不同覆跨比下浅埋软弱隧道的破坏模式

摘要

To analyze the failure mode of shallow-buried weak tunnel surrounding rockatdifferent thickness-span ratios, the failure processwasstudiesthrough a number of model tests. The results of model tests were verified by means of finite difference numerical simulation using the theory of strength reduction method, and a basic consistent conclusion wasobtained. Through the analysis of numerical simulation and model test results, a modified method based on the theory of rock pillars was derived. Theresultshows that the failure zone of shallow-buried weak tunnel surrounding rock initiates from arch crown of tunnel. Due to the damage zone of arch crown formation, the damage effect of similar landslide, namely ‘two stage’ failure of shallow-buried weak tunnel surrounding rock, develops on both sides of arch crown. When the thickness-span ratio is relatively small, with high speed of collapse and small volume of rock collapse,the self-supporting capability of surrounding rock is weak. Hence thecaving collapse occurs. When the thickness-span ratio equals 3.0, the failure zone of the surrounding rock which forms a shallow-buried pressure arch cannot reach the surface. When the thickness-span ratio equals 2.5, the volume of surrounding rock collapse and the influence of failure zoneisthe largest. In order to ensure the safety, tunnel support should be done timely during construction.%为了研究不同覆跨比条件下浅埋软弱隧道围岩的破坏模式，通过室内模型试验对隧道围岩破坏的过程进行模拟；利用强度折减法原理对模型试验进行有限差分数值验证，得出了二者基本一致的结论；通过对模型试验与数值模拟结果的分析，推导基于岩柱理论的修正算法。研究结果表明：浅埋软弱隧道围岩的破坏最早从拱顶开始，由于拱顶塌落区的形成，拱顶两边产生类似滑坡的塌落效应，即浅埋破碎围岩隧道的“二阶段”破坏；当覆跨比较小时，围岩的自承能力弱，围岩塌落速度快，塌落体积少，形成塌穿型塌方；当覆跨比为3.0时，形成了浅埋压力拱，破坏已不能到达地表；当覆跨比为2.5时，围岩塌落形成的塌落体体积及破裂区影响区域最大，施工时支护应及时，保证其安全。