bluuebunny/crossref_metadata_2025_split huggingface dataset:
Finite element simulation of time dependent fracture and fragmentation processes in rock blasting
Authors: Digby P. J. , Nilsson L. , Oldenburg M. 
Published: August 2005

AbstractTwo constitutive models for the simulation of fracture and fragmentation processes in rapidly loaded rocks are studied. The models were included in a wave propagation finite element code. The results obtained from the two models were compared by a study of the intensity and extent of fracturing obtained from two different configurations of explosive charge and reflecting surfaces in a plane strain problem. The evolution of the time dependent fracture pattern and fragmentation process is also presented.
Dynamic analysis of piles and pile groups embedded in non‐homogeneous soils
Authors: Senm R. , Kausel E. , Banerjee P. K. 
Published: August 2005

AbstractA hybrid boundary element formulation for the steady state analysis of piles and pile groups embedded in a soil stratum in which the modulus increases linearly with depth is presented. The piles are represented by compressible columns or flexible beams and the soil as a hysteretic, layered medium. The explicit Green's function corresponding to dynamic loads in the interior of a layered stratum, developed earlier by Kausel is used in the study.The governing differential equations for the pile domain are solved for a distributed periodic loading intensity and those for the soil domain by a system of boundary elements at the pile‐soil interface. These are then assembled into a system of algebraic equations by satisfying interface equilibrium and compatibility.The results of the analysis have been compared against those from alternative formulations, e.g. finite elements, and confirm the accuracy of the proposed formulation. Representative results for single piles and pile groups are presented.
Some aspects of coupled FEBEM analysis of underground openings
Authors: Varadarajan A. , Sharma K. G. , Singh R. B. 
Published: August 2005

AbstractThe finite element method (FEM) and the boundary element method (BEM) are two well established numerical methods used for the analysis of underground openings. The advantages of both the methods are utilized by adopting FEBEM in which finite elements are coupled with boundary elements. A coupling procedure is presented in this paper. In using FEBEM, the effect of the location of interface boundary between finite element and boundary element regions, effect of Poisson's ratio and effect of stress ratio are discussed. It is shown that Poisson's ratio and stress ratio have significant effect on the accuracy of the results. Different discretization schemes are discussed to study their effect on accuracy and computation time. The use of different material properties in the FE region is presented. A comparative study is made with FEM for all the cases. It is shown that use of FEBEM is more advantageous than FEM.
Geotechnical aspects of remedial design for a gold tailings dam
Authors: Sully J. P. 
Published: August 2005

AbstractRemedial measures were required for a gold tailings dam in South Africa which had undergone a minor slope failure. Information from laboratory and field measurements was used for evaluation of the present and future stability as the height of the dam increased. To aid the design process, numerical methods were used for prediction of in situ conditions. Stability analyses by computer were then used to optimize the type of remedial measure.
A variational inequality approach to free surface seepage in an inhomogeneous dam
Authors: Westbrook D. R. , Gilmour Grant J. 
Published: August 2005

AbstractThe current work uses Baiocchi's transformation to obtain heuristically a formulation of the inhomogeneous dam problem. When finite element methods are applied the finite dimensional problem is a variational inequality which may be solved to obtain approximate solutions. The main advantage of the method is that it uses a fixed mesh.The finite dimensional problem is solved by means of succesive overrelaxation with projection. Although the standard convergence theory1 for this method does not apply in this case, because the stiffness matrix is not symmetric, satisfactory and rapid convergence was obtained in all of our examples.Numerical results are given for some examples.
Numerical Laplace‐Fourier transform inversion technique for layered‐soil consolidation problems: I. Fundamental solutions and validation
Authors: Vardoulakis I. , Harnpattanapanich T. 
Published: August 2005

AbstractA numericl method for solving consolidation problems of layered soils is developed. Starting from the governing differential equations for the coupled poro‐elastic medium, the governing partial differential equations are reduced to ordinary differential equations by means of the appropriate displacement functions and Laplace‐Fourier transformation. Once the fundamental solution in the transformed domain has been found, the solution in the physical domain is obtained by numerically inverting the transformations. A series of soil consolidation problems have been solved and validated against existing solutions in order to compare the feasibility and the accuracy of the present technique.
Analysis of axial pile‐soil interaction in clay
Authors: Heydinger Andrew G. , O'Neill Michael W. 
Published: August 2005

