Micromechanical analysis of the particle corner breakage effect on pile penetration resistance and formation of breakage zones in coral sand

Although particle corner breakage has proven to be the major breakage mode of irregular grains, most pile–soil interaction analysis has focused on particle fracture breakage, thus the microscopic mechanism of sharp settlement/stress change for piles in coral sand remains unclear. This particle corner breakage–based study features laboratory pile penetration tests as well as DEM simulations. In the laboratory tests, in-situ sand samples that avoid slipping loss of corner debris are obtained and adopted. During DEM simulations, the cluster method is adopted with the linear parallel bond model. Unlike with classical friction resistance of piles, the particular shrinkage of friction resistance of piles in coral sand can be seen as resulting from a dual effect of corners. An additional increase in confining pressure was not efficient at improving the ultimate friction-bearing capacity of piles in crushable angular grains. As indicated by a diagram describing relationships between corner breakage and effective contacts, the force transmission in soil is newly generated, allowing interpretation of the sharp decrease of pile friction-bearing capacity. Findings indicate that higher grain angularity increases particle breakage within a narrower shear zone in soil samples. Finally, a particular relationship between particle breakage mode and the breakage zone around the pile tip is derived. This study sheds light on the microscopic mechanism of pile penetration in crushable granular soils, offering guidance for evaluating the ground-bearing capacity of angular granular soils.