The Research Of Hazard Evaluation And Prediction For Debris Flow In Aoyitake-bulunkou Section Of The G314 National Highway

The China-Pakistan highway is the only land route linking China and Pakistan,which has an important position in the national strategic layout?The AoyitakeBulunkou section of the G314 national highway,which is an important part of the China-Pakistan highway,is located in the western margin of Trim Basin and west Kunlun mountain hinterland.Since the highway was built and opened to traffic,it has been under the influence of debris flow disaster for its extremely bad geographical environment.Nowsdays,China focus on promoting ?The Belt and Road Initiative? strategy,which put forword higher requirement to the highway,so it is necessary to control the debris flow disaster immediately.In order to provide reasonable and scientific basis for the treatment of debris flow disaster and the line selection of the highway reconstruction and extension,our research group entered the study area twice to investigate detailedly from May to September in 2015 and September to October in 2016.Based on field investigation and a lot of data collected,the types of debris flow disaster along the highway and the present management situation were studied at first,and then the background,which debris flow formatted,and the temporal and spatial distribution of debris flow were analyzed,finally the hazard evaluation and risk range predition for debris flow were researched.In addition,the formation mechanism and dynamic parameters of several key gullies were discussed,which can provide scientific reference for the design of prevention engineering.The main conclusions are as follows:(1)The main types of debris flow disaster that the highway suffered were burial,impact,erosion and washout by flood,which burial and washout were the main two types.Prevention engineering were bridge,tunnel,culvert,retaining wall,blocking slag net,diversion wall,drainage groove and overflow pavement.Based on field investigation,viaducts and tunnels have significant effects,others were not ideal.(2)According to the analysis of environment that the debris flow formatted,the key control factors of debris flow in different sections were revealed,namely the debris flow in K1548-K1587 section was controlled by rainfall,that in K1597-K1619 section was controlled by glacier meltwater,and that in K1587-K1597 section was controlled by the comprehensive effect of rainfall and glacier meltwater.(3)According to the statistical analysis of debris flow disaster in previous years,the spatial-temporal distribution of debris flow was revealed.The temporal distribution characteristics reflected in three aspects: daily period,month period and age period,debris flow outbroke at 16:00-24:00 from May to September,small-scale debris flow outbroke every one to two years,medium-scale debris flow outbroke every three to five years,large-scale debris flow outbroke every five to ten years.In space,the density of debris flow gullies,types,damage degree in different sections were different.Slope aspects have an effect on debris flow distribution;debris flows on sunny slope were more development than that on shade slope.Based on the analysis of regional environmental change,it can be concluded that the debris flow disaster will increase in the next 3 to 5 years,and then become stable.(4)Based on the field investigation,the environment that debris flow formatted and the previous research results,the debris flow risk evaluation index system was built,and then the hazard evaluation models were established based on the grey clustering evaluation theory and set pair membership theory,and they were applied to evaluate the hazard of 27 gullies in the region.The calculation results showed that: compared to the inveatigation results,the coincident rate of grey clustering model was 88.9%,the remaining 11.1% were lower risk level than investigation results;the coincident rate of set pair membership model was 92.6%,the others were higher risk level than investigation results;Comparison results illustrated that: in consideration of the accuracy and the risk prevention,the set pair membership model was more reasonable and suitable for risk assessment of debris flow in the region.On the basis of the evaluation of the theoretical model and the field investigation,the debris flow risk zoning map was made(5)Based on the MATLAB software,the multivariate nonlinear regression equations between risk range parameters(maximum accumulative length and width)and predictors(outbreak of scale,the basin area,watershed relative elevation,main channel length)were established,and then the risk range prediction model of debris flow in the region was built.The application results showed that the relative error of the predicted value was within 15%,which met the requirements of the initial prediction accuracy.The prediction model can be used to predict the risk range of debris flow in the study area or other areas with similar geological background.(6)The formation mechanism and dynamic characteristic parameters of three debris flow gullies in K1558+800,K1561+952 and K1564+520 were key researched,which can provided some important parameters for the design of prevention and control engineering.The research results of this paper have important practical significance for the control of debris flow disaster in the study area,and it can provide some scientific references to the route selection and parameters selection for the design of prevention and control engineering as well.