PFC2D SIMULATION OF INFLUENCE OF PARTICLE SHAPE AND INITIAL FABRIC ON MECHANICAL PROPERTIES OF QUASI-SANDS IN DIRECT SHEAR TEST

摘要

In this study,a series of numerical direct shear tests are carried out on quasi-sands with different particle shapes and initial fabric by using the commercial discrete element code PFC2D.Four particle groups with different outlines are generated by the command of clump in PFC2D.Different initial depositions and fabric characteristics of the test samples have been generated with unidirectional method,random method and deposition method.The shear strength and dilatancy which affected by particle shape and initial fabric anisotropy have been studied,and how the force chain derived in shear process have been analyzed,and how the particle rotated inside or outside the shear zone have been studied also.The results show that:the shear strength of materials increases with the decrease of shape coefficient; the irregularity of particle shape also result in the decrease of strong force chain and the inhomogeneity of velocity field; the original fabric have great impact on shear strength,but little on material dilatancy and internal friction angle; principal stress axis deflects during shear process,and the contact angle moves closely to the principal stress direction; grains rotate mainly in 8 times the average particle radius,and the particle long axis orientation also deflect with the same direction of main stress; the particle rotation speed in the shear zone is also affected by the initial fabric of the assemblages.