bluuebunny/crossref_metadata_2025_split huggingface dataset:
Generalized plasticity and the modelling of soil behaviour
Authors: Pastor M. , Zienkiewicz O. C. , Chan A. H. C. 
Published: August 2005

AbstractThe paper outlines the theory of generalized plasticity in which yield and plastic potential surfaces need not be explicitly defined, and shows how a very effective general model describing the behaviour of sands and of clays under monotonic or transient loading can be developed. The model is currently one of the simplest and yet one of the most effective ones for describing the full range of behaviour.The hierarchical structure of the model limits the number of parameters which have to be experimentally determined for a given material to those strictly necessary for the problem at hand.A discussion of currently used models is included.
In‐plane vibrations of soil deposits with variable shear modulus: I. Surface waves
Authors: Vrettos Ch. 
Published: August 2005

AbstractThe propagation characteristics of dispersive SV/P surface waves are analytically studied in a linear‐elastic, isotropic, compressible half‐space with constant mass density and Poisson's ratio and shear modulus increasing according to a continuous, bounded function of depth. Dispersion relations for the particular wave modes are evaluated over wide ranges of the parameters involved. Displacement profiles are presented for typical values of these parameters. Finally, an equivalent depth is given for use in connection with steady‐state vibration techniques for site investigation.
Buckling of layered elastic media: A cosserat‐continuum approach and its validation
Authors: Papamichos E. , Vardoulakis I. , Mühlhaus H.‐B. 
Published: August 2005

AbstractIn this paper the stability of layered, anisotropic, hypoelastic media under initial stress is investigated. The bifurcation problem is formulated and solved numerically by use of a semi‐analytical transfer matrix method. An alternative analytical approach in dealing with inhomogeneous media is developed by representing a periodically layered medium as a homogeneous Cosserat continuum. The Cosserat‐continuum approach is validated against the numerical transfer matrix solution.
A residual force finite element approach to soil–structure interaction analysis
Authors: Lai J. Y. , Booker J. R. 
Published: August 2005

AbstractAn iterative process based upon a hybrid ‘residual force’ method is presented for solving elasto–plastic soil–structure interaction problems. In this approach the soil and the structure are treated as separate bodies and related only by compatibility of displacements and equilibrium of forces at the soil–structure interface. This scheme enables a significant improvement in numerical stability and rate of convergence over the conventional initial stress method. It is also shown that various interface conditions such as shear failure, slip and breakaway, and frictional and dilatant behaviour can be readily accounted for. Some practical aspects associated with the proposed scheme are emphasized for a number of numerical examples.
Interaction of multiple cracks and formation of echelon crack arrays
Authors: Du Yijun , Aydin Atilla 
Published: August 2005

AbstractFracturing of rock under compression is a product of a series of processes, including nucleation, growth, interaction and coalescence of multiple microcracks. The formation of echelon arrays of microcracks and macrocracks is one of the crucial rings in the processes. We use a superposition and asymptotic approximation technique to analyse the interaction of multiple cracks with various geometrical configurations. It is shown that crack geometry has a strong influence on crack interaction. Echelon crack arrays produce the strongest interaction and are the preferred geometrical configuration for multiple cracks prior to the formation of through‐going shear fractures. This technique provides parameter‐dependent global behaviour, and is more efficient and easier to use.
Numerical analysis of the shape effect on the tensile strength evaluation of axisymmetric specimens
Authors: Zhang L. C. 
Published: August 2005

AbstractThis paper analyses the shape effect on the tensile strength of axisymmetric rock specimens by an improved adaptive dynamic relaxation method. It is shown that the present approach is convenient and efficient. Numerical results for spheroidal specimens with different shapes reveal the variation of stress distributions along the loading axes and suggest that loading along the shorter principal axis is preferable in strength tests. Furthermore, an empirical formula based on the failure criterion of maximum tensile stress is proposed to evaluate the tensile strength of specimen materials.
Simple shear of isotropic elasto–plastic soil
Authors: Frydman S. , Talesnick M. 
Published: August 2005

AbstractThe implications of assuming isotropic elasto–plasticity to model the behaviour of soil under simple shear conditions are considered. For small strains, use of such a model implies the following three consequences: (1) strains and strain increments at any stage of shearing may be expressed as the sum of elastic and plastic components; (2) principal directions of stress and of plastic strain increment are collinear; (3) principal directions of stress increment and of elastic strain increment are collinear. These consequences are used in order to establish relationships between the stresses, stress increments and strains which develop in a simple shear test. No additional assumptions with regards the form of the yield function, the flow rule or the hardening function are required for this development. By defining the ratio of the plastic to the total shear strain increment on the horizontal plane (the plane of zero extension) as λ, it is possible to define the horizontal normal stress σx in terms of λ and other stresses and strains which are normally known during simple shear loading. As a result, all components of the stress tensor in the simple shear plane may be defined. Results of some direct simple shear tests on soft clay have been interpreted using the model and found to be generally consistent with some of the observations reported in the literature from tests in which boundary stresses were measured.
On the solution of steady unconfined seepage towards semi‐infinite slopes
Authors: Muleshkov Angel , Banerjee Sunirmal 
Published: August 2005

