Micromechanical analysis of the particle corner breakage effect on pile load performance in coral sand

Corner breakage was less analyzed in pile-soil interaction research, causing the mechanism of particular pile load behaviors in coral sand to remain unclear. This study investigates the particle corner breakage effect on pile load performance in coral sand at both the macro-scale and particle-scale via indoor pile load model testing and Discrete Element Method and Finite Difference Method (DEM-FDM) coupled simulations. In numerical simulations, corner grains were constructed by the cluster method. Results revealed that compared with the fracture breakage, the corner breakage has a more obvious soil loosening effect. The coupled effect of corner interlock and corner breakage well explained the side friction distributions and the load share of pile tips in breakable corner grains. Besides, after obvious corner breakage, a much narrower pile-affected width around pile sides and a deeper stress transmission under pile tips were discovered in corner grains. Moreover, the decrease in effective contacts and change in soil skeletons have been proven to be essential factors behind the narrower pile-affected width and deeper stress transmission in breakable corner grains. Finally, compared with breakage effects in the previous research, the particle corner breakage effect was proved to have advantages in explaining large and sudden settlements of piles in coral sand with the use of a positive feedback loop. This study highlights the advantages of using particle corner breakage effects to explain specific pile load behaviors in coral sand and provides insight into the mechanism of pile-soil interaction in breakable granular soils.