bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subsidence due to pumping from layered soil—a perturbation theory
Authors: Fallou S. N. , Mei C. C. , Lee C. K. 
Published: August 2005

AbstractPersistent pumping of groundwater is known to cause subsidence of the ground surface. When the soil is composed of alternating layers of sand and clay, subsidence is, in general, a consequence of pressure change in and deformation of all layers. Even with various simplifications, the mathematical task for the mechanics of a layered soil is complex and, in the past, many idealizations have been introduced in the literature. Among the existing approximations, a well‐known approximation by Hantush1 for well‐hydraulics in leaky aquifers is intuitively attractive. He used the fact known to be strictly true for simple flows in a soil system with horizontal layers, that the flow must be mainly horizontal in a relatively porous aquifer and mainly vertical in a highly impervious aquitard, and invoked the same approximation for transient flows induced by well‐pumping. In this paper we shall apply a perturbation analysis to give a mathematical confirmation of the hydrological approximation and to show its degree of accuracy. In particular, we treat a three‐layered system, where the middle layer is a relatively soft aquitard, and the well withdraws water from the artesian aquifer at the bottom. The upper aquifer has a phreatic surface. Physically, we examine the often ignored effects of self‐weight which is important for thick aquitards. The perturbation theory is worked out for sufficiently weak pumping rates and small soil deformation. Subsidence in the vertical direction due mainly to the deformation of the soft aquitard is studied. Results show that the common assumption of constant total stress with respect to depth is valid only when the storage coefficient is very small.
Modelling of vibratory pile driving in sand
Authors: Wong Daniel , O'Neill Michael W. , Vipulanandan C. 
Published: August 2005

AbstractA model for vibro‐driving of rigid piles in sand is proposed incorporating the interaction of the vibrator–pile–soil system. The vibro‐driver force and the non‐linear soil resistance (dynamic f–w and q–w relationships) have been quantified in terms ofin situstress, relative density and particle size. The influence of relative density (0·65 and 0·90), particle size (effective grain size of 0·2 mm and 1·2 mm) and in situ stress (up to 20 psi) on the vibro‐driving of a closed‐ended pipe pile was investigated experimentally using a large‐scale laboratory testing system. The vibro‐driving model predicted the observed driving history reasonably well. A computer program (UHVIBRO) has been developed to analyse vibratory pile driving using the dynamic soil resistance relationships developed along with correlation factors from the systematic laboratory study.
A consistent formulation of a dilatant interface element
Authors: Snyman M. F. , Martin J. B. 
Published: August 2005

AbstractThe paper considers a plane joint or interface element suitable for implementation into a standard non‐linear finite element code. The element is intended to model discontinuities with rough contact surfaces, such as rock joints, where dilatant behaviour is present. Of particular concern is the formulation of a constitutive model which fully caters for all possible histories of opening, closing and sliding (accompained by dilation or contraction) in any direction.The non‐linear incremental constitutive equations are formulated in a manner appropriate for a back‐ward difference discretization in time along the path of loading. The advantage of such an approach is that no essential distinction need be drawn between opening, closing and sliding. Further, a convenient formulation of the constitutive equations is facilitated by representing the different contact conditions in relative displacement space. The state diagram in relative displacement space, however, changes from one time step to the next, and evolution equations for the updating must be formulated.These concepts are illustrated for two rock‐joint models: a sawtooth asperity model and a limited dilation model. The models are based on a penalty formulation to enforce the contact constraints, and explicit equations for the tangent stiffness matrix and for the corrector step of the standard Newton–Raphson iterative algorithm are derived. These equations have been implemented as an user element into the finite element code ABAQUS7. Three examples are presented to illustrate the predictions of the formulation.
A finite element slideline approach for calculating tunnel response in jointed rock
Authors: Schwer Leonard E. , Lindberg Herbert E. 
Published: August 2005

AbstractThe general purpose finite element code DYNA2D is used to calculate the response of an unlined tunnel in jointed rock, with sliding interfaces used to represent the joints. The model problem selected for analysis closely follows a calculation using the discrete element code UDEC. Results for two cases [(1) jointed rock with lubricated joints (no joint friction) and (2) jointed rock with frictional resistance to joint motion] are presented and compared with each other and the UDEC results.
Three‐dimensional modelling of junctions at the Channel Tunnel project
Authors: Pöttler R. 
Published: August 2005

