bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computing costs for FEM analysis of foundation engineering problems and possible ways of increasing efficiency
Authors: Schad Hermann 
Published: August 2005

AbstractThe application of finite element methods (FEM) is often restricted by the available computer capacity and the computing costs. The purpose of this paper, therefore, is, to present test results and to discuss possible ways of achieving a substantial reduction in computing times. Dividing the numerical analysis into the five levels–hardware, software, element‐mesh and element‐type, iteration technique (approximation of non‐linearity) and constitutive model–one can show that the computing time can be reduced by about 20 per cent at every level. In particular, the use of the modified Newton‐Raphson method for approximation of non‐linearity and the constitutive model–apart from the theoretical concept (elastoplastic, hypoelastic etc.)—must be formulated in a manner which does not produce substantial changes in the coefficients of the material matrix caused by small stress changes. On the whole, computing time can be reduced to about 10 per cent of present computing costs. Thus, it would even be economically viable to solve three‐dimensional non‐linear problems by FEM.
On the choice of elastic parameters for sand
Authors: Loret B. 
Published: August 2005

AbstractWhen soils are considered as elastoplastic materials the elastic moduli are much higher than the plastic one(s). However the amount of elastic strain cannot be disregarded as it appears when undrained loading occurs. Based on experimental or theoretical observations, a number of elastic models with stress dependent moduli have been proposed. Attention is focused here on the consequences of this stress dependency on the recoverability of strain and work done after a closed stress path. A necessary and sufficient condition for an elastic material to be hyperelastic is given and the way to obtain practical solutions is shown on examples. The study is restricted to isotropic material undergoing small strains.
The behaviour of an elastic non‐homogeneous half‐space. Part I‐line and point loads
Authors: Booker J. R. , Balaam N. P. , Davis E. H. 
Published: August 2005

AbstractIn the first part of this paper solutions are developed for the response of a non‐homogeneous half‐space subjected to either a surface point load or a surface line load. The non‐homogeneity considered is a variation in Young's modulus (E) with depth (z) which takes the form E=mEZα where mE is a constant and α is referred to as the non‐homogeneity parameter.The variation of these solutions as the non‐homogeneity parameter α varies between the limits of zero (homogeneous soil) to unity (Gibson soil) gives some fresh insight into both these limiting cases.
The behaviour of an elastic non‐homogeneous half‐space. Part II–circular and strip footings
Authors: Booker J. R. , Balaam N. P. , Davis E. H. 
Published: August 2005

AbstractSolutions developed in the first part of this paper (i.e. describing the response of a non‐homogeneous half‐space subjected to surface point and line loads) are used in this part to obtain solutions for a variety of surface loadings. Consideration is given to a distributed load acting over a circular area or strip and a rigid disk or strip subjected to applied normal load and moment.It is established that the profiles of surface settlement due to uniformly distributed loads acting over a strip or circular area are strongly dependent on the degree of non‐homogeneity. This dependency is reduced when the footing is rigid. When α = 1 the moduli variation is identical to the Gibson soil and the equivalence with the Winkler soil model is established.
Modelling two‐dimensional heat and moisture transfer in unsaturated soils, including gravity effects
Authors: Thomas H. R. 
Published: August 2005

AbstractA theoretical model is presented to predict simultaneous transient coupled heat and moisture transfer in partly saturated soils. The formulation is in terms of volumetric moisture content, is two dimensional, includes gravitational flow and takes into account latent heat of vaporization effects. The numerical solution of the problem is accomplished by means of a finite element solution algorithm. Predictions from the numerical model are used to investigate the importance of gravitational flow, for the case of a soil stratum subjected to evaporation losses at the surface. The results achieved show good qualitative agreement with expected behaviour.
Finite layer analysis of viscoelastic layered materials
Authors: Booker J. R. , Small J. C. 
Published: August 2005

AbstractA method is presented for obtaining the creep settlement of strip or circular loadings applied to horizontally layered soil profiles. The solution method involves applying a fourier (strip loading) or Hankel (circular loading) transform to the governing equations, which reduces the two of three dimensional problem to one involving a single spatial demension. This leads to great savings in computer storage and data preparation time, and since an exact solution may be found for each layer of material, the method has advantages over conventional finite layer techniques where field quantities must be approximated at a number of positions within each layer.The type of formulation presented hearein makies it possible to work in terms of the creep functions of the soil rather than the relaxation functions. This has distinct advantages, as it is often easier to measure the creep behaviour of a soil in the laboratory.Numerical techniques are used to invert the laplace and Hankel transforms and this means that any type of creep function (which is invertible) may be used to describe the material properties of the soil.
Time dependence of axial pile response
Authors: Murff J. D. , Schapery R. A. 
Published: August 2005

