bluuebunny/crossref_metadata_2025_split huggingface dataset:
A finite element analysis of direct shear tests on stiff clays
Authors: Cividini Annamaria , Gioda Giancarlo 
Published: August 2005

AbstractA finite element analysis is presented of some direct shear tests carried out on samples of a stiff, heavily overconsolidated clay. The effects of softening are accounted for through a simple material model which views this phenomenon as a consequence of an intrinsic loss of strength of the material taking place when plastic strains increase. After illustrating the main characteristics of the finite element approach, with particular reference to the correct determination of the non‐reversible strains, its use in the interpretation of the mentioned shear tests is discussed. Some comments are also presented on the mesh dependence of the numerical results, and on the use of a relation between material parameters and element size which reduces this negative effect. Finally, the solution procedure is applied to the simulation of a compression test in order to investigate the possibility of numerically detecting the ‘spontaneous’ (i.e. not directly induced by the boundary conditions) formation of shear zones within the specimen.
Analytical modelling of hammer impact for pile driving
Authors: Deeks A. J. , Randolph M. F. 
Published: August 2005

AbstractEstimation of the drivability of piles requires modelling of the hammer impact in order to provide the input force wave at the pile head. Historically, this has been achieved through a numerical model of the hammer components (ram, cushion and anvil), which is then linked with that of the pile in order to effect the drivability analysis. This paper presents an analytical model of hammer impact, based on lumped ram and anvil masses separated by a cushion with internal damping, and connected to the pile which is modelled as a dashpot. Force–time responses derived from the analytical model are compared with actual field data, and also with results from commercially available numerical models of hammer impact. The analytical model is then used to explore the characteristics of hammer impact, with particular attention to combinations of parameters that lead to hammer bounce and, hence, significant loss of energy transferred to the pile.
Modelling coupled heat and contaminant transport in groundwater
Authors: Hensley P. J. , Savvidou C. 
Published: August 2005

AbstractThis paper presents the results of a research programme conducted on the geotechnical centrifuge at The University of Western Australia to investigate coupled heat and contaminant transport in the soil surrounding a buried waste source. The phenomena which govern heat and contaminant transport through porous media are discussed, the principles of geotechnical centrifuge modelling are outlined, and relevant scaling laws that govern the relationship between a centrifuge model and the prototype, with respect to the problem of coupled waste transport, are presented. A model test, simulating two‐dimensional migration from a buried heat and contaminant source, is described, and the results from four model tests are presented. The experimental data show that hydraulic instability is responsible for the transport of contaminant in the soil around the source and that the mode of instability is determined by the magnitude of the effective Rayleigh number.
Finite element modelling of three‐phase flow in deforming saturated oil reservoirs
Authors: Lewis R. W. , Sukirman Y. 
Published: August 2005

AbstractA numerical simulation is presented for three‐dimensional three‐phase fluid flow in a deforming saturated oil reservoir. The mathematical formulation describes a fully coupled governing equation systen which consists of the equilibrium and continuity equations for three immiscible fluids flowing in a porous medium. An elastoplastic soil model, based on a Mohr–Coulomb yield surface, is used. The finite element method is applied to obtain simultaneous solutions to the governing equations where displacement and fluid pressures are the primary unknowns. The final discretized equations are solved by a direct solver using fully implicit procedures. The developed model is used to investigate the problems of three‐phase fluid flow in a deforming saturated oil reservoir.
An ellipse‐based discrete element model for granular materials
Authors: Ting John M. , Khwaja Mahmood , Meachum Larry R. , Rowell Jeffrey D. 
Published: August 2005

AbstractThe discrete element method (DEM) models granular materials numerically as a collection of particles rather than as a continuum. Difficulties can arise when using the more common circular and polygonal shapes for modelling real granular materials. In particular, use of discs and spheres leads to typically low aggregate internal friction angles compared with real materials. This paper presents the detailed formulations for using the ellipse shape in discrete element modelling. Robust algorithms for computing ellipse‐ellipse and ellipse‐wall intersections are presented. Also shown are equations to assist in parameter selection and evaluation of macroscopic stresses and strains from the contact data. An initial validation test suite on rods of varying particle aspect ratio are presented. These results indicate that the ellipse‐based DEM results in mechanical behaviour that is similar, both qualitatively and quantitavely, to the behaviour of real soils.
Numerical solution for the dilation of a fluid‐saturated porous elastic sphere due to a point source of fluid at the centre of the sphere
Authors: Solomon A. , Mason D. P. , Nicolaysen L. O. 
Published: August 2005

