MODEL FOR PLASTIC CREEP OF ROCK-LIKE MATERIALS ACCOUNTING FOR THE KINETICS OF FRACTURE

The constant stress creep behaviour of rocks is studied. A model is presented employing assumption that time-dependent microcracking is responsible for the macroscopic viscoplastic deformation. Irreversible volumetric creep is included as the main concern is the material behaviour for stress-levels over the 'discontinuity' locus which is identified with the initial yield point. A modified formalism of plasticity theory is used with a scalar crack-density parameter. The steady-state and tertiary creep stages (up to failure) are described by the simplified theory. identification of material parameters is discussed and an example of creep curves for the case of homogeneous biaxial compression is given to illustrate applicability of the model. © 1979.