bluuebunny/crossref_metadata_2025 huggingface dataset:
On hypoelasticity and plasticity approaches to constitutive modelling of inelastic behaviour of soils
Authors: Mróz Z.
Published: August 2005

A comparative discussion of constitutive rate equations generated by using the hypoelasticity and plasticity theories is presented. If is shown that these two approaches are equivalent for the loading process but differ essentially in defining the unloading (or reverse loading) paths. The multisurface plasticity formulation proves to be more convenient in incorporating memory rules of particular loading events, whereas loading‐unloading criteria used in hypoelasticity may result in an unrealistic prediction of material response for some loading paths, and in particular, for cyclic loading. The violation of the continuity condition between loading–unloading domains in proposed constitutive relations3,4 limits their applicability to some particular classes of loading paths.
Settlement of inhomogeneous consolidating soils—II: The symmetrically loaded mass
Authors: Mahmoud M. S. , Deresiewicz H.
Published: August 2005

We continue our study of the consolidation of inhomogeneous clay soils with an analysis of the response of a soil mass, whose shear modulus increases linearly with depth, to axially symmetric pressure on its surface. This extends the work reported in Part I on the corresponding one‐dimensional problem of a clay column, and generalizes researches of Gibson and coworkers on the elastic model of the soil (i.e., the initial response).

Because of great mathematical complexity when Poisson's ratio is allowed to assume arbitrary values, we have confined ourselves (as did Gibson in several of his papers) to variations of the modulus from a zero surface value, this being in reasonable accord with published test results on London clay. The deflection of points within this region, the deflection relative to the central one (that is, the shape of the deformed loading area), as well as the absolute deflection of surface points exterior to the load.
A simplified analytical method for soil penetration analysis
Authors: Yankelevsky David Z. , Adin Moshe A.
Published: August 2005

A new one‐dimensional model for penetration analysis of a rigid projectile into a soil target is presented. The soil medium is represented by a set of discs of constant thickness, responding in the radial direction under plain strain regime. When penetration through a typical disc occurs, the projectile displaces soil material and a radial plastic shock wave propagates in the disc. The interaction pressure between the projectile and soil material is compatible with the motion of the contact boundary, between them. The instantaneous resistive force is obtained by summation of the contributions of all the discs which are in contact with the nose surface of the projectile. Soil is considered as a ‘floating’ ideally locking material, in which the locking volumetric strain is adjusted to the physical stress–strain properties of the soil material. Friction between projectile and soil is assumed to be negligible. Comparison is made with both twodimensional computer program results and experimental data, and very good agreement is observed. Comparison with other analytical methods reveals that the present model most closely resembles existing experimental results and permits further analysis of the problem as predictions of target response and of stress distribution on the projectile nose. The calculations require very small amounts of computer time. Analysis with the present model yields an efficient and comprehensive means to analyse penetration and perform parameter analysis.
Hysteretic and viscous material damping
Authors: Molenkamp Frans , Smith Ian M.
Published: August 2005

Hysteretic and viscous material damping are compared in the context of soils. Popular assumptions about damping are shown to lead to different results for the rocking mode of surface foundations at low frequency.
A concept of correction functions to account for non‐associative characteristics of geologic media
Authors: Desai C. S. , Siriwardane H. J.
Published: August 2005

A new and simple concept based on the idea of correcting for non‐associative characteristics of (geologic) media is presented. A special form of the concept is adopted and introduced in a critical state plasticity model. An example problem of behaviour of a soil tested under triaxial conditions is included. The concept can permit a simplified treatment of non‐associativeness and under certain assumptions can allow use of existing formulations of plasticity by maintaining symmetry of the associated matrices.
Boundary element methods for two‐dimensional problems of transient ground water flow
Authors: Banerjee P. K. , Butterfield R. , Tomlin G. R.
Published: August 2005

Direct and indirect formulations of the boundary element methods are described for two‐dimensional problems of transient ground water low. A numerical algorithm for obtaining solutions to complete any two‐dimensional problem is outlined. The algorithm has been applied successfully to several problems which demonstrate its usefulness in practice.
Earthquake waves in a random medium
Authors: Chu L. , Askar A. , Cakmak A. S.
Published: August 2005

Measurements are conducted with small samples in the laboratory and thus for all practical purposes the medium is macroscopically homogeneous. On the other hand, the uncertainties and the irregular changes in situ are macroscopic inhomogeneities. This work is an attempt to account for these stochastic changes in the elastic properties and density in a rational manner. The method used is that of Karal and Keller which is based on the use of the Green's function and neglect of third‐order correlations. The resulting integral equations are solved by Laplace transform. The analysis indicates that the energy decay in the mean motion through random mode coupling introduces damping into even a purley'elastic medium and enhances the damping in a significant manner in a hysteretic viscoelastic medium. This consideration is important in relating the damping and dispersion characteristics of wave in situ to those measured in the laboratory. The formulation is extended to multilayer systems through transfer matrices and to arbitrary inputs by Fourier transform. Sample calculations are presented for single and multilayer systems to obtain response spectra and for the response to Gaussian and actual earthquake input motions.
Mixed discretization procedure for accurate modelling of plastic collapse
Authors: Marti Joaquin , Cundall Peter
Published: August 2005

