Study On The Development Characteristics And Danger Of Debris Flow In A14 Section Of Jiu Mian Expressway

As a highway connecting Jiuzhaigou and Mianyang in Sichuan Province,Jiu Mian Expressway plays an important role in developing tourism resources along the route and promoting local economic and cultural development.The A14 section starts from the Baima Tibetan Township forestry team in Pingwu County and ends in the wooden block Tibetan township.The total length is about 30 km.The geological structure along the line is complex,the earthquake is frequent,and the debris flow is extremely developed,posing a huge threat to the road.Based on the investigation of debris flow system along highways,this paper studies the formation conditions,influencing factors and development laws of debris flow,uses the analytic hierarchy analysis method to evaluate the risk of debris flow,and uses multiple regression method to establish the dangerous range prediction model and combines with highway design.,proposed prevention measures for debris flow.The results provide a scientific basis for the disaster prevention and mitigation of the debris flow of the Jiu Mian Expressway,and have certain theoretical significance for the study of regional debris flow.The paper has achieved the following main research results.(1)A total of 27 debris flows were developed in the study area,all of which belonged to the torrential rain-type debris flow,and the fluid properties were thin.Based on the understanding of the general characteristics of the debris flow in the study area,the formation conditions and laws were systematically studied through the analysis of five typical debris flow ditches.The study area is located on the northwest side of the Longmenshan fault zone,and the neotectonic activity is The large-scale intermittent strong uplift,the landform is mainly composed of high-mountain geomorphology,and the lithology in the area is complex and diverse,resulting in the development of debris flow in the study area.(2)Based on the basic characteristics of the debris flow in the study area,the extensional analytic hierarchy method was used to select the relative height difference of the basin,the length of the main channel,the area of the basin,the frequency of the explosion,the source of the material,the maximum amount of the debris flow,and the recharge section of the sediment.A total of 9 evaluation factors,length ratio,cutting density,and maximum rainfall within 24 hours,established a risk assessment model for debris flow,and concluded that there were 14 highly dangerous debris flows in the study area,12 moderately dangerous debris flows,and 1 mild dangerous debris flow,combined with the impact of debris flow on the highway,is mainly caused by the work shovel trench,thunder trench,Pingshibangou,Minzugou,butterflyzigou and Lujiagou.(3)Using the multivariate nonlinear regression method,the three relative predictors of the relative height difference of the basin,the solid excavation volume of the debris flow,and the length of the main ditch are selected to establish a multivariate regression equation for the risk range of the debris flow,and the prediction model of the debris flow hazard range in the study area is obtained..Comparing the predicted results with the measured results,the results show that the error of the predicted value of the debris flow risk range of more than 85% is less than15%,and the error value of the predicted risk range of the debris flow of more than65% is less than 8%.Based on FLO-2D software,the debris flow range prediction of5 typical point debris flows in the study area was carried out.The obtained dangerous range parameters were compared with the results obtained by multiple nonlinear regression methods,and the two methods were used for self-test.The accuracy was greater than 82%,indicating that the multivariate regression prediction model has high credibility and can be applied to the prediction of the danger range of debris flows in the study area and similar geological conditions.(4)According to the relevant kinematic characteristics of each debris flow ditch combined with the engineering design of the highway,this paper combines the block and the lead discharge with the mechanical parameters of each debris flow ditch obtained from the on-site investigation,and uses corresponding engineering measures to prevent and control the debris flow.