Karst Leakage Analysis Of The Dashixia Hydropower Station At The South Foot Of Tianshan

Under certain geological conditions, when the head of the reservoir elevation, watermay be driven through the underground passage to the adjacent areas or leakage, thusreduce the storage capacity of the reservoir, and affect the reservoir to play its normalbenefit. The proposed Dashixia hydropower project is located in a tributary of AksuRiver Kumalake River. In Wensu and Wushi County, Aksu area, Xinjiang UygurAutonomous Region. The maximum height of250m and the maximum head of wateris225m. The dam site located in the in Dashixia Canyon export. The Lithology of thereservoir and dam area is Devonian limestone. Because complex geologicalconditions in the karst area, so it is necessary to study the security and stabilityconditions on the dam region of the soluble rock. Kumalake River basin is located inthe typical northwest arid climate zone. There is few research about large-scaleprojects in northwest China at this stage. This paper to explore the dam area of Karstdevelopment regularity of Dashixie hydropower project.It’s good for researching thearid areas of Karst.This paper studied on geological environment conditions, By22hole survey and70drill hole data consolidation, analysis of karst groundwater system in the area ofhydrology geological condition and hydrodynamic characteristics, identification ofsurface and underground Karst developmental level and size, summary of the maindistribution on Karst erosion, evaluation of karst medium permeability distribution ofspace. On this basis may exist underground Karst leakage in the channels anddifferent modes of analysis of reservoir numerical simulation using Modflow software,calculate the thin Ridge may be parts of the risk of leakage and seepage volume, so asto further evaluation of seepage in the dam area. Main research results have the following aspects：(1) Collected and analyzed of basic geological data of the study area, includingtopography, lithology, geology and karst hydro-geological structure, regional structurestability conditions, to study the engineering hydrological conditions of the area.(2) Focused on research in the dam area of karst development characteristics, typeof karst development in the dam area in the main tubes, caves on a small scale-soluble;Level mainly in the dam’s location on the river and700m River, vertical in the widerange of650m, main right bank of development of vertical upward corrosion1510m,elevation1700m, left bank near the elevation1560m; Dissolution phenomenon ofmainly grade Ⅲ in the dam area （stripping holes, calcite Crystal Cave）, cutoffeffect is small.(3) Seepage model of crack leakage of potential leakage channels, analysis ofstructural development and spatial combination law, the study of drilling waterpressure test data analysis of rock mass, permeability of rock in the dam area is weak,lugeon value less than20Lu. Summary of karst rock in the dam area in the horizontaland vertical spatial distribution of permeability, permeability distribution along theterrain, depth greater permeability less, generalizability to provide a basis for a model.(4) Analysis on seepage in the dam area in channels and hydraulic conditions.Preliminary calculation of seepage volume of leakage passage, first in thin mountainridge on the left bank seepage volume without adding anti-seepage curtain ofmaximum, up to2128m3/d, seepage of dam Foundation of420m3/d, left and right damabutment seepage volume of630m3/d.(5) Using Modflow software in three dimensional numerical simulation analysis,under natural conditions, reservoir and reservoir+plus anti-seepage curtain of threedifferent operating conditions, the simulation of groundwater seepage field of thestudy area. Respectively on several key parts of seepage volume computation ofseepage, leakage of thin Ridge on the left bank of3523.395m3/d; Seepage of damFoundation of1088.933m3/d; Left bank abutment seepage volume of499.1182m3/d;Abutment seepage on the right bank of465.7903m3/d. Plus after the anti-seepagecurtain, main channel seepage volume of leakage:1913.525m3/d first in thin Ridge onthe left bank; Foundation351.2941m3/d; Left bank abutment of174.9472m3/d; Rightabutment of340.1415m3/d.(6) By means of these Karst features in the dam area, permeability of rock underdifferent conditions and simulation analysis of seepage field of the reservoir area,think the Dashixia reservoir area of karst development in less rock mass permeabilityof weaker, less likely to be massive leakage, has little effect on the project. But by itsresults see the main channel seepage volume of leakage is still a large, imperviousmeasures against leakage of important parts, ensuring safe operation of reservoirnormal.