Test and Simulation Analysis of Cement Soil Pile Composite Foundation after Shield Tunneling Pile Cutting

To investigate the impact of changes in end-bearing conditions, resulting from shield tunneling, on the bearing capacity of an upper cement-soil pile composite foundation, this study is conducted based on a specific section of the Zhengzhou Metro Line 5 where shield machines cut through cement-soil piles. According to the principle of similarity, a reduced-scale model test of a single cement-soil pile within a composite foundation was designed for laboratory testing. Based on this, a corresponding finite element analysis model was established. By comparing the results from the reduced-scale model test and numerical simulations, the variation patterns of side resistance and end-bearing resistance of the cement-soil pile composite foundation were analyzed as the pile characteristics changed. Studies indicate after the lower part of the cement-soil pile composite foundation undergoes shield tunneling while maintaining a constant vertical load above, there is primarily a redistribution of stress within individual piles, characterized by a transformation between side resistance and end-bearing resistance to balance the upper load. Simultaneously, the neutral point of the side resistance of the cement-soil pile composite foundation moves downward, and its position relative to the pile length is less than that observed in the case where only the pile length is shortened. The change in the length of the cut pile significantly influences the development of side and end-bearing resistances; the contribution of side resistance decreases with an increase in the cut length, whereas the extent to which end-bearing resistance is mobilized slightly increases as the cut length grows.