兰渝铁路毛羽山隧道出口段穿越薄层状碳质板岩地层,区域原岩应力较大且以水平构造应力为主,隧道开挖过程中出现严重的大变形情况.通过分析,认为高地应力、最大水平主应力与隧道轴线呈大角度相交是大变形的主要因素.隧道施工过程中,通过采取提高支护体系刚度、合理预留变形量,以及采用长锚杆、多重支护和超短台阶法等常规措施控制了围岩变形;基于对围岩动态演化机制的认识,提出了高地应力隧道超前导洞法应力控制释放技术,开展了大型工程试验.阶段性试验成果表明,采用超前导洞有效地降低了正洞施工时的变形速率、对上中台阶影响尤为显著.通过对应力控制释放技术研究的进一步深化,有望探索出安全、高效的高地应力软岩施工新技术.%The exit of Maoyushan tunnel on Lanzhou -Chongqing railway is embedded in thin -layered carbonaceous slate stratum with high in-situ stresses of primary rock and horizontal tectonic stresses. During tunnel excavation, intensive large deformations and serious failures occurred due to high in-situ slresses and maximum horizontal principal stresses intersected with the tunnel axis with a large angle. Measures such as improving support system stiffness, lengthening systematic bolts, reasonable allowances for deformation and multisupport as well as super-short bench excavation were adopted to control the deformation of surrounding rocks. In addition, based on the understanding of the mechanism of dynamic evolution of rock masses, the technology of stress releasing by advance adit was adopted, and large-scale engineering tests were carried out. Test results showed that the advance adit efficiently reduced the deformation rate during the main tunnel construction,especially during the excavation of upper bench and middle benches. It is expected to find a safe and efficient construction method of tunnels in soft ground with high in-situ stresses by further study on stress releasing technology by adopting advance adit.
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