AbstractThis communication describes an approximate method for generalizing homogeneous, linearly elastic, subgrade type solutions of axial pile response to account for soil creep behaviour. The method is very simple to apply and can be used in conjunction with either analytical or numerical elastic solutions. Exact solutions for limiting cases and finite difference solutions in both space and time are presented to confirm that errors introduced by the approximations are small. Because of the theoretical basis of this approach it is anticipated that method can be used with other pile problems, lateral and axial, for both subgrade adn continuum idealizations. Methods for generalizing the results to more complex conditions such as non‐homogeneity or time varying loads are given.
The behaviour of layered soil or rock containing a decaying heat source
Authors: Small J. C. , Booker J. R. 
Published: August 2005

AbstractSolutions are presented for the behaviour of layered soil or rock deposits which contain a heat source. Such a problem arises when high level nuclear waste is placed in deep underground depositaries, as the waste continues to generate heat for many years after placement. This heating of the surrounding soil or rock may lead to expansion and cracking with subsequent contamination of ground water. Results are presented for heat soureces with different decay rates and for heat sources in layers of material with different coefficients of expansion. An example using realistic data for rock is also given.The solution method involves applying Fourier or Hankel transforms to the field quantities and this reduces the two‐dimensional or axisymmetric problem to one involving a single spatial dimension. In cases where the soil or rock is horizontally layered, the method has great advantages over other numerical methods such as finite element or finite difference techniques, since little computer storage and data preparation time is required.Solution of the time‐dependent problem is carried out by applying Laplace transforms to the field variables, obtaining solutions and then using numerical means to invert the transformed solutions. This enables easy solution of problems involving time‐dependent (i.e. decaying) heat sources.
Interaction between jack‐up rig foundations and offshore platform piles
Authors: Chow Y. K. 
Published: August 2005

AbstractThis paper presents a study of the interaction between the foundations of a jack‐up rig and the pile foundations of an adjacent steel offshore platform. Parametric solutions are presented to evaluate the effect of the rig footing load on the performance of the pile foundation. Homogeneous and non‐homogeneous soil conditions have been considered. An example is used to illustrate the application of the solutions in a practical problem.
Optimal estimation of in‐situ ground stresses from displacement measurements
Authors: Feng Z. L. , Lewis R. W. 
Published: August 2005

AbstractThis paper presents a study on the optimal estimation of initial in‐situ stresses, in which the in‐situ stresses may be constant or linearly changing along a co‐ordinate axis, from a set of relative measurements between adjacent measuring points utilized for monitoring the stability of tunnels. Displacements occurring before installation of measuring devices can be taken into account. The approach may be used for a variety of models used to simulate the ground media through which the tunnels are being excavated and has the advantage of being easy to implement on the computer and having both good precision and calculation stability. Finally, an analysis is carried out on the stability of the algorithm and computational time for different numerical examples.
A nonlinear analysis of two‐dimensional heat and moisture transfer in partly saturated soil
Authors: Thomas H. R. 
Published: August 2005

AbstractThe subject of this paper is the nonlinear analysis of heat and moisture transfer in partly saturated soil. In particular, an extension of the previous work of the author to two‐dimensional applications is presented. Problems of greater complexity and engineering significance can hence be solved. The theoretical basis of the problem is first outlined before the two‐dimensional formulation of the numerical solution is given. The finite element method is employed to give the spatial distributions of the variables, with a finite difference scheme being used to predict the temporal variations. The method allows the nonlinear nature of the soil parameters to be modelled, predictions being given of the coupled transient simultaneous transfer of heat and volumetric moisture content. The two‐dimensional nature of the work is illustrated for the case of surface evaporative soil moisture losses from sloping ground. Subsoil conditions of a uniform deposit of loam are considered with values of representative material parameters assumed after a literature search. The coupled nature of heat and mass transfer is illustrated by means of an analysis of the moisture migration patterns that occur. Two‐dimensional moisture flow, out of and into the soil, is shown to take place.
A large strain theory and its application in the analysis of the cone penetration mechanism
Authors: Kiousis Panos D. , Voyiadjis George Z. , Tumay Mehmet T. 
Published: August 2005

