基于压力拱理论的极软岩隧洞衬砌应力变形研究

Study on Stress Deformation of Extremely Soft-Rock Tunnel Lining based on Pressure Arch Theory

软岩隧洞开挖后未能及时支护时,会导致围岩变形过大而坍塌,进而对后续衬砌结构造成不利影响。通过采用压力拱理论和数值模拟结合计算分析的方法,对仅一衬支护、仅二衬支护(厚度0.5、0.8 m和1 m)和一衬与二衬联合支护等3种工况下拱顶中心内侧、拱肩内侧和边墙中心内侧等3个监测点应力及变形进行分析。结果表明:仅一衬支护工况下3个监测点以及仅0.5 m厚度二衬边墙中心的拉应力均超过强度设计值,可能会发生拉坏现象;3种工况下作用在衬砌上的压应力均未超过设计强度值,说明衬砌在山岩压力的作用下出现压坏现象的可能性较小。研究结果可为极软岩隧洞坍塌形成压力拱后支护设计提供理论支撑。

When the soft rock tunnel is not supported in time after excavation,the surrounding rock will collapse due to large deformation,which adversely affect the subsequent lining structure.By using the method of combining pressure arch theory and numerical simulation,the stress and deformation at the three monitoring points including the inner side of the lower tunnel arch center,the inner side of the spandrel and the inner side of the side wall center under the three working conditions of only one-lining support,only two-lining support(thickness 0.5,0.8 m and 1 m)and the combined support of one-lining and two-lining are analyzed.The results show that the tensile stresses at the three monitoring points and the center of only 0.5 m thick second lining side wall under the condition of only one-lining support all exceed the design strength,and tensile failure may occur;the compressive stresses acting on the lining under the three working conditions are all below the design strength,indicating that the lining is less likely to be crushed under the action of rock pressure.The study results provide theoretical basis for the support design of tunnel after the collapse of extremely soft rock tunnels and emerging of pressure arches.