开挖与回填过程中隧道受力和承载拱效应研究

为研究开挖和回填过程中既有隧道受力变化及其与承载拱之间的联系,设计模型试验,通过考察开挖与回填过程中既有隧道的位移、内力及围岩压力,得到隧道受力变化规律,并对隧道受力与承载拱之间的联系进行分析。结果表明: 1)既有隧道上方开挖过程中由于承载拱的存在,会使隧道经历无影响、弱影响、强影响3 个阶段,但既有隧道上方回填过程中不会产生承载拱,填方对隧道的影响基本呈线性增加,隧道处于持续受影响状态; 2)回填后的结构受力普遍大于相同覆土高度下开挖后的结构受力,且拱顶和仰拱相对其他部位受影响较大,易因内侧受拉出现裂纹; 3)承载拱的产生与否主要取决于一定埋深隧道围岩应力状态是否经历三向应力-二向应力转变的历程,隧洞开挖时围岩应力的转移和重分布导致了承载拱的产生。

Study on Tunnel Stress and Load-bearing Arch Effect during Excavation and Filling

Model test is designed in order to study the variation of force of existing tunnel and the relationship between force and load-bearing arch under excavation and filling. The variation law of the tunnel stress is obtained by investigating the displacement, internal force and surrounding rock pressure of the tunnel during excavation and filling. And the relationship between tunnel force and load-bearing arch is analyzed. The results show that: (1) Due to the existence of load-bearing arches, the excavation process above the existing tunnel will go through three stages of no influence, weak influence and strong influence; but there will be no load-bearing arch during the filling process above the existing tunnel, and the influence of filling on the tunnel will basically increase linearly, the tunnel continues to be affected. (2) The structural stress after filling is generally greater than that of excavation in the same covering height, and the crown and invert are affected more obviously than other parts, which are liable to crack under internal tension. (3) Whether the load-bearing arch is generated or not mainly depends on the stress state of surrounding rock of the tunnel at a certain buried depth undergoes a process of three-stress to two-stress transformation; the main reason of loadbearing arch formation is the stress transfer and redistribution of surrounding rock during tunnel excavation.