Hou Tian-Xing, Yang Xing-Guo, Xing Hui-Ge, Huang Kang-Xin, Zhou Jia-Wen
State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610065 Sichuan China.
College of Water Resources and Hydropower, Sichuan University, Chengdu, 610065 Sichuan China.
Springerplus. 2016 May 23;5(1):700. doi: 10.1186/s40064-016-2336-9. eCollection 2016.
Estimating groundwater inflow into a tunnel before and during the excavation process is an important task to ensure the safety and schedule during the underground construction process.
Here we report a case of the forecasting and prevention of water inrush at the Jinping II Hydropower Station diversion tunnel groups during the excavation process. The diversion tunnel groups are located in mountains and valleys, and with high water pressure head. Three forecasting methods are used to predict the total water inflow of the #2 diversion tunnel. Furthermore, based on the accurate estimation of the water inrush around the tunnel working area, a theoretical method is presented to forecast the water inflow at the working area during the excavation process.
The simulated results show that the total water flow is 1586.9, 1309.4 and 2070.2 m(3)/h using the Qshima method, Kostyakov method and Ochiai method, respectively. The Qshima method is the best one because it most closely matches the monitoring result. According to the huge water inflow into the #2 diversion tunnel, reasonable drainage measures are arranged to prevent the potential disaster of water inrush. The groundwater pressure head can be determined using the water flow velocity from the advancing holes; then, the groundwater pressure head can be used to predict the possible water inflow. The simulated results show that the groundwater pressure head and water inflow re stable and relatively small around the region of the intact rock mass, but there is a sudden change around the fault region with a large water inflow and groundwater pressure head. Different countermeasures are adopted to prevent water inrush disasters during the tunnel excavation process.
Reasonable forecasting the characteristic parameters of water inrush is very useful for the formation of prevention and mitigation schemes during the tunnel excavation process.
在开挖过程之前及期间估算地下水流入隧道是确保地下施工过程安全和进度的一项重要任务。
在此，我们报告锦屏二级水电站引水隧洞群在开挖过程中涌水预测与防治的案例。引水隧洞群位于山区和峡谷，水压头高。采用三种预测方法来预测2号引水隧洞的总涌水量。此外，基于对隧洞作业区周围涌水的精确估算，提出了一种理论方法来预测开挖过程中作业区的涌水量。
模拟结果表明，使用Qshima法、Kostyakov法和Ochiai法得到的总涌水量分别为1586.9、1309.4和2070.2立方米/小时。Qshima法是最佳方法，因为它与监测结果最为接近。根据2号引水隧洞的大量涌水情况，安排了合理的排水措施以防止潜在的涌水灾害。可以利用超前钻孔的水流速度确定地下水压头；然后，利用地下水压头预测可能的涌水量。模拟结果表明，在完整岩体区域周围，地下水压头和涌水量稳定且相对较小，但在断层区域周围存在突然变化，涌水量和地下水压头较大。在隧道开挖过程中采取了不同的对策来防止涌水灾害。
合理预测涌水特征参数对于在隧道开挖过程中形成预防和缓解方案非常有用。
