Study On The Numerical Simulation Of The Nibashan Tunnel Advanced Predictiction

NIB ASH AN tunnel is the controlling key project in the expressway from Ya’an to Lugu, which is located in high and middle mountains of Daxiangling at the junction of Hanyuan and Yingjing, Ya’an, Sichuan Province. Due to the length, depth, and complexity of the engineering geological conditions, the tunnel becomes high-risky with frequent rock burst, landslides, large deformation, water and mud bursting and some other geological disasters, which makes advanced geological prediction of particular importance. Closely related with the engineering practice of NIBASHAN tunnel and the project for geological forecasting technology of NIBASHAN tunnel construction and its application, an analytical research of numerical simulation is carried out in this article, taking the advanced geological prediction as the main line.In recent years, with the improvement of computer function, the numerical simulation technology has undergone unprecedented development, owning to which the problem of huge computation in the numerical simulation is resolved and quantitative research moves forward. Detailed analysis of the engineering geological conditions of the NIBASHAN tunnel construction is conducted in the study. Rock data are obtained and collected with geological method and geophysical method. Since the findings could be directly applied to the NIBASHAN Tunnel construction in Ya-Lu highway, advanced geological prediction carried out through the method of numerical simulation shall be easy to operate with practicality. A comprehensive model is established to simulate all sorts of geological disasters. Boundary stress is employed to simulate ground stress and the rock nature is reflected through the parameter to realize the same model simulating different geological disasters.In the paper some criteria are proposed. They help determine the degree of collapse in terms of the collapse depth, the extension depth of plastic zone in FLAC Simulation, and the standards of water and mud bursting is divided by rock pore water pressure. The results show that the model can meet the demand for strong calculation ability, reasonable computation time and simplicity. Meanwhile the forecast accuracy of the entire tunnel was76.5%, which met the requirements of practical engineering.Researches in the thesis enrich contents and methods of the tunnel advanced geological prediction and enhance the reliability of advanced geological prediction. Also methods and means are provided for the development of the tunnel advanced geological forecasting.