bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling of concrete response to fluctuating load
Authors: Jiang J. , Pietruszczak S. 
Published: August 2005

AbstractAn elastoplastic constitutive model for concrete subjected to cyclic loading conditions is presented. The model is an extension of a recently proposed constitutive concept.7 An initial active loading process is described, using the conventional framework of the rate independent theory of plasticity. An appropriate hardening/softening parameter is introduced which allows one to model the sensitivity of material characteristics to varying confining pressure, including a smooth transition from stable to unstable response. For stress histories that include stress reversals, the formulation invokes a set of neutral loading loci defining the conditions of the neutral state.8 The field of hardening moduli is specified through an appropriate interpolation rule which enables one to simulate adequately the effect of cyclic degradation of the material. The performance of the model is verified for some typical cyclic loading histories, and the results are compared with existing experimental data.
Bifurcation analysis of deep boreholes: II. Scale effect
Authors: Papanastasiou P. C. , Vardoulakis I. G. 
Published: August 2005

AbstractThis paper is a continuation of a previous one on bifurcation of deep boreholes under uniform stress at infinity,1 and it focuses on the effect of borehole radius on borehole stability. Rock is described by the equations of a deformation theory of plasticity for cohesive‐frictional, incompressible materials with Cosserat structure. The inhomogeneous bifurcation problem is formulated and the corresponding eigenvalue problem is solved numerically by the finite element method. It is demonstrated that the combined Cosserat and stress‐gradient effects lead to an increase of the bifurcation stress with decreasing borehole radius (scale effect).
A two‐dimensional poroelastic displacement discontinuity method for hydraulic fracture simulation
Authors: Vandamme L. , Detournay E. , Cheng A. H.‐D. 
Published: August 2005

AbstractThe coupled diffusion and deformation phenomena induced by the opening of a hydraulic fracture in a poroelastic medium are modelled using an extension of the displacement discontinuity method. This method consists in distributing fluid source and poroelastic displacement discontinuity singularities along the locus of the fracture, and over time. As an illustration, the problem of a suddenly pressurized crack in an infinite formation is examined.
An expression for the permeability of anisotropic granular media
Authors: Meegoda Namunu J. , King Ian P. , Arulanandan K. 
Published: August 2005

AbstractThere are many expressions proposed for the permeability of isotropic media based on flow channel and pore size distribution concepts, but there are no such expressions for anisotropic media. In this paper an expression for the permeability of an anisotropic medium is proposed, which has been verified in the laboratory.The mechanism behind fluid flow through soil was investigated using microscopic computer simulations to propose an expression for macroscopic permeability. The soil was assumed to be a spatially periodic porous medium, and the Navier‐Stokes equation was solved using the FEM with appropriate boundary conditions for several different arrangements of the porous medium. The basic variables influencing flow through soil at the microscopic level were identified as specific surface area, void ratio, particle shape, material heterogeneity and the arrangement of particles in a porous medium. A sensitivity analysis was carried out to obtain an expression for the permeability in terms of the above variables.The corresponding macroscopic variables for the above microscopic variables are average specific surface area, average void ratio, anisotropy, tortuosity due to material heterogeneity, and the arrangement of particles respectively. An expression for the directional permeability is proposed in terms of these variables for the most common occurrence of particles in a porous medium.For the verification of the proposed equation, the permeability values of a fine‐grained sand were measured at different void ratios and were compared with those predicted by the proposed equation. The results show that the predicted permeability values from the proposed equation are very close to the measured values.
System analysis in calculation of cantilever retaining walls
Authors: Dembicki Eugeniusz , Chi Tran 
Published: August 2005

AbstractThe paper is concerned with the solution and determination of the optimum shape of a retaining wall modelled by the co‐ordinates of a set of points which belongs to a certain permissible space.An optimum design method is formulated as a non‐linear multiobjective optimization problem. The following two objective functions, which are mutually conflicting and non‐commensurable with each other, are considered: (a) to minimize the total weight of the wall, (b) to maximize the structure stability.A set of Pareto optimum solutions is derived numerically by adopting a logical algorithm, and a Pereto optimum solution is obtained by investigating the trade‐off relationships among design objectives.
Thin flow element and the problem of ill‐conditioning
Authors: Valliappan S. , Khalili‐naghadeh N. , Murti V. 
Published: August 2005

