Theoretical analysis of the vertical bearing characteristics of cemented soil mixed (CSM) pile considering the effect of confinement pressure

Existing theoretical models of the vertical bearing characteristics of cemented soil mixed (CSM) piles generally neglect the confining pressure effect when establishing the interface constitutive relationship. These models assume that the interface shear stress-relative displacement relationship remains constant along the entire pile length, thereby failing to reflect the regulating effect of increasing confining pressure with depth on the interface mechanical behavior. To address this issue, a four-linear constitutive model for the core pile-cemented soil (CP-CS) interface considering confining pressure effects is proposed in this study. The total interface shear stress is decomposed into bond stress and friction stress, and a linear enhancement mechanism of confining pressure on the friction stress is incorporated. The proposed theoretical model was validated by comparing its computational results with those of the traditional model and with static load test results on CSM piles conducted under four different confining pressure conditions. Subsequently, the load transfer behavior was analyzed, revealing the five-stage failure evolution mechanism under the homogeneous soil condition. Finally, the sensitivity analysis of key parameters was conducted. This study provides a theoretical basis for the bearing capacity assessment and failure mode prediction of CSM piles, and offers guidance for the optimization design of key parameters.