bluuebunny/crossref_metadata_2025_split huggingface dataset:
An axisymmetric lagrangian technique for predicting earth penetration including penetrator response
Authors: Schwer Leonard E. , Rosinsky Russel , Day James 
Published: August 2005

AbstractA computational technique for earth penetration is presented which includes the direct coupling between the deformable target model and a deformable model of the penetrator. In this fully Lagrangian approach, both the target and penetrator are discretized to represent the anticipated terradynamic and structural responses. A sliding interface is used between the two models to provide the time‐dependent terradynamic‐to‐penetrator interaction. This technique has the unique advantage of including the target‐to‐penetrator interaction in one calculation in a continuous and consistent manner. Comparisons of calculated penetration with full‐scale field test data are given.
Pseudo‐plane strain analysis of wave propagation problems arising from detonations of explosives in cylindrical boreholes
Authors: Ang K. K. , Valliappan S. 
Published: August 2005

AbstractWave propagation problems, such as blasting for excavation of a new tunnel oriented perpendicular to an existing tunnel, are truly three dimensional in nature. Dynamic finite element analysis with three‐dimensional elements is, however, very expensive. The cheaper and simpler alternative would be to model the problem approximately in two dimensions. This paper shows that dynamic finite element analysis of such problems using conventional two‐dimensional plane strain elements produces responses which are erroneously excessive. This is accredited to the inability to the inability of the two‐dimensional elements to correctly model the rapid attenuation of the amplitudes of the outward propagating waves. To overcome this problem, a pseudo‐plane strain concept is introduced and has been found to be a viable alternative. Numerical results are presented to demonstrate the application of the concept.
Analysis of double shearing in frictional materials
Authors: Teunissen J. A. M. , Vermeer P. A. 
Published: August 2005

AbstractThe concept that the flow of granular materials is governed by shear on certain critical planes is used to formulate an elastic–plastic model. When the elastic strains are neglected, the Double Shearing model becomes identical to the rigid‐plastic model of de Josselin de Jong which he named the Double Sliding model. After a discussion of the model, the small strain formulation is used to describe general boundary‐value problems. A comparison is then made between the coaxial Mohr–Coulomb yielding and the Double Shearing model on the basis of several numerical simulations. The non‐coaxiality of the axes of principal plastic strain rate and principal stress in the Double Shearing model leads to essentially different behaviour for stress rotations in comparison to the coaxial model. The Double Shearing model predicts in general lower limit loads because, for a given state of stress, it allows for several possible directions of plastic flow rather than a unique direction which derives from a plastic potential.
A variational principle for granular materials
Authors: Chandler H. W. 
Published: August 2005

AbstractA major problem in the mathematical modelling of the deformation of granular materials has been the lack of an easily usable variational principle. This is because the frictional dissipation of energy in these materials does not allow the use of the classical extremum principles. In this paper, a variational principle is constructed which is valid even when frictional dissipation occurs. Its derivation uses results from the mathematical theory of envelopes. Both the stresses and the strains can be varied, and for the case of non‐frictional plasticity it reduces to the maximum work principle of Hill. An example is presented to show how this new principle can be used to obtain approximate solutions to boundary‐value problems with granular materials. The only requirements in advance are a displacement field that obeys the kinematic boundary conditions, and a stress field that obeys equilibrium and the static boundary conditions. The principle is therefore quite straightforward to apply.
Dispersion law of rayleigh‐type waves in a compressible gibson half‐space
Authors: Vardoulkis I. , Vrettos Ch. 
Published: August 2005

AbstractAn analytical‐numerical examination has been made of the behavior of harmonic Rayleigh‐type waves in a compressible elastic half‐space of constant density and whose shear modulus increases linearly with depth. The dispersion law is presented for values of Poisson's ratio of 1/2, 1/3 and 1/4 for wide ranges of degree of inhomogeneity.
Thermal stress analysis of underground openings
Authors: Kumar P. , Singh B. 
Published: August 2005

AbstractIn the use of underground space for storage of solar energy, storage of excess heat from thermal power plants and containment of nuclear waste, the host medium is subjected to a thermal field accompanied by a thermal stress field. These stresses may endanger the stability and integrity of the structure. In this paper, the stress field, in circular and spherical openings, due to a given thermal field is analytically determined and numerically verified. Both lined and unlined openings are considered. The numerical and analytical results are in a satisfactory agreement. The lining stresses, support pressure and radial interface displacement depend only on the thermal field in the lining. A simplified method of stress computation applicable to a thin lining is also presented.
Effect of a shear seam in the foundation of Karjan Dam
Authors: Varadarajan A. , Sharma K. G. 
Published: August 2005