AbstractThe problem of ill‐conditioning in anisotropic and heterogeneous flow regions using plane and axisymmetric conditions is studied. A new concept, conditioning ratio, which covers all the possible factors significantly affecting the problem of ill‐conditioning (e.g. aspect ratio, heterogeneity and anisotropy) is proposed. It has been shown that there is an upper limit for this conditioning ratio, beyond which the stiffness matrix of the modelled region will be ill‐conditioned. Using this limiting value and considering the fact that flow behaviour in a single fracture is, basically, independent of the value of permeability normal to the plane of the fracture, k1, a criterion is established to calculate the value of k1 for thin elements. By adopting this criterion the problem of ill‐conditioning could be avoided, regardless of the value of the aspect ratio. The reliability of the proposed criterion is examined by using thin elements with very large aspect ratio (up to 106) in modelling the pumping problem from a well fully intersecting a vertical fracture. The comparison of the numerical results with the available analytical solutions is found to be very satisfactory.
Boundary element approach to the dynamic stiffness functions of circular foundations
Authors: Alarcon E. , Cano J. J. , Dominguez J. 
Published: August 2005

AbstractA boundary element approach for time harmonic axisymmetric problems using the complete space point load fundamental solution is presented. The fundamental solution is integrated numerically along the azimuthal co‐ordinate of each axisymmetric element. To increase the accuracy of the numerical integration a simple co‐ordinate transformation is proposed. The approach is applied to the computation of the dynamic stiffness functions of rigid circular foundations on layered viscoelastic soils. Three different sites are considered: a uniform half‐space, a soil layer on a half‐space, and a soil consisting of four horizontal layers and a compliant half‐space. The numerical results obtained by the proposed approach for surface circular foundations are very close to corresponding published results obtained by different procedures.
Earth pressure behind a gravity retaining wall
Authors: Bakeer R. M. , Bhatia S. K. 
Published: August 2005

AbstractThis paper presents the results of an investigation of the static earth pressure behind a gravity wall with dry cohesionless backfill. A comparison is made between the results of finite element analyses and those of several experimental studies on wall models. The results of the investigation indicate that current design methods do not account adequately for some parameters that may influence the magnitude and distribution of the earth pressure. The study shows also that the design of earth‐retaining structures should be based on the amount of displacement permitted in the structure.
Analytical model for the design of grouted rock bolts
Authors: Indraratna B. , Kaiser P. K. 
Published: August 2005

AbstractAn analytical model which represents the behaviour of a reinforced rock mass near a circular underground opening in a homogeneous, uniform stress field has been developed. The theory adopts the concepts of elastoplasticity and considers a proper interaction mechanism between the ground and the grouted (or friction) bolts. It highlights the influence of the bolt pattern on the extent of the yield zone and tunnel deformation. A dimensionless parameter is introduced as a design tool which relates the tunnel convergence to the bolt spacing for a given bolt length. This publication contains the derivation of the analytical model and an illustration of the effect of bolts on the stress and displacement field near an opening. Its application to tunnel design is discussed briefly. The verification of the theory by laboratory simulation and field measurements will be presented, in detail, in a future publication.
Instability and ill‐posedness in the deformation of granular materials
Authors: Schaeffer David G. 
Published: August 2005

AbstractA linear stability analysis of the partial differential equations of granular flow is performed. The constitutive relations include (i) elastic effects, (ii) non‐associated flow rules and (iii) shear‐strain hardening. Conditions for the equations to be well‐posed and to be stable are derived. It turns out that there are two qualitatively different kinds of instability; which appears first depends on the parameters of the constitutive relations. If one kind appears first, then in a constitutive test a period of inhomogeneous deformation is predicted to occur before the formation of shear bands. If the other kind appears first, then shear bands are predicted to form in an approximately homogeneous sample. Some constitutive experiments are analysed from this viewpoint, and the analysis suggests some new experimental work.
Probabilistic foundation stability analysis
Authors: Ronold Knut O. 
Published: August 2005

AbstractA probabilistic model for stability analysis of a deepwater gravity‐based platform foundation is defined, based on theory for wave loading in conjunction with conventional slip surface considerations. The model accounts for uncertainties in loading as well as in soil properties, and model uncertainties are also considered. The model is updated through in‐service measurements of some of the governing variables, and measurement uncertainties are included. The practical application of the model is illustrated by presentation of calculations for a typical foundation. Probability calculations are performed by first‐order reliability methods.
Double‐porosity modelling of oscillatory gas motion and contaminant transport in a fractured porous medium
Authors: Nilson R. H. , Lie K. H. 
Published: August 2005

AbstractA double‐porosity model is used to describe the oscillatory gas motion and associated contaminant transport induced by cyclical variations in the barometric pressure at the surface of a fractured porous medium. Flow along the fractures and within the permeable matrix blocks is locally one‐dimensional. The interaction between fractures and blocks includes seepage of fluid as well as diffusion of contaminant. To guard against artificial numerical diffusion, the FRAM filtering remedy and methodology of Chapman is used in calculating the advective fluxes along fractures and within blocks. The entire system of equations, including the fracture‐matrix interaction terms, is solved by a largely implicit non‐iterative algorithm which remains stable and conservative even when the computational time step is large compared to the cross‐block transit time of pressure waves. The numerical accuracy is tested by comparison with exact solutions for oscillatory and unidirectional flows, some of which include diffusion interaction between the fracture and the matrix. The method is used to estimate the rate of vertical transport of radioactive gases through the rubblized chimney produced by an underground nuclear explosion.
Stress strain curve generation from simple triaxial parameters
Authors: Griffiths D. V. , Prevost J. H. 
Published: August 2005

