Comprehensive Analysis On The Characteristics Of In-situ Stress Field Of Wudongde Hydropower Station And Adjacent Area

Based on the tectonic background of Wudongde Hydropower Station and its surrounding area and combined with a large number of geological survey data, seismic data and the measured In-situ stress data, this paper systematically study and analyze the tectonic system and tectonic stress field of the region from the time and space scales. The main works of this paper are as follows:(1)The landform system and tecnotic system in Wudongde Hydropower Station and adjacent area is divided systematically. Moreover this paper studys the regional tectonic activity and evolution.(2) The tectonic stress field of C huanDian is partitioned according to the previous research. A large number of focal mechanism solutions indicate that the earthq uakes in the research area mainly attribute to horizontal tectonic movement. At the West of Xiaojiang Fault Belt, the direction of dominant compressive stress is NNW; At the West of Xiaojiang Fault Belt, the direction of dominant compressive stress is NWW. Inversion results not only shows the sliding motion at north-south direction of Central Yunnan block, but also shows that from west to east the direction of dominant compressive stress in the study area was from NNW to NWW transition phenomenon.(3) The inversion of the tectonic stress field is based on the main fault slip data,and the fracture in research zones can reflect two stages of tectonic stress, respectively for the early quaternary period and today tectonic stress field, two time boundaries for initial stage of late Pleistocene to Holocene. Based on the tectonic evolution history of Southwest C hina, this paper analyz the formation mechanism and evolution of the regional tectonic stress field, and explain the formation of the two time stress in the research area. By comparing the results of two inversion results of slip fault and focal mechanism, this paper analyze the contact and difference at the time and space scales respectively.(4) According to the measured stress, this paper analyzed the superficial and deep stress field distribution characteristics in Wudongde Hydropower Station and its surrounding area, and inferred that with the increase of the depth, maximum horizontal principal stress direction gradually parallel to the direction of the main compressive tectonic stress. The transformation of the stress field by the formation of the deep valleys determined the distribution of the maximum horizontal principal stress direction. The contrast between the measured stress and the tectonic stress can show that there is a big difference between the two stress, which the maximum main stress and the tectonic principal compressive stress at a large angle intersection.(5) The stress field of regression analysis results at dam area showed that at the bottom of the deep valley the maximum horizontal principal stress presented stress concentration phenomenon, while the larger the slope height ratio was, more obvious the stress concentrated and the greater amount of value was. Also stress direction and valley trend are vertical or angled intersected; with the increased of the depth, the influence range of deep valley to its surrounding rock decreased gradually. Exceeded a certain range, the direction of the maximum horizontal principal stress and principal compressive tectonic stress reached agreement. And within the rock stress field was no longer affected by topographic effects, mainly due to the self weight of the rock mass and the regional structure combined effect.