| More than two thirds of our country’s territory runs through mountains,and is rich in coal resources.With the construction of a large number of transportation infrastructure such as highways,the frequency of tunnels passing through coal-bearing strata tunnelc is increasing.In addition to various disaster forms faced by conventional tunnel construction,such as collapse,water inrush and rock burst,there are also specific disasters caused by coal seam,such as gas explosion,gas suffocation,coal seam outburst and coal seam collapse,etc.Therefore,the construction is in very high risk.Major production safety accidents caused by improper construction have occurred many times in engineering construction,resulting in bad influence.Resultly,it is of great significance to deeply analyze the influencing factors of coal measure stratum tunnel construction safety and evaluate the construction risk to ensure the safe and smooth construction.Thus,based on the analysis of risk generation mechanism,this paper established and designed the risk assessment index system,model and development trend prediction model of coal-bearing strata tunnel construction risk by using the theories and methods of WBS-RBS method,interval number,interval 2-tuple linguistic,attribute mathematical theory,cloud model,game theory and MABAC,and forms the following research results:(1)By analyzing the generation mechanism of coal-bearing strata tunnel construction risk,the paper determined that the overall construction risk is caused by various risk events,and then designed an evaluation system that the overall risk level is composed of the probability level and the consequence level of risk occurrence.(2)According to different working procedures and risk sources,construction work breakdown structure(WBS)and risk breakdown structure(RBS)were carried out for coal-bearing strata tunnel respectively.Expert investigation was conducted on the seven working procedures and four types of risks obtained from the decomposition,and 68 basic risk events were obtained by constructing the WBS-RBS coupling matrix,and an index system composed of three assessment indexes was established according to the risk source classification.Finally,using the Spearman rank correlation coefficient method to test the accuracy and reliability of the index system.(3)The risk assessment model of tunnel construction in coal-bearing strata is established according to the risk classification standard.In the model,the expert survey was conducted in the form of interval number and interval 2-tuple linguistic theory to obtain the initial evaluation information of expert group,and the attribute measurements function and fuzzy sets were used to transform the initial evaluation information into the initial evaluation matrix,a consensus reaching mechanism was constructed to identify and modify the initial evaluation information by computing expert and group consensus,introducing risk preference parameter p reflects the experts decision-making attitude contained in the evaluating information output from the consensus reaching mechanism.For evaluation information of each p value,the cloud model based on MATLAB simulation was used to realize the uncertain transformation from index probability information to probability membership degree,the fuzzy set was used to determine the membership degree of index consequence,using the risk matrix method to calculate the comprehensive membership degree of index combining with the grade classification standard.Based on the idea of recognition and correction of consensus degree,the subjective weight of the index system was calculated by using 2-tuple linguistic method,and the other two sets of weights were determined by combining the improved analytic hierarchy process and the improved entropy weight method.Finally,based on the game theory,the optimal combination of subjective and objective weights was obtained to gain the optimal combination weights of the index for each p value.MABAC method(Multi-Attributive Boundary Approximation area Comparison method)was introduced into the risk assessment model to realize the fusion of index information.The approach coefficient between each construction risk level and the boundary approximate area was calculated by the comprehensive membership matrix and weight vector of the index system for each p value,sorting and determining the risk level.(4)A prediction model for the development trend of coal-bearing strata tunnel construction risk was established by combining the determined index comprehensive membership matrix and applying the idea of set pair analysis.The development trend state of each risk was obtained by calculating the partial relation number and set pair potential of the total construction risk and the comprehensive risk of each index under different p value conditions.The risk assessment model for tunnel construction in coal-bearing strata tunnel in this paper was applied to the construction of the coal crossing section of Gui Ga La tunnel.By the work of risk assessment,it is determined that the overall construction risk of Gui Ga La tunnel through coal section is at a high level when p is calculated from [-1,1] with a step size of 0.5,and has a tendency to develop towards a very high direction in the future when p value is-1.Therefore,targeted measures should be taken to reduce the construction risk level during the construction.To verify the accuracy of the evaluation model,this paper using the fuzzy hierarchy comprehensive evaluation method and the accident consequences equivalent estimation method to carry on the comparative analysis.The results shows that the risk assessment model of coal-bearing strata tunnel construction established in this paper has reliability and engineering applicability,and can be used to guide the implementation of the practical project. |
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