# Risk Assessment Method and Application for Tunnel Lining Demolition Construction
## 3 Risk Assessment Method of Tunnel lining demolition Construction
### Weight Analysis of Risk Assessment Indicators  
(1) Analytic Hierarchy Process  
Analytic Hierarchy Process (AHP) is a decision analysis method that decomposes the decision-making problem into different levels of structure, including the target layer, the criterion layer, and the scheme layer. This method is mainly to quantitatively describe the subjective judgment of people so as to make qualitative and quantitative analyses of decision-making problems [38]. The essence of the AHP method is a kind of thinking method. It makes full use of people's analyses, judgment, and comprehensive abilities to hierarchical decision-making problems, so as to facilitate decision-making on complex problems. In practical applications, the AHP method usually includes the following steps [39]:  
(a) Establish a hierarchical structure: decompose the decision-making problem according to the overall goal, sub-goal, evaluation criteria, and alternative levels. (b) Construct a pairwise comparison judgment matrix: For each level, it is necessary to construct a pairwise comparison judgment matrix to represent the relative importance of each element. Figure 7: Fuzzy comprehensive evaluation process. (c) Calculate the weight vector: By solving the eigenvector of the judgment matrix, the priority weight of each level element to a certain element at the previous level is obtained. (d) Hierarchical total sorting: According to the weight vector, the hierarchical total sorting is carried out to obtain the weight of each level element to the total target. (e) Application examples: The analytic hierarchy process is applied to specific problems, each index is compared in pairs, the judgment matrix is constructed, and the relative advantages and disadvantages of each evaluation index are calculated. Through the above steps, the analytic hierarchy process can help decision-makers analyze complex problems systematically so as to make more scientific and reasonable decisions. (2) Weight analysis  
Through the preliminary selection of risk assessment indicators for local demolition of tunnel lining construction, it can be seen that there are many evaluation indicators, and the system is too large. If all indicators are selected, it is likely to have a negative impact on the comprehensive evaluation, making the evaluation results meaningless [40]. According to the principle of establishing an indicator system, when selecting evaluation indicators, they should be representative and reflect the essence of the evaluation problem. Therefore, in order to ensure the objectivity of the evaluation, it is necessary to screen the evaluation indicators, distinguish between primary and secondary, and form a reasonable and feasible evaluation indicator system. Due to the large number of risk assessment indicators for local demolition of tunnel lining construction, some indicators have significant correlations, and some data collection is difficult. In order to reflect the importance of each evaluation indicator in the evaluation system, this article uses the analytic hierarchy process to determine the weight of the indicators and screens the indicators based on the size of the weight. Removing some indicators with relatively small weights is not only beneficial for simplifying decision-making problems but also avoids errors in judgment caused by too many indicators [41]. Analytic Hierarchy Process (AHP) was used to calculate the weights of four influencing factors: adjacent lining cracking, accidental lining falling or collapse, surrounding rock collapse, and the impact on the operation of adjacent lines. The specific results are shown in Tables 1-5.