Study On The Quantified Site Selection For The Entrance And Exit Of Nujiang River Tunnel In Yongba Township,Tibet

The proposed bridge project from Changdu to Linzhi is the controlling bridge position across the Nujiang River.The bridge position is selected based on geological conditions and controlled by the bank slope position and tunnel opening position.To this end,this paper conducts a qualitative zoning study of engineering geology for the location of the Nujiang Bridge,and uses fuzzy comprehensive evaluation method,information quantity method,modified gray clustering method and quantitative location study based on Python language and Arc Gis software to determine the Nujiang extra large The location of the bridge entrance and exit provides an important basis.The main results are as follows:(1)Topography and stratigraphic lithology as the main basis,the study area is divided into three Ⅰ,Ⅱ,Ⅲ engineering geology area,find out the different engineering geological characteristics.A number of typical bank slopes were selected in each region for analysis and evaluation.(2)Three quantitative methods were used to evaluate the stability of bank slope,(Fuzzy comprehensive evaluation method,Add weight information method and Modified grey clustering method).The paper innovates the traditional information method and grey clustering method.Through the analytic hierarchy process,the weight is multiplied by the value of information quantity,the weighted information quantity is obtained and the stability is determined.Based on the traditional grey clustering method,the index weight is given by the coefficient of variation method,and the final weight is obtained by multiplying with the clustering weight.(3)Ten evaluation factors were selected: human engineering activity,weathering,river action,engineering geological rock formation,slope,slope height,slope structure,fracture density,disaster scale and distribution density,and the evaluation index system of bank slope stability was established.Based on the definition of surface hydrology,the bank slope unit of the study area is divided.Based on the above evaluation factors.The most stable bank slope is optimized.(4)The suitability evaluation system for tunnel entrance engineering was established,including 9 evaluation factors: lithology,slope,slope strike,elevation,distance from ridge line,scale of dangerous rock mass in slope,distance from fault,distance from existing highway and shortest distance from corresponding position on opposite bank.The grid element is used as the evaluation unit of hole suitability.The topographic map of the bank slope is optimized to generate a DEM grid model of10m×10m by Arcgis.Based on the fuzzy comprehensive evaluation method and the modified grey clustering method,the results of the suitability partition were obtained by using python language.And the grid suitability level was expressed in Arcgis.(5)Give the hole location on the most stable bank slope,through the evaluation of engineering geological conditions of the bank slope are optimized,the bank slope stability zoning,rock mass and the boulder development present situation and the threat to the mouth of the cave,and has carried on the comprehensive evaluation,to the location of the mouth of the cave and the mouth of the cave engineering suitability evaluation result contrast,verifying the rationality of the entrance location.This step is cycled to obtain the optimal position of the hole.