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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 138 (1992), S. 207-228 
    ISSN: 1420-9136
    Keywords: In situ stresses ; crustal strain ; gravity ; plastic flow ; viscoelasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Five models for near-surface crustal stresses induced by gravity and horizontal deformation and the influence of rock property contrasts, rock strength, and stress relaxation on these stresses are presented. Three of the models—the lateral constraint model, the model for crustal stresses caused by horizontal deformation, and the model for the effects of anisotropy—are linearly elastic. The other two models assume that crustal rocks are brittle or viscoelastic in order to account for the effects of rock strength and time on near-surface stresses. It is shown that the lateral constraint model is simply a special case of the combined gravity-and deformation-induced stress field when horizontal strains vanish and that the inclusion of the effect of rock anisotropy in the solution for crustal stresses caused by gravity and horizontal deformation broadens the range for predicted stresses. It is also shown that when stress levels in the crust reach the limits of brittle rock strength, these stresses become independent of strain rates and that stress relaxation in ductile crustal rocks subject to constant horizontal strain rates causes horizontal stresses to become independent of time in the long term.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Hydrology 161 (1994), S. 109-131 
    ISSN: 0022-1694
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Architecture, Civil Engineering, Surveying , Geography , Geosciences
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Rock mechanics and rock engineering 28 (1995), S. 185-209 
    ISSN: 1434-453X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Summary The edge function method is considered as an alternative to conventional numerical schemes for the solution of plane problems in rock mechanics. The essence of the approach is the approximation of the solution by a linear combination of solutions of the field equations. The unknowns in the linear combination are obtained from a system of equations which follows from the approximation of the boundary conditions by a boundary Galerkin energy method. No mesh generation is required over the domain or boundary of the problem. Previous edge function work in anisotropic elasticity is enhanced by the incorporation of a special solution for the effect of gravity. Examples are presented to illustrate the applicability of the method in determining stresses in various rock mechanics problems. A high level of accuracy is achieved with a relatively small number of degrees of freedom. Convergence is rapid because of the inclusion of special analytic solutions to model stress concentrations. The inclusion of the gravity force does, however, lead to a small increase in the number of degrees of freedom needed to achieve acceptable results. The optimum use of the edge function method, at present, may be as a special element within more general finite element or discrete element codes.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Computational mechanics 19 (1997), S. 308-316 
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents a boundary element formulation for 3-D linear and viscoelastic bodies subjected to the body force of gravity. The Laplace transformation is first used to suppress the time variable, and solutions of displacements and stresses are found in the transformed domain. The time domain solutions are then found by an accurate and efficient numerical inversion method which requires only real calculations for all quantities. Input and output data, and solutions in the transformed and time domains are connected through an Interactive Data Language code written by the authors. While particular solutions of stresses and displacements related to the body force of gravity (which is applied at time t = 0 and is kept constant) are derived, the Green's functions in the Laplace domain are obtained through the correspondence principle. The new formulation has been implemented into an existing 3-D BEM program, and several numerical examples involving 3-D viscoelastic bodies are presented. Although the discussion in this paper focuses on Maxwell viscoelastic and isotropic media, other linear isotropic and even anisotropic viscoelastic models can also be incorporated, without difficulty, into the 3-D viscoelastic BEM program.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Rock mechanics and rock engineering 15 (1982), S. 167-180 
    ISSN: 1434-453X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Summary The Influence of Rock Anisotropy on Stress Measurements by Overcoring Techniques A medium is anisotropic if its properties vary with direction. This is the general characteristic of many rocks, for example, schists, slates, gneisses, phyllites and other metamorphic rocks. Bedded and regularly jointed rocks also display anisotropic behavior. This paper is concerned with the influence of rock anisotropy on in-situ stress measurements. It is limited, to stress measurements by overcoring techniques for which strains and displacements are recorded either on the walls of a pilot hole at the end of one or several boreholes or within instrumented solid or hollow inclusions perfectly bonded to the surface of the pilot hole. The rock is described as homogeneous, continuous, anisotropic and linearly elastic. The following questions are answered with special emphasis on rocks that can be classed as transversely isotropic or orthotropic: the number of independent measurements obtainable in a single borehole; the number of boreholes required to determine the in-situ stress field; the influence of rock anisotropy on these numbers; the influence of the anisotropy type and the error involved by neglecting rock anisotropy.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-1529