AbstractAnalytical solutions for the two‐dimensional problem of unconfined seepage towards semi‐infinite slopes are described. The analysis employs complex variable techniques. Conformal mappings have been used to reduce the problem to solving an ordinary differential equation. The resulting integrals are presented in terms of special functions. The solutions for the location of the phreatic surface and the exit point have been obtained in parametric form. Some additional results and asymptotic expansions of the solutions are also presented. The numerical results have been calculated and plotted for different values of the slope angle in dimensionless co‐ordinate space.
Response of circular footings and anchor plates in non‐homogeneous elastic soils
Authors: Rajapakse R. K. N. D. , Selvadurai A. P. S. 
Published: August 2005

AbstractThe axisymmetric elastic response of circular footings and anchor plates in a linearly non‐homogeneous elastic soil is analysed. It is assumed that footings/anchors are flexible and subjected to axisymmetric vertical loads. The response of the footing/anchor is modelled by using the classical Poisson–Kirchhoff thin plate theory. A variational technique is used to analyse the interaction problem. A representation for the contact stress is established by using a fundamental solution corresponding to a unit vertical pressure acting over an annular region in the interior of the non‐homogeneous soil. The fundamental solution can be derived by using rigorous analytical procedures. The influence of the footing flexibility and the degree of soil non‐homogeneity on the displacements, bending moments and contact stresses of a surface footing is examined over a wide range of governing parameters. In the case of anchor plates the influence of depth of embedment, degree of soil non‐homogeneity and anchor flexibility on the anchor displacement is investigated.
Axially loaded vertical piles and pile groups in layered soil
Authors: Chin J. T. , Poulos H. G. 
Published: August 2005

AbstractA numerical method is described for the analysis of axially loaded vertical piles and pile groups embedded in layered soil. The ‘hybrid’ approach is utilized whereby the single‐pile response is represented by load‐transfer (t–z) curves while the pile–soil–pile interaction is obtained accurately using the analytical solutions of Chan et al. for a two‐layered system and in an approximate manner for a Gibson soil. For the single‐pile response a simple rational procedure is suggested for the determination of the averaged rm value (radial distance at which the shear stress becomes negligible). Solutions are presented and compared with the elastic continuum solutions for such soil profiles. Finally, comparisons with actual field measurements of vertical piles and pile groups embedded in such a soil profile show favourable agreement.
A boundary element method for identifying orthotropic material parameters
Authors: Ohkami T. , Ichikawa Y. , Kawamoto T. 
Published: August 2005

AbstractA new approach is proposed for identifying elastic constants for orthotropic material bodies by using the boundary element method. The material parameters which must be determined are two Young's moduli, a shear modulus and two Poisson's ratios. The method is applied to geotechnical engineering problems.
Comment on the postulate of three plane strain mechanisms
Authors: Gutierrez Marte , Lacasse Suzanne 
Published: August 2005

AbstractThis note discusses the inconsistencies that are inherent in the postulate of three plane strain mechanisms. It is shown that this postulate violates the principle of invariance and one obtains different results depending on the choice of the reference axes. If formulated in the principal stress space, this postulate requires that the principal stress and principal plastic strain increment directions be coaxial. Constitutive models based on this postulate cannot be used for general loading situations involving principal stress rotation where significant non‐coaxiality is obtained.
A non‐linear numerical model for soil mechanics
Authors: Ng T. ‐T. , Dobry R. 
Published: August 2005

AbstractA new computer program (CONBAL‐2) is developed for 2D numerical simulations of granular soil by random arrays of spheres. CONBAL‐2 uses the discrete‐element method and is based on 3D program TRUBAL, previously presented by Cundall. As in TRUBAL, the new program models a random array of elastic spheres in a periodic space. The main modification of TRUBAL is the implementation by the authors of a rigorous solution for the force–displacement relation at the interparticle contacts. This force‐displacement relation is a function of the elastic constants, friction coefficient and sizes of the spheres, with the properties of quartz used to simulate sand. Other specific features of CONBAL‐2 include its 2D character, the lack of particle rotation and its capability to simulate shear loading on any plane. Simulated laboratory test results are presented using CONBAL‐2 and several random arrays of 531 spheres having two particle sizes. These simulations include monotonic loading drained and undrained (constant volume) ‘triaxial’ experiments, as well as a cyclic‐loading, constant‐volume ‘torsional shear’ test. The stress–strain curves, effective stress paths, volume changes, as well as the ‘pore water pressure’ build‐up behaviour obtained in the simulations compare favourably—qualitatively and in some aspects quantitatively—with similar laboratory results on sands. However, the simulated soil is somewhat stiffer and stronger due to the perfectly rounded particles, limited range of grain sizes, lack of particle rotation and 2D character of the model.
A transient finite element analysis of linear viscoelastic material model
Authors: Wang Yue‐Cong , Murti Viriyawan , Valliappan Somasundaram 
Published: August 2005

