Abstract:The columnar jointed rock mass is considered as a macroscopic composite material in a broader sense. A softening model of mixed multi-weakness planes is developed. Based on the second developing platform of constitutive model in FLAC3D,the mixed softening model has been successfully established and embedded. Taking the geological conditions of Baihetan Hydropower Station as research background,uniaxial and triaxial compressions of columnar jointed rock mass are simulated;and then the failure processes of test blocks with different dip angles and directions are analyzed. The distribution of fractured planes and the failure modes are achieved;and the failure law of general significance is summarized. Through triaxial compression test,it is obtained that the strength of columnar jointed rock mass and cohesion of joint surface can reach high level under certain in-situ stress level,which agrees well with the results of field investigation. Meanwhile,the laws of load and deformation,occurrence of failure zone,distribution and development of fractured zone as well as energy dissipation are studied. Failure mechanism in many respects is discussed so as to better understand the mechanical properties.