AbstractThe use of the limit equilibrium method for the analysis of a dam foundation with a weak shear seam has many limitations. There is further uncertainty in such an analysis by this method when the seam is intercepted by a concrete key. The finite element method is the best alternative means of analysing such problems. In this paper, the finite element analysis of the Karjan Dam (India) foundation, which has a shear seam, is presented with and without the foundation treatment (i.e. the concrete key). The seam is simulated by joint elements. It has been found that a concrete key located near the toe of the dam significantly improves the stability of the foundation.
Mechanics of a sandy subsoil subjected to cyclic loadings
Authors: Sawicki Andrzej , Swidzinski Waldemar 
Published: August 2005

AbstractA simple model for compaction of a sand, that may be useful in various geotechnical applications is presented. The model has been formulated in terms of the cyclic stress and strain amplitudes. The compaction properties of a dry sand are characterized by a common compaction curve described by two coefficients.The second aim of this paper is to show some applications of the theory proposed. The attention has been restricted to the two extreme cases of practical importance, namely to the behaviour of a dry sand (or a saturated sand but in free draining conditions), and to the behaviour of saturated sand in undrained conditions. Some numerical algorithms showing how to deal with those problems are presented and illustrated on the following examples: settlement and pore pressure generation in a soil stratum subjected to an earthquake, settlement of a foundation, pore pressure generation and liquefaction in a sea‐bed.The results obtained suggest that the model proposed, as well as a method of dealing with boundary value problems can serve as a useful tool for the analysis of a sandy subsoil subjected to cyclic loadings.
Finite element analysis of underground openings
Authors: Sharan S. K. 
Published: August 2005

AbstractA highly efficient technique is presented for the finite element analysis of stresses around underground openings surrounded by an infinite extent of linearly elastic rock mass. The effect of unbounded rock is incorporated in the analysis by using elastic supports around the finite element model. Expressions for stiffnesses of the elastic supports are derived and these are found to depend on the location of elastic supports, the shear modulus and Poisson's ratio of the rock, and the ratio of horizontal to vertical initial stresses. With the use of the proposed technique, the extent of the finite domain to be considered in the analysis is highly reduced. This results in a great computational advantage. The other principal merit of the proposed technique is that a standard finite element code for stress analysis may be used without making any modification. Results of some numerical tests are reported to demonstrate the effectiveness and efficiency of the proposed method. The technique has the potential of being applied to more complex problems of unbounded domains in geomechanics.
A mathematical model of permeability alteration around wells
Authors: Olarewaju Joseph S. 
Published: August 2005

AbstractThis paper presents an analytical solution of the permeability alteration problem around the wellbore. This alteration may be a permeability reduction due to drilling fluid invasion or mudcake formation around the wellbore. On the other hand, the alteration may be a permeability increase resulting from stimulation by acidizing the formation matrix around the well. This permeability discontinuity in a reservoir forms a composite reservoir system. With the composite model, both the degree and the radial extent of permeability alteration can be adequately predicted. The conventional skin concept is inadequate and physically unrealistic in most of these cases.This paper describes the application of an automatic weighted constrained least‐squares parameter estimation technique and the analytical model for pressure transient analysis. The parameters of the composite reservoir system are determined from a match of the pressure transient data. The behaviour of the pressure transient in such composite systems is presented using the analytical solution.
Land subsidence due to gas/oil production in inhomogeneous transversally anisotropic half‐space by a boundary element method
Authors: Sartoretto Flavio , Gambolati Giuseppe , Rinaldo Andrea 
Published: August 2005

AbstractIn a previous paper1 the authors have developed and implemented a new boundary element (BE) model to simulate and predict land subsidence occurring over three‐dimensional gas/oil fields in a homogeneous and isotropic half‐space. The approach relies on Betti's reciprocal theorem and makes use of the classical fundamental solution of Boussinesq in the framework of the theory of linear poroelasticity. The BE method is here extended to inhomogeneous, transversally anisotropic soils by the aid of a two‐dimensional finite element (FE) model which provides a fundamental numerical solution for the actual multi‐layer setting of the subsurface system. The new FE–BE approach is then used to simulate the subsidence caused by gas production over the deep reservoir of Campo Ravenna Terra, Ravenna (Italy) from 1950 to 1980. The results compare very favourably with the outcome from a full more expensive three‐dimensional FE model of the same occurrence.
Contaminant migration in a regular two‐ or three‐dimensional fractured network: Reactive contaminants
Authors: Rowe R. K. , Booker J. R. 
Published: August 2005