Collapse loads are overestimated by finite‐element or finite‐difference procedures when the material discretization does not allow locally incompressible plastic flow: for example, constant‐strain triangles or tetrahedra give unacceptable results. The use of different discretizations for the isotropic and deviatoric parts of the strain tensor is advocated for preventing this problem. The technique can be easily implemented in existing two‐ and three‐dimensional computer programs. Its effectiveness is demonstrated by several examples.
Finite layer analysis of consolidation. II
Authors: Booker J. R. , Small J. C.
Published: August 2005

The theory developed in Part I of this paper is extended to apply to the consolidation of horizontally layered soils under both axially symmetric and general surface loading. The method again leads to a considerable reduction in the amount of core storage necessary for computer solution and can be implimented on a mini‐computer.
A continuum finite element approach for rock failure and rubble formation
Authors: Benzley S. E. , Krieg R. D.
Published: August 2005

A continuum finite element formulation that models the failure of a rock mass, the collapse of this rubble into a void space and the associated bulking of the rubble is presented. This formulation is incorporated into a finite element computer program that treats the large deformation non‐linear motion of axisymmetric and two‐dimensional continua. A dynamic relaxation procedure is used for the solution algorithm. Example calculations are given that demonstrate the formulation.
Slope stability analysis for earthquakes
Authors: Chug Ashok K.
Published: August 2005

The method of slices commonly used for estimating static stability of natural slopes and embankments is extended to include the dynamic effects due to earthquake loading. The equation of motion of a typical slice along a path different from its base is derived. The calculations of displacement of a slide mass using the Newmark procedure are discussed and illustrated with an example problem.
Simulation of air storage aquifer by finite element model
Authors: Meiri David , Karadi Gabor M.
Published: August 2005

A finite element model is developed to simulate the behaviour of an aquifer used as storage space for a compressed air energy storage (CAES) system. The governing equations describing a two‐phase flow of air and water are coupled non‐linear partial differential equations and are solved by the Galerkin approach. The resulting computer model is applied to a gas percolation problem. Upon verification of the numerical results, the model is employed to simulate the air‐water displacement in a storage reservoir during daily air cycling. The corresponding saturation variations and the effects of reservoir permeability on the system are presented. The results obtained are essential in establishing storage design and stability criteria for long‐term operation of compressed air energy storage systems.
Deformation behaviour of Talbingo Dam
Authors: Adikari G. S. N. , Parkin A. K.
Published: August 2005

Talbingo Dam is a well instrumented, 162m high rockfill structure with an upstream sloping silty clay core, located in the southern New South Wales, Australia. A non‐linear finite element analysis of its behaviour was carried out under plane strain conditions, simulating its construction, reservoir filling and steady seepage loading stages. Material parameters are determined from triaxial tests on the rockfill, core, filter and transition materials, compacted to field dry density and moisture content. All materials show non‐linear stress–strain behaviour, with rockfill exhibiting work softening at large strain. Mohr envelopes for rockfill are slightly curved but linear approximations are acceptable. When compared with stresses and deformations at maximum cross section, the analytical results show good agreement in most areas. A non‐linear model for pore pressure response is used successfully to predict the high pore pressures in the lower region of the core. A stability analysis performed for the end of construction stage, based on finite element stresses, shows that the design safety factors are slightly conservative.
Finite‐element modelling of folding and faulting
Authors: Reddy J. N. , Stein R. J. , Wickham J. S.
Published: August 2005

The paper is concerned with the finite‐element modelling of geologic phenomena. More specifically, the paper presents numerical models of folding and sait doming. A (penalty‐) finite‐element model based on the equations governing a viscous incompressible fluid is used to simulate the folding is used to simulate the folding of a viscous layer in a less viscous matrix and the salt dome formation, and to predict the location of active faulting and deformation in prograding delta systems on continentalmargins. The initiation and development of drape folding and associated faulting are also modelled. The United States continental margin of the Gulf of Mexico is used as an example of prograding delta system. The finite‐element predictions seem to agreewith the published results.
Finite‐element modelling of fracture density in single layer folds
Authors: Wickham J. S. , Tapp G. S. , Reddy J. N.
Published: August 2005

