Abstract：Deformation and fracture of brittle marble is closely related to the extension of internal microcracks，and the macroscopic mechanical response of marble depends on its mesoscopic structures. Because the micro cracks are sealed in rock bodies，it is very difficult to grasp the development mechanism of the internal microcracks. With the help of the three-dimensional theory of particle flow and introducing the BPM model and the technology of super unit clump，a mesoscopic structure model of marble in terms of the mineral configurations was established on the basis of the testing result of SEM on the mineral contents of marble from the underground powerhouse of Jinping I hydropower station. The mesoscopic mechanical parameters of marble based on the sensitivity analysis was determined according to the indoor testing results of the uniaxial and triaxial compression and the mesoscopic numerical model of marble was also constructed. The deformation and fracture and the expansion process of marble under different stress states and stress paths were analyzed through numerical simulations. The numerical results of the macroscopic mechanical response of marble were found to agree well with the laboratory testing results. The numbers of microcracks grew slowly initially and soon exponentially under the condition of uniaxial and low confining pressures，however，the growth curve was approximately an “S” shape under the condition of high confining pressure. As the increasing of the confining pressure，the proportion of the tensile cracks reduced gradually，and the shear cracks increased. Under the identical initial confining pressure，the axial strain at the peak strength of rock was smaller and the proportion of tensile cracks was higher in the unloading stress path than the ones in the loading stress path. The tensile cracks played the leading role in the unloading process and eventually caused the tensile macro fracture surface to be formed，indicated that the volume expansion effect of marble under unloading was more significant and the brittle characteristics was more obvious. Under the different stress states and stress paths，the control mechanism of tensile crack propagation interacted with the one of shear crack friction，one grew slowly，the other grew fast.
2014, Vol. 33 
