导洞超前开挖施工性态空间效应分析

ANALYSIS OF SPATIAL EFFECTS OF CONSTRUCTION BEHAVIOR ON PILOT TUNNEL EXCAVATION

围岩变形机制及稳定性控制是隧道施工过程中关键技术之一。针对导洞超前开挖施工性态空间效应,采用有限差分软件FLAC3D模拟分析隧道施工过程中围岩变形规律,并与全断面法、上下台阶法作对比分析。研究表明:导洞超前开挖施工引起的水平收敛、拱顶沉降位移变化速率最小,开挖形成临空面之后产生的水平收敛和拱顶沉降值最小,有利于隧道围岩的稳定;水平收敛值随隧道埋深、侧压力系数的增大呈线性增大;拱顶沉降值随埋深的增大呈线性增大,随侧压力系数的增大呈非线性增大趋势;隧道埋深越大,水平收敛、拱顶沉降先行位移占总位移比例越大;侧压力系数越大,水平收敛先行位移所占比例越大,而拱顶沉降先行位移所占比例越小。结合宜巴(宜昌至巴东)高速公路石门垭隧道施工现场监测数据,验证所得结论的可靠性,可为同类工程借鉴,具有一定的科学意义和工程实用价值。

The deformation mechanism and stability control of surrounding rock are one of the key technologies in tunnel construction. According to the spatial effects of construction behavior on pilot tunnel excavation,the deformation law of surrounding rock in tunnel construction was simulated and comparatively analyzed with full face method and bench tunnel construction method by using the finite difference software FLAC3D. Results show that the displacement rate and the displacement after excavation caused by pilot tunnel construction are smaller than the other two methods,which are beneficial to the stability of surrounding rock. With the increase of buried depth,the displacement increases linearly,whereas the horizontal convergence increases linearly and the crown settlement increases non-linearly with the increase of lateral pressure coefficient. The proportion of the displacement before excavation increases with the increase of the depth,whereas the proportion of the horizontal convergence before excavation increases and the proportion of the crown settlement before excavation decreases with the increase of the lateral pressure coefficient. Combined with the field monitoring data,the reliability of conclusions was verified. The obtained conclusions have certain reference to similar projects,important significance and engineering value.