The present study is a continuation of the numerical modelling of geologic structures by the authors (see J. N. Reddyet al., Finite‐element modelling of folding and faulting, this journal). The present paper is concerned with the computation of the stress and fracture density distributions in single layer folds by the finite‐element method. It was found that variations in fracture patterns are related to several variables: (i) the viscosity of the competent layer, (ii) the ratio of the viscosity of the competent layer to the viscosity of the matrix, (iii) the cohesive strength of the material, and (iv) the boundary velocities during deformation. The fracture prediction is based on the Mohr–Coulomb criterion, which is a function of the stresses only. Prediction of fracture density is based on a function of the strain energy. It is found that there is a good correlation between the computer predicted fractures and the fracture pattern produced by the expermental buckiing of rock‐beams. Itis, concluded that the viscosity ratio controls the location of fractures in single layer folds.
Propagation of shock waves at the surface of heterogeneous soil grounds
Authors: Holzlöhner U. , Auersch L.
Published: August 2005

The paper deals with the propagation of shock waves at the surface of soils. Heterogeneity and damping are introduced into analytical half‐space solutions. The suggested model explains two phenomena, often observed with shock propagation in actual soils, that differ from the behaviour of the homogeneous half‐space: the pronounced decay of the disturbances with distance and the elongation of the disturbance into a train of waves. The effects of heterogeneity and damping are discussed quantitatively.

The response of footings on heterogeneous soils has been investigated by several authors. Awojobi4 considered the Gibson soil in which the shear modulus increases linearly with depth. Luco5 and Gazetas and Roesset6 investigated a multi‐layered soil, the shear modulus being constant within each layer. Gazetas7, using a technique suggested by Gupta8 extended this method to layers with linearly varying shear modulus. Little work is available on the propagation of waves in heterogeneous bodies. Some results concerning the modes and the mode shapes in heterogeneous soils were reported by Ewing, Jardetzky and Press9 and Bath.10 The modes have to be superposed in an appropriate way to obtain the displacement field at the surface. This has been approximately achieved by the finite element formulations of Lysmer, 11, Lysmer and Waas12 and Waas.13 Auersch14 applied this method to a homogeneous layer on a rigid base. He found some dispersion of the Rayleigh wave within a narrow frequency range. Finite elements combined with discrete Laplace transforms, however, consume much computer time. Rao and Goda15 and Rao16 calculated surface vibrations of a half‐space with exponentially varying shear modulus and density. Their method is similar to Lamb'S1 procedure for the homogeneous half‐space. Only one mode–the Rayleigh wave–occurs in their heterogeneous half‐space. The examples show the considerable effect of heterogeneity on wave propagation. In the present paper, more general variations of the shear modulus are considered.
An analytical solution for the transient response of saturated porous elastic solids
Authors: Simon B. R. , Zienkiewicz O. C. , Paul D. K.
Published: August 2005

The general forms for the field equations governing the transient response of poroelastic media given by Biot and by Zienkiewicz are compared and relations between the material constants are obtained. A one‐dimensional analytical solution is presented for the situation where the solid and fluid materials satisfy Biot'S dynamic compatibility relation. The transient response of porous media is illustrated for varying degrees of solid and fluid compressibility when subjected to step, cyclic and short duration spike surface tractions. The results obtained (for the special situation where the materials are dynamically compatible) exhibit the overall characteristics of wave propagation in porous media and will provide representative test problems which allow a quantitative evaluation of the accuracy of various numerical solution methods (e.g. finite element models).
Seepage analysis in a zoned anisotropic medium by the boundary element method
Authors: Chugh Ashok K. , Falvey Henry T.
Published: August 2005

A simple and effective extension to the boundary element method for solving Laplace'S equation (∇2u = 0) for boundary value problems is presented to solve steady confined and (or) steady unconfined seepage problems in zoned anisotropic mediums. Sample problems indicating the accuracy of results are given.
A non‐linear rheological analysis of deeply located tunnels
Authors: Akagi Tomoyuki , Ichikawa Yasuaki , Kuroda Hidetaka , Kawamoto Toshikazu
Published: August 2005

A rheological model which is able to explain the delayed failure phenomenon has been proposed and applied to the analysis of the time dependent behaviour of deep tunnels. The model is the three element Voigt type before yielding and becomes the five element Voigt type after yielding. This means that the stiffness of the model is decreased by yielding. It is assumed that the yielding takes place when the stored elastic energy density of distortion reaches a certain maximum value. Some experiments to determine material constants are proposed. The numerical results clearly exhibited a delayed failure state of the rock masses around the tunnel surface. It was found that the extension of the yielding zone due to tunnel excavation depends on the opening method.
Plate loading tests on sloping rock
Authors: Vreede F. A.
Published: August 2005

