Breakage effect of calcareous sand on pile tip resistance and the surrounding soil stress

Abstract

Due to the irregular shape, high porosity and fragility of calcareous sand particles, the construction of reef engineering is seriously affected, and the application of pile foundation engineering technology in calcareous sand stratum is also faced with great challenges. Based on the discrete element method (DEM), the pile installation process in the fractured calcareous sand stratum and non-fractured silica sand stratum are simulated, respectively, and the influence of particle breakage of calcareous sand on soil stress around the pile and pile tip resistance are discussed. The results show that the particle contact has no obvious dominant direction, and the particle breakage has little contribution on the variation of the particle contact normal directions while has great influence on the number of contact normals and the magnitude of contact normal force which is more uniform after particle breakage. The vertical and horizontal stresses in calcareous sand stratum are obviously lower than that in siliceous sand stratum. With the increase of the pile penetration depth, the number of crushing particles increases gradually. The particle breakage only can be found within the range of 3 times of pile diameter at the bottom of the pile and also within the range of 1 time of pile diameter around the pile. The effect of particle breakage on pile tip resistance is mainly reflected in the later stage of pile sinking. In calcareous sand, when the pile tip resistance increases to a certain extent, particle breakage occurs and the stresses in the soil cannot continually increase. Therefore, the pile tip resistance fluctuates around a stable value (∼0.3MPa). This is the reason that the pile tip resistance in calcareous sand is far less than that in siliceous sand, which is prone to pile foundation failure.