The Risk Assessment And Measures Analysis Of Rockfall In Wenchuan-marerkang Highway

In recent years,collapse events occurred frequently,and the project construction developed quickly,so,the geological disasters of highway slope get more and more attention.Along with the construction of Wenchuan-Marerkang and Yaan-Kangding highway,geological disaster along the highway is highlighted in construction.Those devolution disaster in deep canyon and steep slope is especially secretly and harmful.Started with Wen-ma highway,this paper researches 41 spots and 142 crag spot along highway and find its regularities of distribution.It evaluate the risk after the collapse of dangerous rocks and forecast the range threatened by collapse,its distance,its effect on construction and the hurt to people.We rank those survey spots according to their risks,and use different treatment measure based on different risks level,during which process,the risk analysis is always used.The process and results of the survey are as follows:( 1) According to the survey along with highways,the instability of crag is mainly influenced by landform,geologic structure,formation lithology,and structure character. At the same time,complex and changeable weather and the growth of vegetation in high altitude area also affect the stability of crag.( 2) Risk is an important segment of risk assessment,it directly relate the possibility of disaster of crag and the possibility of reaching to the protective porject.In order to evaluate the risk in geological disaster area,we combine data and DEM graph,and use information-theoretic method to evaluate 7 factors include gradient,exposure,lithology,seismic intensity,fault distance,dot density and vegetation status,and then,we decide the ratio of different factor through analytic hierarchy process and superpose them in arcgis software.RHRS method is used to examine factors include geology,topographic feature,meteorology and hydrology,rock cutting size,the collapse scale and its history of collapse to evaluate the risk of slop.Finally,we combined dangerous factors that are used in GIS method and RHS method which may cause disasters into an entirety.Those two evaluation methods evaluate the risk of the whole line from regional view and single point of view.Combining two evaluationmethods and classifying based on evaluation criterion put forward by Pierson,we can evaluate the risk of slope accurately and directly.As a result,we conclude the comprehensive risk zone and summarize the zone chart to complete risk assessment which is one way must be passed to complete risk management(3)vulnerability classify according to the type of hazard-affected body,and is used to evaluate fixed hazard-affected body(construction)and unfixed hazard-affected body(people in construction).Firstly,we should calculate the impact force when a rolling stone reaching the building.secondly,we figure out the ultimate value of impact resistance bearing capacity in parts such as bridge deck,pier可能性,and so on.Thirdly,we contrast the impact force and impact resistance bearing capacity,and quantize the vulnerability of fixed hazard-affected body into probability.Combined Peila and Guardini event tree method,we figured out the death rate of accident caused by collapse like traffic congestion,rolling stone accident,pavement damage and so on.Finally,we distinguish the level of vulnerability according to the death rate,and determine the vulnerability,which is an vital node of risk assessment.(4)According to the hazard assessment and vulnerability assessment,we can accurately evaluate the risk of the construction talked in this paper.We worked out the risk of 41 survey spot and forecast the the risk in 2020 and 2030.We verify the accuracy and reliability of our method by examining landslide accident of this road in recent years.We investigate the spot of landslide in Sanganqi,Shidaguan village,Menggu village in lixian and Chediguan,and then make risk assessment of these three slide accident to verify the reliability of risk management evaluation.We put forward different protective measures according to different risk level,which help us to chose a more safty,economical,and suitable protection construction.