STRENGTH CRITERIA OF DEEP ROCK MASS

The most distinguished difference between deep and shallow levels is the so-called high geostress.The failure mode of the shallow rock mass is brittle failure.The failure modes of the deep rock mass may be brittle failure or ductile failure that depend on the property of rock mass and the geostress state.Mohr-Coulomb criterion,Hoek-Brown criterion,Druck-Prager criterion and unified strength criterion are suitable for brittle failure of the shallow rock mass.A new strength criterion,which is applicable to deep rock mass,is proposed.The new strength criterion,in which the effect of intermediate principal stress is considered,can consider the brittle failure and ductile failure of the deep rock mass.Moreover,the new strength criterion that is relative to the rock mass rating(RMR) classification can be applied to the research of the tensile failure of deep rock mass.All the parameters have clear physical concept,which can be conveniently determined by experiments or RMR in the presented criterion.Finally,in order to examine the proposed strength criterion,the comparison between the present strength criterion and the experimental data is performed.It is shown that the presented strength criterion is in good agreement with the experimental results.