The plate loading test is performed in order to determine the deformation modulus of a rock mass in situ. In the standard execution of this test the loading is applied perpendicular to the rock surface. The displacements are measured on the axis of symmetry, since for an isotropic material with linear deformation characteristics exact formulae are known which are valid at this location. For horizontal strata this presents no problem as it is easy to provide loading in a vertical direction. When the rock strata are dipping it is imprectical to use nonvertical load and it is then necessary to calculate the modulus from the displacements in a non‐axisymmetrical arrangement. Using the well‐known method of the Taylor series approximate formulae are derved which are sufficiently accurate for all practical cases of sloping rock.
Implementation of a general constitutive model for geological materials
Authors: Faruque M. O. , Desai C. S.
Published: August 2005

A generalized constitutive model is described with particular attention to determination of material constants, and its implementation. The model involves use of only a single function to characterize the complete range of plastic yielding, and employs a special function to describe plastic hardening. Laboratory behaviour of an artificial soil is used to iliustrate the determination of the constants and verification of the model.
A quasi‐explicit modification of the two time level family of schemes for non‐linear transient analysis
Authors: Kujawski J. , Desai C. S.
Published: August 2005

A quasi‐explicit modification of well‐known two time level implicit schemes for first‐order, non‐linear initial value problems is presented. Stable and accurate quadratic families for the quasi‐explicit generalized trapezoidal method (GTM) and the generalized midpoint method (GMM) are derived. Accuracy, stability and oscillatory behaviour of the proposed algorithms are studied. Much higher stability and oscillatory levels are obtained for quasi‐explicit modification of the generalized trapezoidal method than those of the generalized midpoint method.
Simple model for transient soil loading in earthquake analysis. I. Basic model and its application
Authors: Zienkiewicz O. C. , Leung K. H. , Pastor M.
Published: August 2005

Several models describing soil response under cyclic loading and the ‘liquefaction’ potential have been introduced in recent years with limited success. Most of these are over‐complex for realistic parameter identification and have not been widely adopted for practical use. In this paper we introduce a relatively simple modification of the well‐known critical state model which accounts reasonably well for the phenomena observed under cyclic tests and indeed improves the performance of critical state, models in monotonic loading.

This model is compared with experimental results and with the ‘densification model’ introduced earlier by the authors and shows good predicitive capacity.

The model is of a generalized plasticity‐bounding surface type. In its simplest form, suitable for clay‐like materials, it requires the identifications of a single parameter additional to those required for a standard, critical state model.
Two‐dimensional consolidation analysis using an elasto‐viscoplastic constitutive equation
Authors: Oka F. , Adachi T. , Okano Y.
Published: August 2005

A two‐dimensional consolidation analysis of clay deposits was made with an elasto‐viscoplastic constitutive model and Biot's consolidation theory. One‐ and two‐dimensional consolidation problems were analysed numerically by the finite element and finite difference methods. Results show that the proposed method can describe the effect of sample thickness and aging on consolidation phenomena. The two‐dimensional behaviour of a clay foundation during the construction of embankments also was simulated.
Three‐dimensional analysis of a pile‐group foundation
Authors: Muqtadir A. , Desai C. S.
Published: August 2005

A non‐linear three‐dimensional finite element procedur is developed and applied for the analysis of pile group foundations. The numerical procedure allows for elastic, non‐linear elastic and elastic‐plastic hardening behaviour of sand. In order to include the interaction effects involving relative slip and debonding, the thin‐layer interface element is used. The predictions for displacements and loads obtained from the numerical procedure are compared with laboratory model test results of a pile group. Displacements, stresses and forces distribution in various components of the pile group are also examined. Furthermore, the effects of the non‐linear soil response and relative motions at the interface are indentified and discussed.
An analytical solution to the design of precast concrete pavements
Authors: Bull John W.
Published: August 2005

Precast concrete pavement units are used in areas with low subgrade CBR values and high static and dynamic loadings. Unlike flexible pavements and rigid pavements, there are no design charts from which pavement engineers can design precast concrete pavements. The author has investigated analytically the relative importance of the factors affecting the ultimate stress and subgrade bearing pressures in precast concrete pavements. Presenting the results in graphical form, the design charts are used toillustrate the new design method.
Limits to the Jaumann stress rate
Authors: Molenkamp F.
Published: August 2005

In this paper it is shown that the Jaumann stress rate is not accurate for moderate deformations with deviatoric strains of more than 10 per cent; in such cases the objective stress rate is better calculated using the material rotation rate as calculated by polar decomposition. For very large deformations of granular materials this approach becomes invalid too because then the fabric tends to rotate together with principal stresses. Apparently in general the fabric rotation of a granular material cannot be described by continuum mechanics alone. For the numerical calculation of the material rotation for moderate deformations a numerical subroutine, based on polar decomposition, has been developed.
A hybrid boundary element‐finite element analysis procedure for fluid flow simulation in fractured rock masses
Authors: Elsworth D.
Published: August 2005

