bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling heat and fluid flow in sedimentary basins by the finite element method
Authors: Wangen Magnus 
Published: August 2005

AbstractIn this article we solve the equations for a 2D model of compaction of sedimentary basins saturated with water by the finite‐element method. This compaction model considers the rock described by the porosity as a function of effective stress, and both the anisotropic permeability and the anisotropic heat conductivity as functions of porosity. The water density is approximated linearly in the water pressure and temperature, and the water viscosity is a function of temperature. The main variables in the model are the water excess pressure and the temperature, and we account for an implicit solution scheme where we solve for both main variables simultaneously. The non‐linearities in the model are either dealt with by the Newton method or by fixed‐point iterations. We compare the coupled solution of temperature and pressure with the same decoupled equations. Then we study the contribution to the temperature by convection, the effect of the non‐constant water density, and some anisotropic case examples.
Pore‐pressure response due to penetration through layered media
Authors: Elsworth Derek 
Published: August 2005

AbstractA solution is developed for a point dislocation traversing a slab of saturated porous material under prescribed upper and lower hydraulic boundary conditions as an analogue to penetration in a layer of finite thickness. Pressure response is conditioned by geometrical parameters and those of dimensionless penetration rate UD, dimensionless time following penetration initiation tD, and dimensionless time following penetration arrest t′D. The extended set of dimensionless parameters controlling the response makes parameter determination problematic and questionably non‐unique. Pressure response in the proximity of a lower permeable or impermeable boundary is indistinguishable from the homogeneous case for coefficients of consolidation c in excess of 2 cm2/s. Below this threshold, penetration‐generated pore pressures are visibly modified in the presence of a discrete boundary. In situ parameters inferred directly from pressure magnitudes, without due consideration for the influence of layering, may therefore be in considerable error. In the hydraulically visible range, the influence of layering on the generated tip pressures is apparent at a separation of the order of 1·5 cm for standard penetration. Although absolute pressure magnitudes are strongly modified in the presence of boundaries, dissipation rates remain relatively unaffected and are consistent with those recorded in the absence of boundaries. The monitoring of dissipation rates, post‐arrest, is suggested as the most reliable and accurate method of extricating parameters, in situ.
Dynamic response of concrete gravity dams including dam–water–foundation interaction
Authors: Valliappan S. , Zhao Chongbin 
Published: August 2005

AbstractIn this paper, the gravity dam–water–foundation system including the physical and mechanical properties of the sediment at the reservoir bottom is modelled using a finite element and infinite element coupling model. The sediment at the reservoir bottom has been assumed to be a viscoelastic solid medium. The effects of thickness, elastic modulus, Poisson's ratio and material damping of the sediment on the response of the dam have been studied. The related numerical results from this study illustrated that the existence of the sediment at the bottom of the reservoir has significant effects on the response of concrete gravity dams since the soft layer of the sediment plays two main roles in the dam–water–foundation system, the energy dissipation of the system and the amplification of the incident wave on the water–sediment interface. It is the amplified acceleration on the water–sediment interface that results in different mechanisms of the effect of the sediment on the response of the dam. Therefore, apart from the incident wave, the thickness, the softness and the damping ratio of the sediment can also affect the response of the dam.
Finite‐element analysis of time‐dependent large‐deformation problems
Authors: Chopra Manoj B. , Dargush Gary F. 
Published: August 2005

AbstractAn updated Lagrangian finite‐element formulation has been developed for time‐dependent problems of soil consolidation involving finite deformations. Large plastic strains as well as rotations occur in such problems and nominal stress measures are introduced in the formulation to redefine stresses. This leads to corrective terms for equilibrium and yield violations in addition to geometric stiffening terms in the governing integral equations. The soil is considered to be either a linear elastic or an elastoplastic, critical‐state material. Some simple numerical examples are studied to validate the formulation, followed by a detailed analysis of the problem of penetration of a pile into soil. The results of this problem are viewed with emphasis on the physical interpretation and practical significance.
Implicit integration in soil plasticity under mixed control for drained and undrained response
Authors: Alawaji H. , Runesson K. , Sture S. , Axelsson K. 
Published: August 2005

AbstractAn algorithm is outlined for the implicit integration of isotropic plasticity models for an arbitrary choice of mixed stress and strain control variables. Drained as well as undrained behaviour is considered. The closest‐point‐projection method in conjunction with a completely strain‐driven format is used in a core algorithm. In the drained case strain response variables are determined via iterations to satisfy equilibrium of prescribed and calculated stresses that correspond to the strain response variables. In the undrained case, on the other hand, strains and pore pressure are determined via simultaneous iterations to satisfy equilibrium and the incompressibility condition. The algorithm is applied to a new generalized cam‐clay model, and various iteration techniques are assessed. In particular, Newton iterations which employ the matrix of algorithmic tangent stiffness moduli are shown to compete favourably with more conventional methods.
Influence of construction technique on the performance of a braced excavation in marine clay
Authors: Smith I. M. , Ho D. K. H. 
Published: August 2005

