bluuebunny/crossref_metadata_2025_split huggingface dataset:
A mapping technique for steady‐state unconfined seepage analysis
Authors: Morland L. W. , Gioda G. 
Published: August 2005

AbstractAn approach is presented for the analysis of the unconfined steady‐state seepage through homogeneous trapezoidal dams based on a bijective mapping between the flow domain, having an unknown shape, and a fixed triangular domain. It is shown that the geometrically non‐linear unconfined analysis is equivalent to the problem of determining the unknown distribution of permeability, within a triangular domain with known shape, that satisfies the set of transformed boundary conditions. The flow problem in the triangular domain is solved through a finite‐element technique analogous to that adopted for confined analyses and, on the basis of this solution, the shape of the free surface in the physical space is evaluated. The proposed approach is applied to the determination of the influence of the water levels in the upper and lower reservoirs on the elevation of the free surface seepage point.
Finite element analysis of two cylindrical expansion problems involving nearly incompressible material behaviour
Authors: Burd H. J. , Houlsby G. T. 
Published: August 2005

AbstractThe displacement formulation of the finite element method is well suited to the analysis of elasto‐plasticity problems involving compressible material behaviour, but it is well known that numerical difficulties occur when the material is incompressible or nearly incompressible. The effect of these additional constraints depends on both element formulation and mesh topology. A two‐dimensional plane strain finite element formulation suitable for the solution of problems involving large strains and displacements (but small rotations) based on the isoparametric approach is described. The kinematics of deformation are defined in terms of the Eulerian strain rates that are invariably used in small strain analysis; the formulation therefore retains some of the character of small strain theory but includes additional geometrically non‐linear terms. The results of a series of plane strain finite element analyses of two cylindrical expansion problems are presented. These results confirm the previously observed trend that as Poisson's ratio approaches 0·5 then the quality of the calculated stress deteriorates. The study also indicates that the solution quality depends increasingly on mesh topology as perfect incompressibility is reached.
Estimation of geometrical parameters of key discontinuities within an engineering rock region
Authors: Xing Zhang 
Published: August 2005

AbstractDiscontinuities that have unfavourable orientation and are continuous within overall engineering rock regions can have a dominant effect on the strength, deformability and permeability of the rock mass. The concepts of geometrical parameters of basic discontinuities and engineering discontinuities are proposed in this communication. Further, the engineering discontinuities are divided into key discontinuities and non‐key discontinuities. Within any region of the rock mass, the spacing, trace length and probability of engineering discontinuities can be estimated from the geometrical parameters of the basic discontinuities. In general, the geometrical parameters are different from those of the basic discontinuities. Finally, two examples are given to illustrate how to apply these parameters to rock engineering problems.
Primary and remote fracture around underground cavities
Authors: Carter B. J. , Lajtai E. Z. , Petukhov A. 
Published: August 2005

AbstractThe development of fractures around cavities in rock is examined using physical and numerical models. In uniaxial compression, fracture proceeds from primary through remote to compressional (slabbing) fracture. There is a wide stress interval where the only event is the stable propagation of the primary fracture. When the crack length becomes equal to about the size of the diameter of the cavity, the critical stress condition shifts to either side of the primary fracture, leading to the nucleation of remote fractures. Almost simultaneously, failure at the compressive stress concentration follows. With increasing stress, fracture in the remote region is seen to extend away from and towards the compressive region, eventually merging with the slabbing fractures. Increasing the confining pressure shortens the stress interval during which primary fracture is the only process and shifts failure to the remote and the compressional fracture zone.
Embankment reliability versus factor of safety: Before and after slide repair
Authors: Wolff Thomas F. 
Published: August 2005