Extension of numerical techniques to the analysis of fissure flow in three‐dimensional rock masses of realistic complexity and extent constitutes an important facility in civil engineering and resource exploitation practice. Migration velocities of contaminants and fluid discharge will always be higher for a true three‐dimensional network over a two‐dimensional representation in that the effect of critical, out‐of‐plane intersections may be correctly accommodated. Revised direct boundary element formulations are developed that are capable of discretizing individual fissure discs and their intersections with adjacent fissures. Discretization coverage, by definition, is limited to the fissure edges and internal intersections, with this factor alone being a major advantage of the technique over the more conventionally utilized domain methods. Appropriate manipulation of the resulting set of equations is shown to yield a fully populated, positive definite, symmetric tensor representing the geometric conductivity of a single fissure disc. The retained degrees‐of‐freedom for the ‘super element’ are purely in terms of the fissure intersections with a minimum of 1 degree‐of‐freedom required per intersection. Global matrix assembly and solution is accomplished by standard finite element techniques, the global matrix being, in general, sparsely populated. The procedure is ideally suited to micro‐computer solution in that a reduced degree‐of‐freedom system is obtained from a much larger and computationally, intractable system. The advantages of boundary solution procedures are realized with minimal data input requirements and effective representation of high potential gradients. The sparsely populated and symmetric from of the global matrix retains one of the more favourable assets of the secondary finite element formulation.
Constants for an elastic–plastic cap model for limestone
Authors: Chu H. S. , Brandt H.
Published: August 2005

Triaxial fracture tests with overburden pressures ranging from 0.69 to 136 MPa were performed to determine the material parameters involved in a cap model for limestone. Three material parameters A, B and C, were evaluated through Powell's optimization method and the remaining parameters through simulation‐curve fitting procedure. The resulting cap model was tested against separate triaxial fracture and hydrostatic compression tests. Modification of the original hardening function, as proposed by DiMaggio and Sandler, provided an improved fit for the experimental data.
Modelling of sand behaviour under earthquake excitation
Authors: Pietruszczak S. , Stolle D. F. E.
Published: August 2005

In this paper, liquefaction potential of loose sand deposit subjected to an earthquake loading is evaluated. The analysis is performed by using a finite element technique incorporating the equations of dynamics of saturated porous elastoplastic media. The soil response is modelled by an anisotropic hardening rule, similar to that as proposed by Poorooshasb and Pietruszczak.1 The concept is based on the theory of bounding surface plasticity incorporating a non‐associated flow rule and the idea of reflected plastic potential. The present paper provides a modified formulation to that discussed in Reference 1. Modifications are aimed at simplifying the concept for numerical implementations.
A nonlinear programming analysis of unconfined steady‐state seepage
Authors: Gioda Giancarlo , Gentile Carmelo
Published: August 2005

A finite element, variable mesh analysis of unconfined steady‐state seepage problems is presented based on a nonlinear programming algorithm. It is shown that the minimization of an objective function which merely represents a measure of the total flux leaving or entering the mesh at the free surface nodes (except those that belong also to pervious boundaries) does not permit a unique definition of the free surface geometry. This problem, which is apparently related to the numerical instabilities often met when using variable mesh approaches, can be eliminated by adding to the objective function a term representing a sort of overall ‘regularity’ condition for the shape of the free surface. The modified solution procedure turns out to be stable and able to provide meaningful results for practical problems even when rather coarse meshes are adopted.
Response of pile groups subjected to lateral loads
Authors: Leung C. F. , Chow Y. K.
Published: August 2005

An approach is presented for the prediction of linear and nonlinear load–deformation behaviour of laterally loaded pile groups. The individual pile response is obtained by the conventional p–y curve technique, while group interaction is modelled using the Mindlin's solution. Good agreement is observed when comparing the present method of analysis with the commonly used interaction factor approach for the computation of response of pile groups embedded in a homogenous, isotropic elastic half‐space. The predicted pile group behaviour also compares favourably with existing field data on laterally loaded pile groups in soft clay.
Boundary element elastic analysis of layered soils by a successive stiffness method
Authors: Maier G. , Novati G.
Published: August 2005

The elastostatic analysis of layered systems (such as a soil consisting of a set of L individually homogeneous strata) is tackled here on the basis of discretized boundary integral equations (boundary element method). By exploiting the peculiar chain‐like pattern of the system, a recursive formula is obtained which generates economically a ‘stiffness matrix’ of the first n layers (from bottom) at the upper interface with the subsequent layer (n = 1…L). The ‘successive stiffness’ method proposed is shown to imply noteworthy advantages with respect to both the standard boundary element method by zones (or subregions) and another ad hoc, earlier method resting on a boundary element approach combined with the transfer matrix concept. This conclusion is corroborated by two‐dimensional examples.
Viscoplastic model for geologic materials with generalized flow rule
Authors: Desai C. S. , Zhang D.
Published: August 2005

