Analysis of working characteristics of composite foundation with flexible pile under rigid pile-cap

Based on the coordination conditions of deformation and the mechanics theory, a set analytical formula for the pile-soil stress ratio, the distribution of axial force and the relationship of loading-settlement have been obtained by systemic analysis on bearing characteristics of the composite foundation with flexible pile and pile-cap. Calculation results show as follows: in most instances, the loads on flexible pile can not be transferred to the pile-end and there is an effective length of the pile, which disagrees with the rigid pile. Meanwhile, tendency of pile-soil stress ratio varied with load have relations with column rigidity, shear rigidity of pile side and compressive rigidity of pile-end soil. If load corresponding with the relative deformation s/b=0.004 similar to 0.01 was used as bearing capacity eigenvalue of the composite foundation, the bearing capacity will increase 1/3 similar to 1/2 when the column rigidity was twice as large as the primary. To verify the feasibility of the proposed method, the results of model test are compared with the calculated results in this paper, which shows that the proposed method is meaningful for design and calculation of composite foundation with flexible pile.