Behavior of Side Friction of X-section Cast-in-place Concrete Pile Composite Foundation

Based on static load tests in Qiaobei sewage treatment plant in Nanjing,finite element models were established by ABAQUS for single pile and pile group with the configurations of equilateral triangle and square to simulate the distribution of side friction.The results show that the neutral points emerge at the 1/4 to 1/3 of pile depth.The area of negative friction is smaller than that of positive friction,in other words,X-section cast-in-place concrete pile(XCC pile) is a typical friction pile.The side friction increases with the increasing of pile modulus,surrounding soil modulus and pile length,and decreases with the increasing of cushion thickness.The capacity of side friction is affected by pile configurations.In order to improve the side friction,the pile spacing should be large enough within bearing capacity.