ANALYTICAL METHOD FOR PILE COMPOSITE GROUND UNDER FLEXIBLE FOUNDATION
LU Wenzhi1，2，YU Jianlin1，GONG Xiaonan1
(1. MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering，Zhejiang University，Hangzhou，Zhejiang 310058， China；2. Key Laboratory of Geotechnical Mechanics and Engineering of Ministry of Water Resources，Yangtze River Scientific Research Institute，Wuhan，Hubei 430010，China)
Abstract：Interactions among flexible foundation，cushion，composite ground，and underlying soils have not been well researched. A simplified analytical model is presented considering the above four parts as an interactive system. The method allows the relative movement between piles and soils，and assumes different settlements of foundation soil at the same level plane. The force equilibriums of a typical element are established. And then，according to the compatibility of stress and deformation on the interfaces between these four components，the formulas for settlement and stress ratio of pile-soil，which are used to characterize the behaviors of the composite ground，are derived. Comparisons demonstrate that the results from this solution are in accordance with the measured ones of a project in China¢s Zhejiang Province，and they are closer than those obtained using the recommended method of the current codes in China. The pile-soil load ratio and the load transfer law of pile composite ground under flexible foundation are different from those of rigid foundations. More attentions should be paid to the concepts of equal settlement plane and neutral point plane for the engineering designs. Finally，same suggestions are proposed for further study of analytical method of pile composite grounds under flexible foundation.