AbstractA simple hyperbolic function is often used to illustrate typical stress‐strain behaviour of geomaterials during monotonic loading. This approach has the disadvantage that the failure condition is approached asymptotically, whereas in reality failure must occur at a finite value of strain. A modified hyperbolic function with one adjustable parameter is proposed in this paper. The function is shown to be capable of spanning all likely soil stress‐strain data up to and including peak strength.
Finite element analysis of progressive failure in long slopes
Authors: Wiberg N.‐E. , Koponen M. , Runesson K. 
Published: August 2005

AbstractProgressive failure in long natural clay slopes with an underlying weak shear zone is studied. The clay slope is assumed to be elastic–perfectly plastic, whereas the shear zone may have an elastic–plastic strain softening behaviour. The failure will occur due to the development of large shear deformations in the weak zone. The general behaviour, including the possibility of progressive failure, can be studied by the use of a one‐dimensional finite element model. Other interesting matters which can be studied are critical load, critical disturbance and critical length of the slope. Numerical examples show the overall behaviour due to different residual shear strengths of the weak layer, end disturbance or change of pore pressure in the weak layer. Although simple, the proposed finite element model provides a practically applicable tool for the prediction of whether progressive failure will occur and in which manner the local failure will propagate.
Vertical and horizontal deformation of an inhomogeneous elastic half‐space
Authors: Oner Mete 
Published: August 2005

AbstractVertical and horizontal deformations of surface footings have been studied for an inhomogeneous elastic half‐space in which the shear modulus increases with an arbitrary power of depth, n, and Poisson's ratio is constant. A general solution for displacements has been obtained first for point loads applied in vertical and horizontal directions. These are then used in obtaining closed‐form solutions for displacements of uniformly loaded circular and rectangular footings. Finally, a numerical method is described that can be used to analyse a rigid footing of an arbitrary shape, and results for rigid rectangular footings are given.
An endochronic plasticity theory with shear‐volumetric coupling
Authors: Valanis K. C. , Peters J. F. 
Published: August 2005

AbstractThermodynamic and physical principles are applied in conjunction with the concepts of endochronic plasticity to develop a theory of constitutive behaviour of soils with dilatant capability. Three separate constitutive models are derived within the framework of the proposed theory, all capable of accounting for shear–volume coupling of soil within the context of endochronic plasticity. One specific model is singled out as the most appropriate on the basis of its analytical simplicity and the plausibility of its thermodynamic and physical foundations. A simple example is worked out for the purposes of illustration.
A BEM–FEM approach for analysis of distresses in pavements
Authors: Subei N. , Saxena S. K. , Mohammadi J. 
Published: August 2005

AbstractA combined boundary‐element–finite‐element method is presented for the analysis of distresses in pavements subjected to mechanical and environmental effects. Owing to the spatial dimensions of the problem, the non‐homogeneity and the irregular geometry at the pavement joints, a combination of the two methods proves to offer a more realistic solution technique. The advantage of the finite element method (FEM) is in its capabilities of modelling near‐field regions at or around the vicinity of the joint, whereas the boundary element method (BEM) is more suitable to model the far‐field region at infinity.The three major distresses affecting the serviceability of the pavement system are the temperature, moisture and the applied mechanical loads. The model analyses the stresses and strains resulting from both mechanical and environmental factors in the analysis of a pavement system. Moreover, the infiltration of water through pavement joints, which causes weakening of the subgrade soil, is also analysed. Secondly the curling of the pavement concrete slab under the mechanical and thermal loads and induced friction may cause separation of the pavement structure from its supporting subgrade. Both are treated and modelled in this study. A detailed analysis of the pavement joint with its load transfer device is also performed for the proper assessment of the separation and further extension of the loss of support in the pavement system.
Numerical study of the electrical double‐layer repulsion between non‐parallel clay particles of finite length
Authors: Anandarajah A. , Lu Ning 
Published: August 2005

AbstractThe study presented herein concerns the double‐layer repulsive force that exists between clay particles in a clay–water–electrolyte system. The objective is to examine the nature of the double‐layer repulsive force between two negatively charged clay particles that are inclined to each other and have finite length. The finite element numerical technique is used first to determine the spatial distribution of the electric potential. The net repulsive force and its location are then evaluated from this known distribution of the potential on the basis of the theory of electrostatics. A systematic parametric study is performed by varying certain dimensionless system variables, particularly to investigate the effect of orientation, surface potential and particle length. It is found that for non‐parallel orientation, as the value of inclination and surface potential increase, the repulsive force decreases and its location shifts towards the particle ends that are closer to each other.
Properties of the 20‐node brick
Authors: Smith I. M. , Kidger D. J. 
Published: August 2005

