半硬半软岩层小净距隧道洞口段监测分析

针对雷公浦小净距隧道后行左洞洞口段具有半硬岩层半软岩层的特点,在开挖过程中,按照新奥法对隧道地表沉降、拱顶下沉、水平收敛、中间岩柱的位移、锚杆轴力、围岩压力和钢拱架应力等项目进行监测。监测结果表明,采用预留核心土法可以较好地控制围岩变形和应力;后行洞的拱顶沉降大于先行洞,且软岩一侧的下沉量更大;中间岩柱较薄弱,开挖初期往先行洞方向移动;降雨对围岩变形和压力影响较大,施工中应引起重视。研究结论可为类似条件下工程的设计、施工和监测提供借鉴。

Monitoring analysis of outlet section of tunnels with small clear-distance in half-hard and half-soft rock strata

Based on the characteristics of half-hard and half-soft at outlet section of latter excavated left hole of Leigongpu tunnel with small clear-distance, the monitoring programs including ground settlement of the tunnel, vault settlement, horizontal convergence, the displacement of the middle pillar, axial force of the anchor, surrounding rock pressure and the stress of steel frame, and so on are conducted in the excavation process of the tunnel according to the new Austrian tunneling method. The monitoring results show that: the reservation soil core method can better control the deformation and stress of the surrounding rock; the vault settlement of the latter hole is greater than that of the foregoing hole, and the settlement on the side of the soft rock is much greater; the middle pillar is relatively weak, which moves to the foregoing hole in the initial excavation; rainfall greatly influences the deformation and pressure of surrounding rocks, which should be paid much attention in the construction process. The experiences and conclusions presented can be adopted in the design, construction and research of similar tunnels.