Numerous models of the discontinuities within a rock mass have been developed in attempts to simulate their mechanical effects. These models fall into two categories: discontinuous models and continuum models, each with its advantages and disadvantages under particular applications. The discontinuous models are those. that explicitly model individual discontinuities (faults, joints, etc.), e.g., Goodman, et al [1968], and Ghaboussi, et al [1973]. Continuum models are those which simulate some effects of discontinuities within a portion or all of the problem domain without modeling the discontinuity itself. A continuum-type compliant joint model was developed so that joints can be spread throughout the volume of interest, and aperture changes can be monitored. Validation ensures that the mathematical field theory embodied in a computer code is a correct representation of the phenomena it simulates. The validation process includes comparing calculations with measurements and observations made during field and laboratory studies. This paper presents a brief description of the compliant joint model, description of laboratory experiments used for this validation, the numerical idealization of those experiments, and the calculated results that complete this preliminary validation analysis. An evaluation of observed differences is made.
The model requirements evolved into a model with two components: a rock matrix and discontinuities. Joint will be used as a generic name for mechanical discontinuities. The model characteristics included continuum joints at each Gauss point, up to four non- orthogonal joint sets, and joint compliance in directions normal (nonlinear elastic) and transverse (linear elastic) to their plane of orientation. The model parameters are measurable in the laboratory or can be inferred from published data. The joint model is incorporated in the finite element code SPECTROM-31 [Key, in preparation]. The joint model is elastic and therefore requires no yield strength criterion. The primary effect of the joints to be incorporated into the overall model (matrix plus joints) response is the deformability. Derivation of the model deformability assumes continuity of normal and shear stress across a joint. The equivalent deformability of the rock mass is represented by the effective moduli E and G, which are the reciprocals of the sum of the matrix and joint compliances. (mathematical equation)(available in full paper)