AbstractSince the attenulation of propagating waves through soil/rock is related to the localized material properties as well as the strain developed, the commonly used Rayleigh‐type damping model and its variations are not suitable for dynamic finite element analysis of such materials.A linear viscoelastic material model based on the concept of the relaxation spectrum is manipualted in place of the damping model in this paper. The method proposed by Day and Minster11 to transform the convolutional form of the stress–strain relationship to a set of differential operators using the Pade approximant method is generalized to non‐scalar waves and implemented for transient finite element analyses. A time‐marching scheme is also proposed to incorporate the resultant differential operators into the governing equation of motion. The accuracy related to the Pade approximant method and the time‐marching scheme is investigated by critically analysing some scalar wave propagation problems. The proposed technique is further verified using two one‐dimensional stress wave propagation problems and a two‐dimensional transient propagating wave through an unbounded linear viscoelastic medium. Some encouraging results have been obtained using the proposed technique and guidelines for using this technique are also presented. Comparisons of analytical solutions obtained by Fourier synthesis and numerical results have been provided.
Modelling and analysis of non‐random uncertainties—fuzzy‐set approach
Authors: Juang C. Hsein , Huang Xin H. , Elton David J. 
Published: August 2005

AbstractThis paper addresses the issue of uncertainty treatment in geotechnical engineering. Emphasis is placed on modelling and analysis of non‐random uncertainties using fuzzy sets. Although uncertainties were modelled with fuzzy sets in this study, subsequent analysis or processing of the uncertain information was performed using traditional, non‐fuzzy techniques. These techniques, including the vertex method and Monte Carlo simulation, are discussed in detail. An example application using soil liquefaction susceptibility is presented. The paper concludes that non‐random uncertainties can be successfully modelled and processed using fuzzy sets.
Finite element modelling of pressuremeter tests and footings on frozen soils
Authors: Puswewala U. G. A. , Rajapakse R. K. N. D. , Domaschuk L. , Lach R. P. 
Published: August 2005

AbstractA finite element code is developed to model the structure‐frozen soil/ice interaction using a time incrementing, fully implicit, iterative algorithm, and a constitutive model based on the concept that total strain tensor consists of an elastic and a creep component. The code is used to investigate the applicability and limitations of the power law as the creep model for frozen soil by simulating two pressuremeter tests. Two extended phenomenological models based on the generalized power law are used in axisymmetric finite element analyses to simulate two, long‐term, stage‐loaded pressuremeter tests, and comparison of results with test data indicates that one model demonstrates a better ability to approximate the actual response to subsequent load steps, under certain restrictions. Stress analyses demonstrate the ability of the constitutive model to show transient as well as subsequent quasi‐stationary stress stages in creep analysis. Additional simulations of short‐term pressuremeter tests on ice are performed to further illustrate some limitations of the power‐law model. Examples for prediction of creep settlements on frozen geomaterials are demonstrated by considering the interaction of fully flexible circular footings and concrete cylindrical footings (of different embedment depths) with frozen sands.
Prediction of dilation and permeability changes in rock salt
Authors: Stormont J. C. , Daemen J. J. K. , Desai C. S. 
Published: August 2005

AbstractA numerical procedure has been developed for predicting dilation (porosity) and gas permeability changes in rock salt. The hierarchical single‐surface constitutive model of Desai and co‐workers is used a finite element program to calculate the state of stress and strain surrounding excavations in rock salt. The elastoplastic constitutive model accounts for strain hardening, a non‐associative volumetric response and stress‐path‐dependent behaviour. The calculated stress and strain fields are used in a flow model based on the equivalent channel concept to predict permeability. Parameters for both the mechanical and permeability models are developed from laboratory test results. Two field experiments adjacent to underground excavations are modelled. The extent of the dilated rock zone around the excavation is predicted well, but the magnitude of the porosity and gas permeability is underpredicted very near the excavations. This discrepancy is attributed to model parameters derived from loading‐only laboratory tests, whereas significant unloading occurs in the field. The shape of the yield surface was found to be an important factor in dilation and permeability predictions. Similar stress, strain and permeability fields were obtained with different model types (plane strain or axisymmetric) and initial stress states, and with instantaneous and progressive excavation.
Blast vibration control in the presence of delay scatter and random fluctuations between blastholes
Authors: Blair D. P. 
Published: August 2005

