Micromechanical analysis of shear characteristics of core pile-cemented soil interface in stiffened deep cement mixing pile

Abstract

The shear behavior of the core pile-cemented soil interface is crucial for understanding the load transfer mechanism of stiffened deep cement mixing (SDCM) piles. In this study, a core pile-cemented soil shear model was developed using the continuum-discrete coupling method in order to investigate the shear characteristics of the core pile-cemented soil interface from the microscopic perspective. The core pile-cemented soil interaction during shear was analyzed, including the number of core pile-cemented soil contacts, the porosity, the force chain and the contact force characteristics, etc., and the reasons for the change of the interface skin friction with the relative displacement in three stages were explained. The results show that interface skin friction increases with displacement due to bond strength and force chain formation during the initial shear stage. Beyond the peak, bond failure and force chain collapse cause particle rearrangement and skin friction reduction. Finally, the skin friction remains stabilized due to horizontal particle interlocking and tangential sliding. Furthermore, the effects of core pile-cemented soil interface bond strength, core pile diameter and vertical pressure at the top of the soil on the core pile-cemented soil shear characteristics were investigated. Finally, a constitutive model of skin friction-relative displacement response for core pile-cemented soil interface considering the soil confining pressure around the pile was proposed. This study reveals the microscopic mechanism of shear at the core pile-cemented soil interface and provides guidance for evaluating the bearing capacity of SDCM piles.