AbstractThe present paper deals with a three‐dimensional FE analysis for the Channel Tunnel project. The main objective is to describe the application and the results of a FE calculation and the impact of it's results on engineering practice especially on the design of the permanent lining. The tunnel excavation was executed in accordance with the principles of the shotcrete tunnelling method (NATM). The paper represents a report from the practical engineer's point of view.
Coupled heat and mass transfer in unsaturated soil—a potential‐based solution
Authors: Thomas H. R. , King S. D. 
Published: August 2005

AbstractAn analysis of coupled heat and moisture movement in unsaturated soil in terms of the fundamental potentials for flow is examined. The approach adopted is based on the assumption that the total potential for liquid flow consists of two components, the elevation and the capillary potential. The fundamental potentials employed in the work are, therefore, temperature and capillary potential.The full theoretical formulation of the problem is presented, together with full details of the solution algorithm employed. Spatial discretization is achieved via the use of the finite element method, with the time‐varying behaviour described by a finite difference technique. Soil parameter variations as functions of both temperature and moisture content are included in a one‐dimensional approach.The work is applied to a practical engineering problem, namely heat and mass transfer in the upper layers of a soil stratum. This problem is of importance to the utilities, since many services are buried in this zone. Material parameters obtained from an associated programme of experimental work are employed. Moisture content and temperature profiles indicating the extent and rate of penetration of drying and heating fronts are produced.
A virtual surface concept for nested yield surface plasticity
Authors: Salah‐Mars Said , Kavazanjian Edward 
Published: August 2005

AbstractA return mapping algorithm based on the concept of virtual surfaces is presented for stress integration in the numerical solution of boundary value problems using an elastoplastic multiple yield surface model. Both kinematic hardening and isotropic softening yield surfaces are addressed. With the implementation of virtual surfaces, the active yield surface is located before a stress update is implemented. The return mapping algorithm consists of only two steps. The first step consists of performing the intermediate update of the trial stress corresponding to the translation of all yield surfaces inside the active yield surface. Little calculation is involved in this step. The second step consists of performing the conventional explicit one‐step radial return mapping of the updated trial stress on the corresponding active yield surface. The algorithm efficiency resides in the virtual surface based return mapping which preserves the elastic predictor representation of the updated trial stress, and limits iterations to at most two steps.
A study on one‐dimensional consolidation of layered systems
Authors: Lee P. K. K. , Xie K. H. , Cheung Y. K. 
Published: August 2005

AbstractA general analytical solution, which is more explicit than the one given by Schiffman and Stein,1 for the problem of one‐dimensional consolidation of layered soils is presented. A relevant computer program is developed and the computed results on some examples are included. From these results, an in‐depth study on the one‐dimensional consolidation behaviour of layered systems is then made. It is demonstrated through these examples that both the solution technique and the computer program developed are very efficient. It is found that the effects of coefficients of permeability and volume compressibility of soil on the consolidation of layered systems are different and cannot be embodied into the coefficient of consolidation of soil. The stiffness of soil layer also plays an important role on the rate of consolidation.
Parametric infinite element for seepage analysis
Authors: Honjo Yusuke , Pokharel Gyaneswor 
Published: August 2005

AbstractA set of mapping functions in the form of convergent series for an infinite element, which is capable to include the infinitely distanced constant head boundary condition from the area of disturbance (e.g. pumping), is proposed based on the asymptotic far‐field behaviour of typical seepage flow problems. The derived mapping functions have been successfully used in three‐dimensional point symmetric, two‐dimensional axi‐symmetric and one‐dimensional unidirectional flow for the fixed head boundary at infinite distance. The result shows excellent agreement with analytical solution. For the first time, the mapping function of an infinite element is presented in the form of a convergent series. The infinite elements are really capable of reducing the cost and efficiency of conventional finite element analysis. Finally, a figure is also proposed to indicate the required size of the near field to obtain accurate drawdown at specified locations based on some calculations for two‐dimensional radial flow case.
Green's functions for a fully coupled thermoporoelastic material
Authors: Smith David W. , Booker John R. 
Published: August 2005

AbstractThe Green's functions for a set of fully coupled linear equations governing thermal consolidation of a homogeneous isotropic material are presented. The Green's functions are evaluated for one, two and three spatial dimensions, and in the Laplace and real‐time domains. The Green's functions are employed in a boundary integral analysis of a simple problem to demonstrate the influence of full coupling on the field quantities.
Shakedown in layered pavements under moving surface loads
Authors: Collins I. F. , Wang A. P. , Saunders L. R. 
Published: August 2005

