强降雨条件下某互层隧洞冒顶失稳过程与机制

The Process and Mechanism of Roof Fall Instability of an Interbedded Tunnel under Heavy Rainfall Conditions

基于小浪底北岸灌区某引水隧洞来分析揭示强降雨条件下隧洞围岩冒顶形成机制。结果表明:(1) 互层隧洞冒顶失稳是一个渐进过程,软弱层先垮塌,历经洞内掉块→塌方→涌水和涌土,直至形成大范围塌方;(2) 强降雨引起的围岩力学参数劣化是造成工程区隧洞失稳塌方的重要因素;(3) 模拟结果显示,天然工况围岩保持稳定;降雨条件下经水–岩作用力学参数劣化,支护结构破坏,造成大范围的围岩失稳塌方;施加一定支护后,围岩稳定性得到大幅提高。Based on a diversion tunnel in the north bank irrigation area of Xiaolangdi, this paper analyzes and reveals the formation mechanism of roof fall of tunnel surrounding rock under the condition of heavy rainfall. The results show that: (1) The roof fall instability of the interbedded tunnel is a gradual process. The weak layer collapses first, and then goes through the falling block in the tunnel→collapse→water gushing and soil gushing, until a large-scale collapse is formed. (2) The deterioration of mechanical parameters of surrounding rock caused by heavy rainfall is an important factor causing the instability and collapse of the tunnel in the engineering area. (3) The simulation results show that the surrounding rock of the natural working condition remains stable;under the condition of rainfall, the mechanical parameters of water-rock interaction are deteriorated, and the supporting structure is destroyed, resulting in a large range of surrounding rock instability and collapse. After applying certain support, the stability of surrounding rock is greatly improved.