浅埋暗挖黄土隧道地层及围岩力学特性变化规律

以新建蒙华铁路运煤通道青化砭隧道为依托,埋设地层变位和围岩应力测试元件,对开挖时黄土地区大跨径浅埋隧道的地层及围岩力学特性变化规律进行了研究。结果表明：拱顶沉降和水平收敛变形可分为均匀变形阶段和稳定变形阶段,竖向地层沉降随埋深的增大先增大后减小；当工作面稳定时,横截面方向和轴线方向的水平位移超前影响距离分别为8m、15m。滞后和超前开挖时,周围土体横截面方向和轴向水平位移分别向隧道内侧和背离隧道方向发展；初期支护施做后,衬砌应力重新分布,仰拱压力增大,而左右拱腰压力不变。所得结论可为黄土地区浅埋暗挖大跨度隧道的设计和施工提供参考。

Study on the Variation of Mechanical Properties of Formation and Surrounding Rock in Shallow Buried Covered Excavated Loess Tunnel

The experiment is based on the Qinghuabian Tunnel which is a newly-built coal transportation railway from Mengxi to central China. The deformation of strata and the stress test elements of surrounding rock are embedded, and the variation of mechanical properties of strata and surrounding rocks of long-span shallow tunnels in loess area during excavation is studied. The results show that the dome settlement deformation and horizontal convergence deformation caused by construction are composed of two parts: uniform deformation stage and stable stage, The vertical settlement of strata increases at first and then decreases with the increase of buried depth; when the working surface is stable, the advance influence distance of the horizontal displacement of the tunnel cross section is about 8m, and the advance influence distance of the horizontal displacement of the axial direction is about 15m. When observing the lag of the section and advance excavation surface, the cross section direction and axial direction horizontal displacements of the soil around the tunnel develop toward the inside of the tunnel and away from the tunnel respectively; After the initial branch is completed, the lining stress is readjusted, the pressure on the left and right arches is not increasing, and the pressure on the invert is continuing to increase. The conclusions can provide reference for the design and construction of shallow-buried subsurface-excavating long-span tunnels in the loess area.