| Wudongde Hydropower Station is the first cascade hydropower stations in the lower reaches of the Jinsha River with the total storage capacity of 7.43 billon m3, total installed capacity of 10200 MW and annual average generating capacity of 40.11 billion kWh.The maximum dam height is 265 m.It is a large(1) type of engineering.The power plant is located within Sichuan-Yunnan anticline in the Yangtze paraplatform. It has duplex structure with basemental and cover which shows polyphasic and inheritance features.The stratum under the plant is composed of metamorphic carbonate rocks by the Lower Proterozoic Age and carbonate rocks by the Sinian System to Permian System. It has complex geological conditions. The KW3 karst groundwater revealed during the construction of power plant has temperature of 30 degrees, the stability of flow up to 200m3/h. The karst groundwater consists a hot water system along the left bank of Jinsha River with linear growth characteristic with the upstream Reshuitang hot springs and downstream waterworks springs, as well as hot water in No.1-2 high elevation tunnel line.The construction of hydropower station under complicated geological and hydrogeological conditions, with the construction of plant,tunnel and reservoir impoundment for typical model, is bound to destroy the groundwater circulation system, and influence the groundwater environment.Based on the groundwater system as the guiding ideology, combined with many hydrogeological problems on the left bank of dam under complicated geological conditions of the Wudongde Hydropower Station,and use the theory and method,such as groundwater system, groundwater dynamic and equilibrium, water chemistry, isotope, hydrogeochemical simulation,this thesis construct a hydrogeological structure model of the left bank of dam and divide it’s groundwater system division study on its characteristics. On the basis of the study on underground water, deepen the study of underground hot water development characteristics and formation model on the left bank of the plant as well as the formation mechanism of KW3 karst groundwater, combined with the hydrogeology and environmental science theory, to study the effects of engineering construction on groundwater environment. Main achievements of this dissertation are:(1)Deepen the study of the geological structure of Wudongde Hydropower Station dam area from the aspects of regional geological background, tectonic framework, structural evolution history, the Jinsha River valley evolution, karst development characteristics,established the hydrogeological structure on the stack, and the aquifer alternate with aquitard under the complicated geological conditions.(2)Through the comprehensive arrangement and analysis of Wudongde dam water chemical data, the dam site area water chemical characteristics are researched by the method of cluster analysis and Novak coefficient. It’s believed that the water bodies on both sides of the dam with significant differences in water chemistry, showing control of the hydrochemical characteristics from the river basin.Meanwhile, the high correlation between SO42-and Mg2+,Na+ and Cl- have theoretical and practical significance in identifying the abnormal ion and groundwater source.After water balance calculation of different strata and river basin on the left bank of the dam area, research shows that on the left bank of river water surface there is a serious imbalance, containing water system in each basin have relationship of mutual recharge and discharge cross river surface watershed. There is a possibility that groundwater in deeper areas may recharge and discharge from far distance. The left bank of the dam is a groundwater flow system with complex and independent characteristics.(3)On the basis of researching in the hydrogeological structure, water chemistry and water dynamic equilibrium,and the surface watershed boundary, fault boundary, stratum contact boundary, the left bank of the groundwater system is divided into Luo Zuo fault-watershed area(I), Sinian-Cretaceous cover area(II) and Lower Proterozoic boundary near the dam area(III). According to the flow characteristics of vertical groundwater, the groundwater on left bank of the river is divided into Luo Zuo fault northeast shallow fracture circulation belts, deep circulation belts on on left bank of the dam area, shallow circulation belts near the dam area,Jurassic and Cretaceous sandstone and mudstone weathering fissure water belts, that is "three districts and four belts".And study on the dynamic characteristics,hydrogeochemical characteristics,recharge, runoff, discharge mode of the left bank groundwater system.(4)Through the study of hydrochemistry, isotope, reservoir temperature, depth of water cycle, the hot water on left bank of Jinsha River is divided into three independent hot groundwater system which are named hot pond fault hot water zone, Lower Proterozoic hot water zone near the dam area and the Permian Emeishan basalt hot water zone respectively. Research shows that, by using the normal geothermal temperature increase as the heat source, the hot water is rainfall recharge. Each hot water system has independent thermal reservoir and cap rock condition.Controlled by the hot water pond fault, the hot pond fault hot water zone is independent from the Lower Proterozoic hot water zone near the dam area. They do not have the geological, hydrogeological conditions related to each other. leakage channel around and through the plant will not be formed.(5)The KW3 karst underground water belongs to water-filled karst groundwater system with bedding development characteristics. It’s shown from the hydrochemistry mode that KW3 karst groundwater "most likely" to accept the Laohei mountain area rainfall and groundwater recharge, under the combined effect of geological folds and faults near the dam area as well as use the mesh faults from LuoZuo fault zone as bedding runoff channel, excrete to Jinsha River from Eagle mouth area on a small scale with the form of fracture flooding. KW3 karst groundwater will not form leakage channel around and through the plant, but will give the impervious curtain on the left bank of the dam a 9 MPa hydraulic pressure, curtain design should conduct feasibility demonstration of engineering.(6)The power plant construction project will not damage the exposed hot pool of natural hot springs, but reservoir dam upstream of the reservoir due to hot water will disappear, hot spring water downstream is still as a tourism resource development value.The engineering expose in the construction of the power station won’t destroy the water pond natural hot springs group, but the upstream hot water will disappear due to reservoir impoundment, the downstream water springs still have the value of tourism resources development. After reservoir impoundment groundwater circulation intensity weakened, water rock interaction weakened, groundwater corrosion problem of high SO42- on the left bank of dam will be improved.KW3 will drain line on the left bank in groundwater supplies 11% of the resources, the existing hydrogeological conditions is mainly to the consumption of static groundwater reserves, after the construction of anti-seepage curtain on the left bank of dam, groundwater resources will be gradually restored, will not bring significant impact on water resources of Luo Zuo fault zone. |
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