AbstractMathematical modelling of the ascent of free fluid through relatively strong rock, deep in the Earth's mantle, presents a challenge in geomechanics. Here the medium is considered as fluid‐saturated, porous, elastic and bounded, and the fluid enters at a point source. An explicit finite difference method is developed for the numerical solution to the problem of the dilatation of a fluid‐saturated porous elastic sphere due to a point fluid source of constant strength at the centre of the sphere. A cubic spline interpolant is used to evaluate a definite integral which occurs in the boundary condition for the pore fluid pressure at the surface of the sphere. The numerical solutions for the dilatation and pore fluid pressure are compared with analytical solutions and the absolute and relative errors of the numerical solutions are calculated. When the fluid source is switched on, the pore fluid pressure starts to decrease, reaches a minimum value and then steadily increases. The initial time rate of decrease of the pore fluid pressure is independent of the radial distance from the source. It decreases as the radius of the sphere increases and vanishes for a point fluid source in an infinite porous elastic medium.
A review of models for predicting the thermomechanical behaviour of soft clays
Authors: Seneviratne H. N. , Carter J. P. , Airey D. W. , Booker J. R. 
Published: August 2005

AbstractThis paper critically examines the use of the modified Cam clay stress–strain model in predicting the thermomechanical behaviour of soft clays. The equations governing the thermomechanical behaviour of a saturated soil are summarized and their methods of solution are briefly discussed. The observed thermomechanical soil behaviour reported in the literature has been compared with the predictions made using the modified Cam clay model. In making these comparisons, two extensions of the well‐known modified Cam clay model have been considered: one proposed by Britto et al.1 in which heating induces thermal stresses and strains in the soil but has no direct effect on the work hardening, and the other proposed by Hueckel and Borsetto2 in which a change in temperature also affects the yield surface. The comparisons are confined to the behaviour of normally and lightly overconsolidated clays, where the modified Cam clay is known to perform well. Apart from the effect of a single heating–cooling loop, cyclic behaviour is not considered. It is concluded that both models provide reasonable predictions under isotropic stress conditions. Although exhaustive comparisons have not been made for deviatoric stress excursions (because of the lack of experimental data), it appears from preliminary studies that neither model performs particularly well for this form of loading.
Continuum model and analysis of wick‐drained systems
Authors: Amirebrahimi Amir M. , Herrmann Leonard R. 
Published: August 2005

AbstractAn equivalent homogeneous continuum theory is developed for modelling discretely drained soil stratum. The model accounts for the local horizontal flow to discrete vertical drains such as wick or sand or stone columns as well as direct vertical drainage of the soil and global horizontal flow due to non‐uniform horizontal conditions. Calibration curves for the model are presented for the case of no soil smear due to the drain installation and for the case when smear exists. The model is implemented in both analytical and finite element analyses for those cases where no well resistance is present and when it is of importance. The accuracy and applicability of the model is demonstrated for simple one‐ and two‐ layered problems including smear and well resistance.
An approximate analysis procedure for piled raft foundations
Authors: Clancy P. , Randolph M. F. 
Published: August 2005

AbstractA piled raft foundation comprises both piles and a pile cap that itself transmits load directly to the ground. The aim of such a foundation is to reduce the number of piles compared with a more conventional piled foundation where the bearing effect of the pile cap, or raft, is ignored. This paper describes a ‘hybrid’ approach for the analysis of piled raft foundations, based on a load transfer treatment of individual piles, together with elastic interaction between different piles and with the raft. The numerical analysis is used to evaluate a simple approximate method of estimating the overall response of the foundation from the response of the component parts. The method leads to estimates of the overall foundation stiffness, the proportion of load carried by the pile group and the raft, and an initial assessment of differential settlements. Parametric studies are presented showing the effect of factors such as raft stiffness and pile spacing, length and stiffness, and a worked example is included demonstrating the accuracy of the approximate design approach.
Numerical modelling of transient contaminant migration problems in infinite porous fractured media using finite/infinite element technique. Part II: Parametric study
Authors: Zhao Chongbin , Valliappan S. 
Published: August 2005

AbstractUsing the numerical model presented in the first paper of this research,1 a parametric study has been carried out in this paper to investigate the effect of several important parameters on the transient contaminant transport in infinite porous fractured media. From the related numerical results, it has been demonstrated that: (1) transmissive coefficient between the porous block and the fissured network has a significant influence on the value of the concentration but has little effect on the speed of contaminant transport; (2) porosities in the porous block and fissured network have a significant influence on the maximum value of the concentration; (3) average linear velocity of flow has a significant influence on both the concentration distribution and speed of contaminant transport; (4) dispersion coefficient of the medium affects not only the shape of the concentration versus time curve but also the peak value of the concentration.
Interpretation of cone penetration results in multilayered soils
Authors: Vreugdenhil Roger , Davis Rob , Berrill John 
Published: August 2005

