Analysis of bearing capacity of the bottom uplift pile based on pile-soil shearing characteristics

NIE Yongjiang;SHAO Guanghui;College of Civil Engineering,Nanjing Forestry University;

bottom uplift pile;;load transfer function;;bearing capacity;;shearing characteristic

Bottom uplift pile is a new type pile,and its bearing capacity theory still needs to be improved.The shear behaviors of pile-soil interface have an important influence on the ultimate bearing capacity of pile pulling.The determination of ultimate bearing capacity based on pile-soil shear characteristics can more accurately reflect the actual work.In order to investigate the ultimate bearing capacity of bottom uplift pile in the sandy ground,the multistage linear load transfer function of pile-soil was established based on the development process to analyze the pile-soil shearing state.The analytical expressions of pile internal force and displacement under different conditions were derived.The analytical solution of the load-displacement of the pile was obtained.The ultimate bearing capacity and its influence factors of the bottom uplift pile were discussed based on an engineering case.The results indicatesd that the ultimate bearing capacity could be calculated according to the peak shear strength of the pile-soil system for bottom uplift pile in the loose sand ground.On the other hand,the shear softening characteristics of the soil around pile should be considered in the calculation process of the ultimate bearing capacity of the bottom uplift pile in the dense sand ground.When the ultimate failure reached,the shear stresses of pile-soil at different depths could not reach the ultimate strengths synchronously,and the ultimate bearing capacity of bottom uplift pile was lower than that calculated by the traditional theory.The ultimate bearing capacity of bottom uplift pile was obviously higher than that of the ordinary uplift pile,and the displacement of bottom uplift pile was much smaller than that of the ordinary uplift pile when the ultimate bearing capacity reached.The softening coefficient was an important factor to affect the ultimate bearing capacity of the pile in the dense sand ground.The lower the softening coefficient was,the lower the ultimate bearing capacity was,and the greater the difference was from the traditional theory.