AbstractIt is becoming increasingly important, from an environmental viewpoint, to minimize vibrations induced in urban dwellings by blasting. The present study illustrates how the delay interval between blastholes can be chosen to control and minimize the vibration energy within the structural response band of most houses. In particular, it is shown that the only possibility of reducing such energy is to employ a delay interval in the range 10–35 ms. However, the induced vibrations are also dependent upon the accuracy of the delay initiators as well as the level of random fluctuations between each blasthole signature. It is shown that only very accurate electronic delays give the possibility of utilizing fully the delay sequence in order to control structural vibrations. If the vibration emission from each blasthole is totally uncorrelated with that of any other blasthole then the resulting amplitude spectrum of the blast will be totally unpredictable. This situation occurs irrespective of the delay initiation sequence or its accuracy. Under these conditions it is impossible to predict the blast‐induced energy lying within the structural response band.
Simulation of groundwater flow and contaminant transport at a landfill site using models
Authors: Franz Thomas J. , Rowe R. Kerry 
Published: August 2005

AbstractNumerical and analytical modelling studies were conducted for the analysis of groundwater flow and contaminant transport at the Innisfil landfill site in the Town of Innisfil, County of Simcoe, in Ontario, Canada. Previously conducted field studies categorized the upper stratigraphy at the site into three units: upper sand unit, upper silt/clay unit and Intermediate Sand unit. Essentially horizontal groundwater movement in the two sand units and vertical downward flow in the silt/clay unit were reported by the field hydrogeologists. In the following, application of three computer models (FLOWPATH, USGS MOC and POLLUTE) for the simulation of the groundwater flow and contaminant transport processes at the Innisfil landfill site is described. The paper focuses on the calibration of groundwater flow and contaminant transport systems, and demonstrates how the insight gained during the contaminant transport calibration was used to improve the initial groundwater flow characterization of the hydrogeological system.
Finite element modelling of transport of organic chemicals through soils
Authors: Kuppusamy T. 
Published: August 2005

AbstractAquifer contamination by organic chemicals in subsurface flow through soils due to leaking underground storage tanks filled with organic fluids is an important groundwater pollution problem. The problem involves transport of a chemical pollutant through soils via flow of three immiscible fluid phases: namely air, water and an organic fluid. In this paper, assuming the air phase is under constant atmospheric pressure, the flow field is described by two coupled equations for the water and the organic fluid flow taking interphase mass transfer into account. The transport equations for the contaminant in all the three phases are derived and assuming partition equilibrium coefficients, a single convective – dispersive mass transport equation is obtained. A finite element formulation corresponding to the coupled differential equations governing flow and mass transport in the three fluid phase porous medium system with constant air phase pressure is presented. Relevant constitutive relationships for fluid conductivities and saturations as function of fluid pressures lead to non‐linear material coefficients in the formulation. A general time‐integration scheme and iteration by a modified Picard method to handle the non‐linear properties are used to solve the resulting finite element equations. Laboratory tests were conducted on a soil column initially saturated with water and displaced by p‐cymene (a benzene‐derivative hydrocarbon) under constant pressure. The same experimental procedure is simulated by the finite element programme to observe the numerical model behaviour and compare the results with those obtained in the tests. The numerical data agreed well with the observed outflow data, and thus validating the formulation. A hypothetical field case involving leakage of organic fluid in a buried underground storage tank and the subsequent transport of an organic compound (benzene) is analysed and the nature of the plume spread is discussed.
Modelling of fluid expulsion and deformation behaviour of dewatering sediments
Authors: Chang F. Tom , Lennon Gerard P. , Pamukcu S. , Carson B. 
Published: August 2005

AbstractA finite element model is developed for modelling coupled fluid expulsion/deformation behaviour of dewatering sediments subjected to external loadings under isothermal conditions. The non‐linear deformation behaviour of the sediment (soil) skeleton is based on the force equilibrium equation in which the constitutive relationship of stress and strain is implemented by the modified Cam‐Clay model in soil plasticity. The fluid flow behaviour in the model is described by the generalized porous media flow equation. The model allows temporal and spatial variations of porosity and permeability. The fluid viscosity and density are assumed to be temperature‐dependent. The model also allows the development of single and multiple faults, depending upon the material (sediment and fluid) properties, loading and boundary conditions.Procedures are implemented for (1) updating the material properties such as porosity, permeability, fluid density and viscosity and (2) the development of faults which allow the formation of high‐permeability conduits for fluid flow. The solution algorithm for displacements of the sediments and the excess pore (fluid) pressure is based on a residual load technique to handle the non‐linear (elastic‐plastic) deformation behaviour of the sediment skeleton. The model can be applied to one‐ and two‐dimensional problems. Examples of a plane strain saturated sediment layer subjected to stepwise horizontal tractions versus time are given.