Coarse grained material is the aggregation of rock particles with certain gradation

which has special physical and mechanical properties. Based on the results of consolidated-drained triaxial tests and three-dimensional particle flow code theory

the numerical model of triaxial test for coarse grained materials is obtained by programming and redevelopment of PFC3D (particle flow code of three-dimension) from the view of mesoscopic scale. The influence of particle shape on strength and deformation of coarse grained materials is considered by introducing clump particles. The relations among dilation

particle breakage and rearrangement are analyzed. The numerical results show that particle shape is the main factor affecting the strength and deformation of coarse grained materials. Changing the particle shape can significantly affect the mechanical behavior of coarse grained materials in the case of other mesoscopic parameters unchanged. The stress-strain relationship of bonded-particle model (BPM) is agreed with experimental result only under low confining pressure; the deviation is growing larger with the increase of confining pressure. The stress-strain characteristics of coarse grained materials in consolidated-drained triaxial tests are simulated by PFC3D model using clump particles accurately. The BPM and clump particles are both rigid particles. The shear dilatancy is too large because the particle deformation and breakage are not considered.