高地应力硬脆性围岩隧道失稳机理及处置措施

为探究高地应力硬脆性裂隙围岩区隧道失稳及结构破坏机理,并提出系统的处置措施,笔者通过对在建米仓山隧道进行现场调查,分析了高地应力破碎围岩区隧道开挖引发的围岩失稳破坏的特点,并结合特定的地质条件,利用能量理论对隧道施工过程进行数值模拟,分析模拟结果得到:米仓山隧道掌子面失稳主要原因是高地应力引起的能量超过岩体的最大承受能力,而岩体破碎是导致支护破坏的直接因素。基于此,文中提出了以下处置措施:(1)降低隧道围岩体内的能量;(2)采用“短进尺、弱爆破”的方式掘进;(3)初期支护结构采用双重支护,并加强监控量测;(4)将径向锚杆更换成兼起应力释放、锚杆、注浆填充作用的径向小导管。

Study on Instability Mechanism and Disposal Measures of Brittle Fractured Surrounding Rock Area in High Geo-stress Tunnel

In order to explore the instability and structural failure mechanism of brittle fractured surrounding rock area in high geo-stress tunnel, and to propose system disposal measures, this paper has analyzed the characteristics of surrounding rock instability caused by excavation in high geo-stress tunnel and has carried on the numerical simulation to the construction process combined with specific geological conditions and energy theory. Simulation results showed: The main reason of instability of heading face in Micangshan tunnel was that the energy caused by high geo-stress exceeds the maximum bearing capacity of surrounding rock, and rock fragmentation directly led to the destruction of support. Based on this, the following disposal measures are proposed: (1) reducing energy in the surrounding rock; (2) using “short footage, weak blasting” method to excavate; (3) initial support structure adopts double support and strengthen monitoring and measurement; (4) replacing radial bolts with radial ducts which have a role of stress relief, bolt and grouting filling.