岩溶病害水库的渗漏通道探测方法——以广西全州县洛潭水库为例

Detection method of leakage passages in karst disease reservoirs. A case study of Luotan reservoir in Quanzhou county of Guangxi

由于岩溶地区的水文地质条件极为复杂,故对岩溶渗漏通道的准确定位一直是令人头疼的问题。经试验验证,利用综合物探可以对岩溶渗漏水库的岩溶渗漏通道进行精确定位,其中大功率充电法、常规充电法、自然电场法等方法可以在平面上对岩溶渗漏通道的位置进行准确定位;高密度电法、跨孔地震声波透视法可以确定岩溶渗漏通道的深度及发育特征,从而可以结合地质情况对其渗漏机理进行分析。通过大功率充电法、常规充电法、自然电场法等方法在洛潭水库测区的探测结果分析,在测区内共存在有3条推测岩溶渗漏通道,其中Ⅱ号推测岩溶渗漏通道为水库渗漏的主要通道,并经过示踪法验证是准确的。根据高密度电法、跨孔地震声波透视法探测结果显示,在洛潭水库的东侧存在一逆冲断层F1,在该断层的上盘岩石比较破碎,并存在一系列平行的张性断层F2~F5,经分析认为洛潭水库的渗漏与断裂破碎带的存在密切相关,导致水库渗漏的Ⅱ号推测岩溶渗漏通道主要沿断层F5发育。

It is difficult to accurately locate karst leakage passages due to the extremely complex hydrogeological conditions in karst regions. Field tests have verified that comprehensive geophysical methods are effective in the surveys of reservoir karst disease and its leakage passages, including the high- power mise-a-la-masse method, general mise-a-la-masse method, and self-potential method for pinpointing such seepage channels on a plane. The seismic sonic perspective method can determine the high-density resistivity method and cross-borehole depth of a karst leakage passage and its developing characteristics, providing key information for analysis of the leakage mechanism in corresponding geological conditions. In a case study of the Luotan reservoir region, our field measurements revealed three possible karst leakage passages developing in this region, via a comprehensive analysis of the survey data collected using the first three methods. And Channel No. II, a speculated karst leakage passage, was detected as the major passage of reservoir leakage. All the results had been confirmed by trace experiments. Using the data of the resistivity and sonic methods, we have detected a thrust fault, namely Fault F1 featured with broken rocks of smaller sizes on the plate of fault at the east side of this reservoir, along with a series of parallel tensional fractures Faults F2-F5. Thus, we come to a conclusion that the leakage of Luotan reservoir had a close relevance to the presence of fracture zones that had caused the development of a speculated karst leakage passage, i.e. Channel No. Ⅱ, approximately along Fault F5.