Abstract:

Granular materials exhibit irregular shapes under natural conditions, and the particle shape has great effects on its macro mechanical behaviors. Direct shear tests are simulated by using discrete element model (DEM) with clumps of spheres resembling the real shapes of granular materials, and the effects of different particle shapes on the shear strength are discussed. A clump is constructed by clumping spheres with different numbers, diameters, orientations and overlaps. The quaternion method is introduced to transform the rotation, the resultant force and the moment acting on a clump in global and local coordinates. The interactions between particles are described by Hertz-Mindlin contact model incorporated with the nonlinear normal viscous force and Mohr-Coulomb friction law. Seven different clumps with the same mass probability distribution are generated and used to simulate direct shear tests under different normal stresses. For each clump, the shear strength is analyzed. With the simulated results, it is shown that the interlocking among particles can be simulated well with the clumps of spheres. The presented model provides a foundation for analyzing the macro behaviors of irregularly shaped granular materials.

Key words: discrete media, particle shape, shear strength, direct shear test, discrete element