Research on Settlement Calculation Method of Super-Long Pile Foundation

Abstract

For deep foundation of super high-rise building, pile box (raft) foundation is mostly adopt, and pile foundation is usually formed by super-long bored piles with large diameter, only a few super high-rise buildings are of super-long steel pipe pile (for example, for Jinmao Tower in Shanghai, steel pipe pile over 80m long is used. Generally, super-long drilled pile’s diameter d ≥800mm, while pile length l ≥-50m. At present, in the latest Technical Code for Pile Foundations of Building (JGJ94-94) of China, the vertical load capacity and other parameters of under water bored piles are determined by modifying prefabricated piles in Code for Design of Foundation and Subgrade of Building (GBJ7-89) combined with measured data of under water bored piles. In China, more and more super high-rise buildings have been built in soft subgrade area, such as Shanghai, Tianjin, Wuhan, Fuzhou, Shantou, Wenzhou, Wuxi, Nanjing, Zhengzhou, Xi’an and etc, and large number of super-long bored piles are used, and there is undergoing trend. After 100 years’ application and research of bored piles, admittedly there have been much study on short pile, middle-long pile and long pile, and there have also been much data & material accumulated. But for super long pile, there have been reletively less study and test data. The reason is that it is difficult to form a pile and also difficult to reach the ultimate bearing capacity of pile in pile compression test for engineering. So it is very pressing and important to study the performance and settlement of super-long pile. In this chapter, settlement characteristics and engineering application of super-long pile are researched, and some suggestions and opinions about using super-long pile are put forward. Meanwhile, settlement calculation method of pile foundation is presented, which is derived from Code for Design of Foundation and Subgrade of Building (GB50007-2001).