金川水电站地下厂房裂隙围岩渗控效应数值模拟与评价

Numerical simulation and assessment of seepage control effects on surrounding fractured rocks of underground powerhouse in Jinchuan Hydropower Station

针对金川水电站工程区复杂的地质条件和渗控措施,分别建立基于排水孔等效模拟的坝基整体模型和基于密集排水孔"弃孔算法"精细模拟的左岸厂区子模型,采用Signorini型变分不等式和自适应罚函数相结合的稳定渗流分析方法对厂区围岩的长期渗控效应进行论证和敏感性分析。在数值模拟中,为了克服传统分析所采用的均质各向同性渗透系数不能反映裂隙岩体渗透特性的不足,首先根据两岸和坝基岩体优势裂隙组的空间展布情况,基于统计学方法初步确定其渗透系数张量并获得主值及主方向,再根据钻孔压水试验资料确定的等效渗透系数对其进行修正,并通过坝址区的地下水位反分析对该方法进行了验证。结果表明,运行期工况下防渗排水系统对山体地下水位具有控制作用,主变洞和发电机层底板处于自由面之上,厂房和调压室底板稍有承压性。帷幕的渗透特性、辅助排水孔幕以及排水孔间距对渗流场分布影响很小但能显著减小厂房洞室及排水廊道的渗漏量,因此应保证防渗帷幕的施工质量并建议设置辅助排水孔幕,建议中层廊道以下的排水孔间距设为3 m,中层廊道以上的排水孔间距放宽到4.5 m。

A global model of equivalent modeling and a submodel of accurate modeling based on ＂abandoned hole algorithm＂ for densely deployed drainage holes are established respectively to simulate the complicated seepage control measures and geological conditions for the underground hydropower cavern area at the left bank of Jinchuan Hydropower Station. The long-term seepage control effects of the surrounding rocks of the underground powerhouse and the sensitivity analysis of seepage control measures for the project design are performed by using the stationary seepage analysis method and combining the variational inequality formulation of Signorini＇s type with an adaptive penalty Heaviside function. The method of determining the hydraulic conductivity tensor is modified so that it can accurately overcome the disadvantage of ignoring the permeability characteristics of the fractured rock mass. The principal values and directions of the hydraulic conductivity tensor are first determined by the statistical method based on the measurements of the spatial spreading of fractures, and are then modified using the estimates of isotropic hydraulic conductivity that are calculated according to the water permeability rate from a field water-pressure test, and finally are verified using the inversion analysis. The results show that the integrated seepage-proof drainage system will control the water flow from the reservoir and mountain area efficiently; the cavern walls of generator floor and transformer room will be above the ground water surface under the operating conditions; the floor of the machine hall and the surge chamber are both under pressure slightly. The seepage distribution is not sensitive to the permeability of grouting curtains, auxiliary drainage hole arrays and spacing of drainage holes, which however can reduce the flux from drainage holes obviously. It is suggested that the quality for grouting curtain should be guaranteed and the auxiliary drainage hole arrays should be arranged. A spacing of 3 m can be taken for the drainage holes below the middle drainage tunnels and a larger spacing（e.g., 4.5 m） is suggested for those holes above the middle drainage tunnels.