SUMMARYThe idea of using a thin solid element, called a thin-layer element, in soil-structure interaction and rock joints is proposed. A special constitutive model is used and various deformation modes such as no slip, slip, debonding and rebonding are incorporated. The shear stiffness is found from special laboratory tests and the normal stiffness is assumed to be composed of participation of the thin-layer element and the adjoining solid elements. A parametric study shows that the thickness of the thin-layer element can be such that the ratio of thickness to (mean) dimension of the adjacent element is in the range of 0.01 to 0.1. A number of simple and practical problems are solved to illustrate the success of the thin-layer element for soilstructure interaction problems.

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SUMMARYMixed finite element procedures with triangular and quadrilateral elements are evaluated and applied for nonlinear elastic and elastic-plastic analysis of some engineering problems. The elastic-plastic analysis involves implementation of von Mises, Drucker---Prager and Cap models. A number of special techniques such as symbolic programming, utilization of dihedral symmetry and the frontal solution are used to achieve computational economy. The procedure is also adopted for simulation of construction sequences in geomechanics such as excavation involving stress-free surface. The proposed procedures are evaluated and verified with respect to closed-form solutions, other finite element (displacement) procedures and field observations.

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