Evaluation Of Geological Hazard Risk Based On Geological Information System In Nyingchi Section Of Sichuan-Tibet Railway

The construction of Sichuan-Tibet railway is an important measure for the Party to implement the strategy of governing Tibet in the new era,and it is also a key project of the 14 th Five-Year Plan of the state.It is of great significance to safeguard the reunification of the motherland,promote the unity of all nationalities,stabilize the frontier of our country,and promote the economic and social development of the western region,especially the Sichuan-Tibet region.The Nyingchi section has become one of the most frequent geological hazards such as landslide,debris flow and collapse due to the complicated geomorphological influence and frequent earthquakes and heavy rainfall.Based on the actual situation of field investigation and the natural geography and geological environment conditions of Nyingchi area,this paper makes a detailed analysis of the development characteristics and disaster control factors of landslide,debris flow and collapse in the study area,and combines the fuzzy mathematical method with the hierarchical analysis model in the Arc GIS.The main research results are as follows:(1)The topography height difference is mainly concentrated in180?1239 m,marine glacial development and abundant water system.As a whole,Nyingchi City is located at the junction of Eurasian plate and Indian Ocean plate,the strata are broken,the crust is active,the tectonic background is complex Cenozoic suture zone,fault structure is extremely developed,earthquake frequency occurs,the area is mainly igneous rock and metamorphic rock,and its distribution is obviously restricted by geological background,which has become the high risk area of geological disaster.(2)Through remote sensing interpretation and field investigation and statistics: 66 landslides,108 collapses,224 debris flows,debris flow has become the most important geological disasters in the region,and often induced secondary disasters such as landslides.The distribution features of geological hazards are as follows: mainly along the Yarlung Zangbo River,Nujiang River and Chayuqu and its tributaries,especially at the high altitude junction with Jiali-Chayu,the southern foothills of the Himalayas and the Yajiang fault zone,high frequency of vertical slope drop,seasonal occurrence frequency,most of them are in the development period;the main form of damage is traction type,which leads to the occurrence of rockfall,rock mass and other deposits in the disaster area,the interruption of roads,the serious blocking of rivers and the formation of barrier lakes,which has a great impact on the safety of people's life and property along the way.(3)In this paper,three typical geological hazards,such as debris flow,"102" landslide and Yigong landslide,are analyzed in detail.The fuzzy mathematical method and hierarchical analysis model are used to evaluate the study area,and nine evaluation factors,such as geomorphology,fault zone distribution and annual rainfall are selected.The evaluation system is established by mathematical fuzzy method,the weight of each factor is determined by the hierarchical analysis model,and the risk assessment of Nyingchi geological hazard is preliminarily obtained.Finally,the geological hazard risk of Nyingchi section is verified by Google map and actual investigation results.Among them,about 40% of the very low and low risk areas need to be strengthened.The remaining 60% are middle and high risk areas,and the management and control of disaster management is urgent.In particular,the spatial distribution of the extremely high risk areas is mainly located in the tributaries of the main river and the transition zone between the middle and middle risk areas.The high risk areas are mainly distributed in the north of Nyingchi area,and the whole county of the middle and low risk area is distributed.(4)From the qualitative results,the geological hazard risk zoning map is superimposed with the accuracy verification point,and the probability of the disaster distribution point located in the middle,high and extremely high risk areas is large.From the quantitative point of view,the overall results have good accuracy and rationality.The key prevention and control of areas with high disaster degree can provide scientific basis for the prevention and control of geological disasters in the region.