The Tectonic Features And The Engineering Adaptability Evaluation Of Jiacha Regions In Tibet

The hydraulic resources of the middle of Brahmaputra River are rich, and is located in Tibetan political, economic and cultural center of Jiacha area in Tibet, planning the Jiacha hydropower station built not only satisfy the demand of national power in Tibet, and promote economic development and social stability.Brahmaputra River and adjacent areas of the youngest situated continental orogenic belt– Tethys - the Himalayan orogenic belt, Brahmaputra River roughly along the Brahmaputra suture zone distribution, most are in or near the main Brahmaputra deep fault. Therefore, the geological tectonic background complex, new tectonic movement and intense, modern seismic activity is frequent, seismic intensity is higher; River valleys cover is deep, landslide, collapse accumulation cross-strait development, physi-geologic phenomena in this section are the water resources development and hydropower station have significant influence.Jiacha is the development of hydropower superior conditions and prospects, but the global famous hydropower anchordoguy Jiacha zonally tectonic - tethys eastern mountains (with) made, regional geological tectonic conditions, earthquake geological background and engineering geological conditions are more complicated. Brahmaputra tectonic fault of first-order 3km from downstream dam near inclined to wear the Brahmaputra, overall along Brahmaputra River exhibition cloth, to nearly things, steep sloping slightly north, south or the arc protruding southward, the span more than 1,000 km. The fault zone is a large scale of qinghai-tibet plateau, the southern border, the tectonic India's several stages to Eurasia plate subduction of the collision of the tectonic evolution -- results. Along fault zones development cretaceous ophiolites sets, melanges belt and Cenozoic base sex, super base sex intrusive rocks, and control of the early Cenozoic north of acid, alkali intrusive rocks distribution and lava eruption. The Brahmaputra Faults control the Oligocene - Miocene and pliocene - pleistocene basin, performance for multiple thrust south poured hundreds of meters, broken bandwidth to km above, dynamic metamorphism, remarkable fault scarp, fault triangle surface features feature is apparent, shows a certain active late quaternary period. Area of immense size on the outside of nearly ns-trending the Brahmaputra fracture zone, nearly ns-trending, north east - north east north to and north west to fracture also relatively complicated. In addition to the geological structure in the dam site area and near-zone strata, lithology is more complex.Situated in the Jiacha area kernel part of the Himalayan orogenic belt, the new tectonic movement, earthquake, geothermal activity and Cenozoic magmatism most intense regions.The qinghai-tibet plateau new tectonic fault blocks the most intuitive performance is strong vertical uplift and block level sliding. Its movement characteristics in time in the new stage, the inheritance and has, on the space natural are different, etc. Main show is widespread overall, intermittent sharp elevating fault; Fault block of successive, new activities with difference fault and so on naturally.In this paper, on the basis of field geological survey by remote sensing geology, geophysics and geochemistry, microscopic structure, chronology, earthquake geology, data processing method and technique and tactics, and, for the Brahmaputra River middle plus check district activities tectonic characteristics were studied, especially the activity of the fracture structure of engineering adaptability made an objective evaluation.Through the survey found the Brahmaputra fracture with obvious subsection sexual activity, the general, who is stronger, the east activity for the holocene active faults; Who is weak, west fracture activity mainly for the latest activities in era of late Pleistocene.Jiacha hydropower station with near-zone late pleistocene activity characteristic.In the dam site area were found 11 of the faults. And mainly for quaternary structure surface, many for brittle-ductile faults. These faults are direction, same properties, smaller, bedding or nearly bedding features.In the dam site area quaternary system development, dam site is located in the secondary, tertiary terraces platform. The tectonic background complex, north from Brahmaputra River regional faults 2-3km, add check in the dam site area covering layers of quaternary system under the larger regional existence, is this project concealed fault the Paramount concern. In order to solve the problem, this project concealed fault from the following aspects: one is based on macro tectonic deformation law judge; But by far and near tracking survey, determine whether more large-scale faults in the dam site area; to delay Three is geophysical and geochemical prospecting method shall be confirmed. Comprehensive use of the above methods, covering layer in the dam site area under that only development several smaller fault, not there is greater, with regional scale fault.Through the middle reach of Brahmaputra River in the Jiacha area geology survey research foundation, according to the topography, formation, rock, structure, physical geology functions, structure stability factors considered, think of the Jiacha hydropower development conditions are good.