AbstractA simple approximate analysis is presented for interpretation of cone penetration results when the cone resistance is affected by layering of soils with different stiffnesses. It is argued that the cone resistance senses the presence of a nearby layer elastically, and an approximate elastic analysis is developed to quantify the effect. Good comparisons with calibration chamber experimental results are found.
A three‐invariant smooth cap model with mixed hardening
Authors: Schwer Leonard E. , Murray Yvonne D. 
Published: August 2005

AbstractA cap model is presented that uses a multiplicative formulation to define a smooth (continuous derivative) failure surface that includes the third stress invariant. This formulation offers several advantages over previous cap model formulations: elimination of ‘corner’ coding, resulting in a numerical algorithm suitable for vectorization; a three stress invariant implementation that is easily specialized to classical failure surfaces or generalized to represent observed material response; and a framework for easily implementing additional model features such as kinematic hardening as demonstrated.
Unified 3D critical state bounding‐surface plasticity model for soils incorporating continuous plastic loading under cyclic paths. Part I: Constitutive relations
Authors: Crouch Roger S. , Wolf John P. 
Published: August 2005

AbstractThe unified three‐dimensional (3D) critical state bounding‐surface plasticity model gUTS enables clays, silts and sands to be treated within a single framework. Furthermore, loose and dense states of a particular soil subjected to a wide range of confinements are viewed as a single material defined by the same set of constants. The model is able to handle both monotonic and complex cyclic paths including those involving a rotation of the principal stress directions. The model incorporates the following features: combined use of radial and deviatoric mapping rules and the use of an apparent normal consolidation line for sands; use of a non‐associated flow rule where the ratio of the rates of volumetric plastic strain to deviatoric plastic strain is a function only of the ratio of deviatoric to mean effective stresses and the Lode angle; adoption of a bi‐linear critical state line projected onto the plane of the void ratio versus logarithm of mean effective stress; inclusion of a sub‐elliptic, or super‐elliptic, segment in the plastic dilatancy surface for stress ratios less than critical; use of elliptic segments in the deviatoric planes; movement of the projection centre in the deviatoric mapping region and incorporation of a plastic stiffening effect for cyclic paths which repeatedly load in the same deviatoric direction.
Wave‐induced soil response in an unsaturated anisotropic seabed of finite thickness
Authors: Hsu J. R. C. , Jeng D. S. 
Published: August 2005

AbstractAn analytical solution for the wave‐induced soil response is developed for a seabed of finite thickness subject to a three‐dimensional (3‐D) wave system produced by two intersecting waves of equal properties. These 3‐D exact solutions for the pore pressure and effective stresses, proposed for a non‐cohesive soil matrix of finite depth in a homogeneously unsaturated and anisotropic condition, are readily reducible to the limiting two‐dimensional cases of progressive and standing waves, for which no explicit solutions are available for finite thickness. The effects of soil isotropy, degree of saturation, seabed thickness and grain size on the wave‐induced pore pressure are discussed in detail. The explicit solutions presented in this study for the wave‐induced pore pressure and effective stresses should benefit the laboratory experiments and field monitoring programs carried out in soil of finite depth.
Localization problems in plasticity using finite elements with adaptive remeshing
Authors: Zienkiewicz O. C. , Huang Maosong , Pastor M. 
Published: August 2005

AbstractVarious computational procedures have from time to time been suggested to solve problems involving strain localization. One of these is adaptive remeshing — but here occasional failures were experienced if the original mesh was not suitably aligned. We show in this paper that such failures are mainly due to non‐robust formulation of the plasticity problem — and illustrate an automatic and generally applicable adaptive procedure on several examples.
Response of a circular opening in a friable low‐permeability medium to temperature and pore pressure changes
Authors: Wang Yarlong , Dusseault Maurice B. 
Published: August 2005

AbstractA general analysis using an incremental elastic, perfectly plastic constitutive stress–strain relationship for poroelastoplastic materials is presented to simulate an opening in a low‐permeability friable porous medium under non‐isothermal conditions. Analytical solutions are obtained for the stresses and strains around a 2‐D plane strain circular borehole. An expansion potential is introduced by combining the strains induced by temperature and pore pressure changes. Steady‐state pressures and temperatures are considered, and a non‐associated plastic flow rule is applied to calculate plastic strains. Focusing on stress distribution near a circular opening, the classic solutions for those stresses under dry and isothermal conditions are used to compare with the newly derived solution. The general poroelastoplastic effect and the thermal effect on sand production and borehole stability are addressed. We suggest that the knowledge of stress history is critical to achieve adequate solutions for displacement and stress in friable media such as clays, shales and oil sands.
Crack stability analysis for rock fracture toughness tests
Authors: Wang Qi‐Zhi 
Published: August 2005