AbstractA computational method, based on an advanced elasto‐plastic large strain formulation, well suited for the analysis of the cone penetration problem, is presented.A new approach of finite strain elasto‐plastic analysis is employed.13 The basic (non‐rate) constitutive relations are developed in a spatial reference space to preserve their physical significance. They are subsequently transformed in Lagrangian co‐ordinates, and through simple time differentiation, their rate equations are introduced. The method is computationally implemented with the finite element method and special provisions are taken to allow for the moving boundary conditions of the problem.
A semi‐analytical solution for swelling around a borehole
Authors: Carter J. P. 
Published: August 2005

AbstractPrevious field and laboratory studies have shown that the creation of a borehole in a saturated cohesive soil mass induces significant pore water suctions in the vicinity of the hole. The dissipation of these pore water suctions (swelling) leads to local increases in the moisture content and hence a softening of the soil around the hole. This softening may have important consequences for the stability of the hole and also for the ultimate load capacity of any foundation elements (bored piles or drilled shafts) constructed in these holes. This paper presents a semi‐analytical solution for the radial dissipation of pore water pressure around a freshly created, vertical hole. It is assumed the soil deforms elastically during the swelling process. The solutions are presented in the form of isochrones of excess pore water pressure and may be used to obtain estimates of the time required for the soil around the hole to swell and therefore to soften. Both permeable and impermeable borehole interfaces have been considered, together with either no support for the hole or partial support provided by hydrostatic pressure within the hole.
The analysis of consolidation by a quasi‐Newton technique
Authors: Borja Ronaldo I. 
Published: August 2005

AbstractA quasi‐Newton algorithm is implemented for the solution of multi‐dimensional, linear consolidation problems. The study is motivated by the need to implement an efficient equation‐solving technique for the solution of large systems of equations typical in problems of consolidation of saturated porous media. The proposed procedure obviates the need to reassemble and re‐factorize the global coefficient matrix every load increment, albeit the time step may be held variable in the analysis. The method employs the combined techniques of ‘line search’ and BFGS updates applied to the coupled equations. A numerical example is presented to show that the proposed method is computationally more efficient than the conventional direct equation‐solving scheme, particularly when solving large systems of finite element equations.
Pollutant migration from deeply buried repositories
Authors: Rahman M. S. , Booker J. R. 
Published: August 2005

AbstractSemi‐analytic solutions are developed for the migration of pollutants from cylindrical and spherical repositories buried deep in a homogeneous and isotropic soil in the presence of a uniform and unidirectional advection. The techniques adopted involves taking the Laplace transform of the governing equations, finding an analytic solution in transform space and then numerically inverting the transform to obtain the concentrations of the contaminants at selected positions and times. Numerical results are presented, and practical implications discussed.
A numerical and laboratory investigation into the behaviour of a dry underclay beam
Authors: Afrouz A. , Hassani F. P. 
Published: August 2005

AbstractA simple and inexpensive laboratory device has been developed and used to simulate the behaviour of a dry underclay beam as the floor of an underground roadway subjected to a uniformly distributed uplift pressure. The Airy stress function method proved to be a useful means of expressing and predicting of the uplift of such beams. This method has been related to both classical beam theory and laboratory investigations. It was found that the Airy stress function method, utilizing polynomial equations, provides a closer fit to the mechanism of beam deformation and stress developments under dry laboratory conditions.
Use of the finite element method in modelling a static earth pressure problem
Authors: Bhatia S. K. , Bakeer R. M. 
Published: August 2005

AbstractResults obtained with the finite element method are greatly affected by the overall dimensions of the mesh and the number and size of the elements used. Proper choice of the boundary conditions is also necessary to obtain an accurate estimate of the unknowns of the problem. This paper discusses some factors that influence the results of a finite element idealization of the problem of earth pressure behind a gravity wall with a dry, cohesionless backfill.
Initial moduli of particulated mass with frictional contacts
Authors: Chang Ching S. , Sundaram Sivanuja S. , Misra Anil 
Published: August 2005

AbstractThe stiffness characteristics of a packing of granules are influenced by the particle interactions at contacts, the void ratio, the co‐ordination number and the packing structure. A stress‐strain relationship for the packings of spheres is presented. The relationship explicitly includes the contact force‐displacement law and the parameters characterizing the packing structure. The initial moduli computed using this relationship are compared with experimental measurements and empirical equations for sands. The theoretical results are also compared with experimental results on packings of glass balls. Closed‐form solutions are derived for statistically isotropic packings under initial isotropic stress conditions. Numerical solutions for the stiffness properties are obtained for anisotropic initial stress conditions and anisotropic packing structures.
Formulation and application of element methods in the simulation of pressure and temperature history of geological basins
Authors: Søreng Jan 
Published: August 2005

