基于“三段法”的锚拉桩桩身内力计算方法与应用

针对抗滑桩常因地质条件、地形地貌等原因导致受荷段底面与嵌固段顶面不在同一水平面的情况，将此段划为次受荷段，并推导了次受荷段桩后设计荷载大小计算公式和荷载分布公式，以及在弹性地基梁和悬臂梁模型下的适用于悬臂桩和锚索桩内力与挠度计算通用公式。以巴东县焦家湾移民安置点库岸防护工程预应力锚索桩为例，研究次受荷段对抗滑桩内力和挠度影响。结果表明:忽略次受荷段后土压力作用的传统计算方法会使桩身弯矩计算结果偏小，导致桩身配筋量不足，存在设计安全隐患。再以锚索排数、位置为控制变量，研究其对预应力锚索桩内力和挠度的影响，提出预应力锚索可有效地降低抗滑桩工程造价；增加预应力锚索的排数有利于调节抗滑桩内力分布，设计时应优先考虑将锚索设置为多排锚索。 

Calculation method and application of internal force of anchor pile based on "three-stage method"

In view of the fact that the bottom surface of the loaded section and the top surface of the embedded section are not in the same horizontal plane due to geological conditions, topography and other reasons, this paper classifies this section as a secondary load section and derives the formula of designed load calculation and distribution about this secondary load section. As well as general formulas for the calculation of internal force, deflection of cantilever piles, anchor cable piles under elastic foundation beam and cantilever beam models. Taking the prestressed anchor piles of the reservoir bank protection project at Jiaojiawan resettlement site in Badong County as an example, the influence of the internal force and deflection of the anti-slide piles in the secondary load section is studied. The results show that the traditional calculation method that ignoring the effect of the earth pressure after the secondary load will make the calculation result of the pile bending moment smaller and leads to insufficient reinforcement of the pile, which really has a safety risk. Taking the number and position of the anchor cables as the control variables, the influence on the internal force and deflection of the prestressed anchor cables is studied, and it is proposed that the prestressed anchor cables can effectively reduce the construction cost of anti-slide piles; increasing the number of prestressed anchor cables which is beneficial to adjust the internal force distribution of anti-slide piles, and multi-row anchor cables should be given priority in the design.