AbstractProbabilistic slope stability analyses incorporate more information regarding the input variables than do traditional deterministic analyses. Consequently, more information is contained in the results. A probabilistic method for slope stability analysis for very general problems was presented by Wolff and Harr.1 The method allows analysis of a broad range of slope stability problems. In this Application Brief, the method is reviewed and used to illustrate the significant change in reliability of a dam slope from the time of an actual slide to the time the slide was repaired by the construction of a rock toe berm.
Application of numerical analyses for tunnelling
Authors: Duddeck H. 
Published: August 2005

AbstractThe paper reviews the application of numerical methods in tunnelling, the achievements and the shortcomings, hence also the future tasks for closing the gap between real ground behaviour in critical tunnelling situations and the present approaches by numerical models. After discussing the role of the structural model within the entire design procedure for a tunnel project, problems are mentioned where numerical methods are essential. This is explained for soft ground tunnelling as well as for tunnels in rock. A special section is devoted to the kind of numerical models needed for the interpretation of field measurements. There is still much to do, especially in covering failure modes of tunnels by numerical analysis. The paper is a shorter version (e.g. without photographs of the actual tunnelling work) of a lecture presented at the Innsbruck Conference on Numerical Methods in 1988.
Determination of asperity damage parameters for constitutive models of rock discontinuities
Authors: Plesha Michael E. , Hutson Robert W. , Dowding Charles H. 
Published: August 2005

AbstractDilatancy and contact surface damage are important phenomena affecting the behaviour of rock joints and other geological discontinuities. Effective constitutive laws that incorporate these behaviours have recently been developed but require the specification of new material parameters that govern damage of asperity surfaces. Determination of the parameters that control damage is currently a difficulty that confronts practitioners. This brief will summarize the findings of Hutson and Dowding's investigation of joint surface asperity degradation and elaborate on the implications for application.
Interface elements for singular plasticity points
Authors: Van Langen H. , Vermeer P. A. 
Published: August 2005

AbstractZero‐thickness interface elements are applied to solve plasticity problems involving singular points where stresses and displacements are non‐unique. Singular points occur in soil–structure interaction, e.g. at the ridges of footings, buried structures and foundation piles. Here the introduction of potential displacement discontinuities appears to give quite accurate finite element solutions. This is demonstrated for indentation problems both for plane strain and axisymmetric situations. In all problems the soil behaviour is modelled by the elastic–plastic Mohr–Coulomb model.
Wave‐induced stresses and pore pressures in sloping seabeds
Authors: Gatmiri Behrouz 
Published: August 2005

AbstractBy using the Mellin transform, a general solution is obtained for the total stresses and pore pressure distribution in an infinite wedge under fairly general conditions of loading. The results for the particular case in which each surface is subjected to static sinusoidal pressures are given in an explicit form. The infinite integrals can be evaluated by numerical integration methods. This analytical method is verified by different cases. The results of this study could be used to determine the total stresses and pore pressures induced by a wave on a sloping seabed.
An interpretation of initial stress and strain methods, and numerical stability
Authors: Stolle Dieter F. E. 
Published: August 2005

AbstractThis paper explores similarities and differences between initial stress and initial strain methods of analyses. The author takes the position that both methods, although perhaps conceptually different, are actually numerically the same. A simple approach for providing closed‐form stability criteria for explicit and implicit time‐marching procedures is described. For the case of associated, non‐hardening viscoplasticity the approach provides criteria which are identical to those of Cormeau for explicit schemes. An implicit time‐marching scheme which avoids the compliance matrix inversions at the constitutive level is also presented. Like many other implicit methods, this implicit time‐marching scheme is unconditionally stable for θ≥½.The connection between initial strain plasticity and an explicit viscoplastic time‐marching scheme is also addressed.
A comparison of field‐monitored and numerically predicted moisture movement in unsaturated soil
Authors: Thomas H. R. , Rees S. W. 
Published: August 2005

