浅埋层状岩体偏压隧道滑移破坏机理及判定方法

渝涪高速公路鸭江隧道是典型的层状岩体隧道,其出入口段更是兼具了浅埋、地形和地质偏压等多重特点。基于鸭江隧道出口段的围岩参数,利用UDEC软件对不同岩层倾角条件下的浅埋层状岩体偏压隧道破坏过程进行了模拟。数值模拟的结果发现,当岩层倾角较小时易沿结构面垂直方向发生弯折破坏,当岩层倾角较大时易沿结构面发生滑移破坏。通过对隧道拱顶上方被挖断岩层建立受力模型,得出了拱顶上部岩层下滑力计算公式,并确定了下滑力大于零时会发生滑移破坏的判定准则。岩层倾角、地面坡角、隧道开挖范围内岩层厚度这3个因素的值越大,越易发生滑移破坏;结构面内摩擦角、岩层埋深这两个因素的值越小,越容易发生滑移破坏。研究成果对浅埋层状岩体隧道的设计、施工具有理论和现实指导作用。

Sliding Failure Mechanism and Its Criterion of Unsymmetrical Loading Shallow Buried Tunnel in Layered Rock Mass

Yajiang tunnel, which is located on Yufu express way, is a typical tunnel buried in layered rock mass. The entrance and exit of Yajiang tunnel own multiple features of shallow-buried, unsymmetrical loading from both terrain, and geology. Based on the parameters of Yajiang tunnel's exit, failure process of unsymmetrical loading shallow tunnel buried in layered rock mass under different dip angles was simulated by UDEC. Numerical test results reveal that bending destruction occurs perpendicular the structure plane when dip angle is small, while sliding destruction occurs along the structure plane when dip angle is steep. Sliding force computational formula of the layered rock mass up the tunnel which have been excavated was deduced by establishing a mechanical model, and the criterion that sliding occurs once sliding force exceeded zero was set up. Sliding force is tending to be greater than zero if dip angle, surface slope angle, and thickness of rock mass is bigger. And the friction angle of structure plane, buried depth of rock mass is smaller, which means sliding destruction is more easily to happen. Research achievements have important theoretical and practical significance to design and construction of shallow tunnel buried in layered rock mass.