Working characteristics and failure mechanism of concrete-cored deep cement mixing (CDCM) piles under tensile load

The concrete-cored deep cement mixing (CDCM) piles have been widely used as uplift piles in soft soil areas of Eastern China with high groundwater levels in recent years, while the research on the behavior of CDCM pile under uplift loads remains limited. This paper presents a group of model tests of CDCM pile under uplift loads to study its uplift bearing capacity. Subsequently, the numerical simulations are conducted to analyze the failure mechanism in detail. The influencing factors such as core length ratio and core pile content ratio on the bearing capacity and failure modes of CDCM pile are discussed based on the simulation results. The research results indicate that the maximum tensile stress in the CDCM pile occurred at the pile head, gradually decreasing with depth. The uplift capacity of CDCM pile increases with the increase of core length ratio. The overall tensile stress in the composite section of the cemented soil column is relatively low, while a stress surge occurs near the bottom of the concrete core. Adopting an appropriate core content rate can reduce the risk of tensile failure in the pile shaft. The research findings can provide a basis for the design and practical application of CDCM piles.