浅埋岩溶隧道灾变机制及其防治

DISASTER-INDUCED MECHANISM AND ITS TREATMENT IN SHALLOW-BURIED KARST TUNNEL

针对重庆云雾山隧道浅埋岩溶段施工中发生的岩溶地质灾害事故,对浅埋岩溶隧道地质灾害的关键致灾因子及相互关联进行理论分析,并结合现场岩溶处治实践,对其实施效果进行评价。研究结果表明,浅埋岩溶隧道五大致灾因子为埋深浅、上覆地层松软、岩溶发育程度和规模、补给水源以及工程因素,其中施工揭穿顶部和两侧的溶洞连通地表水涌入塌陷区是主要诱因,含溶洞断面的位移释放主要发生在开挖前和开挖瞬间。同时,浅埋岩溶隧道地表水对隧道稳定性影响比地下水更为明显,故解决岩溶灾害的根本途径在于采用合理的设计施工方法,实现施工扰动条件下岩溶动力系统平衡状态的平稳过渡。

Aiming at disasters that happen in shallow-buried Yunwushan karst tunnel, the disaster-induced mechanism is theoretically analyzed, and also the stability of surrounding rock and its support system are evaluated through numerical simulation and in-situ monitoring. It shows that, the five key disaster-induced factors in shallow-buried Yunwushan karst tunnel are shallow-buried depth, soft cover, karst development and scale, groundwater supply, and engineering factors. The inrush of surface water into the collapsing area is a dominant factor for collapse expanding. From simulating and monitoring results of stresses and displacements, the surrounding rock and support system are proven to be stable after the implement of support enhancement; and the conclusions would be helpful for the further research related to shallow-buried karst tunnels and similar engineering practices in China or other regions with karst geological problems. It would be highly essential to take quick and appropriate measurements in the excavation of karst tunnel. What is more, the measurements must be subjected to the existing geological conditions, therefore, the frequency ofkarst disasters can be possibly reduced to avoid the increase of engineering costs, and to accelerate construction progress.