AbstractThis paper presents the results of the application of a numerical model of flow of water in unsaturated soil to simulate real field behaviour. Numerical predictions are compared with field‐monitored results as part of an assessment of the approach adopted.The numerical approach is based on a finite element solution of Richards' theoretical formulation, adopting a finite difference recurrence relationship to model the transient nature of the problem. The field results have been collected by British Gas in Kimmeridge clay at a site in Swindon.The simulation addressed the autumn wetting of the soil during 1983. Comparisons of volumetric moisture content readings from the field and numerical predictions give good correlation. It is concluded that the numerical model has adequately represented field behaviour over the depth of interest. Taken in conjunction with previous results, it is claimed that the model should now be capable of use in a predictive mode.
Stability of openings in jointed rock
Authors: Vaughan David K. , Isenberg J. 
Published: August 2005

AbstractThe slide line approach is combined with the finite element method to represent the action of a removable block on a lined tunnel. The present paper examines the strength and ductility required of the tunnel liner to resist the forces imposed by a block when the surrounding rock mass is subjected to explosive loading. Key block theory developed by Goodman and Shi provides the conceptual framework for simplifying a general jointed domain to a manageable size for analysis with finite element models.
A semi‐discrete procedure for dynamic response analysis of saturated soils
Authors: Chohan Harpal S. , Sandhu Ranbir S. , Wolfe William E. 
Published: August 2005

AbstractBiot's equations of wave propagation through fluid‐saturated porous elastic media are discretized spatially using the finite element method in conjunction with Galerkin's procedure. Laplace transformation of the discretized equations is used to suppress the time variable. Introducing Laplace transforms of constituent velocities at nodal points as additional variables, the quadratic set of equations in the Laplace transform parameter is reduced to a linear form. The solution in the Laplace transform space is inverted, term by term, to get the complete time history of the solid and fluid displacements and velocities. Since the solution is exact in the time domain, the error in the calculated response is entirely due to the spatial approximation. The procedure is applied to one‐dimensional wave propagation in a linear elastic material and in a fluid‐saturated elastic soil layer with ‘weak’, ‘strong’ as well as ‘moderate’ coupling. With refinement of the spatial mesh, convergence to the exact solution is established. The procedure can provide a useful benchmark for validation of approximate temporal discretization schemes and estimation of errors due to spatial discretization.
Probabilistic analysis of an impulsively loaded deep‐based structure
Authors: Harren S. V. , Fossum A. F. 
Published: August 2005

AbstractA deep‐based (i.e. deeply buried) structure subjected to stress wave loading is analyzed probabilistically. The finite element method, coupled with a fast probability integration technique, is used to perform the analysis. Randomness due to uncertainties in loading and stratum material properties is addressed. The results presented, although for an idealized linear elastodynamic problem, clearly demonstrate that more realistic probabilistic analyses of impulsively loaded deep‐base structures are feasible.
Coupling versus uncoupling in soil consolidation
Authors: Lewis R. W. , Schrefler B. A. , Simoni L. 
Published: August 2005

AbstractCoupling and uncoupling between the equilibrium and mass balance equations in soil consolidation problems in investigated in detail. A procedure for judging the strength of coupling is indicated. In the applications, particular emphasis is given to subsidence problems where the coupled nature of the problem is still sometimes questioned. It is shown that even in the case of a single pumped aquifer most situations are coupled.
Efficient multigrid solution of boundary element models of cracks and faults
Authors: Peirce A. P. 
Published: August 2005