AbstractFinite element analyses are used to quantify the effects of construction technique on the performance of braced excavations. It is first shown that the computations can be continued to ‘collapse’ and that the results agree with limit plasticity solutions. A case study involving stratified deposits of marine clay and sand is used to carry out a Class C1 ‘prediction’ of field performance. The influence of construction technique on deformations and strut loads is shown. The results of the computations are in agreement with field observations, assuming a relatively ‘flexible’ construction technique. However, even if much ‘stiffer’ techniques had been used, large field deformations would have been unavoidable under certain circumstances.
Effect of sand lenses on groundwater flow and contaminant migration
Authors: San K. W. Edward , Rowe R. Kerry 
Published: August 2005

AbstractThe effect of homogeneous sand lenses on the groundwater flow in an otherwise homogeneous clayey deposit is examined by performing Monte Carlo simulations using a finite element flow model. In the simulations, the locations of the sand lenses are assumed to be mutually independent. The paper examines the effect on the flow field in a clayey deposit of (a) different percentages of sand lenses, (b) different hydraulic conductivities of the sand lenses, (c) different average sand lens sizes, (d) non‐uniformity of the sizes of the sand lenses, and (e) localization of the sand lenses. The effect of these non‐uniform flow fields on contaminant migration is then examined using a finite element contaminant transport model. For the range of cases considered it is shown that: the volume of sand lenses present has a greater influence than the shape, size, location and hydraulic conductivity of the sand lenses; simplified calculations performed using the geometric and harmonic means of hydraulic conductivity bracket the behaviour evident from more complex analyses; and the maximum impact on an aquifer separated from a waste disposal facility by a deposit containing sand lenses can be modelled to sufficient accuracy, using quite simple flow and contaminant transport models.
Transient response of a circular cavity in a poroelastic medium
Authors: Senjuntichai T. , Rajapakse R. K. N. D. 
Published: August 2005

AbstractThis paper considers the transient response of a pressurized long cylindrical cavity in an infinite poroelastic medium. To obtain transient solutions, Biot's equations for poroelastodynamics are specialized for this problem. A set of exact general solutions for radial displacement, stresses, pore pressure and discharge are derived in the Laplace transform space by using analytical techniques. Solutions are presented for three different types of prescribed transient radial pressures acting on the surface of a permeable as well as an impermeable cavity surface. Time domain solutions are obtained by inverting Laplace domain solutions using a reliable numerical scheme. A detailed parametric study is presented to illustrate the influence of poroelastic material parameters and hydraulic boundary conditions on the response of the medium. Comparisons are also presented with the corresponding ideal elastic solutions to portray the poroelastic effects. It is noted that the maximum radial displacement and hoop stress at the cavity surface are substantially higher than the classical static solutions and differ considerably from the transient elastic solutions. Time histories and radial variations of displacement, hoop stress, pore pressure and fluid discharge corresponding to a cavity in two representative poroelastic materials are also presented.
A finite element formulation in Lagrangian co‐ordinates for heat and fluid flow in compacting sedimentary basins
Authors: Wangen Magnus 
Published: August 2005

AbstractThis article presents a numerical model of heat and fluid flow in compacting sedimentary basins formulated in Lagrangian co‐ordinates. The Lagrangian co‐ordinates are the sediment particle positions of the completely compacted basin. A finite element formulation of excess water pressure and temperature in these Lagrangian co‐ordinates is presented, in addition to an equivalent formulation in the real co‐ordinates. The later formulation is also Lagrangian of nature, since the elements of the grid in the real co‐ordinates always frame the same sediment particles. In other words, it is the Lagrangian grid mapped to the real space. This is done in an iterative loop which solves for excess water pressure, and then updates the real co‐ordinates of the sediment particles. By comparing the two finite element formulations it is concluded that the one in real space is the simplest, most efficient and most precise.The model is validated by comparison with two dimensionless one‐dimensional solutions, one analytical for the linear case, and one numerical for the non‐linear case. Both these one‐dimensional solutions are obtained on the unit interval, where the moving top boundary caused by continuous sedimentation is incorporated.
Finite element analysis of axisymmetric flow into partially penetrating wells
Authors: Singh Kamala K. , Dasgupta Shambhu P. , Ojha Triveni P. 
Published: August 2005

AbstractThe finite element method was used to solve the problem of flow to a partially penetrating strainer well in a leaky confined aquifer under steady and unsteady conditions. Predictions of the model were compared with reported pumping test data. A good agreement was obtained between them. The effects of penetration and screen position on discharge through imperfect well were studied. Results were compared with analytical solutions and presented graphically.
A finite element solution of a fully coupled implicit formulation for reservoir simulation
Authors: Sukirman Y. , Lewis R. W. 
Published: August 2005

