EFFECT OF SPATIALLY VARIABLE FRICTION COEFFICIENT OF GRANULAR MATERIALS ON ITS MACRO-MECHANICAL BEHAVIORS USING BIAXIAL COMPRESSION NUMERICAL SIMULATION

This study proposed a method for biaxial compression numerical simulation considering a spatially variable inter-particle friction coefficient. A random field model is employed to represent the spatial variability of an inter-particle friction coefficient. The Karhunen-Loève (K-L) expansion method is used to discretize the random field of inter-particle friction. A computer program that combines the discrete element method with random simulations is developed in Matlab. The effects of a spatially variable inter-particle friction coefficient on the shear responses of dense sand specimens are investigated. The results indicate that the proposed method can effectively evaluate the influences of the spatial variability of an inter-particle friction coefficient on the macro-mechanical behaviors of particle material. The uncertainty of the inter-particle friction coefficient has a substantial effect on the evolution of deviator stress and volumetric strain during biaxial compression. The stochastic response curves are identical with each other at the initial loading and begin to vary with the constant loading for the dense sand specimen. In addition, it is shown that the correlation distance in the vertical direction has a more significant influence on the mean values and standard deviation values of peak deviator stress than that in the horizontal direction. The local average values of the inter-particle friction in the domain of the specimen has a more prominent effect than that of the space distribution of the inter-particle friction. However, the space distribution of the inter-particle friction affects the locations of the shear bands significantly.