悬臂式抗滑桩内力计算的“三段法”

针对现行按嵌固段和受荷段两段划分计算抗滑桩内力和位移的方法（简称“两段法”）不适应受荷段和嵌固段接触面非水平面、受荷段底面与嵌固段顶面不在同一平面的情况,根据荷载类型和作用强度的差异,将抗滑桩受荷段进一步划分为主受荷段和次受荷段（简称“三段法”）。基于抗滑桩嵌固段桩周岩土体服从文克尔（E.Winkler）假定,以悬臂式抗滑桩为例,推导了次受荷段在不受桩后推力作用和受桩后推力作用两种情况下悬臂式抗滑桩内力与位移通用计算公式,并论证了现行“两段法”只是其特解。结合具体的工程实例,抗滑桩“两段法”相较“三段法”计算出的弯矩和剪力在整个抗滑桩部分大多偏小,且偏小程度较大,尤其是在抗滑桩嵌固段;按“两段法”对抗滑桩进行设计将给工程安全带来不利的影响。

Three-section method for calculating internal force and deformation of cantilevered anti-slide pile

At present, the internal force and displacement of anti-slide piles are calculated on the basis of two sections: the loaded segment and the embedded segment (called "Two-section method"). However, this method does not adapt to the situation when the contact surface of the loaded segment and the embedded segment is not a horizontal plane or the bottom of the loaded segment and the top of the embedded segment are not at the same height. The loaded segment is divided into the primary loaded segment and the secondary loaded segment according to the difference of load type and intensity. The cantilevered anti-slide pile is taken as an example, and because the surrounding rock mass of the embedded segment is subjected to the E. Winkler’s assumption, the general formula for calculating the internal force and displacement is derived considering the secondary loaded segment suffering no force or suffering lateral rock-soil pressure (called "Three-section method"). It is demonstrated that the "Two-section method" is just the special case of the "Three-section method". Based on specific engineering examples, the calculated bending moment and shear force on the whole pile by the “T-section method” are mostly smaller than those by the "Three section method" and the deviation is also larger, especially for the embedded segment of anti-slide pile. Therefore, it will bring adverse effect to the engineering safety to design the anti-slide piles according to the "Two-section method".