AbstractA mathematical model treating the compaction of sediments in geological basins is derived. The model is based on the principle of conservation of mass and energy, and gives a consistent and complete set of equations for compaction, pressure and temperature history of sedimentary basins.Further, the paper describes a numerical model based on the mathematical equations, derived by using the finite element method. This derivation starts with the time‐discretized versions of the conservation laws of mass and energy. The result is the time‐discretized equations for pressure and temperature. The numerical derivation is parallel with the mathematical deductions. By integrating these time‐discretized equations spatially the element equations are obtained. Hence, the element equations are derived directly from the underlying physical laws. This approach to developing element equations in a compacting medium is believed to be new. The model has been tested successfully on some geological basins, and the results of a simulation are included at the end of the paper.
Comparison of laplace transform and finite difference solutions for an evolving permafrost region
Authors: Morland L. W. , Kelly R. J. 
Published: August 2005

AbstractLaplace transform solutions are derived for an evolving permafrost region in saturated ground when the freezing interface moves with constant speed. The solution is inverse in the sense that the melting temperature at the interface and the groud surface temperature are prescribed functions of time. The solution procedure incorporates an initial temperature distribution in a domain extended above the ground surface. This allows, by asymptotic analysis, the construction of initially continuous melting and surface temperatures with bounded first and second derivatives. Solutions for two classes of initial conditions are determined by numerical inversion of the transforms. These solutions are used to test the corresponding solutions obtained by a direct finite difference algorithm developed earlier.1 Good agreements for both interface path and temperature profiles are obtained in both classes.
In‐plane vibrations of soil deposits with variable shear modulus: II. Line load
Authors: Vrettos Ch. 
Published: August 2005

AbstractThe dynamic response of an inhomogeneous, linear‐elastic half‐space to a time‐harmonic vertical line load on its surface is studied. The mass density and the Poisson's ratio are assumed to be constant and the shear modulus to increase continuously with depth according to a function which is bounded at infinity. This model can describe a wide range of uniformly deposited soil strata. Analytical solutions for the displacement field at the surface are obtained using the classical contour integration method by means of the residue theorem. The dependence of the displacement field on distance from the source, frequency and shear modulus variation is examined as well as the relative contribution of the higher surface wave vibration modes to the total displacement.
3D‐boundary element analysis of the lowered groundwater level for tunnels driven under compressed air
Authors: Chen Z. S. , Hofstetter G. , Mang H. A. 
Published: August 2005

AbstractA direct boundary element method for the iterative analysis of the lowered groundwater level and the steady‐state airflow in porous soil for tunnels driven under compressed air is presented. The soil may be zoned and anisotropic. It is shown that disregard of the compressibility of the air leads to results for the excess air pressure and the flow of air through the surface of the soil, which are on the unsafe side. The lowered groundwater level is determined by means of an iterative procedure. During the iteration large changes of the shapes of boundary elements may occur. In order to reduce the resulting danger of divergence of the iteration, the boundary element mesh is adapted suitably in the course of the iteration process.
Computer‐aided calibration of a soil plasticity model
Authors: Anandarajah A. , Agarwal D. 
Published: August 2005

AbstractA non‐linear optimization technique based on the quasi‐Newton approach is employed to back‐calculate certain model parameters of a simple, bounding surface, soil plasticity model from in situ pressuremeter data. The theoretical response corresponding to a given set of parameters is generated by finite element analysis. A semi‐analytical procedure is developed for the accurate and efficient evaluation of the gradient of objective function with respect to the model parameters of interest. The BFGS update is used to update the Hessian. Results of a series of numerical experimentation using artificial pressuremeter responses is first reported and discussed. A set of laboratory cavity expansion data is then used to calibrate the constitutive model.
Consolidation of clays subjected to three‐dimensional embankment loadings
Authors: Small J. C. , Zhang B. Q. 
Published: August 2005

AbstractA Fourier transform technique is presented which may be used to analyse three‐dimensional consolidation problems for soils which are loaded by embankment shaped loadings that are rectangular in plan (or of arbitrary shape which can be divided into rectangles in plan). The introduction of a Fourier transform effectively reduces the three‐dimensional problem to one involving only two spatial dimensions and this reduces computer storage and saves computing and data preparation time. The material properties of the soil may vary arbitrarily in the plane which is perpendicular to the axis associated with the variable eliminated during the Fourier transform. Solutions obtained using the method are compared with existing solutions in order to verify the theory and assess accuracy, and illustrative examples are given for problems involving the consolidation of soils under embankment loadings.