DEM analysis of cyclic liquefaction behaviour of cemented sand

This study presents an investigation of cyclic liquefaction response of cemented sand using discrete element method (DEM). To reproduce the effect of cementation for cemented sand, an existing bond contact model was introduced in a DEM code, and then a series of undrained cyclic triaxial tests were simulated, where different cement contents (CCs) and cyclic stress ratios (CSRs) were considered. Finally, the evolutions of some important macro and micro-scale variables were analyzed. For cemented sand, if the CC is large or the CSR is small, few bond breakages occur, the mechanical coordination number almost remains unchanged, and the input work mainly contributes to the increase in the elastic energies at particle contacts and bond contacts, not leading to the onset of liquefaction. In the case of the liquefied cemented sand, with increasing CSR, bonds break more intensely, and the mechanical coordination number declines faster. The elastic energies at particle contacts and bond contacts tend to be zero faster, and the dissipated energies due to sliding friction, rolling rotation, and twisting rotation reach their maximum more promptly. In addition, the normal orientations for the bonded contacts, unbonded contacts, broken bond contacts, and total contacts, all tend to be isotropic more rapidly.

Automated summary

In cemented sand, with a high cement content or low cyclic stress ratio, there are few bond breakages and the mechanical coordination number remains almost unchanged. The increase in input work mainly contributes to the elastic energies at particle contacts and bond contacts, rather than leading to liquefaction. In liquefied cemented sand, as the cyclic stress ratio increases, bond breakages become more intense, the mechanical coordination number decreases faster, and various energy dissipation mechanisms reach their maximum more promptly. Additionally, the normal orientations for different types of contacts tend to become isotropic more rapidly.