AbstractA semi‐analytic solution for the migration of dilute reactive contaminant species in a fractured medium having a one‐, two‐ or three‐dimensional fracture network is presented. The application of the technique to practical problems is discussed and illustrated by examples. The effects of sorption in the matrix and on the surface of the fractures are considered for a range of parameters. It is demonstrated that the synergistic interaction of the various parameters is such that the effect of changing a single variable may not be immediately obvious and a designer should perform computations for the range of expected parameters to determine the maximum impact. For example, it is shown that it is not necessarily conservative to consider only one‐dimensional or only three‐dimensional diffusion into the matrix; which of these cases is most critical will depend on the values of other parameters. It is also shown that an effective leachate collection system may significantly reduce the impact of those contaminants which do escape into the fractured media.
Pore fluid frictional heating and stability of creeping landslides
Authors: Davis R. O. , Smith N. R. , Salt G. 
Published: August 2005

AbstractAn examination of the effects of frictional heating of pore fluid in relation to long‐term slope stability is presented. It is found that increases in pore‐fluid pressure due to heat‐induced expansion may act to enhance creep rates and possibly lead to total loss of stability. Conditions for total stability loss are examined and an approximate critical value of average shear stress is determined. This value must be exceeded for a sufficiently long period of time in order to induce rapid failure.
Three‐dimensional discrete element method for granular materials
Authors: Ghaboussi Jamshid , Barbosa Ricardo 
Published: August 2005

AbstractThis paper describes a three‐dimensional discrete element method of analysis for granular materials. Individual particles are modelled as rigid, six‐sided solids with six degrees of freedom. Various types of contacts are possible among the three‐dimensional discrete elements. Models for these contact types are described. Computational aspects of the method, such as techniques for contact detection and data structure, are addressed. Selective results of three examples that demonstrate the application of the method to granular flow problems are presented and discussed.
Size effect on damage parameters for softening in simulated rock
Authors: Desai C. S. , Kundu T. , Wang G. 
Published: August 2005

AbstractLaboratory uniaxial tests on cylindrical specimens of a simulated rock are used to identify the influence of the diameter (D) and height (L) of the specimens on the damage parameters. The relations are expressed in terms of the characteristic parameter C = L2/D.
A linearized integration technique for incremental constitutive equations
Authors: Bardet J. P. , Choucair W. 
Published: August 2005

AbstractA numerical technique is proposed to obtain stress–strain response curves from rate‐type and incremental constitutive equations during generalized loadings. The proposed method linearizes the loading constraints of laboratory experiments, links them to the constitutive relations, and forms a linear system of ordinary differential equations. It circumvents the difficulties associated with the non‐uniqueness and bifurcation of boundary value problems. The method is illustrated for the elastoplastic von Mises and Roscoe and Burland models subjected to torsion, circular stress path, and undrained triaxial compression. The approach pertains to most stress–strain relationships and laboratory experiments of geomechanics. It is useful for research on material modelling, engineering practice and computational mechanics.
Vertical stress distribution due to an arbitrarily shaped foundation using triangulation and an analytical expression for a triangular loaded region
Authors: Murti V. , Wang Y. C. 
Published: August 2005

AbstractUsing the basic Boussinesq's equation, the expression for the vertical stress distribution (σz) underneath any point on the ground surface due to a general triangular loaded region in a preferred orientation with a linearly varied loading has been successfully derived. When the triangle is not in a preferred orientation, a simple axis transformation is required and the expression will be equally applicable. Based on this expression, σz due to an arbitrarily shaped loaded foundation can simply be determined by first triangulating the loaded area and summing up the contributions from each generated triangular region. The procedures for triangulating and calculating the stress distribution can be simply automated through computer programs.
Verification for numerical modelling of jointed rock mass using thin layer elements
Authors: Fishman K. L. , Derby C. W. , Palmer M. C. 
Published: August 2005

AbstractThin layer finite elements are employed to model the response of rock joints in finite element analyses of rock mechanics problems. The case of a circular opening embedded in a rock mass is investigated. Results are obtained for both solid and jointed rock masses, and the effects of the presence of joints on the stress and strain field are investigated. Results from the finite element analysis are verified with respect to measurements from physical modelling. It is shown that the comparison between measured and computed results is satisfactory and that the presence of joints has a pronounced effect on the stress and strain field as compared to that realized in the absence of any rock joints. This study provides valuable data which contribute to the verification of thin layer finite elements for modelling the response of rock joints.
Material instability for drained and undrained behaviour. Part 1: Shear band generation
Authors: Molenkamp F. 
Published: August 2005

AbstractTo increase the insight into the phenomenon of liquefaction a theoretical study has been performed of material instability for undrained behaviour. Material instability concerns the instability of an equilibrium state of an infinite homogeneous solid for both uniform deformation and shear‐band generation. In this paper shear‐band generation is considered. In a companion paper the case of uniform deformation is elaborated and combined with the current results. In this paper it is shown that, for a contractant material, shear‐band generation is accelerated by decreasing the drainage.
Continuum modelling of jointed porous rock
Authors: Cho Taechin F. , Plesha Michael E. , Haimson Bezalel C. 
Published: August 2005

