numerical Modeling of Failure, Localized Deformation and Gravity Driven Flows -- Part 4 Soil-tool/Machine Interaction -- Part V Geomechanics for Energy, Environment and Geophysics -- Part VI Micromechanics and Multi-scale Analysis of Instabilities and Degradation -- Part VII Hans Muhlhaus Tribute

Description / Table of Contents: This book contains the scientific contributions to the 11th International Workshop on Bifurcation and Degradation in Geomaterials (IWBDG) held in Limassol-Cyprus, May 21-25, 2017. The IWBDG series have grown in size and scope, since their inception 30 years ago in Germany, covering more and wider areas of geomaterials and geomechanics research including modern trends. The papers cover a wide range of topics including advances in instabilities, localized and diffuse failure, micromechanical, multiscale phenomena, multiphysics modeling and other related topics. This volume gathers a series of manuscript by brilliant international scholars who work on modern recent advances in experimental, theoretical and numerical methods. The theoretical and applied mechanics are linked successfully with engineering applications in traditional and in emerging fields, such as geomechanics for the energy and the environment. The quality of the contributed papers has benefited from the peer review process by expert referees. This book can be used as a useful reference for research students, academics and practicing engineers who are interested in the instability and degradation problems in geomaterials, geomechanics, geotechnical engineering and other related applications

Type of Medium: Monograph available for loan

Pages: XVI, 623 Seiten , Illustrationen

ISBN: 9783319563961 (print) , 9783319563978

Series Statement: Springer Series in Geomechanics and Geoengineering

Language: English

Branch Library: RIFS Library

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Representation of crack-tip plasticity in pressure sensitive geomaterials (2000)

Papanastasiou, Panos ; Atkinson, Colin

Springer

International journal of fracture 102 (2000), S. 271-286

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ISSN: 1573-2673

Keywords: Dislocation model ; superdislocation ; crack-tip plasticity ; pressure sensitive material.

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract This paper presents a model based on dislocation theory for representation of crack tip plasticity in a pressure sensitive material. The basic equations are derived from a simple model of the crack tip plasticity which represents the plasticity by superdislocations placed at the effective centres of the complete slip process distributed around the crack tip. The positions and strengths of the superdislocations are determined by imposing the following conditions: (i) the total stress-intensity factor at the crack tip is zero (ii) the total stress minus the self stress of the superdislocation acting at the superdislocation position is just equal to the friction stress due to the Mohr-Coulomb yield criterion and (iii) the total crack opening displacement produced by the model is maximized. Condition (iii) enables the angle of the slip band on which the superdislocation lies to be determined. The results are presented in a dimensionless form allowing the discussion of particular cases and the recognition of the dominant parameters. A series of parametric studies are carried out to demonstrate that the model can capture the essentials of the crack tip plasticity.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1007681730743

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Hydraulic fracture closure in a pressure-sensitive elastoplastic medium (2000)

Papanastasiou, Panos

Springer

International journal of fracture 103 (2000), S. 149-161

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ISSN: 1573-2673

Keywords: Hydraulic fracturing ; fracture closure ; closure stress ; elastoplastic analysis ; coupled problem

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract This paper examines fracture closure in a Mohr-Coulomb pressure-sensitive dilatant material. The analysis is based on fracture propagation and closure of a plane strain geometry using a fully coupled elastoplastic hydraulic fracturing model. It is shown that the closure pattern of a fracture which has first been propagated is completely different from the closure pattern of a pressurized stationary fracture. A pressurized stationary elastoplastic fracture closes uniformly but remains open after the applied load is released. An elastoplastic fracture which has first been propagated, makes surface contact initially near the fracture tip and subsequently towards the mouth of the fracture. Applications of fracture closure pattern can be found in different aspects of hydraulic fracturing such as in the insitu parameters determination from the inversion of the pressure vs time record and in the closure stress on propped fractures.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1007634723191

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The influence of plasticity in hydraulic fracturing (1997)

Papanastasiou, Panos

Springer

International journal of fracture 84 (1997), S. 61-79

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ISSN: 1573-2673

Keywords: Hydraulic fracturing ; plasticity ; net pressure ; finite elements

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract This paper examines the influence of plasticity in hydraulic fracturing. Fluid flow in the fracture is modelled by lubrication theory. Rock deformation is modelled by the Mohr–Coulomb flow theory of plasticity and the propagation criterion is based on the softening behaviour of rocks. The coupled, nonlinear problem is solved by a combined finite difference–finite element scheme. The results show that plastic yielding near the tip of a propagating fracture provides an effective shielding, resulting in an increase of the rock effective fracture toughness by more than an order of magnitude. Higher pressure is needed to propogate an elasto-plastic fracture than an elastic fracture, and the created elasto-plastic fracture is shorter and wider than the elastic fracture of the same volume.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1007336003057

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The Effective Fracture Toughness in Hydraulic Fracturing (1999)

Papanastasiou, Panos

Springer

International journal of fracture 96 (1999), S. 127-147

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ISSN: 1573-2673

Keywords: Hydraulic fracturing ; fracture toughness ; net pressure ; plasticity ; coupled model ; finite elements.

