Micromechanical analysis of capillary suction effect on bearing capacity of unsaturated fine granular foundation soil using coupled CFD-DEM method

Abstract

The micro- to macro-scale bearing capacity characteristics of unsaturated fine granular soil have remained unclear. This study is the first to investigate the capillary suction effect on the bearing capacity of unsaturated fine granular soil in a plate load test via a series of coupled CFD-DEM simulations. The bearing capacities of fine granular soils in dry, unsaturated and saturated conditions are compared at both the macro- and microscales. The findings reveal that in addition to sharply improving the bearing capacity, capillary suction is useful for increasing allowable settlement in fine granular soil. Moreover, the study uncovers a much deeper particle migration as well as a much larger triangular zone of contact force distribution in the unsaturated soils compared to saturated soils. The existence of a huge triangular rigid zone under the plate in unsaturated fine granular soil is the major reason behind the high soil bearing capacity, and the capillary suction effect is partly similar to the surcharge effect on soil bearing capacity, leading to an explanation of this phenomenon in a micro-scale context.