Analysis of strength anisotropy of rock mass with a set of persistent joints

HAN Zhiming; QIAO Chunsheng; TU Hongliang

Abstract：Jointed rock mass is a kind of geologic body containing both continuum and discontinuum,which leads to its strength significant anisotropic.The numerical manifold method (NMM) can solve the continuous and discontinuous problems in a unified way.Based on the elastoplastic program of NMM,the compression tests of rock mass with different joint inclination and joint spacing under different stress state were simulated.The results show that the strength of rock mass with small joint inclination is lower than that of intact rock,even through the rock mass does not slip along the joint.The curve of rock mass strength-joint inclination is shaped like a spoon with asymmetrical sides.The variation of rock mass strength with joint spacing conforms to the rule of negative exponential function.The effect of joint spacing is significant anisotropic.The anisotropy of rock mass strength decreases with the increase of confining pressure.Based on the regression analysis of simulation results,a new joint distribution parameter was proposed,and then a new strength prediction model was established for the rock mass with a set of persistent joints.In this model,the effects of joint inclination,joint spacing and confining pressure are comprehensively considered.It can provide good technical support for underground engineering.