AbstractThree‐dimensional elastoplastic analyses are increasingly feasible as computing power increases. Candidate finite elements for this work are 20‐node bricks. In elastoplastic situations, yielding creates ‘soft’ regions within a stiffer surrounding matrix and propagation of spurious modes is possible under reduced integration. In this paper, the intrinsic properties of the 20‐node brick are analysed, with a view to avoiding numerical complications in plasticity analyses.
Cavity expansion in sands under drained loading conditions
Authors: Collins I. F. , Pender M. J. , Yan Wang 
Published: August 2005

AbstractSolutions for the expansion of cylindrical and spherical cavities in sands are presented. The sand is modelled using recently proposed critical‐state models in which the values of the friction and dilation angles depend on the deformation history. Similarity solutions are obtained which enable the limit pressure to be calculated as a function of the initial conditions. Comparisons with existing perfectly plastic theories are made and consequences for the interpretation of cone penetrometer measurements are indicated.
Simulation of excavation in a poro‐elastic material
Authors: Hsi J. P. , Small J. C. 
Published: August 2005

AbstractA method is presented which allows the computation of the displacements and pore pressures which are generated in an elastic soil when excavation is carried out. The formulation is based on Biot's theory and is fully coupled, with consideration also given to the effects of the lowering of the water table which often accompanies the excavation of soil. Example problems are solved to illustrate the theory which has been presented.
Stress distribution beneath rigid circular foundations on sands
Authors: Balakrishna C. K. , Murthy B. R. Srinivasa , Nagaraj T. S. 
Published: August 2005

AbstractThe calculation of stresses induced inside the soil mass by the foundation loads forms an essential step in most of the geotechnical engineering problems dealing with the probable behaviour of foundations. The distribution of stresses on horizontal planes containing reinforcements at various depths is required in the analysis and design of reinforced soil foundations. An accurate evaluation of contact pressure distribution at the interface is a prerequisite for the computation of stresses inside the soil mass. Of the several approaches the elastic‐plastic approach of computing the contact pressure distribution appears to be reasonable. Using this approach non‐dimensional equations have been derived for calculating the contact pressure distribution beneath rigid circular foundations on sands. The contact pressure distribution so derived has been used for computing the stresses at various points using elastic theory. The results have been graphically presented and are compared with Boussinesq's distribution for uniform contact pressure.
A finite element procedure for calculation of strain from interpolated displacements
Authors: Carr James R. 
Published: August 2005

AbstractSecond‐order universal kriging is proposed as an accurate model for interpolating displacements measured in the field to nodal points of a superimposed finite element mesh. These interpolated displacements are used in a modified finite element procedure to calculate strain. This model is compared to a local trend model to judge superiority. Interpolation models are tested by randomly sampling displacements obtained in a finite element analysis, then applying interpolation in attempts to reconstruct the original results.
Numerical analysis of sampling disturbances in clay soils
Authors: Budhu Muniram , Wu Chang S. 
Published: August 2005

AbstractIn this paper, an insight is provided into the quality of soil samples during the penetration of soil samplers. An updated Lagrangian finite element formulation with the second Piola–Kirchhoff stress rate (the Truesdell stress increment) to account for the large deformation behaviour near the sampling tube is used to determine the mechanical disturbances to a soft clay. The penetration of the sampler is simulated by splitting a group of nodes ahead of the penetration route up to a sufficient depth and applying incremental displacements to match the geometric configuration of the sampling tube. Consolidation effect is included to account for the rate of penetration. Thin‐layer elements are added at the inside wall of the sampling tube to model the soil–sampler interface.The numerical results show that the central core of the sample is subjected to three distinct stages of vertical strain history, compression–extension–recompression, with the primary irrecoverable disturbances due to the compression stage ahead of the sampler. The degree of disturbance for a frictionless sampler was found to be constant after a penetration depth of 75 per cent of the sample tube diameter, while for a frictional sampler the degree of disturbances keeps increasing as the penetration proceeds. The results of a parametric study to determine the influence on sampling disturbances due to the rate of penetration, the thickness and the tip angle of the sample tube and sampler type are also presented.
The integration of the Melan solution over a line segment—implementation for boundary element modelling of surface excavations
Authors: Meek J. L. , Dai C. 
Published: August 2005

AbstractIn this paper, we have deduced the integration solution of the Melan problem (concentrated force at a point in the infinite half‐plane) over a line segment directly from the two‐dimensional result by the complex variable function method. The BEM dependent on these integration solutions is shown to be valuable for modelling surface and near‐surface excavations. Examples are given of the comparison with Mindlin and analytic solutions.