AbstractA method for predicting the maximum mobilized side resistance and unit shaft resistance‐displacement curves (load transfer functions) on piles in clay is described. The method was derived using a numerical solution to model pile installation effects and a finite element scheme to model pile loading. Results of three well‐documented pile load tests on steel piles were used to develop intermediate steps and final solutions, and the method was verified by comparing predicted results to two other load tests. An expression is proposed to represent load transfer functins for use by practitioners for the design of bridge and other foundations in clay.
A numerical study of the effects of wall deformation on earth pressures
Authors: Potts D. M. , Fourie A. B. 
Published: August 2005

AbstractWhen designing any earth retaining structure it is necessary to estimate the limiting earth pressures. This is usually achieved by assuming a linear pressure distrigution and by using active and passive pressure coefficients obtained by either limit equilibrium, stress field solutions of limit analysis. These coefficients are approximate in a theoretical sense, do not distinguish between modes of wall movement, and provide no pre‐failure information. In practice, wall movements are dependent on the construction method and support conditions provided. Any effect of such movements on earth pressures is therefore of practical interest. In this paper the finite element method is used to investigate the effect of the mode of wall movement on the generation of earth pressure. Both smooth and rough walls are considered. It is shown that the distribution of earth pressure is highly dependent on the assumed mode of deformation. The resultant forces on the wall are also affected, but to a lesser degree. The, effect of soil dilatation, the initial horizontal stress and the distribution of soil stiffness with depth are also examined.
Stratified subsoil modelled by a cross‐anisotripic elastic half‐space
Authors: Sekowski Jerzy 
Published: August 2005

AbstractA method of analysing horizontally stratified subsoil by using as a substiutive model a homogeneous anisotropic elastic half‐space is presented. the material parameters for the substitutive model are dependent on the geometric and mechanical properties of the stratified soil.
Kinematics of axisymmetric vertical slopes at collapse
Authors: Drescher A. 
Published: August 2005

AbstractThis paper discusses the kinematic admissibility of axisymmetric velocity fields for the upper bound stability analysis of slopes surrounding cylindrical openings in frictional materials. The governing kinematic equations for two corner regimes of the Mohr–Coulomb yield condition are analysed. Although the equations can be solved by the method of characteristics, the characteristics and the characteristic relations for each regime differ significantly, for the Haar–von Karman regime the characteristics are non‐orthogonal and strong discontinuities are admissible, whereas for the other regime the characteristics are orthogonal and strong discontinuities must be excluded. Examples of simple velocity fields and the corresponding stability numbers are, given and compared with the partial collapse mechanisms. The solutions are verified against certain inequalities which must be satisfied for kinematical admissibility of axisymmetric velocity fields.
Rheological behaviour effects of non‐Newtonian fracturing fluids on propagation of a vertical hydraulic fracture
Authors: Pascal H. 
Published: August 2005

AbstractThis communication investigates the effects fo the non‐Newtonian behaviour of the fracturing fluids in the hydraulic fracturing mechanism. These effects are illustrated on the propagation of a vertical hydraulic fracture into an oil reservoir, in which the fracturing fluid is of power law and of pseudo‐plastic type. The analytical solutions for evaluating the fracture lengrhs are presented for the cdases of large fluid loss and for no fiuid loss. The results obtained should be useful in the design of fracture treatments, permitting the finding of the rheological properties of the injected fluid for obtaining the desired fracture length and width.
A plasticity model for the mechanical behaviour of anisotropically consolidated clay
Authors: Banerjee P. K. , Yousif N. B. 
Published: August 2005

AbstractAn incremental plasticity theory has been developed to describe the mechanical behaviour of anisotropically consolidated clays. The theory removes some of the shortcomings of the existing critical state models by incorporating the effects of the initial anisotropy due to a known depositional stress history and its subsequent alteration during further plastic deformation under a general stress system.From the extensive comparisons with the reported results in the literature, it is established that the model is satisfactory in predicting the various aspects of drained as well as undrained behaviour of K0‐consolidated clays.
A probabilistic permeability model and the pore size density function
Authors: Juang C. H. , Holtz R. D. 
Published: August 2005

AbstractMathematical interpretation of the pore size disribution (PSD) data as measured by mercury intrusion porosimetry was revealed in detail. The PSD data were commonly presented as cumulative intruded volume per gram of specimen versus pore size. In this paper, however, they were expressed in a dimensionless term for convenient mathematical operations. The pore size density function was deduced from the PSD data using the finite difference approximation and curve‐fitting technique. For the prediction of permeability, first the published correlations between permeability and pore geometry were critically reviewed. A probabilistic permeability model based on the pore size density function was then developed, which can be thought of as a generalization of Childs and Collis‐George's model. Predictions of permeability of the compacted soils studied using the developed model were very good for a wide range of permeabilities.
Constitutive models for rock discontinuities with dilatancy and surface degradation
Authors: Plesha Michael E. 
Published: August 2005

