土岩“二元基坑”吊脚桩支护体系锁脚锚杆预加轴力计算方法研究

Study on Calculation Method of Preloaded Axial Force of Foot-lock Anchor in Support System of Soil and Rock Dualistic Foundation Pit End-Suspended Pile

为解决土岩二元基坑吊脚桩支护体系中吊脚桩、岩肩与锁脚锚杆之间的相互作用力学机制,根据吊脚桩桩底位于岩质边坡潜在滑动面的位置,分别提出锁脚锚杆预加轴力的计算方法:1)当吊脚桩位于潜在滑动面以下位置时,锁脚锚杆的预加轴力等于岩层基坑未开挖时的被动区合力减去岩肩能提供的反力;2)当吊脚桩位于潜在滑动面以上位置时,锁脚锚杆的预加轴力等于滑块对吊脚桩嵌固段的推力加上岩层基坑未开挖前被动区的土压力。并给出2种工况下锁脚锚杆预加轴力的计算公式。最后通过有限元方法进行数值验证。结果表明:按照提出的计算方法得到的锁脚锚杆预加轴力基本合理。

The interaction mechanics among the end-suspended pile,rock shoulder and foot-lock anchor should be studied.Hence,the calculation methods of preloaded axial force of the foot-lock anchor are proposed based on the positions of end-suspended pile at the bottom of potential sliding surface of rock slope.When the end-suspended pile is located below the potential sliding surface,the preloaded axial force of foot-lock anchor is equal to the passive zone combined force minus rock shoulder reaction force when the rock foundation pit is not excavated.When the end-suspended pile is above the potential sliding surface,the preloading axial force of foot-lock anchor is equal to the passive zone combined force plus the thrust of end-suspended pile when the rock foundation pit is not excavated.And the calculation formulas of the preloaded axial force of foot-lock anchor under two conditions are given.Finally,the results are verified by the finite element method.The results show that the calculation results of the preloaded axial force of foot-lock anchor according to the calculation methods are basically rational.