AbstractElastic–plastic deformations in pavements consisting of layers of different frictional materials are investigated. The upper bound, kinematic shakedown theorem is used to obtain estimates of the critical shakedown loads. Fully general three‐dimensional deformations are considered. The influence of the loading distribution, interactions between loads, and the effect of varying the thickness, stiffness and strength of the layers are explored. Consequences of this investigation for particular existing designs of flexible pavements are investigated. In particular, it is found that the strength of the subgrade has no effect on the magnitude of the critical shakedown load.
Calculation of kinetic rate constants from steady‐state soil profile concentration measurements
Authors: Barry D. A. , Parlange J.‐Y. , Hensley P. J. 
Published: August 2005

AbstractWe derive a simple approximation for the steady‐state distribution of solute subject to an arbitrary, irreversible transformation in a soil profile under the condition of steady fluid flow. The approximation accounts for the effect of dispersion in both the surface boundary condition and the transport equation. The accuracy of the approximation is determined explicitly for the cases of zero‐ and first‐order kinetics, where exact solutions are available. Data from a numerical scheme are used to check the approximation's accuracy for the widely used Michaelis–Menten kinetic rate. It is shown that existing approximations in which the effect of dispersion in the transport equation is ignored can affect significantly the value determined for the Michaelis–Menten saturation constant. Parameters found when the new method is applied to experimental data are found to agree closely with those estimated directly from a least‐squares fitting.
On overestimation of displacements in numerical calculation of zoned dams
Authors: Doležalová Marta 
Published: August 2005

AbstractOverestimation of displacements in numerical calculations can occur if some requirements are not met by the constitutive relations. Along with consideration for small strain behaviour of soils1 the stiffening effects of unloading in shear should be taken into account. The latter problem is analysed in the paper using embankment dams as a typical example. Strain and stress paths in their cores and shells were derived from field measurement results and frequent path direction changes during seemingly monotonic loading process were discovered. Proportional loading test results of isotropically and anisotropically consolidated sand allowed interpretation of the in situ paths by the incremental theory of plasticity and distinction between the sections where unloading and reloading in shear develop. Furthermore, the analysis of these tests showed a marked stiffening of the soil due to unloading as well as neutral loading in shear. The strain redistribution due to material inhomogeneity, either inherent or introduced by the loading process, was identified as a common reason for the frequent occurrence of this phenomenon. Consequently, overestimations in displacement calculations can be brought about by neglecting this important effect by the constitutive model used. Accordingly, the unit response envelopes of some typical constitutive laws have been checked from this special point of view, and the models properly describing this phenomenon selected.
Analysis of fully coupled thermomechanical behaviour around a rigid cylindrical heat source buried in clay
Authors: Seneviratne H. N. , Carter J. P. , Booker J. R. 
Published: August 2005

AbstractThe problem of fully coupled consolidation and heat flow around a rigid cylindrical heat source buried in clay has been studied. The governing equations of the problem are summarized in the paper and a finite element time‐marching scheme to obtain an approximate solution to the governing equations is described. The stress–strain behaviour of the skeleton of the saturated soil has been represented by both a linear elastic model and the modified Cam clay soil model. The results of a limited parametric study are presented with the aim of understanding the major mechanisms of soil behaviour close to buried canisters of hot radioactive waste. A range of soil properties has been included in the study, and the effects of soil disturbance during canister emplacement have also been considered.
Boundary element analysis of Biot consolidation in layered elastic soils
Authors: Chiou Yaw‐Jeng , Chi Shue‐Yeong 
Published: August 2005

AbstractBiot's linear consolidation analysis of three‐dimensional fluid saturated layered soils is investigated. The time marching method, uncoupled boundary element method, and successive stiffness method are applied for the numerical modelling of this study. Settlement induced by surface loading and land subsidence due to pumping is studied. The results show that settlement induced by surface loading is mainly influenced by the properties of the soil layer, and that the settlement is larger for soil layers with smaller stiffness and greater thicknesses. The land subsidence induced by pumping is influenced by the properties of the soil layer as well as by the permeability of the pumped layer and the conditions at the top and bottom boundaries. The land subsidence is larger for soil layers with a smaller stiffness, lower permeability of the pumped layer, deeper pumping depth, larger pumping rate and an impervious top surface.
Cyclic mobility behaviour of sand by the three‐dimensional strain space multimechanism model
Authors: Akiyoshi T. , Matsumoto H. , Fuchida K. , Fang H. L. 
Published: August 2005

