X形桩桩土相互作用对截面形状的力学响应

现浇X形混凝土桩（简称XCC桩）是一种新型的异形截面桩，其桩土相互作用明显受截面形状的影响。前期已通过平衡分析法推导得到了考虑XCC桩截面形状的单桩荷载传递计算方法，但控制桩土相互作用的一个重要参数即桩土剪切作用系数对截面几何形状的力学响应尚未得到系统的研究。文中分析了桩土剪切作用系数对不同荷载形式下XCC桩3个截面控制参数（外包圆半径R、开弧间距2a、开弧角?X）的影响，并与等截面面积的圆形桩进行了对比。分析结果表明，截面参数变化时，桩土相互作用也随之变化，在截面面积、周长和桩土剪切作用的共同作用下桩身轴力随外包圆半径和开弧角度的增大而减小，随开弧间距的增大而增大，且始终小于等截面面积的圆形桩。

Mechanical response of pile-soil interactions of X-section cast-in-place concrete piles to cross-sectional shape

The X-section cast-in-place concrete pile (XCC pile) is a new shaped pile. The pile-soil interactions are influenced by the cross-sectional geometry. The load transfer mechanism of the XCC pile dependent on the cross-sectional geometry has been derived by means of equilibrium analysis. However, the mechanical response of the vertical shearing coefficient, governing the pile-soil interactions, for the cross-sectional geometry have not been fully understood. This paper represents the effects of the three geometrical parameters (the diameter of the surrounding circle R, the distance between two adjacent cutting circulars 2a and the central angle of the cutting circle ?X) of the X-shaped cross-section on the vertical shearing coefficient. Comparative analyses between the XCC pile and circular pile of the same cross-sectional area are carried out. It is found that the pile-soil interactions vary with the changes of the geometrical parameters. Influenced by the cross-sectional area, the pile parameter and the vertical sharing coefficient, the axial force increases with the increasing of R and ?x, but decreases with the increasing of 2a. In addition, the axial force of XCC piles is always smaller than that of circular piles of the same cross-sectional area.