The Application Research Of Extension Evaluation Method In The Evaluation Of Tunnel Construction Stability

With the development of the transportation infrastructure construction in China, a large number of highway tunnels and railway tunnels are built every year, the number of tunnel will continue to increase in the coming decades. Usually, tunnel built in underground rock and soil, the construction is a complicated process. Due to the limitations of the complexity of the geological conditions and preliminary engineering design of the tunnel construction process, a lot of disasters and accidents have been caused in the process of tunnel construction. Therefore, how to make a reasonable evaluation of the tunnel-construction stability is very important. Tunnel construction monitoring is an important part of NATM, which can timely feedback the deformation and stress conditions in the process of tunnel construction, so it is an important method to judge the stability of tunnel construction. An important basis for the deformation monitoring is usually as a result of the tunnel stability in the previous evaluation methods. Combining the results of theoretical research and numerical simulation for analysis, it indicates tunnel stress monitoring also has an important influence on reasonable stability evaluation of the tunnel, on the basis of displacement monitoring management level on the establishment of a tunnel stability rating. The extension evaluation method will be introduced to the comprehensive evaluation of stability of tunnel construction, the deformation and stress monitoring results as an important indicator of the tunnel stability evaluation, utilizing extension evaluation method to establish the level of stability of tunnel construction. In practical engineering applications, this method is proposed to achieve comprehensive and objective evaluation. The main contents and results are as follows:(1) Summarize the current common tunnel stability evaluation method, point out the problems and deficiencies the existing stability evaluation method,it proposes to monitor the stability of the tunnel should focus on the results of the evaluation deformation monitoring and stress monitoring the same time, based on the tunnel displacement monitoring management level proposed tunnel stability grade division.(2) By learning the extension theory and application of the results extension evaluation method in geotechnical engineering, master the basic principles of extension evaluation method to summarizing the specific application of evaluation instruments and procedures. The introduction of extension method to evaluate the stability of tunnel construction, tunnel construction monitoring according to the index value established for grade division tunnel stability matter element extension assessment, the use of extension evaluation method for evaluation of tunnel stability rating. Evaluation indicators used mainly to change the size of the analysis based on entropy method to determine the weight of each index, to achieve the project monitoring and numerical values of the rate required to take into account, so the extension evaluation method is more in line with the requirements of the stability of tunnel grade evaluation.