AbstractA physically motivated constitutive law for the behaviour of geologic discontinuities with dilatancy and contact surface degradation (damage) is presented. In the formulation of the law, the paper distinguishes between macroscopic and microscopic features of the contact surface. Through macroscope considerations. an incremental constitutive law is derived which is applicable to a large class of contact‐friction problems. By idealizing the microstructure to consist of interlocking asperity surfaces, the constitutive equations are specialized for the description of rock joints including effects such as dilatancy, asperity surface degradation and bulking. Several examples are considered demonstrating the law's behaviour and agreement with experimental data. The incremental form of the equations that are derived are amenable to implementation in numerical procedures such as finite element and discrete element (rigid block) computer programs.
Determination of a spatial fracture network
Authors: Thomas A. , Pineau A. , Blin‐Lacroix J. L. 
Published: August 2005

AbstractHydraulic and mechanical properties of rock masses are largely dependent upon the distribution and variation of fracture areas. Consequently, it is essential to develop good models for analysing the spatial geometric characteristics of fracture fields. The latter, however, may be ascertained only by measuring open cuts or boreholes. The most important factor from the analysis of areas is to be able to determine spatial networks. Without an exhaustive and expensive inventory, the classical methods involving measurements of dip and strike do not provide either a correct estimation of fracture orientations in space, or a good estimation of their distribution.At present, automatic analysis of linear traces on large plane areas is used by several authors1,2 and the field strike and dip measurements are applied only for verification purposes. This method of computing spatial networks is especially suitable because of the nature of data so obtained, since it permits various simulations on computed networks. It is based upon classical methods of vector geometry that involve a measurements data matrix and provide a means of solving a double system of equations. Results are the directional spatial fracture densities. The object of this paper is to define the geometric parameters of this problem and the computation method, to present an example and, finally, to conclude with critical comments supported by certain proposals for a variety of applications.
Deformation and fracturing behaviour of discontinuous rock mass and damage mechanics theory
Authors: Kawamoto Toshikazu , Ichikawa Yasuaki , Kyoya Takashi 
Published: August 2005

AbstractThe mechanical behaviour of a rock mass is strongly affected by discontinuities such as faults and joints. In this paper, a damage mechanics theory is proposed which deals with some sets of discontinuities distributed in a rock mass, for example, joint systems. In this theory, the distributed discontinuities are characterized by a second‐order symmetric tensor, called the damage tensor. By introducing the damage concept, the deformation and fracturing behaviour of the rock mass can be reated in a framework of continuum mechanics. A numerical procedure is developed in order to implement the damage mechanics model by using the finite element method. The theory and numerical analysis are applied to several laboratory tests and a practical underground opening problem. Numerical results are compared with measured data.
Lower bound limit analysis using finite elements and linear programming
Authors: Sloan S. W. 
Published: August 2005

AbstractThis paper describes a technique for computing lower bound limit loads in soil mechanics under conditions of plane strain. In order to invoke the lower bound theorem of classical plasticity theory, a perfectly plastic soil model is assumed, which may be either purely cohesive or cohesive‐frictional, together with an associated flow rule. Using a suitable linear approximation of the yield surface, the procedure computes a statically admissible stress field via finite elements and linear programming. The stress field is modelled using linear 3‐noded traingles and statically admissible stress discontinuities may occur at the edges of each triangle. Imposition of the stress‐boundary, equilibrium and yield conditions leads to an expression for the collapse load which is maximized subject to a set of linear constraints on the nodal stresses. Since all of the requirements for a statically admissible solution are satisfied exactly (except for small round‐off errors in the optimization computations), the solution obtained is a strict lower bound on the true collapse load and is therefore ‘safe’.A major drawback of the technique, as first described by Lysmer,1 is the large amount of computer time required to solve the linear programming problem. This paper shows that this limitation may be avoided by using an active set algorithm, rather than the traditional simplex or revised simplex strategies, to solve the resulting optimization problem. This is due to the nature of the constraint matrix, which is always very sparse and typically has many more rows that columns. It also proved that the procedure can, without modification, be used to derive strict lower bounds for a purely cohesive soil which has increasing strength with depth. This important class of problem is difficult to tackle using conventional methods. A number of examples are given to illustrate the effectiveness of the procedure.
Analysis of one‐dimesional wave propagation in a fluid‐saturated finite soil column
Authors: Hiremath Mahantesh S. , Sandhu Ranbir S. , Morland Leslie W. , Wolfe William E. 
Published: August 2005

