368A

observed shear band orientation in all cases. The theory pro- vides necessary, but not sufficient, conditions for shear band formation, and increases understanding of the phenomenon.

static sinusoidal pressure, which can be applied to determine distributions of pore pressure and total stress induced in a sloping sea bed by wave action.

916295 Simple shear of isotropic elasto-plastic soil Frydman, S; Talesnick, M Int J Num Anal Meth Geomech VI5, N4, April 1991, P251- 270

The direct simple shear test is popular and widely used. The implications of using an isotropic elastoplastic soil model to interpret these tests are considered. Three consequences are implicit for small strains: strains and strain increments at any stage can be expressed as the sum of elastic and plastic compo- nents; principal direction of stress and of plastic strain incre- ment are collinear; and principal direction of stress increment and elastic strain increment are collinear. These consequences are used to establish relations between stresses, stress incre- ments, and strains during the simple shear test, no additional assumptions being necessary concerning yield function, flow rule, or hardening function.

916296 Interface elements for singular plasticity points Van Langen, H; Vermeer, P A Int J Num Anal Meth Geomech V15, N5, May 1991, P301- 315

A special use of interface elements is illustrated, modelling of displacement singularities. A formulation for a zero thickness interface element is presented. A punch problem is solved numerically to demonstrate the effect of singular plasticity points. Indroduction of a potential slip line into the finite ele- ment mesh is seen to improve computational results. Possible mesh dependence is investigated. Pile penetration problems are finally addressed and it is shown that the use of potential slip lines is essential for such an axisymmetrical problem.

916297 Continuum modelling of jointed porous rock Cho, T F; Plesha, M E; Haimson, B C lnt J Num Anal Meth Geomech V15, N5, May 1991, P333- 353

Continuum representations for the mechanical and hydraulic properties of an intact rock mass and each of the joint sets are superposed to produce constitutive equations for mechanical and hydraulic behaviour of a saturated rock mass with joint sets at specified orientations. Fluid diffusion through the vari- ous interconnecting flow paths and anisotropy of the mechani- cal properties due to joint stiffness are described. A simple example of a rock mass with one set of joints at different dip angles is illustrated. More realistic applications to slope stabil- ity and reservoir induced seismicity are also considered.

916298 Wave induced stresses and pore pressures in sloping seabeds Gatmiri, B lnt J Num Anal Meth Geomech V15, N5, May 1991, P355- 373

Design of seafloor structures requires knowledge of wave- induced pressures and stresses in the seabed. A general solu- tion is obtained for the total stress and pore pressure distribu- tions in an infinite wedge under fairly general conditions of loading by using the Mellin transform. An explicit form is obtained for the case in which each surface is subjected to

916299 Surface instabilities in elastic anisotropic media with surface- parallel Griflith cracks Vardoulakis, I; Papamichos, E Int J Rock Mech g in Sci 1/28, N2/3, May 1991, P163-173

Buckling under plane strain conditions due to a horizontal compression of an elastic, anisotropic half space containing coplanar cracks at arbitrary locations is considered. A numeri- cal procedure based on the Displacement Discontinuity Method is developed and validated against the analytical solu- tion of a half space with a single crack. It is demonstrated that the critical buckling stress decreases dramatically as the dis- tance between free surface and the cracks diminishes. Auth.

916300 Displacements from relief of in situ stress by a cylindrical hole Smither, C L; Ahrens, T J Int J Rock Mech Min Sci 1/28, N2/3, May 1991, P175-186

The holographic in situ stressmeter records by holographic interferometry small displacements on a borehole wall gener- ated by drilling of a small stress relief hole. Far-field stress can be obtained from analysis of a set of holograms at different azimuths at a single depth in the borehole. The previously used model of the borehole wall as a flat elastic plate of thick- ness twice the depth of the stress relief hole has been shown to be inadequate in certain cases. An improved model, based on the approach of Youngdahl and Sternberg, which considers a cylindrical hole in an elastic,isotropic half-space is presented.

916301 Properties of granular packings under low amplitude cyclic loading Chang, C S; Misra, A; Sunderam, S S Soil Dynam Eartlul Engng II10, N4, May 1991, P201-211

A stress strain relation for granular materials considering par- ticle interactions and packing structure is presented. Hertz- Mindlin theory of contact of two elastic spheres is used to describe contact displacement behaviour under oscillating forces. The experimentally observed influences of void ratio, coordination number, particle properties, and structural ani- sotropy on initial tangent and secant moduli and damping ratio can be reproduced by the constitutive model.

916302 Mechanisms of fabric evolution in granular media Rothenburg, L; Bathurst, R J; Matyas, E L Proc 12th International Conference on Soil Mechanics and Foundation Engineering, Rio de Janeiro, 13-18 August 1989 V1, P753-756. Publ Rotterdam: A A Balkema, 1989

An attempt to quantitatively describe elements of fabric rele- vant to macroscopic stress strain response of granular materi- als is presented. Contact force distribution and orientation and evolution of fabric with contact forces are examined for numerically simulated plane granular assemblies. Theoretical results relative to development of induced anisotropy, dila- tancy, and energy dissipation are used to derive constitutive relations. Conventional macroscopic parameters such as fric- tion angle at constant volume and peak dilatancy rate are expressed explicitly in terms of microstructural characteristics.

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