Abstract:The load-settlement characteristics of a single-pile composite foundation with steel pipe piles are studied through field tests and numerical simulation with the aim of strengthening the weak foundation of a passenger-dedicated line tunnel and understanding the stress state of the pile foundation after reinforcement. The variation rule of side friction, axial force, and bending moment of the pile body are also discussed. Results show that the P-S, S-lgt, and S-lgp curves obtained through field tests lack distinct feature points that are useful for determining ultimate bearing capacity. The characteristic value of the ultimate bearing capacity is 200 kPa in accordance with the code. Numerical simulation can be used as a necessary supplement to field tests in accordance with the total settlement of steel pipe piles in numerical simulation and the normalized curve of load settlement. Numerical simulation results show that the axial force distribution of the pile body has a D-shaped pattern and a maximum value of 59.8 kN. Negative skin friction resistance falls in the range of 2 m from the top of the pile with a maximum value of 130 kPa, and the rest of the pile exhibits positive friction resistance with a maximum value of 50 kPa. The neutral point of the pile is not unique. A small bending moment exists in the upper part of pile body, and its influence on the stability of the steel pipe pile can be neglected.
