Abstract: To analyze the impact of geometrical particle parameters on macromechanical properties of the soil in particle flow method, the conversion formula of the granule number and modified porosity of numerical sample group in the 2D condition was proposed; and the numerical simulation and the laboratory model tests were carried out. It conducted 6 groups of parameter validation tests and 24 groups of variables cross-comparison biaxial compression tests, and included 4 types of gradations, 3 types of porosities and 2 kinds of contact models. The results show that the effect of porosity is larger than that of gradation on soil mechanical properties. With the increase of porosity, the peak value of soil strength gradually decreases; and the axial strains of corresponding points increase accordingly. Compared with the results of the Hertz-Mindlin (H-M) contact model which is focused on the nonlinear relation between the contact force and relative displacement; the results of the linear contact model are more reliable. Meanwhile the behavior of volumetric strain transited from dilatancy to negative dilatancy. And it is suggested when the porosity increases the H-M contact model reflected the subsequent dilatancy effect of soil after peak strength better.

Key words: particle flow, meso-structure parameter, gradation, 2D porosity, contact model, biaxial test