## ABSTRACT

A three-dimensional numerical model, in which matter is discretized into a system of mass points connected with springs, is developed for the study of rocks. This model applies to two dynamic problems: one is stress concentration and failure initiation at a crack tip in plate subjected to a uniform tension and the second is a wave propagation problem in plate. The first numerical example represents the value of the stress intensity factor calculated by the linear elastic fracture theory. The stress state reaches the limitation (tensile strength), then tensile failure surface initiates at the tip. The failure surface is progressively developed and the rate of the development is deeply related to the value of the damping constant in the equation of motion. The second is the propagation of plane harmonic wave. Directional characteristics for the wave through the two lattice structures are displayed.