Calculation and Influence Factors Analysis on Pile-Soil Stress Ratio of CFG Pile Composite Foundation

In view of the present situation that the theoretical research for CFG pile composite foundation with cushion is not perfect and the necessity which would satisfy the calculation of pile-soil stress ratio in engineering practice,based on the deformation mode of the pile unit,and by comprehensively taking the negative friction of pile,the conditions that the top of pile piercing into cushion and the bottom of pile piercing into underlayer into full consideration,the formula of pile-soil stress ratio of CFG pile composite foundation with cushion has been deduced under the assumption that the soil layer is divided into two layers according to the location of equal settlement section.Meanwhile,the simplification and convergence method have been adopted in the course of deducing the formula to obtain the location of the equal settlement section of a CFG pile composite foundation with the pile length as 6.8～7.6 m,which approximately located at the section that 0.6～0.7 length from the bottom of the pile and the value of stress ratio ranging from 14～19.By comparing the calculation value and the test result,it shows a good agreement with the engineering practice.Therefore,the results show that the proposed method is suitable for calculating the pile-soil stress ratio of rigid pile composition foundation.The analysis results of the influencing factors of pile-soil stress ratio adopting this method show that choosing the reasonable pile diameter,cushion materials,spacing and length of pile can give full play to the carrying capacity of CFG pile composition foundation.