Bearing Capacity and Deformation Characteristics of Uplift Piles in Soft Ground

Abstract

Theoretical and experimental studies on the bearing capacity and deformation characteristics of uplift piles have received much attention due to extensive use of uplift piles in underground structures in soft ground. Shanghai World Expo 500kV Underground Transformer Substation and Shanghai Hongqiao Comprehensive Transportation Hub are typical examples. Both types of uplift piles, i.e. uniform-section piles with side-grouting and enlarged-base piles, are often used in engineering practice. Despite of their extensive applications, theoretical studies have lagged far behind engineering practice. Presented in this paper was a comprehensive study on the simplified method for predicting the ultimate bearing capacity of enlarged-base piles with various pile lengths before and after deep excavation, and load-displacement responses of uniform-section piles with side-grouting based on the load transfer method. The good agreement between theoretical predictions and field pile load test results was obtained. The proposed method provides reliable estimates in a simple way for the bearing capacity and deformation characteristics of uplift piles.