    Keywords: joint ; fracture ; constitutive modeling ; shear test ; boundary conditions.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Assessing the shear behavior of intact rock and rock fractures is an important issue in the design of a potential nuclear waste repository at Yucca Mountain, Nevada. Cyclic direct shear experiments were conducted on replicas of three natural fractures and a laboratory-developed tensile fracture of welded tuff. The tests were carried out under constant normal loads or constant normal stiffnesses with different initial normal load levels. Each test consisted of five cycles of forward and reverse shear motion. In this paper, the results of the constant normal load shear experiments are analyzed using several constitutive models proposed in the rock mechanics literature for joint shear strength, dilatancy, and joint surface damage. It is shown that some of the existing models have limitations. New constitutive models are proposed and are included in a mathematical analysis tool that can be used to predict joint behavior under various boundary conditions. © Rapid Science Ltd. 1998
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 77 (1996), S. 161-174 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new formulation of the boundary element method (BEM) is proposed in this paper to calculate stress intensity factors for cracked 2-D anisotropic materials. The most outstanding feature of this new approach is that the displacement and traction integral equations are collocated on the outside boundary of the problem (no-crack boundary) only and on one side of the crack surfaces only, respectively. Since the new BEM formulation uses displacements or tractions as unknowns on the outside boundary and displacement differences as unknowns on the crack surfaces, the formulation combines the best attributes of the traditional displacement BEM as well as the displacement discontinuity method (DDM). Compared with the recently proposed dual BEM, the present approach doesn't require dua elements and nodes on the crack surfaces, and further, it can be used for anisotropic media with cracks of any geometric shapes. Numerical examples of calculation of stress intensity factors were conducted, and excellent agreement with previously published results was obtained. The authors believe that the new BEM formulation presented in this paper will provide an alternative and yet efficient numerical technique for the study of cracked 2-D anisotropic media, and for the simulation of quasi-static crack propagation.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 113 (1995), S. 119-135 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary An analytical method is presented to derive the stresses in anisotropic half-spaces with smooth and irregular surface morphologies. The half spaces can be subjected to body forces, surface tractions, and uniform far-field stresses. The general solution is expressed in terms of three analytical functions using the analytical function method of anisotropic elasticity. These three functions are then determined using a numerical conformal mapping technique and an integral equation method. Numerical examples are presented for the stress concentration at irregular surfaces induced by a uniform far-field horizontal stress. The elastic half-spaces are assumed to be transversely isotropic or isotropic, and their surface morphologies are constructed by the superposition of multiple long and symmetric ridges (mounds) and valleys (depressions). For isotropic media, the stress concentration depends only on the half-space surface geometry. It is found here that for anisotropic media, the half-space surface geometry, as well as the orientation of the planes of material anisotropy, have a great effect on the stress concentration. The degree of material anisotropy, on the other hand, has little influence on the stress concentration.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 31 (1991), S. 1253-1270 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the preparation of finite element meshes, inclusion of transitional blocks is important in order to construct optimal meshes. In this paper, a new method is proposed which is capable of generating quaddominated arbitrary transitional meshes. These meshes are well graded and do not require any mesh smoothening algorithm. The inverse isoparametric mapping combined with an elimination procedure is used to construct transition zones. This new algorithm is described in detail and its efficiency is illustrated with appropriate examples.Different methods available for inverse isoparametric mapping are discussed with their merits and limitations. Many of the existing techniques for inverse isoparametric mapping require the calculation of some special coefficients which may vary with the element type. These techniques lose their clarity and efficiency in the case of three dimensional and higher order two dimensional elements. In this paper, a generalized iterative procedure is proposed to carry out the inverse isoparametric mapping. The computations in this approach are already part of every finite element program based on the isoparametric formulation. Hence implementation of the new algorithm is very simple and straightforward.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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