Engineering Geological Partition Research Based On GIS For The Section Of Across Suture Zone In Sichuan-tibet Railway

The Sichuan-Tibet Railway is an important high-speed transportation channel in southwestern China.The project area will span multiple crust block suture zone such as the Jinshajiang,the Lancangjiang,the Nujiang,and the Brahmaputra.The geological construction-structural features of the plates and the suture zones have great influence and restriction on the railway engineering.This paper took the Sichuan-Tibet Railway to cross the plate suture zone and various blocks as the research scope.Firstly,on the basis of collecting the previous research results,the high-resolution remote sensing geological interpretation of the route area,the plan and exploration of the railway,and the field geological survey data,it was systematically analyzed that the geological construction-structural features of the plates and suture zones.Then,by studying the development characteristics of the various factors that restrict the regional engineering geological environment,seven evaluation factors such as engineering rock groups,topography,geological structure,geological disasters,meteorological and hydrology,terrain variation,and seismic activity were selected to establish the engineering geological evaluation system.Finally,using GIS to superimpose the evaluation factors,the study area was evaluated for comprehensive engineering geological zoning.The main research advances achieved are as follows:(1)The collision and suturing process of the plate has a decisive role in controlling the geo-environmental influencing factors such as regional topography,stratum rock formation,engineering rock groups,active faults,regional hydrogeological conditions,susceptibility to ground disasters,and seismic hazards.(2)Taking the engineering rock group,terrain slope,structural impact degree,geological disaster susceptibility,annual rainfall,terrain variation rate,and ground motion peak acceleration as evaluation factors,an evaluation index system suitable and an analytic hierarchy process for the Sichuan-Tibet railway regional engineering geological environment were established.Among them,the geological structure has the largest weight,followed by the engineering geological rock group.The weight values of terrain and geomorphology and meteorological and hydrological conditions are also relatively high,and the seismic activity,geological disasters,and the weight of the terrain change field are relatively small.(3)The ArcGIS software was used to classify the engineering geological environment in the study area: the plateau areas of the Mangkang Mountain,Taniantaweng Mountain and Boshula Mountain are well-engineered;they are far away from the active faults and are subject to the conditions of other engineering areas with relatively small impacts are relatively good;they are located at the periphery of active faults,but are affected to a certain extent by engineering rock groups,rainfall,topographic relief,seismic activity and other factors belonging to the engineering geological conditions.In the middle area,the tectonic activity is strongly influenced by the boundary areas of the Jinshajiang,the Lancangjiang,the Nujiang,Yarlung Zangbo,the Jiali-Chayu and Gongjueyong-Reyong faults.Due to a variety of adverse factors,the engineering geological conditions are poor.(4)The engineering geological environment of the cross-block combined zone section of the Sichuan-Tibet railway has significant zoning characteristics.According to the differential development characteristics of major geological and environmental factors such as regional geological structure,topography,formation lithology,hydrogeology,and geological disasters,the study area was divided into four suture zones and five engineering geological areas,such as the Jinshajiang suture zone,Lancangjiang suture zone,Nujiang suture zone,and Yarlung Zangbo suture zone,Dege-Baiyu Jade(Plate)Rock Structural Erosion High Mountain-Yahara District Area,Changdu-Mangkang Magmatic-Clastic Rock Tectonic Erosion-Destruction Yamahara Area,Leiwuqi-Zuogong Flake Crystallite-Layer Rock Ablation Plateau Area,Gangdise-Nyainqentanglha Massive Magmatic Rock Structure Erosion Plateau Area,Gao Himalayan Structure Eroded Plate Crystallized Rocky High Mountainous Area.Each section has great differences in engineering geological characteristics and main engineering geology problems.Therefore,when designing and constructing the railway project,it should be considered in different sections.