AbstractBiot's dynamic equations of motion for one‐dimensional wave propagation in a fluid‐saturated linear elastic isotropic soil are solved using Laplace transformation followed by numerical inversion and the results compared with a direct finite element formulation. A soil column of finite dimension subjected to velocity boundary conditions is analysed, allowing for reflection of waves from boundaries. Comparison of time histories at given points along the column shows that the finite element solution gives good agreement with the Laplace transform solution for low as well as high drag.
Numerical analysis of the response of reinforced soils to direct shearing: Part 2
Authors: Juran I. , Ider M. H. , Chen C. L. , Guermazi A. 
Published: August 2005

AbstractA soil‐reinforcement load transfer model was developed by the authors1 to simulate the response of the reinforced soil material to triaxial compression and direct shearing. This paper presents the application of the proposed model for the numerical analysis of direct shear tests on sand samples reinforced with different types of tension resisting reinforcements. A parametric study is conducted to evaluate the effect of the mechanical characteristics and dilatancy properties of the soil, extensibility (elastic modulus) of the reinforcements, and their inclination with respect to the failure surface on the response of the reinforced soil material to direct shearing. An attempt is made to verify the proposed model by comparing numerical test simulations with experimental results reported by Jewell,2 and Gray and Ohashi.3 Comparisons of predicted and experimental results illustrate that the model can provide adequate simulations of the response of the reinforced soil material to shearing. In particular, it allows an evaluation of the effect of soil dilatancy (or contractancy), and extensibility of the reinforcement on tension forces generated in inclusions during shearing.
The influence of out‐of‐plane stress on a plane strain problem in rock mechanics
Authors: Reed M. B. 
Published: August 2005

AbstractThis paper considers the excavation of a cylindrical cavity in a uniformly prestressed mass of brittle Mohr‐Coulomb rock. Previous plane strain displacement solutions have assumed that the out‐of‐plane stress remains the intermediate principal stress at all points. It is here shown that when this assumption breaks down, an inner plastic zone is created in which σr < σz = σθ. A displacement solution is given for this case, using a variable‐dilation plastic flow rule, and results are compared with the previous solution for specific problems. A significant difference is observed only for problems involving a large drop in strength upon yield.
A quadratic variation indirect boundary element method for traction boundary‐value problems of two‐dimensional elastostatics
Authors: Lu Jiali , Watson J. O. 
Published: August 2005

AbstractBoundary integral equations for traction boundary‐value problems of two‐dimensional elastostatics are derived by the indirect boundary element method. Quadratic variation functions for the representation of geometry, fictitious forces and displacements over each boundary element are described. A system of equations approximating to the boundary integral equations is obtained by a Galerkin formulation in which the integral equation is written at Gauss integration points of elements. The method of computation of the Cauchy principal value is described. Examples of application to the analysis of stress and displacement around underground excavations demonstrate the accuracy and efficiency of the formulation.
Numerical simulation of secondary consolidation of soil: Finite element application
Authors: Lewis R. W. , Tran D. V. 
Published: August 2005

AbstractA rheological model has been developed for simulating the secondary consolidation of soils. Numerical procedures have been incorporated into a coupled consolidation program using results from a representative oedometer test. A solution of a two‐dimensional problem has also been performed. The technique is numerically stable and has provided satisfactory predictions for the consolidation settlements and the dissipation of pore water pressure within soils.
An assessment of the bearing capacity of calcareous and silica sands
Authors: Yeung S. K. , Carter J. P. 
Published: August 2005

AbstractA spherical cavity expansion model has been used to study the bearing capacity of foundations on calcareous and silica sands. Two constitutive models have been used to represent each sand: an elastoplastic, collapse‐softening model, and a computationally simpler, elastic/perfectly plastic material. The predictions of the limit pressures for spherical cavity expansion are compared with laboratory data on the bearing capacities obtained from model footing tests. It is shown that the numerical predictions of the limit pressures correlate well with the experimental values of bearing capacity, particularly at higher effective overburden pressures.
The influence of a boundary fracture on the elastic stiffness of a deeply embedded anchor plate
Authors: Selvadurai A. P. S. 
Published: August 2005

AbstractThe problem of the axial loading of a rigid disk‐shaped anchor plate embedded in an isotropic elastic medium of infinite extent is examined. At the boundary of the disk anchor plate the elastic medium contains a cracked region of finite extent. The presence of the cracked region decreases the elastic stiffness of the anchor plate. The mathematical formulation of the problem is developed, and a numerical scheme is presented which can be used to solve the resulting coupled integral equations. The numerical technique is used to evaluate the results, which illustrate the manner in which the elastic stiffness of the anchor plate is influenced by the extent of cracking. Similar results are developed for the flaw shearing mode stress intensity factor at the external boundary of the cracked region.