AbstractWe consider the multigrid solution of a discretized singular integral equation whose solution represents the displacement discontinuity distribution across a pressurized crack or the slip on a fault subjected to a prescribed shear stress. The multigrid technique reduces the operation count for a crack model having N degrees of freedom from O(N3) operations for standard stationary iterative methods to O(N2) operations. In the numerical simulations performed the multigrid approach proves to be extremely efficient even for small values of N. We use Fourier analysis to determine the spectral properties of the coarse grid correction process and the effect of a number of different interpolation operators on the multigrid algorithm. We show that the multigrid technique can be combined with the process of lumping remote influences to yield an algorithm that involves O(N) operations. The performance of multigrid iteration in a nonlinear environment is explored by considering seams filled with nonlinear material. For this purpose a segmented multigrid algorithm is developed that allows for different seam constitutive relations to be used along different line segments. The O(N2) operation count characteristic of linear multigrid iteration is shown to persist in this nonlinear environment and the segmented multigrid approach is shown to provide significant computational savings for values of N well within the range for typical problems that occur in practice.
Analysis of subsidence due to a point sink in an anisotropic porous elastic half space
Authors: Tarn Jiann‐Quo , Lu Cheer‐Chung 
Published: August 2005

AbstractAnalytical solutions of the long‐term consolidation deformation and excess pore water pressure due to fluid withdrawal from a saturated anisotropic porous elastic half space are presented. In the analysis, both the permeability and the elastic properties are considered cross‐anisotropic. Cases of pervious and impervious half‐space boundary are studied. The consolidation settlements as effected by the anisotropy and boundary conditions for pore water are illustrated and discussed.
Implementation of hierarchical single surface δ0 and δ1 models in finite element procedure
Authors: Desai C. S. , Sharma K. G. , Wathugala G. W. , Rigby D. B. 
Published: August 2005

AbstractHierarchical single surface (HISS) δ0 and δ1 models are briefly discussed. An algorithm for the implementation of δ0 and δ1 models in a finite element code and the associated subroutines, written in FORTRAN 77, are presented. The algorithm is general and can be adopted for other computer codes with minor changes. Detailed steps and subroutines are included for easy implementation of the models in specific codes. Two example problems are also presented to enable the user to verify the implementation.
Elastostatic deformation of a half‐space under conical loading
Authors: Hemsley J. A. 
Published: August 2005

AbstractIn the idealised modelling of ground distortion induced by a freely deposited heap of granular material, consideration is given to a fundamental problem in classical elasticity whereby an axisymmetric distribution of vertical conical loading is applied to the surface of a half‐space. Closed‐form expressions are derived for the deformed shape of the surface, and three variations of the integral transform method are described for determining stresses and displacements within the half‐space. Extensive numerical results are presented in graphical form.
Finite layer analysis of laterally loaded piles in cross‐anisotropic soils
Authors: Lee C. Y. , Small J. C. 
Published: August 2005

AbstractThis paper presents a finite layer method for the analysis of laterally loaded piles in isotropic and cross‐anisotropic layered soils. Excellent agreement is found between the isotropic solutions computed by the finite layer method and the more rigorous finite element method. Some theoretical solutions are presented to demonstrate the effect of soil anisotropy. Two full scale field case histories have been analysed by the method using isotropic and cross‐anisotropic soil models.
Pile group settlement: A probabilistic approach
Authors: Quek S. T. , Phoon K. K. , Chow Y. K. 
Published: August 2005

AbstractThe uncertain settlement response of pile groups is determined using a ‘hybrid’ formulation and a first‐order perturbation technique. The spatially varying soil modulus, which gives rise to the uncertainties in the pile group settlement, is modeled as a homogeneous random field. The random field is assumed to be one‐dimensional since the ‘hybrid’ formulation does not account for horizontal variation in the soil properties. Using the proposed method, the coefficient of variation of the pile group settlement is computed. The single‐pile solutions obtained compare favorably with the solutions from a conventional stochastic finite element analysis. Pile groups of sizes ranging from two to twenty‐five piles are studied. It is observed that the coefficient of variation is not significantly affected by the pile spacing as well as the group size. By defining an appropriate performance function, the reliability index of a pile group system is also found to be approximately the same as that of a single‐pile system. These observations suggest that the solutions for a single pile may be used to estimate the uncertainties in the settlement response of pile groups.
Application of non‐linear elastic model
Authors: Molenkamp F. 
Published: August 2005