AbstractConstitutive equations for the mechanical and hydraulic behaviour of saturated porous rock with joint sets of specified orientations are developed by superposing continuum representations for the mechanical and hydraulic properties of the intact rock and each of the joint sets. The resulting continuum theory allows for fluid diffusion through and between interconnected rock pores and joint sets of specified orientation, and also accounts for the anisotropy of the mechanical properties due to joint stiffnesses. The accuracy and reliability of this model are verified by finite element simulation of example problems. The first example considers joint orientation‐dependent rock deformation in a hypothetical porous medium with one joint set of different dip angles. More realistic examples related to rock slope stability and reservoir‐induced seismicity are also considered in which the constitutive law's utility for modelling time‐dependent fluid pressures is illustrated.
Convolution operator techniques and asymptotic expansions for long‐term behaviour of laterally loaded piles in permafrost
Authors: Foriero A. , Ladanyi B. 
Published: August 2005

AbstractLong‐term predictions of pile displacements, bending moments and soil reactions for laterally loaded piles in a hereditary elastic medium are presented. Asymptotic estimates on fractional exponential operators yield predictions for large time.
Dynamic response of a thick plate on viscoelastic foundation to moving loads
Authors: Zaman Musharraf , Taheri Michael R. , Alvappillai A. 
Published: August 2005

AbstractA finite element algorithm is presented to evaluate the dynamic response of pavements including aircraft‐guideway‐foundation interaction. The pavement‐foundation system is modeled by a series of thick plate elements supported by discrete springs and dashpots at the nodal points representing the viscoelastic foundation. The moving aircraft loads are represented by masses each supported by a spring and dashpot suspension system and having a specified horizontal velocity and acceleration. The accuracy of the algorithm is verified by comparing the finite element solution with available analytical results. A parametric study is conducted to determine the effects of various parameters on the dynamic response of pavements to moving loads.
An analytical technique for evaluation of coupled heat and mass flow coefficients in unsaturated soil
Authors: Yong R. N. , Xu D. M. , Mohamed A. M. O. , Cheung S. C. H. 
Published: August 2005

AbstractThis study was done to evaluate a phenomenological approach for determining the coupled heat and water diffusion parameters. This technique requires the use of both theory and experimental data. The transport equation was solved analytically using nondimensional analysis.The calculated diffusion parameters of a compacted sand–bentonite‐based material are presented. The agreement between the back calculated values and the experimental volumetric water content profiles was good. Practical application of the technique is also discussed.
Bounding solutions for the pressuremeter modulus using variational principles in elasticity
Authors: Dormieux L. 
Published: August 2005

AbstractIt is classically assumed that the pressuremeter modulus (determined from the initial slope of the pressuremeter expansion curve) can be used as an estimate for the soil's shear modulus, provided disturbance effects can be neglected. This approximation is only rigorous in the plane‐strain case and requires that the height of the cell be large in comparison with its diameter. The present paper allows to quantify the error that results from this approximation as a function of the height over diameter ratio. The analysis is based on an application of the variational principles of elasticity. It is shown that the static and the kinematic approaches lead, respectively, to a lower‐ and an upper‐bound estimate of the pressuremeter modulus expressed in terms of the soil's elastic coefficients.The calculations are completely carried out in the case of an infinite cavity subjected to a pressure on a finite length. It is shown that the plane‐strain approximation overestimates the shear modulus. Based on the kinematic approach, a method is developed to derive the shear modulus from the pressuremeter modulus which accounts for the finite slenderness of the cell. This method can be extended to more complex geometries and material properties, including soil heterogeneity and anisotropy.
Spurious bifurcation modes for cohesive solids under uniform stress
Authors: Moore Ian D. 
Published: August 2005

AbstractSingularities leading to the calculation of spurious velocity fields have been observed in the tangent stiffness equations assembled during the finite‐element analysis of square blocks of purely cohesive perfectly plastic material. These occur because of weaknesses in conventional implementations of the plastic flow rule. Both twisting and swaying modes occur which interfere with the calculation of uniform velocity fields for blocks responding to uniform applied stress. Various techniques can be used to eliminate the problem. The phenomenon does not eventuate when non‐uniform stress fields are acting, so does not affect the solution of practical plasticity problems.
Liquefaction of unstable slopes
Authors: Koenders M. A. , Sellmeijer J. B. 
Published: August 2005

AbstractTwo liquefaction effects are described here which account for the fluidization phenomena observed in the collapse of water‐saturated sloped‐embankments. A surface erosion effect is a process in which the top layer of a submerged embankment liquefies. The subsequent reconstitution is a gradual process for which the time dependence is calculated.Internal liquefaction takes place suddenly and a criterion is derived to describe its onset. It is shown that the process is associated with the change from loading to unloading of an external shearing loaded on top of the slope and that there is no stable elastic unloading process.