The general yield function in the hierarchical approach for constitutive modelling of materials is used with Perzyna's theory to characterize viscoplastic behaviour of geologic materials: a sand and rock salt. Particular attention is given to determination of the constants from laboratory quasistatic or short term, and creep tests. The proposed model is verified with respect to observed laboratory response of the sand and salt. It is implemented in a non‐linear finite element procedure and applied to analyse time‐dependent behaviour of a cavity in the rock salt.
Axial and lateral response of pile groups embedded in nonhomogeneous soils
Authors: Chow Y. K.
Published: August 2005

A numerical method of analysis based on elasticity theory is presented for the analysis of axially and laterally loaded pile groups embedded in nonhomogeneous soils. The problem is decomposed into two systems, namely the group piles acted upon by external applied loads and pile–soil interaction forces, and a layered soil continuum acted upon by a system of pile–soil interaction forces at the imaginary positions of the piles. The group piles are discretized into discrete elements while the nonhomogeneous soil behaviour is determined from an economically viable finite element procedure. The load–deformation relationship of the pile group system is then determined by considering the equilibrium of the pile–soil interaction forces, and the compatibility of the pile and soil displacements. The influence of soil nonlinearity can be studied by limiting the soil forces at the pile–soil interface, and redistributing the ‘excess forces’ by an ‘initial stress’ process popular in elasto‐plastic finite element analysis. The solutions from this approach are compared with some available published solutions for single piles and pile groups in homogeneous and nonhomogeneous soils. A limited number of field tests on pile groups are studied, and show that, in general, the computed response compares favourably with the field measurements.
Interaction between torsional and axial pile responses
Authors: Georgiadis Michael
Published: August 2005

The effect of axial load on the torsional pile response and the effect of torque on the axial pile response are investigated. To perform this investigation, a computer program was developed which uses the transfer matrix method to analyse a pile supported by a series of coupled axial and torsional elasto‐plastic springs. The study indicated that the ultimate torsional and axial pile capacities, as well as the axial displacements and rotations, are significantly affected by the combined load action.
Multi‐laminate framework of soil models—plasticity formulation
Authors: Pietruszczak S. , Pande G. N.
Published: August 2005

This paper presents plasticity formulation of the multi‐laminate framework of soil models. Soil element is assumed to be an assemblage of perfectly fitting polyhedral blocks and irreversible deformations are assumed to occur due to sliding, separation/closing of the boundaries. Using an appropriate summation of mechanisms, the total plastic strains are obtained by evaluating contributions from an infinite number of randomly oriented planes in space. The paper provides a general plasticity formulation and examines various constitutive theories which can be incorporated into the framework.
An axisymmetric lagrangian technique for predicting earth penetration including penetrator response
Authors: Schwer Leonard E. , Rosinsky Russel , Day James
Published: August 2005

A computational technique for earth penetration is presented which includes the direct coupling between the deformable target model and a deformable model of the penetrator. In this fully Lagrangian approach, both the target and penetrator are discretized to represent the anticipated terradynamic and structural responses. A sliding interface is used between the two models to provide the time‐dependent terradynamic‐to‐penetrator interaction. This technique has the unique advantage of including the target‐to‐penetrator interaction in one calculation in a continuous and consistent manner. Comparisons of calculated penetration with full‐scale field test data are given.
Pseudo‐plane strain analysis of wave propagation problems arising from detonations of explosives in cylindrical boreholes
Authors: Ang K. K. , Valliappan S.
Published: August 2005

Wave propagation problems, such as blasting for excavation of a new tunnel oriented perpendicular to an existing tunnel, are truly three dimensional in nature. Dynamic finite element analysis with three‐dimensional elements is, however, very expensive. The cheaper and simpler alternative would be to model the problem approximately in two dimensions. This paper shows that dynamic finite element analysis of such problems using conventional two‐dimensional plane strain elements produces responses which are erroneously excessive. This is accredited to the inability to the inability of the two‐dimensional elements to correctly model the rapid attenuation of the amplitudes of the outward propagating waves. To overcome this problem, a pseudo‐plane strain concept is introduced and has been found to be a viable alternative. Numerical results are presented to demonstrate the application of the concept.
Analysis of double shearing in frictional materials
Authors: Teunissen J. A. M. , Vermeer P. A.
Published: August 2005

The concept that the flow of granular materials is governed by shear on certain critical planes is used to formulate an elastic–plastic model. When the elastic strains are neglected, the Double Shearing model becomes identical to the rigid‐plastic model of de Josselin de Jong which he named the Double Sliding model. After a discussion of the model, the small strain formulation is used to describe general boundary‐value problems. A comparison is then made between the coaxial Mohr–Coulomb yielding and the Double Shearing model on the basis of several numerical simulations. The non‐coaxiality of the axes of principal plastic strain rate and principal stress in the Double Shearing model leads to essentially different behaviour for stress rotations in comparison to the coaxial model. The Double Shearing model predicts in general lower limit loads because, for a given state of stress, it allows for several possible directions of plastic flow rather than a unique direction which derives from a plastic potential.
A variational principle for granular materials
Authors: Chandler H. W.
Published: August 2005

