Effect of pile length on deformation stability of pile-soil composite foundation

Abstract

Pile foundation is the foundation part of large buildings and infrastructure, and its safety performance directly affects the safety of the whole structure. In this paper, a three-dimensional pile-soil model is constructed by numerical simulation to simulate its mechanical response under different loads. The settlement behavior, axial stress distribution of pile body and the change law of pile-soil stress ratio are analyzed. The result show that:(1) With the increase of pile length, the pile tip settlement shows a decreasing trend, especially when the pile length reaches 33.4 m and is embedded into mudstone layer with strong bearing capacity, the pile tip embedding effect is significantly enhanced, resulting in a decrease in pile tip settlement. The difference between the settlement of raft center point and pile top surface increases with the increase of pile length, which reveals the important load regulation function of mattress layer.(2) When the pile length is short, the maximum axial stress is located at a certain distance below the top of the pile, and spreads along the pile body with the increase of load; For longer piles, the axial stress of pile bottom is larger, and the maximum axial stress point gradually increases with the increase of load. When the pile end is embedded in the strongly weathered mudstone layer, the axial stress distribution shows a “W” shape pattern, which reflects the importance of the embedment effect between the pile end and the rock.(3) With the increase of pile length, pile foundation can still maintain a high bearing capacity under large loads, but its growth rate will gradually slow down after exceeding a certain threshold, indicating that there is an upper limit of the bearing capacity of pile foundation.

Keywords

pile-soil interaction / pile length / numerical simulation / load / displacement