Abstract: Rock mass is a rheological material; under the action of high geostress for a long time, its inner unequal stress could relax as time itself; thus finally tends to be hydrostatic stress state. In such state, although the volume remains elastic, it lost the ability to resist shear deformation; its energy mostly stored in volume deformation. This paper uses a plane compression model to investigate the deformation behavior and energy distribution relationship for rock mass under different stress levels long-term effects; and then discusses the brittle fracture failure for strong unloading, so as to reveal the influence law that initial geostress value(energy distribution relationship) acts on rock mass deformation(inertia, viscosity and elasticplastic deformation). The research results build a basis to establish the loading-unloading constitutive model for deep rock mass.

Key words: deep rock mass, initial geostress state, rheology, energy distribution, unloading damage mechanism