The Method Of Determining The Limit Displacement Of Surrounding Rocks Stability For Underground Engineering Based On The Catastrophe Theory

With the rapid development of transportation industry in our country, the scale of tunnel construction is bigger and bigger. In the process of the construction, the problem of the stability of surrounding rock is becoming more and more serious. Accidents of collapse often happens, it has become a major cause of economic losses in engineering and schedule delays, etc. Therefore, the risk assessment and prediction for stability of the tunnel have a very important significance.The application of catastrophe theory to the research of the theory of limit displacement of tunnel surrounding rock stability is mainly:Energy catastrophe theory, The entropy of catastrophe theory, The displacement catastrophe theory, Hole weeks yield zone area catastrophe theory and Generalized viscoplasticity shear strain catastrophe theory. These theories are based on the research of tunnel plane problems, differ from the actual conditions of three-dimensional construction. In order to serve the engineering practice better, in this paper, we use Volume catastrophe theory to research the plastic yield volume mutation of the surrounding rock in tunnel during the three-dimensional excavation.The selection of relevant test parameters using the method of uniform design, the selection of tunnel section reference from the highway tunnel design specification (JTG D70-2004), Excavation of the tunnel adopts step method. Firstly we use the ANSYS to create the model, then use a simulation software FLAC3D to calculate a three-dimensional construction of excavation process of underground engineering. The catastrophe theory is introduced into the research field to the limit displacement of surrounding rocks stability for underground engineering construction. Based on the numerical results from the displacement of hole weeks to structure cusp catastrophic model, and calculate the catastrophe characteristic value in the process of tunnel construction, then obtain the limit instability displacement of tunnel according to the principle of the surrounding rock instability mutation, and structure the training sample according to the data, then respectively introduce the multiple regression algorithm and evolutionary support vector regression algorithm, to build the regression model based on geological conditions of surrounding rock, buried depth, span, method and support parameters and the displacement of key points, when the tunnel is under the critical state of equilibrium. The mathematical model can be used for the prediction of the limit displacement of the surrounding rocks stability in construction process, to ensure the safety of excavation in the process of tunnel construction and the quality of engineering, and reduce the project cost, thus provide a reference experience and relevant theoretical guidance for the future tunnel design and construction.