Improvement of modified Hoek-Brown criterion under conventional triaxial compression conditions

The modified Hoek-Brown criterion can reduce the deviations of the over-predicted rock triaxial strength values at high confining pressures by HB criterion. However,this criterion still has some application limitations. The point,in the modified HB criterion,that rock critical confining pressure equals to uniaxial compressive strength is not of universality. Rock triaxial strength predicted by the modified HB criterion significantly deviates from the test strength since confining pressure reaches the value of uniaxial compressive strength,and this deviation increases with the in- crease of confining pressure. In order to overcome the aforementioned limitation,the modified HB criterion is improved by employing rock critical state and rock critical state coefficient,and a new criterion called I-HB criterion is pro- posed. The applicability of the I-HB criterion has been verified by using an extensive database of rock triaxial strength tests from literatures. The result shows that this criterion successfully overcomes the limitation of the modified HB crite- rion,and the I-HB criterion predicted rock triaxial strength values are more consistent with the test values. Thus,the I- HB criterion is superior to the modified HB criterion. Furthermore,by comparing with exponential criterion,which is regarded as an outstanding criterion in rock engineering,the I-HB criterion has been verified having a higher accuracy in predicting rock triaxial strength.