A major problem in the mathematical modelling of the deformation of granular materials has been the lack of an easily usable variational principle. This is because the frictional dissipation of energy in these materials does not allow the use of the classical extremum principles. In this paper, a variational principle is constructed which is valid even when frictional dissipation occurs. Its derivation uses results from the mathematical theory of envelopes. Both the stresses and the strains can be varied, and for the case of non‐frictional plasticity it reduces to the maximum work principle of Hill. An example is presented to show how this new principle can be used to obtain approximate solutions to boundary‐value problems with granular materials. The only requirements in advance are a displacement field that obeys the kinematic boundary conditions, and a stress field that obeys equilibrium and the static boundary conditions. The principle is therefore quite straightforward to apply.
Dispersion law of rayleigh‐type waves in a compressible gibson half‐space
Authors: Vardoulkis I. , Vrettos Ch.
Published: August 2005

An analytical‐numerical examination has been made of the behavior of harmonic Rayleigh‐type waves in a compressible elastic half‐space of constant density and whose shear modulus increases linearly with depth. The dispersion law is presented for values of Poisson's ratio of 1/2, 1/3 and 1/4 for wide ranges of degree of inhomogeneity.
Thermal stress analysis of underground openings
Authors: Kumar P. , Singh B.
Published: August 2005

In the use of underground space for storage of solar energy, storage of excess heat from thermal power plants and containment of nuclear waste, the host medium is subjected to a thermal field accompanied by a thermal stress field. These stresses may endanger the stability and integrity of the structure. In this paper, the stress field, in circular and spherical openings, due to a given thermal field is analytically determined and numerically verified. Both lined and unlined openings are considered. The numerical and analytical results are in a satisfactory agreement. The lining stresses, support pressure and radial interface displacement depend only on the thermal field in the lining. A simplified method of stress computation applicable to a thin lining is also presented.
Effect of a shear seam in the foundation of Karjan Dam
Authors: Varadarajan A. , Sharma K. G.
Published: August 2005

The use of the limit equilibrium method for the analysis of a dam foundation with a weak shear seam has many limitations. There is further uncertainty in such an analysis by this method when the seam is intercepted by a concrete key. The finite element method is the best alternative means of analysing such problems. In this paper, the finite element analysis of the Karjan Dam (India) foundation, which has a shear seam, is presented with and without the foundation treatment (i.e. the concrete key). The seam is simulated by joint elements. It has been found that a concrete key located near the toe of the dam significantly improves the stability of the foundation.
Mechanics of a sandy subsoil subjected to cyclic loadings
Authors: Sawicki Andrzej , Swidzinski Waldemar
Published: August 2005

A simple model for compaction of a sand, that may be useful in various geotechnical applications is presented. The model has been formulated in terms of the cyclic stress and strain amplitudes. The compaction properties of a dry sand are characterized by a common compaction curve described by two coefficients.

The second aim of this paper is to show some applications of the theory proposed. The attention has been restricted to the two extreme cases of practical importance, namely to the behaviour of a dry sand (or a saturated sand but in free draining conditions), and to the behaviour of saturated sand in undrained conditions. Some numerical algorithms showing how to deal with those problems are presented and illustrated on the following examples: settlement and pore pressure generation in a soil stratum subjected to an earthquake, settlement of a foundation, pore pressure generation and liquefaction in a sea‐bed.

The results obtained suggest that the model proposed, as well as a method of dealing with boundary value problems can serve as a useful tool for the analysis of a sandy subsoil subjected to cyclic loadings.
Finite element analysis of underground openings
Authors: Sharan S. K.
Published: August 2005

A highly efficient technique is presented for the finite element analysis of stresses around underground openings surrounded by an infinite extent of linearly elastic rock mass. The effect of unbounded rock is incorporated in the analysis by using elastic supports around the finite element model. Expressions for stiffnesses of the elastic supports are derived and these are found to depend on the location of elastic supports, the shear modulus and Poisson's ratio of the rock, and the ratio of horizontal to vertical initial stresses. With the use of the proposed technique, the extent of the finite domain to be considered in the analysis is highly reduced. This results in a great computational advantage. The other principal merit of the proposed technique is that a standard finite element code for stress analysis may be used without making any modification. Results of some numerical tests are reported to demonstrate the effectiveness and efficiency of the proposed method. The technique has the potential of being applied to more complex problems of unbounded domains in geomechanics.
A mathematical model of permeability alteration around wells
Authors: Olarewaju Joseph S.
Published: August 2005

This paper presents an analytical solution of the permeability alteration problem around the wellbore. This alteration may be a permeability reduction due to drilling fluid invasion or mudcake formation around the wellbore. On the other hand, the alteration may be a permeability increase resulting from stimulation by acidizing the formation matrix around the well. This permeability discontinuity in a reservoir forms a composite reservoir system. With the composite model, both the degree and the radial extent of permeability alteration can be adequately predicted. The conventional skin concept is inadequate and physically unrealistic in most of these cases.

