Experimental and Theoretical Research on Interaction Between Soil Wet Expansion and Pile Foundation

To deeply study the stress and denaturation law of pile-expansive soil interaction in the humidity field, the physical simulation test of pile foundation uplift and the deformation or stress change of expansive soil foundation in the same humidity field at different soil depths was established. Through artificial rainfall infiltration to simulate the humidity field environment, and at the same time to monitor the change of pile foundation uplift at different soil depths in the model box, as well as the deformation and stress of expansive soil foundation, to obtain the impact of pile length on the uplift test results. Based on the theory of unsaturated soil mechanics, the distribution of pile lateral friction along pile length was analyzed. The theoretical formula of lateral friction resistance considering the change of soil stiffness and uplift is derived by combining with the shear displacement method, and compared with the results of the unsaturated soil mechanics theory and experiment. The results showed that the upward-lifting would cause unloading at the end of the pile body in the process of water absorption and expansion. With the increase of the pile tip's burial depth, the uplift of the pile tip tended to decrease as a logarithmic function, and the uplift decreased linearly with the increase of depth. The pile side friction theory formula and theory of unsaturated expansive soil pile side friction along the depth values were in good agreement. It was shown that the calculation formula of lateral friction was reliable, and based on the parameter limitation of the theoretical formula, the prediction method of lateral friction was put forward to determine the "neutral point" based on the theoretical formula and determine the value based on the unsaturated soil mechanics theory.