ABSTRACT
As can be seen in the presented figure, stress decreases in time and its value approximates asymptotically to a certain constant value different from zero. At rock relaxation, a change in the ratio of elastic strain to plastic strain probably occurs in the course of test. Plastic strain grows at the expense of elastic strain with the growing duration of loading; the sum of plastic strain and elastic strain remains constant. To maintain the plastic strain, a less force is needed and thus a reduction in stress measured appears.
