关键词: 离散元, 弹性模量, 泊松比, 配位数, 接触力

Abstract: It’s well recognized that the soil response is generally linear and elastic at very small strain level (i.e. below 10-6). Previous numerous experiments showed that the soil elastic properties mainly depended on the effective confining pressure, void ratio, soil grading and sample preparation method. In this paper, the physical experiments on regular packing of steel spheres by Duffy and Mindlin were simulated by three dimensional discrete element method in order to reveal the fundamental mechanism related to soil elastic properties at meso-scale. The simulations showed that the elastic stiffness of the soil depended on the coordination number, the normal contact force and its distribution, which correspond to the macroscopic parameters of void ratio and effective confining pressure. It was found that the stress exponent n was higher than 1/3 as predicted by the Hertz-Mindlin contact model and it was mainly due to the increase of coordination number and uniformity of contact force distribution during the increase of confining pressure. Meanwhile, Poisson's ratio decreased with increasing coordination number instead of a constant as commonly assumed, which was consistent with experimental results.

Key words: discrete element method, elastic modulus, Poisson’s ratio, coordination number, contact force