AbstractThe cyclic mobility behaviour of sand by the three‐dimensional (3‐D) strain space multimechanism model based on the micromechanics of granular material is investigated. The constitutive properties are characterized by the volumetric and shear mechanisms for the initial isotropic soil. The 3‐D shear mechanism is decomposed into a number of microscopic plane‐strain shear mechanisms in various orientations, each of which in turn consists of a number of microscopic simple shear mechanisms. Using an appropriate summation of mechanisms, the total deformation behaviour can be obtained by evaluating contributions from each mechanism. Based on the some assumptions, the dilatancy model proposed by Iai et al.1 is extended from the two‐dimensional (2‐D) space to the 3‐D space. Comparisons of theoretically predicted results are made with experimental measurements.
Monica—A computer algorithm for solving boundary value problems using the double‐hardening constitutive law Monot: II. Algorithm validation
Authors: Hicks M. A. 
Published: August 2005

AbstractThe computer algorithm MONICA1, which incorporates the double‐hardening constitutive law Monot2, has been tested on a large number of numerical examples. This paper summarizes the validation process, which has included consideration of both single element stress paths and multi‐element boundary value problems. These results show MONICA to be effective for analysing practical problems using a soil model of the double‐hardening type. They also demonstrate the ability of Monot to model a wide range of material responses. Problems involving pore pressure changes are identified as an area in which this form of analysis is of particular use3,4.
One‐dimensional, semi‐analytical solution for time‐dependent behaviour of a seam
Authors: Nawrocki Pawel A. 
Published: August 2005

AbstractThe paper provides a one‐dimensional, semi‐analytical study of face advance in a coal seam assuming a Bingham type of material model. The changes in vertical stress and deformation in the seam due to change in the geometric configuration of the excavation are analysed. The general analytical formulae defining stresses and strains for an arbitrary time instant i Δt(i = 1,2,…) are derived, and the size of the viscoplastic zone near the opening and its evolution with time are determined. The influence of the seam extraction rate on the stability of the seam and rock burst occurrence is discussed in the light of the developments presented in this paper.
Modelling convection in solidification processes using stabilized finite element techniques
Authors: Samanta Deep , Zabaras Nicholas 
Published: August 2005

AbstractSolidification of dendritic alloys is modelled using stabilized finite element techniques to study convection and macrosegregation driven by buoyancy and shrinkage. The adopted governing macroscopic conservation equations of momentum, energy and species transport are derived from their microscopic counterparts using the volume‐averaging method. A single domain model is considered with a fixed numerical grid and without boundary conditions applied explicitly on the freezing front. The mushy zone is modelled here as a porous medium with either an isotropic or an anisotropic permeability. The stabilized finite‐element scheme, previously developed by authors for modelling flows with phase change, is extended here to include effects of shrinkage, density changes and anisotropic permeability during solidification. The fluid flow scheme developed includes streamline‐upwind/Petrov–Galerkin (SUPG), pressure stabilizing/Petrov–Galerkin, Darcy stabilizing/Petrov–Galerkin and other stabilizing terms arising from changes in density in the mushy zone. For the energy and species equations a classical SUPG‐based finite element method is employed with minor modifications. The developed algorithms are first tested for a reference problem involving solidification of lead–tin alloy where the mushy zone is characterized by an isotropic permeability. Convergence studies are performed to validate the simulation results. Solidification of the same alloy in the absence of shrinkage is studied to observe differences in macrosegregation. Vertical solidification of a lead–tin alloy, where the mushy zone is characterized by an anisotropic permeability, is then simulated. The main aim here is to study convection and demonstrate formation of freckles and channels due to macrosegregation. The ability of stabilized finite element methods to model a wide variety of solidification problems with varying underlying phenomena in two and three dimensions is demonstrated through these examples. Copyright © 2005 John Wiley & Sons, Ltd.
Numerical treatment of mixed boundary value problems in two‐dimensional elastostatics
Authors: Feldmann Jay W. , Prager W. 
Published: August 2005

AbstractFinite difference treatment of two‐dimensional problems in elastostatics is usually based on the differential equations for the displacement vector or the Airy stress function, depending on whether boundary conditions are on displacement or stress. In either case, determination of stresses requires numerical differentiation and therefore use of a rather fine grid. Moreover, neither method is suited to the treatment of mixed boundary conditions. The alternative method developed in this paper uses the first derivatives of the displacement components at the grid points as basic variables and hence does not require numerical differentiation in the evaluation of stresses. Appropriate finite difference equations are established, and their use is discussed in connection with a specific example with known explicit solution.
A polygonal finite element for plate bending problems using the assumed stress approach
Authors: Alwood R. J. , Cornes G. M. M. 
Published: August 2005

AbstractThe assumed stress distribution approach is used to derive the stiffness matrix of a plate‐bending element of general polygonal shape having any number of nodes. The effect of assuming various numbers of unknown coefficients in the stress distributions is examined and the convergence properties of the resulting elements compared with others derived form assumed displacements.