Contributing Factors And Control Countermeasures Of Sesiman Gully Debris Flow At Jinchuan County,sichuan

With the rapid development of Chinese economy, energy problem becomes more and more important, and the water of the natural non polluting energy source is more and more favored by people.In the past the national energy development in the 13 th five-year plan, water resources and hydropower development is highly valued.Country puts hydropower energy priority to the development of the key position,and the goal of hydropower development, by 2015 the national hydropower installed capacity will reach 350 million kilowatts,and 2020 years ago in key development yalong river and dadu river, jinsha river, lancang river, etc.. The energy in the hydropower development process has repeatedly suffered debris flows, resulting in huge casualties and property losses.AnNing hydropower station which is located in the territory of Jinchuan County, Sichuan Province in Aba Prefecture in the upper reaches of the Dadu River is the first stage of 3 level development of hydropower station from Jinchuan to Danba,and it’s dam site is located in is between of AnNing Township and DuSong Township. Debris flow of Sesiman gully located in Anning Thracian power station dam, a distance of only 300 m, and if it will sufer the debris flow, Sesiman gully has a large influence of hydropower construction and operation. Therefore,it is very necessary to carry out special research on the debris flow of Sesiman gully.Sesiman gully is located in the territory of Sichuan Province, Jinchuan County, on the right bank of the Dadu River a tributary of the valley. Gully region has the high mountains and steep slopes, the rich provenance and the valley of the larger slope, and also provided a favorable terrain for loose solid material handling and participate in the activities of debris flow. According to the survey, Sesiman gully debris flow happened two times and a massive flood, therefore, it is an old debris flow gully. Since twenty-first Century, with no occurrence of debris flow record, but the annual flood occurred and soil erosion is more obvious. Sesiman gully during construction period and operation period is the occurrence of debris flow, and how size of the debris flow, and how to build a reasonable and effective prevention and control measures to prevent is paid attention to the industry and design units. Therefore, this paper focuses on the formation conditions of Sesiman gully debris flow and studies on the causes and prevention countermeasures.Through the field investigation of Debris flow gully, data collection analysis, and with the aid of remote sensing interpretation method, the author analyzes the study debris flow formation conditions in system, mainly from the terrain condition, water conditions and the source condition. First of all, terrain condition analysis starts from the whole. The study area is located in the Northwest Plateau of Sichuan Province, the eastern edge of qinghai-tibet plateau, where there is steep terrain, high altitude and big gap, is more conducive to debris flow outbreak. Then, the research on the study debris flow valleys partitioned. According to the distribution channel of the source, longitudinal gradient ratio will be divided into debris flow into three zones:source area, circulation area and accumulation area,and analysis the debris flow in the study area topography comprehensively. Provenance conditions research mainly through the field investigation and remote sensing interpretation analysis, to identify potential debris flow source distribution, and reserves; at the same time, based on debris flow provenance supply way for inductive classification hydro-geologic debris flow provenance. Study concludes that different provenance types may be involved in the debris flow movement source quantity calculation method; Water conditions are summarized and the existing debris flow type and amount of water supply.Based on the formation conditions of debris flow, debris flow analysis and summarize the characteristics of the development, mainly from the history, gully debris flow impact on characteristics and accumulation characteristics of three aspects. Through field investigation, the auther study the history of debris flow activity; through geological mapping, drilling, rock profile measurement, statistical and field test were used to analyze the characteristics of alluvial fan and channel impulse on the characteristics, causes according to the topography, climate condition, geological structure, stratum lithology distribution and other factors of debris flow. In this paper the development trend and the outbreak frequency of outbreak of debris flow scale through the development characteristics of gully and dynamics characteristic analysis, combined with the layout of hydropower station construction, and puts forward appropriate countermeasures and suggestions.The results of the study show that Sesiman gully of the study area is located in the Northwest Plateau of Sichuan Province, has a deep mountain valley landform typical source of loose solids distribution, rich valley in the region, abundant water power condition and concentrated rainfall and snow melt water supply, on the outbreak of debris flow provided favorable conditions. But because of the better valley in most of the vegetation, the precipitation seep into the groundwater recharge, and the channel is the most coarse particles, the flow conditions of individual pieces of rock was a torrent of start away, but not in the channel whole accumulation so as to form a large-scale debris flow start. Sesiman gully full channel narrows, the channel on both sides of a multiple channel blocking the formation of a collapse of the damming body, before and after the damming body with stacking platform and drop formation, and much greater than 5m in diameter boulders piled up. If the channel blockage formation Lake burst water depth, whether or flow rate will increase rapidly, handling capacity of a geometric growth, therefore, large-scale damming body blocking the channel and burst,and this is an important cause of the outbreak of Sesiman gully debris flow formation. In the construction period of hydropower station, damming dam body is less than 4 m high, mudslides rushed out of the smaller, and the arrangement of the personnel, equipment, equipment have been doing for the outbreak of debris flow must avoid, this storm frequency of debris flow out almost does not affect the normal operation during construction period. When damming dam body to 4 m tall, mudslides in a rushed out of the larger, pose a threat to the normal construction, but can through certain prevention and control of project management, and establish the corresponding early warning system. In damming dam body were greater than 5 m, mudslides rushed out of the huge volume, through the prevention and control of project implementation is difficult and there is no practical significance, but can through the early warning system, notify the construction personnel evacuation in time, as far as possible, minimize the dangers of debris flow. In the running of power plant, considering the reservoir will be out of solid material of debris flow in the backwater effect, reduce the risk, but to consider the effect of the reservoir area, it needs to carry out the corresponding prevention and control engineering.