Finite element analysis of the differential rebound of piles in pit during top-down excavation

Differential rebounds between piles will bring extra stresses in the basement structure during top-down excavation. Methods for minimizing differential rebounds between piles were discussed, including variations in pile location, pile length and pile radius as well as variations in vertical or horizontal connection stiffness of joint between horizontal bracing system and vertical sustaining structure. Results of the finite element method show that: variation in pile length is an effective way to diminish rebounds and differential rebounds of piles and keep differential rebounds unchanged during pit excavation; variation in pile radius helps to diminish differential rebounds between piles, but their effect on differential rebounds are really small; for non-displacement piles, the impact of variation in pile space on rebounds at pile head can be neglected; when piles and retaining wall can slip vertically, the effect of differential rebounds of piles on slabs can be neglected and lateral deflections of piles decrease accordingly; when horizontal support of columns to slabs is weakened, there are sharp increases in rebounds and differential rebounds of piles, resulting in the lateral deflections of piles towards pit center.