AbstractA stable crack extension is a precondition for fracture toughness tests using chevron‐notched specimens. The paper analyses the stability problem for crack extension in two chevron‐notched specimens suggested by ISRM. Stability factors are calculated with various compliances of testing machine under different loading conditions. It is pointed out that the loading manner, compliance of the testing machine, as well as the specimen configurations have great influence on crack growth stability.
On the linear relations of V–ln p and ln v–ln p for isotropic consolidation of soils
Authors: Hashiguchi K. 
Published: August 2005

AbstractThe well‐known linear relation between the specific volume and the logarithm of the pressure for the isotropic consolidation has been widely incorporated into elastoplastic constitutive equations of soils. It is, however, indicated in this article that this relation has several physically unaccepted properties. Instead of this relation it is recommended to incorporate the linear relation between both logarithms of the volume and the pressure into constitutive equations, which does not have any of the unrealistic properties.
Bifurcations at a spherical cavity in a compressible solid with spherical isotropy
Authors: Chau K. T. 
Published: August 2005

AbstractThis paper investigates bifurcations, including surface mode and localized mode of deformations, at a spherical cavity in an infinite compressible solid with spherical isotropy. Two types of surface modes are found satisfying the zero traction rate conditions on the surface of the hole: (1) the torsional modes, corresponding to bifurcations with zero radial velocity and zero rate of dilatation; and (2) the spheroidal modes, corresponding to bifurcations with zero rate of spin on the tangential planes. Both of these bifurcations can be written in terms of surface harmonics of degree n. Three‐dimensional pictures of some of the bifurcation modes are devised for both torsional and spheroidal modes, showing both the displaced nodes and nodal lines. Torsional bifurcation occurs only if the ratio of the radial shear modulus to the tangential shear modulus (Gr/Gt) vanishes. Three types of spheroidal modes are possible depending on the combination of the five material parameters; their eigenvalue equations are obtained analytically. As expected, numerical results show that the conditions of bifurcations are independent of the size of the spherical hole. Radial bifurcation modes (n = 0) are always possible at the peak applied stress; and pre‐peak bifurcations are also possible for mode shapes composed of surface harmonics of higher degree (n > 0). Spherically isotropic solids (i.e. Gt/Gr < 1) are more conducive to bifurcations than isotropic solids if n > 2. Surface mode with large degree (n → ∞ ) is not necessarily the lowest possible bifurcation; this finding differs from the conclusion by Bassani et al.1 for incompressible isotropic solids.
A generalized procedure for the optimum design of nailed soil slopes
Authors: Sabhahit N. , Basudhar P. K. , Madhav Madhira R. 
Published: August 2005

AbstractA new method is proposed for the optimum design of nailed soil slopes. A rigorous method of stability analysis, namely the Janbu's method, is modified in the limit equilibrium formulation, considering the effect of reinforcement. Only the tensile resistance of the reinforcement is included and the effects of shear and bending neglected. The total reinforcement force required to raise the factor of safety to a desired value has been minimized with the inclinations of the reinforcement and the distribution of the reinforcement forces as decision variables. In order to illustrate the efficacy of the proposed method, the results are compared with the available solutions. The effect of the number and relative locations of the reinforcements on the amount of reinforcement required, is studied. The lengths of reinforcement required to raise the factor of safety to various desired values and the corresponding optimum designs are presented. The acceptability of the critical surface is verified, by ensuring that the shear and normal stresses are positive along the critical surface.
Thermoelastic and thermoplastic response of a porous space submitted to a decaying heat source
Authors: Giraud A. , Rousset G. 
Published: August 2005

AbstractA general solution scheme is developed for one‐dimensional and non‐isothermal consolidation problems for fluid‐saturated, porous, thermoelastic media. Two fundamental parameters which describe the coupling effects between thermal, hydraulic and mechanical behaviour are: ratio of thermal and hydraulic diffusivity and ratio of thermomechanical deformabilities in drained and undrained conditions. The solution scheme has been applied to the nuclear waste disposal problem. A solution for a thermoporoelastic rock mass containing a decaying heat source is presented. Numerical results show that coupling effects are most pronounced for low permeability and high porosity media such as deep compressible clays. This corresponds to a low value of the ratio of hydraulic and thermal diffusivities and a high value of the ratio of deformabilities in drained and undrained conditions.Comparison with numerical simulations taking into account the non‐linear and non‐reversible behaviour of the rock mass is presented. It shows that the thermoelastic model is quite correct for temperature and displacement fields, and gives maxima of the pore pressure and stress elevations.