水中自然电场法探测病态水库岩溶渗漏通道——以金鸡河水库一级水电站为例

摘要

Reservoir water or sewage leakages often occur beneath buildings of man-made reservoirs or mine tailings reservoirs in karst areas because of the complicated geological conditions. To clarify passages of these leakages, geophysical prospecting tools are commonly deployed on in dams, abutments and other lands of reservoir areas, which cannot detect and evaluate the karst collapses at the bottom of the reservoirs directly, leading to poor effect of control to this problem. This paper takes the karst leakage passage beside culvert of the first-class hydropower station on the Jinjihe reservoir in North Guangxi as an example to study the principle, field working method and effect of detecting karst leakage passages in reservoir areas using the self-potential method on the water. Outcropping formation in the study area mainly consists by of limestone intercalated with dolomite, dolomitic limestone of Devonian Liujiang Formation (D3l) and dolomite, limestone, argillaceous limestone of the Devonian Donggangling order (D2d), where developed intermedium-degree hidden karst. When the outlet pipe of the hydropower station in the area releases water, a strong negative center regional field of self-potential on the water can be producd. By dividing the regional field of self-potential on the water using the circumferential mean method and calculating the residual local anomalies, 6 secondary negative center residual local anomaly areas of self-potential on the water covered by a strong regional field, which are quasi-equiaxis or elliptical shape, are identified. Checking in the reservoir by the diver, these 6 negative center residual local anomaly zones correspond to karst collapses, karst opening or leaking skylight at the bottom of the reservoir, respectively. Among them, the negative center residual local anomaly with quasi equiaxis shape near the survey points 46-48 of line 16 corresponds to the largest karst collapse at the bottom of the reservoir. The diameter of the collapse pit is about 1.8 m, and its depth is about 2.5 m. The karst opening or leaking skylight at the bottom of the reservoir which correspond to the other anomaly areas are relatively smaller on scale. The simple connected experiments of internal and external water and the engineering geological drilling show a good effect of the geophysical survey. This work demonstrates that the self-potential method on the water can be used to investigate of karst geological problems such as the emergency on the water of karst sick reservoirs, and rapid delineation of the range of the shallow karst leakage passages.%在岩溶区修建的水库或矿山尾矿库等建筑物, 常因库区岩溶地质条件复杂而出现库水或污水渗漏等问题, 岩溶渗漏通道勘察中常用的物探方法多布置在库区的大坝、坝肩等库岸陆地一带, 未能对库内的库底岩溶塌陷等岩溶渗漏通道直接进行探测与评价, 致使探测与治理效果往往不佳.本文以桂北金鸡河水库一级水电站放水涵管旁岩溶渗漏通道探测为例, 研究水上自然电场法探测水库岩溶渗漏通道的原理、现场工作方法及探测效果.研究区出露地层主要由泥盆系榴江组 (D3l) 石灰岩夹白云岩、白云质灰岩, 泥盆系东岗岭阶 (D2d) 白云岩、石灰岩、泥质灰岩组成, 隐伏岩溶中等发育.区内一级水电站放水管入水口放水可引起强烈水上自然电位负心区域场, 经采用圆周平均法划分水上自然电位区域场与剩余局部异常计算, 分离出6个被强烈区域场淹盖了的次级似等轴状或似椭圆状负心水上自然电位剩余局部异常.经潜水员潜水入库内查看, 这6个负心剩余局部异常区在库底均有岩溶塌陷或岩溶开口或库底渗漏天窗一一对应, 其中, 16线46-48号测点附近出现的似等轴状负心剩余局部异常对应的库底岩溶塌陷规模最大, 塌陷坑直径约1.8 m, 塌陷坑深约2.5 m, 其余异常区对应的库底渗漏天窗或岩溶开口规模次之.经库内外水的简易连通实验及工程地质钻探, 物探异常查证效果好.水上自然电场法可用于岩溶病态库区水上应急、快速圈定浅层岩溶渗漏通道范围等岩溶地质问题调查.