This paper describes the application of an automatic weighted constrained least‐squares parameter estimation technique and the analytical model for pressure transient analysis. The parameters of the composite reservoir system are determined from a match of the pressure transient data. The behaviour of the pressure transient in such composite systems is presented using the analytical solution.
Land subsidence due to gas/oil production in inhomogeneous transversally anisotropic half‐space by a boundary element method
Authors: Sartoretto Flavio , Gambolati Giuseppe , Rinaldo Andrea
Published: August 2005

In a previous paper1 the authors have developed and implemented a new boundary element (BE) model to simulate and predict land subsidence occurring over three‐dimensional gas/oil fields in a homogeneous and isotropic half‐space. The approach relies on Betti's reciprocal theorem and makes use of the classical fundamental solution of Boussinesq in the framework of the theory of linear poroelasticity. The BE method is here extended to inhomogeneous, transversally anisotropic soils by the aid of a two‐dimensional finite element (FE) model which provides a fundamental numerical solution for the actual multi‐layer setting of the subsurface system. The new FE–BE approach is then used to simulate the subsidence caused by gas production over the deep reservoir of Campo Ravenna Terra, Ravenna (Italy) from 1950 to 1980. The results compare very favourably with the outcome from a full more expensive three‐dimensional FE model of the same occurrence.
Contaminant migration in a regular two‐ or three‐dimensional fractured network: Reactive contaminants
Authors: Rowe R. K. , Booker J. R.
Published: August 2005

A semi‐analytic solution for the migration of dilute reactive contaminant species in a fractured medium having a one‐, two‐ or three‐dimensional fracture network is presented. The application of the technique to practical problems is discussed and illustrated by examples. The effects of sorption in the matrix and on the surface of the fractures are considered for a range of parameters. It is demonstrated that the synergistic interaction of the various parameters is such that the effect of changing a single variable may not be immediately obvious and a designer should perform computations for the range of expected parameters to determine the maximum impact. For example, it is shown that it is not necessarily conservative to consider only one‐dimensional or only three‐dimensional diffusion into the matrix; which of these cases is most critical will depend on the values of other parameters. It is also shown that an effective leachate collection system may significantly reduce the impact of those contaminants which do escape into the fractured media.
Pore fluid frictional heating and stability of creeping landslides
Authors: Davis R. O. , Smith N. R. , Salt G.
Published: August 2005

An examination of the effects of frictional heating of pore fluid in relation to long‐term slope stability is presented. It is found that increases in pore‐fluid pressure due to heat‐induced expansion may act to enhance creep rates and possibly lead to total loss of stability. Conditions for total stability loss are examined and an approximate critical value of average shear stress is determined. This value must be exceeded for a sufficiently long period of time in order to induce rapid failure.
Three‐dimensional discrete element method for granular materials
Authors: Ghaboussi Jamshid , Barbosa Ricardo
Published: August 2005

This paper describes a three‐dimensional discrete element method of analysis for granular materials. Individual particles are modelled as rigid, six‐sided solids with six degrees of freedom. Various types of contacts are possible among the three‐dimensional discrete elements. Models for these contact types are described. Computational aspects of the method, such as techniques for contact detection and data structure, are addressed. Selective results of three examples that demonstrate the application of the method to granular flow problems are presented and discussed.
Size effect on damage parameters for softening in simulated rock
Authors: Desai C. S. , Kundu T. , Wang G.
Published: August 2005

Laboratory uniaxial tests on cylindrical specimens of a simulated rock are used to identify the influence of the diameter (D) and height (L) of the specimens on the damage parameters. The relations are expressed in terms of the characteristic parameter C = L2/D.
A linearized integration technique for incremental constitutive equations
Authors: Bardet J. P. , Choucair W.
Published: August 2005

A numerical technique is proposed to obtain stress–strain response curves from rate‐type and incremental constitutive equations during generalized loadings. The proposed method linearizes the loading constraints of laboratory experiments, links them to the constitutive relations, and forms a linear system of ordinary differential equations. It circumvents the difficulties associated with the non‐uniqueness and bifurcation of boundary value problems. The method is illustrated for the elastoplastic von Mises and Roscoe and Burland models subjected to torsion, circular stress path, and undrained triaxial compression. The approach pertains to most stress–strain relationships and laboratory experiments of geomechanics. It is useful for research on material modelling, engineering practice and computational mechanics.