3D DEM simulations of basic geotechnical tests with early detection of shear localization

Abstract

This paper deals with elementary geotechnical tests: triaxial and direct shear of cohesionless sand using the discrete element method (DEM). The capabilities of the numerical DEM code are shown, with a special focus on the early phenomena appearance in localization zones. The numerical tests were performed in 3D conditions with spherical grains. Contact moments law was introduced due to simulate not perfectly round sand grains. The influence of different physical parameters was studied, e.g. initial density or confining pressure. The sieve curve corresponded to the Karlsruhe sand [1]; however, in some tests, it was linearly scaled. Special attention was laid on the behaviour of the sand grains inside localization, e.g. rotation, porosity, fluctuations, etc. and forces redistribution. Emphasis was given on the pre-failure regime and early localization predictors.

3D DEM Analysis of Particle Breakage Effect on Direct Shear Tests of Coarse Sand

“…In this study, the grain size of particles is often up-scaled due to computational costs and previous research suggesting that up-scaling to a reasonable factor has a minimal impact on experimental results [ 35 , 39 , 40 , 41 , 42 ]. Given the focus on investigating the effect of grain crushing and the size of the model, the diameter of each sphere was scaled up by a factor of two and selected based on the grain size distribution of the tested sand.…”

“…Several researchers have conducted calibration chamber and centrifuge tests on carbonate sands to better understand what happens when a pile is driven into weak sands [ 5 , 6 , 7 , 8 ]. This phenomenon has also attracted many researchers to conduct laboratory tests to study the influence of particle breakage on the critical state behaviors, shear stress ratios and dilatancy of granular soils [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ] as well as numerical modeling [ 14 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ].…”

“…Recently, studies of direct shear tests at the microscopic level have become more popular using the Discrete Element Method among others by [ 14 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. Seyyedan et al [ 29 ] employed a novel approach that combined the Discrete Element Method (DEM) and Extended Finite Element Method (XFEM) to conduct numerical simulations of direct shear tests.…”