AbstractThe properties of a previously published isotropic non‐linear elastic model with an elastic potential are illustrated in detail. Its parameter determination is elaborated and a parameter list is composed on the basis of published experimental data. The formulation with the elastic potential is shown to enable the minimization of numerical drift in incremental calculations of the deformation for alternating loading.
An updated reference configuration formulation for large‐deformation problems
Authors: Stolle D. F. E. , Schad H. 
Published: August 2005

AbstractThis paper examines difficulties encountered when using the Green‐Nagdi rate and presents an updated configuration formulation for problems dealing with large deformations. It is shown that a natural link can be established between the updated reference configuration and linearized updated Lagrangian formulations, if Truesdell's objective stress rate is used. Owing to this connection, any limitations associated with the described formulation would be expected to also apply to an updated Lagrangian formulation and vice versa. It is pointed out that, if second‐order effects are induced, the Truesdell rate appears in the rate equation for equilibrium even when strains are infinitesimal. By examining a simple‐shear problem, where hypoelastic material behaviour with ‘Hooke's law’ is assumed, it is shown that the spherical state of stress is coupled with the shear stress when using the Truesdell or Green‐Nagdi stress rate. It is suggested that objective stress rates, introduced in large‐deformation formulations, may contribute to erroneous predictions if a constitutive law is developed independent of the adopted stress rate.
Accuracy of four‐node standard finite element
Authors: Molenkamp F. , Kidger D. J. , Smith I. M. 
Published: August 2005

AbstractIn this note the accuracy of the elastic standard 4‐node plane‐strain finite element is investigated by comparing numerically calculated eigenvalues of the element stiffness matrix to those according to higher‐order algebraic approximations. From this study it may be concluded that the ‘hourglass’ eigenmodes are the only inaccurate ones. For selective reduced numerical integration the hourglass eigenvalues may be expected to be of the order of 1/2 to 2/3 of the analytical values.
Numerical treatment of progressive localization in relation to borehole stability
Authors: Papanastasiou Panos C. , Vardoulakis Ioannis G. 
Published: August 2005

AbstractResults of large‐scale finite element computations are presented for the problem of borehole failure due to the high stresses at great depths. Rock is modelled by an extension of the Mohr–Coulomb flow theory of plasticity for material with Cosserat micro‐structure. The introduction of internal length (grain size) improves the computational stability and allows for robust post‐localization computations. The presented results show clearly a progressive failure mechanism and the computed failure modes are in a good qualitative agreement with laboratory and field observations.
Generation of flow nets using fem nodal potentials and bilinear shape functions
Authors: Fan Yuehui , Tompkins F. D. , Drumm E. C. , Von Bernuth R. D. 
Published: August 2005

AbstractA method for generating both equipotential lines and streamlines directly based upon nodal potentials and bilinear shape functions is presented. The method involves post‐processing a finite element (FE) solution utilizing typical four‐node isoparametric quadrilateral elements. The application of the method can be important in the interpretation of FE analysis results, especially when inhomogeneous, anisotropic, unconfined or/and other complicated conditions exist. Compared with conventional techniques to generate flow nets which depend upon both the potential and stream functions, the method presented is simpler and more powerful.
Resilient characterization of pavement materials
Authors: Uzan Jacob 
Published: August 2005

AbstractThe paper presents an approach for characterizing pavement materials using the modified linear elastic behaviour. The secant modulus of elasticity is expressed in terms of the stress invariants and an expression for the secant Poisson's ratio is derived using path independence of the total work along a closed loading cycle. Triaxial test results of granular base–subbase materials which exhibit strong non‐linear behaviour and dilatancy are analysed and presented. The constitutive law is included in a finite element program and results of pavement analyses are discussed. It is found that the secant Poisson's ratio of granular base materials reaches values between 0·6 and 0·7, indicating a volume increase under high stress ratios. The pavement response predicted using the above material characterization is compatible with non‐destructive test results.