龙羊峡大坝同位素示踪方法探测渗流场研究

Survey of the Leakage Passage at Long yang Gorge Dam by Isotopic Tracer Method

论述了同位素及天然示踪方法探测大坝渗流场的基本原理与试验方法．通过夏季与冬季两次不同水位条件下对龙羊峡大坝进行的同位素综合示踪探测，已初步查清了南北大山水沟蓄水池的渗流及工业用水补给是造成左岸地下水位偏高的主要原因；综合示踪试验发现顺河断层Ｆ５７ 存在较为严重的河水渗漏，该渗漏造成左岸地下水位的壅高，阻碍了左岸边坡水的排泄；Ｇ４ 劈理带的渗漏不是引起左岸地下水位偏高的主要原因；跨河断层Ｆ１８ ，Ｆ７１ ，Ｆ７３ 等与顺河断层Ｆ５７ 交汇，将Ｆ５７ 断层的渗漏河水补给这些跨河断层，造成Ｆ１８ ，Ｆ７１ ，Ｆ７３ 等断层中的水位升高，并将渗漏河水补给右岸，造成３４＃ ，１８ ＃ 等孔位附近的地下水位升高．

The basic principle of isotopic tracer,natural tracer theory and some testing methods for surveying the isotopic tracer leakage passage at the Long yang Gorge Dam are enunciated in this paper.According to the results from the isotopic tracer method used in two different seasons,i. e.,summer and winter,the high level of groundwater on the left bank behind the dam is investigated thoroughly.The main reveals of the causes highwater level at the left dam abutment is the leakage from the Nanbeidashan reservoir and its raceway including the seepage of industrial waste water.Isotopic tracer test reveals that at bedding fault F 57 exists serious leakage.The seepage causes high groundwater level and blocks the drainage of the left bank sloping water.The seepage from cleavage G 4 is not the main cause of the high groundwater level.River crossing faults F 18 ,F 71 ,F 73 and bedding fault F 57 intersect at the dam base;the leakage flow from fault F 57 supplies water for the crossing faults and the right bank,resulting in the high groundwater level of the crossing faults and nearby of two nearby observation holes 34 # and 18 #.