| With the development of urbanization in China,the density of urban population is increasing,and the problem of traffic congestion is becoming more and more serious.As an important part of urban public transport,rail transit has become a priority for many cities in China because of its fast,punctual,convenient and environmental protection characteristics.In the process of rapid development of urban rail transit in recent 10 years,more and more cities have entered the gate of network operation,and the indexes of passenger traffic volume and intensity rank the top in the world.With the overall development of rail transit,shield construction has gradually become the main method of interval tunnel construction.For the field of rail transit shield tunnel crossing the Yellow River,due to the special geological structure and engineering characteristics of the Yellow River,there is a lack of experience for reference,and the construction risk control is difficult.In addition,at present,except Lanzhou rail transit has two shield tunnels crossing the Yellow River,according to the planning of Lanzhou rail transit line network and the continuous expansion of the subsequent line network scale,there will be no less than 8 shield tunnels crossing the Yellow River,so it is necessary to study the risk control of shield tunnels crossing the Yellow River.Firstly,this paper analyzes the domestic and foreign research on shield construction,tunnel crossing rivers,construction risk control,and summarizes and studies the process and construction characteristics of shield construction.The risk evaluation model is established by combining AHP and fuzzy comprehensive evaluation method,and the actual background of the project is the section from the Olympic Sports Center Station of Lanzhou Rail Transit Line 1 phase I project to the provincial science and Technology Museum Station under the Yellow River Shield Tunnel,from personnel and management,engineering machinery and equipment,construction materials and components,construction methods,external environment,construction measurement and monitoring Six aspects of risk source identification,get 6 first level risk indicators,50 second level risk indicators,and establish a risk indicator system.By building the model,the fuzzy comprehensive evaluation results are obtained.The main risk management methods used in this paper are expert survey,AHP and fuzzy comprehensive evaluation.First of all,through the design of a questionnaire,the paper conducts a questionnaire survey among industry experts on the comparative relationship between the importance of different levels of risk factors and the probability of risk occurrence and the degree of loss caused by risk occurrence.Secondly,using analytic hierarchy process,combined with the results of the expert questionnaire,the weight values of each risk factor are calculated quantitatively,and the weight values of six first level risk indicators and 50 second level risk indicators are obtained.Finally,it constructs factor set and comment set to make fuzzy comprehensive evaluation.Through the calculation of the established model,the final risk comprehensive evaluation result of the project is fuzzy vector [0.0399,0.2060,0.3740,0.2668,0.0974],adopting the principle of maximum membership degree,the maximum value of the fuzzy vector is 0.3740,and the corresponding comment in the comment set is "moderate risk",so the comprehensive evaluation of the project risk level is "moderate risk",which is acceptable.Finally,according to the comprehensive evaluation results of the construction safety risk of Lanzhou Rail Transit under the Yellow River Shield Tunnel and the weight of each risk factor,the safety risk control suggestions and measures are proposed from four aspects of organization,management,economy and technology. |
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