Mountain Tunnel Collapse Risk Fuzzy Hierarchy Evaluation Study

With generous disasters have emerged in Tunnel and underground construction, people pay more and more attentions to the risk of the tunnel in the tunnel and underground engineering. The collapse happens often, and it is the most harmful hazard in tunnel construction. Therefore, aiming at the characteristics of mountain tunnel construction, this paper makes a study in tunnel construction risk definition, risk identification, risk assessment and risk response, especially focuses on the mountain tunnel collapse risk assessment model. The main contents of this paper are as follows:1. This paper outlines the domestic and foreign status in tunnel risk, and summers up some problems in the research and application of tunnel risk, and makes a definition for mountain tunnel construction.2. Combining with the characteristics of the drill and blast method, this paper puts forth the flow of the tunnel risk assessment, and gives a brief analysis on each flow. By using the verification table, the decomposition analysis and the fault tree, the paper identifies some risk factors which exist in mountain tunnel construction, then based on the generally analysis of the risk estimation methods which are applied to the tunnel risk assessment at present, it compares their advantages and disadvantages and scope of application.3. Through collecting and clearing up massive information and data of collapse in mountain tunnel construction, which includes the surrounding rock grade, excavation span, buried depth, bias, groundwater status and collapse amount in the collapse area, the paper analysis the main reason of the collapse.4. Through collecting and statisticing data of collapse, this paper identifies the risk factors which affect tunnel collapse, and selects six most important as the affecting factors of Fuzzy-Hierarchy assessment, then makes a fuzzy classification for these six factors, and applies the fuzzy statistics and experience to establish a degree of membership function which presents the effect of each factor on the probability of collapse and the loss after collapse occurred, and ensures the weight of each factor by Analytic Hierarchy Process, so as to establish a tunnel risk Fuzzy-Hierarchy assessment model.5. By using the Fuzzy-Hierarchy assessment model, this paper assesses the collapse risk level of Qingshangang tunnel, then educes its collapse risk rank, and at the same time proves the effectiveness and practicality of this assessment model.