About elastic and strength limits of rocks

In this paper we research how rock samples respond to irregular triaxial compression according to Karman’s scheme. We have used known A. N. Stavrogin’s experimental data for some type of rock. As shown [1, 2], these materials originally possessed elastic orthotropic symmetry. Elastic limits in arbitrary stressed states was determined using elastic limit under uniaxial compression on the basis of synthesis Mohr-Kulon’s criterion and the сoncept of sliding in the treatment of M.J. Leonov. We used [3] conclusion: rocks behave as ductile materials from the state of stress when the average principal stress reaches the maximum shear stress to at higher pressures. In other words, in this situation ripping of materials disappears and Mohr-Kulon’s criterion converses in Treska’s criterion. These conditions was realized when establishing strength limits and teoretical determination of cutting angle at failure. Curves of Mohr's circles were constructed.