Abstract:

By carrying out unloading experiments of high stress on granites in the style of unloading confining pressure with loading axial pressure, the stress-strain curves which describe the gradual damage of rock and the degradation laws of mechanical deformation parameters are both acquired, the Mogi-Coulomb strength criterion is applied to explain deformation characteristics, the varying laws of strength parameters and the evolutionary features from compression-shearing cracks to tension-shearing cracks of rocks are also built up. Then the relation between compression-shearing Mogi-Coulomb criterion and tension-shearing Mogi- Coulomb criterion is expressed by the lateral deformation which has a primary affect on unloading damage of rock; and the new strength criterion is established. Finally, based on the above experimental results and stress-strain curves from the unloading experiments, the mechanical constitutive equations, which involves the degradation laws of mechanical deformation parameters, the effect of lateral deformation and the evolutionary features of unloading damage are deduced in the strain space.

Key words: high stress, unloading, strength criterion, constitutive equation