| Sichuan-Tibet road is a part of national road 318. Its overall length is 2155 km from Chengdu to Lhasa in the west. The road was constructed in 1950s and is a traffic life line to link up Tibet and interior of our country, as well as is the shortest passageway to the every province in southwestern china for the economic and cultural exchange. It occupies a quite important place for promoting the economic development in southeastern of Tibet, particularity for safeguarding state unify, consolidating national defense, strengthening national solidarity and speeding up the economic construction of Tibet.South section of Sichuan-Tibet road (the part Tibet) mostly locate along the southeast-Tibet deeply cut narrow valleys with steep sides, where the fractures are much developed, rocks are disintegrated and broken up, the channel is eroded very intensely and the adverse geologic phenomena are distributed in groups. In the region, neotectonic movement is so vigorous as to uplift the mountain and cause an intense incision in the river. The base level of erosion in the main channel is lower down intensely to an incision depth. Fractures in late geological time is still so active violently that earthquake occurs frequently , the seismic movement has accelerated destroy and disintegration of the mountain mass, hence a large number of adverse geologies such as debris avalanches, landslides and rockfalls takes place intensifying the destruction of the hillsides and the erosion in the channel to promote the debris flow activities. For example, the section of road located in the Ninzhi and Bomi of Tibet, where the area is situated at Polongzangbu basin, the first tributary of ualuzangbu River, which is the deepest gorge area in the world. It has been a focus of research on geography at home and abroad. After tramping over Anjiula mountain, Sichuan-Tibet road develops along the north side of Palongzangbu river, due to the special geology, landform and the environment, of hydro climate, mountain disasters along this line become so active, which have entire types of disasters, big distribution density and high frequency more over, as well as huge scale of activity, high extent of hazard and wide range of frequency at home and abroad. Along the Palongzangbu River, the road is 271km whose hazardous length is 71. 63km, making up26. 43% of the road section . there are 399 disaster points, including 9 landslides, 42 collapses, 32-debris flow and 43-road section destroyed by floods.Among all the mountain hazards, debris flow-is one of the most series hazards that threaten the construction and operation of transportation. The large scale glacier debris flow occurred in the Peilongnongba gully along Sichuan-Tibet highway in 1983-1985, and continued to last till 1990. so, it has very important Realistic Significance and scientific value to study the Distribution and mechanic and to summarize the new technique in prevention and control countermeasure of debris flows.Basing on field investigation and research, using risk analysis fuzzy mathematics and other theoretical methods , in this paper, analyzing on the hazard of debris flows along Sichuan-Tibet road and summarize on their prevention and control Countermeasures are carried out. According to the Prediction of debris flow and key problems need to be solved in prevention and control Countermeasures of debris flows due to earthquake in High-intensely earthquake areas, two special Research was done. The main work is following:(1) Study on the technique of prediction and prevention of debris flows along Sichuan-Tibet road. Firstly, the jobs on the Prediction and prevention of debris flows along the main line in Tibet are reviewed and summed up. Secondly, by studying on the types, characteristics, distribution of debris flow, the Activities Risk Zoning of Debris Flow is done, and the prediction is put forwards. By summarizing the existed prevention and cure project for debris flow, the principle of prediction first, combing engineering treatment with maintenance and assensment is established, Prevention and control measures, as well the policy of design, for debris flows where the road across different area are put forward.(2)Study on the debris flows induced by earthquakes along road.On the base of the Analysis and Summary existed regular phenomena between earthquake and debris flow, the model of debris flow Prevention and Counter-measures made according to the reason of earthquakes is established. The Principles of prevention of debris flow due to earth quake in the mountain area under the direction of risk analyzing. Take the Sichuan-Tibet road from Tongmai to 105th highway maintenance station section as experimental section, risk assessment on debris flows induced by Earthquakes in this typical part is carried on, Finally got the map of regionalization of earthquake along the Sichan-Tibet road.(3)Study on critical rainfall of the debris flows. To determine the value of critical rainfall which will cause the occurrence of debris flow is the key problem in debris flow prediction and predication. Generally, it is the determined by analyzing the historical rainfall records. However, at the present there are many gullies along Sichuan-Tibet road which do not have any available rainfall record owing to the lack of nearly meteorological observatories. In order to make it possible to guide the prediction of such debris flow gullies, it is necessary to find other ways to solve the problem more economically and effectively. The purpose of this paper is to describe some of the studies which have been done in this field. First, two researches by means of the analysis of frequencies of debris flow and rain storm and by means of the method of fuzzy similarity selection in the surface conditions of debris flow gullies are described in brief. Then a research on this topic based on the theory of debris flow formation is presented and the results are illustrated as a specific example with a debris flow gully along the Sichan-Tibet road.
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