Abstract:

In geotechnical tests, particle diameter (R) or sample size (L) accounts for the mechanical properties of coarse-grained soils. Correctness and precision of the results modeled with the discrete element analysis (DEA) is limited by the calculation scale, which is also determined by the characteristic length ratio L/R. Scaling law that describes relationship between micro-parameters and macro-parameters of coarse-grained soils is obtained using dimensional analysis; and it is shown that the shear resistance of coarse-grained soils depends on the characteristic length ratio L/R. A series of numerical triaxial tests are performed; it is shown that the L/R has little effects on the shear resistance when L/R is larger than 40; when L/R is less than 30, the shear resistance will be noticeably affected by L/R because of the effects of the boundary friction. The servo-mechanism provided by PFC2D/3D（Particle Flow Code, ITASCA®）is also discussed.

Key words: granular materials, coarse-grained soil, size effect, characteristic length ratio, boundary friction, DEM, scaling law, servo-mechanism