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract This paper examines the effective fracture toughness approach which is used in hydraulic fracturing in order to explain the high net-pressures that are often observed in field operations. The effective fracture toughness is calculated using a fully deterministic elasto-plastic hydraulic fracturing model. Rock is modelled by Mohr–Coulomb flow theory of plasticity for cohesive-frictional dilatant material. Fluid flow is modelled by lubrication theory. A cohesive crack model which takes into account the softening behaviour of rocks is employed as the propagation criterion. The fully coupled model is solved numerically by the finite element method and the effective fracture toughness is calculated using the path independent J-integral. The results show that plastic yielding near the tip of a propagating fracture provides an effective shielding, resulting in an increase in the rock effective fracture toughness by more than an order of magnitude. It is demonstrated that an elastic model based on the concept of effective fracture toughness matches the results of plasticity quite well. The effective fracture toughness increases with formation yielding, which is influenced by the deviator of the in-situ stresses, the rock strength, the elastic modulus and the pumping parameters. Tables of effective fracture toughness for a representative set of physical parameters are presented.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1018676212444

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Numerical treatment of progressive localization in relation to borehole stability (1992)

Papanastasiou, Panos C. ; Vardoulakis, Ioannis G.

New York, NY [u.a.] : Wiley-Blackwell

International Journal for Numerical and Analytical Methods in Geomechanics 16 (1992), S. 389-424

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ISSN: 0363-9061

Keywords: Engineering ; Engineering General

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Architecture, Civil Engineering, Surveying , Geosciences

Notes: Results of large-scale finite element computations are presented for the problem of borehole failure due to the high stresses at great depths. Rock is modelled by an extension of the Mohr-Coulomb flow theory of plasticity for material with Cosserat micro-structure. The introduction of internal length (grain size) improves the computational stability and allows for robust post-localization computations. The presented results show clearly a progressive failure mechanism and the computed failure modes are in a good qualitative agreement with laboratory and field observations.

Additional Material: 17 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/nag.1610160602

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ELASTOPLASTIC ANALYSIS OF CYLINDRICAL CAVITY PROBLEMS IN GEOMATERIALS (1997)

Papanastasiou, Panos ; Durban, David

New York, NY [u.a.] : Wiley-Blackwell

International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 133-149

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ISSN: 0363-9061

Keywords: cylindrical cavity ; Mohr-Coulomb ; Drucker-Prager ; Engineering ; Civil and Mechanical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Architecture, Civil Engineering, Surveying , Geosciences

Notes: A large-strain elastoplastic analysis is presented for a cylindrical cavity embedded in an infinite medium under uniform radial pressure. The investigation employs invariant, non-associated deformation-type theories for Mohr-Coulomb (M-C) and Drucker-Prager (D-P) solids, accounting for arbitrary hardening, with the equivalent stress as the independent variable. The M-C model results in a single first-order differential equation, whereas for the D-P solid an algebraic constraint supplements the governing differential equation. Material parameters and response characteristics were determined by calibrating the models with data from triaxial compression tests on Castlegate sandstone and on Jurassic shale. A comparison is presented between predictions obtained from the two models and experimental data from hollow cylinder tests under external loading. A sensitivity of the results to material parameters, like friction and dilation angles, is provided for the case of a cavity subjected to internal pressure in terms of limit pressure predictions. In all cases it has been found that the results of the D-P inner cone model are in close agreement with those obtained from the M-C model. © 1997 by John Wiley & Sons, Ltd.

Additional Material: 6 Ill.

Type of Medium: Electronic Resource

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ELASTOPLASTIC RESPONSE OF PRESSURE SENSITIVE SOLIDS (1997)

Durban, David ; Papanastasiou, Panos

New York, NY [u.a.] : Wiley-Blackwell

International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 423-441

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ISSN: 0363-9061

Keywords: Mohr-Coulomb ; Drucker-Prager ; flow theory ; deformation theory ; loss of ellipticity ; surface instabilities ; bifurcation ; Engineering ; Civil and Mechanical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Architecture, Civil Engineering, Surveying , Geosciences

Notes: Tensorially invariant constitutive relations are systematically derived for large strain elastoplastic response of geomaterials. The analysis centres on Mohr-Coulomb (MC) and Drucker-Prager (DP) models with arbitrary hardening and non-associated response. Both flow and deformation theories are constructed for each model with emphasis on linear incremental relations between the Eulerian strain rate tensor and the objective Jaumann stress rate tensor.Specifying the results for plane strain compression we find that deformation theory produces a much smaller tangent instantaneous shear modulus than flow theory. It follows that failure of ellipticity and onset of surface instabilities predicted by deformation theory for associated solids occur at much lower levels of strain than the corresponding flow theory results. On the other hand, flow theory predictions admit a considerable sensitivity to the level of non-associativity. In fact, at high levels of non-associativity flow theory predictions for loss of ellipticity can be at strains below those obtained from deformation theory. © 1997 John Wiley & Sons, Ltd.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

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