| Since the national implementation of the strategy of "One Belt And One Road" and"western development",the expressways and national highways in the western area of our country have developed rapidly.More and more long tunnels are being built in high altitude areas such as yunnan-guizhou and qinghai-tibet.In addition to typical risks such as landslides and water gushing,tunnels in high altitude areas also have unique adverse natural environment and geological factors such as plateau hypoxia,complex geology and frozen soil,which multiply the probability and consequences of risks.Now the research of high-altitude long tunnel engineering risk has just started,the risk awareness of practitioners is not strong,the process is not standardized,the method is not scientific,and the system is not comprehensive.As a result,the effect of risk management in practical application is greatly reduced,thus easy to cause accidents,not only caused great econonic losses to the state,also can bring negative effects to the society.This paper starts with the characteristics of long highway tunnels in high altitude areas,summarizes all kinds of typical tunnel accidents,on the basis of the opinions of experts in the industry,the expert investigation method is adopted to identify the overall risk of long highway tunnel in high altitude areas and all kinds of special risks,and according to the identified risks,respectively established six special risk general assessment systems including,general risk assessment system of long highway tunnel in high altitude areas " and "general gas risk assessment system of long highway tunnel in high altitude areas",combined with industry standards and previous research results.The risk classification standards and risk acceptance criteria suitable for long highway tunnels in high altitude areas are given,to provide some reference for the risk management of the subsequent similar projects.In order to verify the applicability of the risk assessment system,this paper,based on the,national highway 569 mandala-datong highway Ningchan tunnel project",established the general assessment system,and in view of the unique characteristics of Ningchan tunnel,consulted with the industry experts for many times and to "check the leakage and make up for the deficiency,of risk factors,finally identified the five primary index and 23 secondary index system of overall risk assessment,and four level indicators and 25 secondary indicators of landslide risk assessment system.After determining the system,the expert survey method and analytic hierarchy process are used to get the weight of each factor.Then the fuzzy concept is used to establish the evaluation set for the probability and consequence of risk occurrence,and the membership degree is determined and the fuzzy matrix of membership degree is obtained.Finally,the weight and the fuzzy matrix of membership degree are fuzzy synthesized,according to the principle of maximum membership degree,the level of the risk occurrence probability and risk loss consequence is obtained,so as to finally determine the overall risk level of Ningchan tunnel is "extremely high",and the risk level of gas special risk is "extremely high",and measures must be taken to reduce the probability and consequence of risk occurrence.Finally,combined with the actual situation of Ningchan tunnel,the corresponding preventive measures are proposed for the risks of high-altitude occupational health,gas explosion,landslides and mud water gushing,which are above "height,risk.Through practice,it has been proved that the overall risk assessment system and the gas risk special assessment system established by this paper are feasible,and the preventive measures for all kinds of risks are also effective,which can provide reference for the subsequent similar projects. |
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