AbstractAn iterative method is presented for solving a fully coupled and implicit formulation of fluid flow in a porous medium. The mathematical model describes a set of fully coupled three‐phase flow of compressible and immiscible fluids in a saturated oil reservoir. The finite element method is applied to obtain the simultaneous solution (SS) for the resulting highly non‐linear partial differential equations where fluid pressures are the primary unknowns. The final discretized equations are solved iteratively by using a fully implicit numerical scheme. Several examples, illustrating the use of the present model, are described. The increased stability achieved with this scheme has permitted the use of larger time steps with smaller material balance errors.
A note on the effect of mesh pattern on the lower‐bound bearing capacity of embedded strip footings
Authors: Sing D. N. , Basudhar P. K. 
Published: August 2005

AbstractThis study deals with the prediction of the lower‐bound bearing capacity of embedded smooth strip footings. The effect of mesh pattern on the result has been studied and a generalized mesh pattern has been proposed. The results obtained are compared with the computed solution using Meyerhof's bearing capacity equation.
Considering the effect of body force for regional land displacements
Authors: Lu Ruey‐Hsing , Yeh Hund‐Der 
Published: August 2005

AbstractIn this study, a general mathematical model was developed for land displacements that occur as a result of the pressure decline in confined and/or phreatic aquifers. Two equations were developed by employing the equilibrium (force balance) equation and the flow equation in a deforming aquifer system. Both of these equations were integrated over the thickness of the aquifer system once a regional model had been formulated. The change of the body force in saturated and unsaturated zones of aquifers was considered in the derivation of the equilibrium equation. It was assumed that no external loading or force acting on the aquifer system was present. Two coupled equations expressed in terms of the averaged dilation and pressure were then obtained. The pumping data sets given in the papers of Bear and Corapcioglu1,2 in 1981 and 1983 were analysed. Drawdown and displacements in a confined aquifer were demonstrated to be identical to those estimated by Bear and Corapcioglu.1 In the case of a phreatic aquifer, however, the results estimated by the present approach were slightly different from those obtained by Corapcioglu and Bear.2 The discrepancies in the results are possibly due to errors in the equations presented by Corapcioglu and Bear.2 The present approach was able to avoid several assumptions and complex procedures used by Bear and Corapcioglu,1,2 especially in the case of a phreatic aquifer, by taking into account the change in the body force.
Amplification of vertically propagating SH waves by multiple layers of Gibson soils
Authors: Davis Rob , Hunt Bruce 
Published: August 2005

AbstractUsing the Haskell–Thomson transfer matrix approach, an analytical solution is obtained for SH wave amplification by multiple layers of Gibson soils (i.e. viscoelastic layers with linearly varying shear moduli). Amplification spectra for typical soil and basement rock properties are calculated. A comparison of the Gibson soil response with that obtained for homogeneous soil models shows generally stronger amplifications associated with the Gibson soil.
Analysis of ‘infinitely long’ excavations using finite and boundary elements
Authors: Beer G. , Poulsen B. A. 
Published: August 2005

AbstractThe paper deals with the analysis of excavations which are very long and can, for all practical purposes, be considered to be infinitely long. Special infinite finite and boundary elements are developed for the modelling of the infinitely long part of such excavations. Test examples are presented which show the accuracy which can be obtained by using these elements. Finally, examples of application in mining and petroleum engineering are shown.
Analysis of compressible axially loaded piles in rock
Authors: Kodikara J. K. , Johnston I. W. 
Published: August 2005

AbstractAnalytical solutions are developed for the prediction of the load–settlement response of a compressible axially loaded cast in situ pile in rock. The principal input parameters are derived from the τ–z curve which applies to the contact zone between the pile shaft and the embedment material. For larger diameter piles in rock, these τ–z curves can differ markedly from curves that apply to piles in clay and may include a significant strain hardening region prior to reaching peak strength. In addition to the complete analyses which would normally require the use of a computer, simplified solutions suitable for hand calculations have been derived for the peak load and the pile head displacement to peak. An example of the application of these simplified design calculations is presented.
Calculation of the critical height of a homogenized reinforced soil wall: A numerical approach
Authors: Abdi R. , De Buhan P. , Pastor J. 
Published: August 2005

