Study Of Regional Crustal Stability In 5 To 7 Step Hydropower Station In Jinshajiang River, Lijiang Section

5 to 7 Step Hydropower Station in Jinshajiang River, Lijiang Section, followed by Jinanqiao Hydropower Station, Longkaikou Hydropower Station, Ludila Hydropower Station. They are located in active structure in NW Yunnan. In this area, the geological environment is complex, the new tectonic movement is very strong, strong earthquake is very frequent and the geo-hazards are serious. The research degree of three Hydropower Stations'regional crustal stability is still weak. Therefore, it has a important Theoretical and practical signification that evaluating the regional crustal stability of Hydropower Station.In this research, multi-disciplinary theories and methods are used. The thesis around two main lines wich the one is seismic risk analysis and the other is assessment of geological hazard. The thesis respectively studies the active faults, deep structural features, tectonic stress field, seismic activity and geological hazards in the study area. The paper mainly discuses the mechanism, laws of earthquake and geo-hazards, and their influences on regional crustal stability. Combining with qualitative analysis and quantitative evaluation, considering earthquake, geological hazards may cause serious destruction. In the perspective of coupling of endogenic and exogenic geological processes, comprehensive evaluation of regional crustal stability in hydropower project area. The main conclusions in this paper include following aspects:1. There are seven large active faults in study area, most of them move in the Holocene, only Qingshui-Zhoucheng fault active in the middle and late Pleistocene, didn't obvious move from Holocene. Chenghai fault has a great effect to Ludila Hydropower Station.2. The crust has a multi-layer structure in the study area, and has horizontal and vertical heterogeneity. The lower velocity (high-conductivity) layer is beneficial to slide between the crust circles. The Strong geophysical anomaly areas are closely related with active faults and earthquakes.3. Mid-strong earthquakes are relative concentrated in study area. Earthquakes are mainly distributed in Dali-Erhai, Jianchuan, Lijiang. Earthquakes have obvious stratification. The 10km depth is an important interface of seismic activity. Earthquake has periodicity, has 6 Seismic active periods. The paper summarizes the five special physical environments which closely related with the earthquake. Taking Lijiang Ms7.0 earthquake a typical example, the paper analyses the special and regular and mechanism of strong earthquake.4. This thesis uses ANSYS software to simulate the regional tectonic stress field. Simulation results show that the maximum principal stress and the minimum principal stress in the fault zone are decreased remarkably, the stress is easily concentrated in intersection and transition site of fault, Strain energy is relatively concentrated in Bingchuan, Yongsheng, Eryuan and west of Dali. The stress displacement is mainly to SSE direction. This is consistent with the regional GPS monitoring data.5. The main type of geo-hazard is landslip, landslide, debris flow and ground subsidence. The thesis summarizes seven aspects factors which closely related to the strong growth of geological disasters. Taking Ludila Hydropower Project Reservoir as a typical section, by the field geological investigation, we find that the main type of geo-hazard is landslip, landslide and the debris flow. There are 84 geo-hazards along the 100km river; the line density is 0.81 per kilometer. The distribution of geological disasters varies from sections of valley, clusters in tributary mouth or ditches mouth and is different in left and right bank. At last, the paper uses Logistic regression model to evaluating susceptibility and risk of Ludila Hydropower Project Reservoir's geological hazards. The results show that the percentage of high geological hazards susceptibility zone in Ludila Hydropower Project Reservoir is 41%. In rainfall and earthquake conditions, the percentage of high geological hazards risk zone in Ludila Hydropower Project Reservoir is 46% and 52%.6. The study area is divided into three Ms 7.5 potential seismic sources, two Ms 7.0 potential seismic sources and three Ms 6.5 potential seismic sources. This paper also uses the method which based on ArcGIS 9.2 platform's AHP and selects 7 indicators to evaluate the regional crustal stability. The results show that the percentage of unstable region is 20%, Ludila hydropower project reservoir's crustal stability is less stable. Combining with qualitative analysis and quantitative evaluation, the comprehensive evaluation result is that Jinanqiao Hydropower Project Reservoir and Longkaikou Hydropower Project Reservoir's regional crustal stability is less stable. Ludila Hydropower Project Reservoir's crustal stability is poor.