某水电站引水隧洞突水数值模拟

Simulation of Sudden Blow in Diversion Tunnel of Some Hydropower Station

离散元软件UDEC可以用来模拟裂隙岩体的开挖以及进行水力全耦合分析。采用UDEC来模拟裂隙岩体开挖后在水力耦合作用下渗流流量与其对应水压力的变化过程并预测可能发生的突水灾害。结果表明开挖洞室以后,在围岩渗流与应力耦合作用下,围岩中裂隙隙宽、裂隙中水压及其渗透流量三者相互作用、相互依赖。裂隙隙宽的减小使得结构面水力梯度变大,作用在裂缝上的渗透压力增大,促进导水裂缝扩展,裂隙连通性增加。裂缝隙宽增大,渗透能力增强,渗流量增大,其渗流压力相应降低。在一定条件下,裂隙隙宽的改变可导致局部水力通道的形成,高压水头从局部涌出,从而促进突水灾害的形成。西南某水电站在深部裂隙岩体中开挖引水隧洞,该处地应力高且外水压大,容易引起突水灾害,对其进行了突水数值模拟,提示了一些可能发生突水的位置。

The discrete element method can be used to simulate the excavation of the fractured rock and conduct the fully-coupled analysis of hydraulics. So UDEC （universal distinct element code） can be used to simulate the chan- ges of flow rate and the corresponding water pressure under the coupling conditions of the seepage and stress after the excavation of the fractured rock, and forecast the possible sudden blow disasters. The results show that the changes of the fracture aperture, water pressure and fracture permeability discharge of the fractured rock mass in the coupling conditions of the seepage and stress are interactive and interdependent. Because of the shortening of the fracture width, the hydraulic gradient and the permeability pressure of the fracture become large. It also promotes the expansion of cracks and fissure connectivity increases. The increase of the crack width will result in the increase of the infiltration capacity and seepage discharge and reduction of seepage pressure. Under certain conditions, changes in fracture aperture can lead to the formation of local water-access, the emission of high pressure head from the local place, and thus promotes the formation of the sudden blow disasters. The sudden blow easily occurs after the excavation of the diversion tunnel situated at the deep fractured rock where the ground stress and water pressure are very high in some hydropower station in the southwest of China. The simulation is done in this article, and some possible positions where the sudden blow occur are revealed.