Study On Tracer Method For Leakage Of Xiaolangdi Left Dam

There are many earth-rock dams and dikes existing kinds of hidden troubles in China. Many of these troubles are caused by leakage more or less, so that it is necessary to study the leakage problems of dams. Most of all, it is necessary to determine the leakage passage efficiently before making reasonable seepage control measures.In the paper, the heat recourse method and environmental tracer method on detecting the leakage of dams are analyzed and discussed deeply. By considering the local situations, the theory is applied in Xiaolangdi hydro project. The location of leakage of the dam is determined by using the combined methods. The results provide scientific basis for take relative strengthened measures to prevent the seepage damage of dam. At the end, some suggestions for dealing with the leakage are proposed. The main researches focus on:The basic theory of using groundwater temperature and electronic conductivity to study leakage has been discussed. After obtaining the temperature and electronic conductivity distribution with depth in the boreholes, the abnormalities of the curves can be figured out. Based on the theory of heat resource method, these abnormalities are used to determine the leakage location of Xiaolangdi dam.Environmental isotope and hydrochemistry are also analyzed to investigate dam leakage. Through the analyses of their fractionation and decay, the hydrogen and oxygen isotopes are used to determine groundwater recharge sources and the depth of water circulation as well. In the hydrochemistry, the evolvement of many kinds of chemic compounds and the reactions between water and rocks are analyzed, and then after compared with the components of possible recharge water, the recharge directions can be determined. These two methods will testify each other and can be used to find the leakage location.Finally, some interconnection tests are designed to testify the above results. After inputing tracer in the selected point, recharging water to make sure that the tracer will flow into the main leakage passage. The distribution of tracer concentration along time is obtained after receive and analyze the tracer in the downstream, then the leakage location is found out. By using the interconnection tests, the above results about the leakage passage location are proved to be correct.Some strengthen measures are poposed based on the detection results. After seepage control measures are made, the operation environments of some underground constructions are improved obviously. The seepage dangers existing in the left mountain of Xiaolangdi hydro project isbasically removed.