强震后软岩隧道变形与破坏机制分析

强震后软岩隧道的变形和破坏特征与一般隧道不同。根据“5.12”强震区唐家山隧道围岩变形与应力监测数据,对震后软岩隧道变形与破坏机制进行了分析。研究表明:(1)震区软岩隧道变形空间分布不对称,水平收敛是拱顶沉降的2~4倍,这是震后软岩的扩容性质和隧道所处的垂直方向高地应力环境所共同决定的;(2)隧道变形的空间效应约束范围为2~3D,在开挖面约束范围内,变形是空间效应和时效应的耦合;(3)隧道不同部位的围岩变形与破坏方式与围压性质密切相关,边墙处围岩在“形变压力”作用下易发生松弛大变形;拱部一定范围内的岩体存在整体下沉现象,拱部围岩易被架空而形成“松散压力”并诱发位移突变和破坏。研究对同类工程具有一定参考价值。

Analyses of Deformation and Failure Mechanism of Soft Rock Tunnel in Meizoseismal Areas

The deformation characteristic and failure mechanism of tunnels in meizoseismal areas are different from general tunnels.Based on the measured data of surrounding rock deformation and stress for Tangjiashan tunnel in meizoseismal area,the deformation and failure mechanism for soft rock tunnel in meizoseismal areas were analyzed.Research found that:(1) the distribution of tunnels deformation in meizoseismal areas was uneven.The value of tunnel horizontal convergence was 2 ～ 4 times larger than that of vault settlement,which was caused by both the soft rock properties of dilatation and the vertical high geostress zone where the tunnel located.(2) The spatial constrained zone affecting the tunnel deformation was in the range of 2 ～ 3D.In the range of spatial constrained zone,the deformation was coupled of spatial effect and time effect;(3) The deformation and failure mode of surrounding rock were closely related to the different properties of rock pressure in different parts of tunnel.The surrounding rock near sidewall under the force of "deformation pressure" was prone to a large yield deformation.The rock mass at the arch of a certain range had a phenomenon of overall sink to cause a relaxation and " loosening pressure" of rock mass,which would make the surrounding rock at the arch of tunnel more prone to a deformation mutation and gravitational damage.The study has some reference value for similar projects.