Abstract: Anisotropy and inter-particle bonding have large effects on the mechanical response of natural sand, which should be considered in engineering practice. In order to study the combined effects of these two factors, an anisotropic pure sand sample with elliptical particles and with a horizontal principal orientation is prepared in a discrete element method (DEM) code NS2D to simulate natural gravitational deposited sand. After the sample being deposited in a gravity field, a new bond contact model calibrated from statics of bond thickness in experiments is installed at the contacts. Finally, biaxial tests are conducted on the anisotropic structured sand sample. The simulation results are compared with laboratory test results to validate the DEM modeling. Besides, the micro-mechanical responses are also studied. Test results show that strain softening and dilation occurred with shearing. The number of bond contacts decreases and the principal direction of bond contacts are vertical during the tests. The variations of bond breakage percent and bond breakage ratio are consistent with the macro stress-strain and volumetric responses. The bonds are primarily damaged in tensile-shear failure mode rather than compression-shear; the principal orientation of particle arrangement is horizontal and the particle percent in horizontal direction increases slightly throughout the tests.

Key words: anisotropic structured sand, elliptical particle, macro and micro mechanical property, discrete element method(DEM)