Influencing Factors of Load Carrying Capacity and Cooperative Work Laws of Metro Uplift Piles

Abstract

The buoyancy of groundwater can reduce the foundation bearing capacity and cause the metro tunnels to float as a whole, which threatens the safety of structures seriously. Therefore, uplift piles are set up to improve the structural stability. In this paper, FLAC3D software is used to establish the calculation models of pile foundation. The bearing failure process of uplift piles was simulated to study the influencing factors on single pile load bearing capacity as well as the cooperative work laws of pile groups. The load-displacement curves of pile top under different length-diameter ratios, pile-soil interface characteristics and pile types are obtained, respectively. The results showed that, increasing the lengthdiameter ratio and the pile-soil interface roughness properly can improve the bearing capacity of uplift piles. Besides, changing the shapes of constant pile section can also improve it, which has the most significant effect concerning of saving material cost. In the loading process of pile groups, the ultimate bearing capacity of corner pile is the biggest, the side pile is the next, and the center pile is the smallest. The deformation characteristics of pile top are as follows: the center pile is the biggest, the side pile is the next, and corner pile is the smallest. Combined with the results, the uplift resistance of group piles can be enhanced pertinently, and the conclusions provide guidance for the design and construction of uplift piles in the actual engineer.