软弱泥质砂岩地层中输水隧洞稳定性研究

泥质砂岩属于黏土岩，具有典型的遇水软化特征。在泥质砂岩富水地层中进行隧道开挖是地下工程的一个挑战性问题。研究了围岩软化与未软化条件下泥质砂岩地层中输水隧洞的稳定性和支护时间。首先，介绍了泥质砂岩遇水软化的力学试验结果；然后，采用基于Hoek-Brown强度准则的岩体参数评价方法，评估泥质砂岩在围岩软化与未软化条件下的力学参数；再后，以兰州水源地引水隧洞为依托工程，采用数值模拟方法对泥质砂岩隧洞软化与未软化工况的围岩稳定性进行了计算分析，得出泥质砂岩遇水软化对隧洞安全性存在显著影响；最后，采用位移收敛法，研究了泥质砂岩软化与未软化工况中，保障隧洞施工安全的合理支护时机。研究表明，泥质砂岩未软化工况中，可考虑隧道围岩初期支护在距掌子面4～5 m位置实施；而在泥质砂岩遇水软化工况中，初期支护建议在掌子面开挖后立刻支护。研究成果可为泥质砂岩地层隧洞的安全施工提供依据。

Stability of a water diversion tunnel in weak sandstone stratum

Argillaceous sandstone shows the typical characteristics of water-weakening due to the high content of clays. Tunnelling in argillaceous sandstone stratum with rich (trapped) water is a challenging issue for underground engineering. This study examined the stability and supporting time for a water conveyance tunnel in the argillaceous sandstone stratum with weakened and un-weakened conditions. Firstly, the water-weakened mechanical test results of argillaceous sandstone were presented. Then, to evaluate the mechanical parameters of the argillaceous sandstone in both water-weakening and un-weakening conditions, the rock mass evaluation method on basis of the Hoek-Brown strength criterion was adopted. Next, Lanzhou water source tunnel project was taken as the research object, and the stability of surrounding rock mass for the tunnel in argillaceous sandstone in both conditions was analyzed by a numerical modelling method. The researches indicate that the water-weakening of argillaceous sandstone significantly influenced tunnel safety. Finally, the convergence confinement approach was utilized to analyze the necessary supporting time to ensure tunnel safety during construction. The results indicate that if the argillaceous sandstone does not weaken, early support measures for the tunnel surrounding rock mass can be considered at the distance of 4 to 5 meters away from the excavation face. However, in the case of argillaceous sandstone water-weakening, early support measures should be employed immediately when the tunnel face is excavated. The research findings can provide the foundation for the safe construction of tunnels in a weak surrounding rock mass with water-weakened conditions.