AbstractThis paper is devoted to the stability analysis of a vertical embankment in reinforced soil, assuming that a very large number of reinforcements are periodically distributed throughout the soil mass. The reinforced soil is modelled as a homogeneous medium that obeys a macroscopic yield condition.Two numerical formulations of the homogenized problem, derived from the lower and upper bound theorems of limit analysis, respectively, with a finite element discretization technique, are described. They both lead to a linear programming problem, which is carried out by means of XPRESS industrial LP code.The practical implementation of both the static and kinematic finite element programs on the case of a vertical reinforced earth wall results in close estimates of its failure height, which are in good agreement with available experimental data. This points to the ability of such programs to provide a rigorous evaluation of the limit loads of structures through the determination of lower bound and upper bound estimates sufficiently close to each other.
Strain localization analysis by elasto‐viscoplastic softening model for frozen sand
Authors: Oka Fusao , Adachi Toshihisa , Yashima Atsushi , Chu Lim Liong 
Published: August 2005

AbstractThe aim of the present paper is to numerically analyse the behaviour of frozen sand by using a viscoplastic constitutive model with strain softening. A constitutive model has been developed introducing the stress history tensor which is a functional of the stress history, with respect to a generalized time measure. It is shown that Adachi and Oka's model is applicable to the results of triaxial tests on a frozen Toyoura sand at different strain rates. First, the instability of the model is discussed within the framework of bifurcation theory. The model is then implemented into a FEM code to numerically simulate the behaviour under plane strain conditions. From the numerical results, it is revealed that the formation of shear bands is possible and the characteristics of strain localization, such as shear banding, depend on the strain rates.
Large strain static and dynamic semisaturated soil behaviour
Authors: Meroi E. A. , Schrefler B. A. , Zienkiewicz O. C. 
Published: August 2005

AbstractThe theoretical and computational aspects of large strain static and dynamic partially saturated soil analysis are presented. The soil is assumed to be a three‐phase material with a solid phase which may yield according to a generalized plasticity theory, whose liquid phase flows according to Darcy's law and where gaseous phase remains equal to the external ambient pressure. Permeability varies not only as a function of the degree of water saturation, but also as a function of the void ratio. These aspects are shown on several examples.
A simple model for inelastic footing response to transient loading
Authors: Deeks A. J. , Randolph M. F. 
Published: August 2005

AbstractThis paper presents a mechanical analogue which models the response of a rigid circular footing on an ideal elastoplastic half‐space to transient loads. In the rational analysis of pile‐driving dynamics, the response of soil at the base of a pile is often approximated by a footing on a semi‐infinite half‐space. Most existing base models employ the well‐known Lysmer analogue to model the elastic response of the soil at the pile base, and account for the inelastic soil behaviour through the inclusion of a plastic slider with a slip load equal to the ultimate failure load of the footing. The improved model provides a force response which is significantly closer to the ideal response than existing models. The paper commences with a review of analytical solutions for the dynamic response of a rigid circular footing on an elastic half‐space. Existing mechanical analogs for the system are reviewed, and an automatic matching process proposed which improves the accuracy of the analogs under transient loading. The inelastic response is then studied using the finite element method, and the mechanical analogs are modified to allow representation of the observed inelastic behaviour. Examples are presented illustrating close agreement between the proposed models and finite element analyses for a range of Poisson's ratio. The improved models have direct application for one‐dimensional models of pile driving, particularly in the back‐analysis of data from dynamic testing of piles. They are also applicable to studies of dynamic compaction.
Micromechanics modelling for stress–strain behaviour of brittle rocks
Authors: Li Chunlin 
Published: August 2005

AbstractA micromechanics model for stress–strain behaviour of brittle rocks has been developed. Microcracking is the mechanism of the non‐linear deformation behaviour for brittle rocks in the pre‐peak stage. The non‐linear behaviour in this stage is simulated by considering the local axial splitting of microcracks. The relationships between the compressive stresses, the growth of microcracks, and the fracture‐induced deformation are analytically established. In the post‐peak stage the shear faulting predominates the process of deformation, which is simulated by a damage model. This micromechanics model is helpful in understanding the failure process in brittle rocks. The model can be used to simulate the complete stress–strain behaviour of rock. The model simulations are consistent with experimental results.
A model for the constant‐head pumping test conducted in vertically fractured media
Authors: Markle J. M. , Rowe R. K. , Novakowski K. S. 
Published: August 2005

AbstractAn analytical model for the constant‐head pumping test is developed for a partially penetrating well that has a finite thickness skin, and intersects a single vertical fracture. In the model, the fracture is fully confined and flow occurs only in the fracture. The model is developed using Laplace transform and finite Fourier transform methods. The model is to be used for analysing well test data from vertically fractured media and for verifying numerical models. Dimensionless curves are used to study the effects of a finite thickness skin and a partially penetrating wellbore. In the presence of a finite thickness skin, or a partially penetrating wellbore, a typical flow response for the constant‐head pumping test has three distinct periods of flow corresponding to small‐, intermediate‐ and large‐time. Small‐ and large‐time approximations are presented for the model. For tests where the wellbore is fully penetrating, or the partial penetration ratio is known, these approximations can be used to analyse field data.