软岩隧洞围岩稳定分析及施工方法研究

Research on Surrounding Rock Stability of Soft Rock Tunnel and Its Construction Method

在软岩地层中开挖大跨度引水隧洞,围岩自稳能力差,如何保证围岩稳定,进行安全施工是最突出的问题。通过现场踏勘调研,根据引水隧洞的工程地质条件,建立三维模型,基于卸荷岩体力学理论与方法,对开挖后的围岩稳定性进行了详细计算分析。计算结果表明,考虑开挖过程中的动态卸荷效应后,围岩产生了较大的变形,但主要集中在断层和隧洞相交的局部位置附近,洞轴线剖面其它位置的拱顶沉降大约在10 mm左右,隧洞周边位移相对值在规范允许范围之内,没有大范围失稳趋势。断层、不整合接触带位置附近的卸荷效应影响尤为明显,出现了明显的塑性区,产生了局部变形和应力集中,应该引起足够的重视,在开挖的过程中要及时或超前支护。最后,根据计算分析结果,提出了一些切实可行的施工方法建议措施。研究成果为引水隧洞的设计和施工支护提供了重要的参考。

When digging large-span long-diversion tunnel in soft rock, because of the poor stability of surrounding rock, one of the pivotal questions is to ensure the stability of the surrounding rock and safe construction. In this paper, a 3D model of the diversion tunnel is established based on engineering ex- ploration and analysis of environmental geological conditions. Then, the surrounding rock stability after excavating is analyzed based on unloading rock mass mechanical theory and method. After taking the effects of dynamic unloading into consideration, the calculation results show that large deformation oc- curs in surrounding rock, which mainly locates in the partial regions near the confluence of faults and tunnel, while the arch subsidence of other cavity axis section is about 10mm, the relative displacements around the tunnel are within the specification tolerance, and the abutment tunnel is stable during and af- ter excavation processes. The influences of unloading effect, such as obvious plastic zones, local defor- mation and stress concentration, are especially remarkable in faults and unconformity contact planes, which should be caused enough attention, that is, it is necessary to take supporting measures in time or take advanced support during excavation processes. Finally, some feasible suggestions about the con-struction method are put forward according to the calculation results. The research results can offer im- portant support for the design and construction of diversion tunnel.