Study On Application Of Hierarchy Extension Model For Risk Assessment On Tunnel Construction

As the development of highway construction in our country, the construction of the tunnel in quantity and quality have made rapid development. At the same time, the security problem in the process of tunnel construction is more and more outstanding. A little bit carelessness would result in huge economic losses and casualties. For tunnel construction, most scholars at home and abroad are only interested in research on its stability and mechanical properties. There are rarely literatures is reported about researching on risk assessment for tunnel construction. Therefore, it has important theoretical value and practical significance to research on risk assessment for tunnel construction.Based on the existed research results at home and abroad, through theoretical analysis and in-site tests, research on risk assessment theory of tunnel construction is carried out in this thesis. According to the characteristics of tunnel construction, aiming at risk identification and risk classification as well as risk control and management and so on were all explored. And focus research on the risk evaluation index system and risk evaluation model for tunnel construction have been performed. The main contents of the research work and the innovative achievements obtained are as follows.The main contents of the thesis1. Through the research on risk evaluation theories and methods at home and abroad, the research contents and the methods as well as the technical route of this thesis are put forwarded.2. Through the analysis on the basis of existed tunnel risk assessment system, combined with the analysis and application of advance geological forecast results, the system structures of risk assessment method for tunnel construction are proposed.3. Combined with the experts geological investigation and advance geological forecast, the risk source recognition system on tunnel construction is established. Moreover, by analyzing the construction principle of index system of risk assessment, the risk evaluation index system for tunnel construction have been built.4. By using the extension theory, a risk assessment model for tunnel construction is established, and the correlation degree of the proposal to be assessed is determined too. Then the index weight is determined combined with the Analytic Hierarchy Process. After calculating the comprehensive correlation degree, ultimately, the levels of comprehensive evaluation are determined.5. the advance geological forecast and in-site monitoring measurement have been carried out respectively, in the construction of the Gejiagou tunnel entrance and the Shirenzigou tunnel body. On this basis, using the proposed method and evaluation model, the actual risk assessment for the above tunnel projects have been carried out.The main innovative achievements of the thesis1. According with risk assessment theory combined with the Analytic Hierarchy Process and the Extension Theory, the connotations of risk assessment for tunnel construction have been expanded, and the index system for risk assessment have been improved.2. In order to improve the reliability of risk assessment for tunnel construction, the principle and method of constructing the evaluation factors are proposed. Including natural, design, engineering geological, technology and management etc. are selected as four key elements as the first class index. And including atmospheric precipitation, bias angle, excavation width, flatness ratio, method of excavation, surrounding rock level, unfavorable geology, underground water, weathering degree of rock, overbreak degree, closed condition of working face, technical level of construction, and management level etc. are selected as 13 key elements as the second class index. Through the combination for each of the second class index and the related evaluation standard, a more reasonable risk evaluation index system for tunnel construction have been built.3. Using extension theory and combined with the Analytic Hierarchy Process, the classical domain and joint domain of every index are determined, and the matter-element matrices of risk assessment for tunnel construction are constructed. Moreover, the calculation method of the correlation degree is put forward. On this basis, a Hierarchy Extension model and the related analysis method of risk assessment for tunnel construction are established.4. Using the established theory and method above, an actual risk assessment for Gejiagou tunnel portal section has been performed. According to the information feedback from in-site monitoring, it has been proved that the risk assessment method based on the hierarchy-extension model for tunnel portal section is reliable. The established model provided a theoretical basis for the risk assessment of tunnel portal section.5. Using the hierarchy extension model, an actual risk assessment for Shirenzigou tunnel body has been performed. According to the information feedback from in-site monitoring, it has been proved that the risk assessment method based on the hierarchy-extension model for large cross-section tunnel is reliable.