| With the rapid development of the national economy, railways merge such as bamboo shoots after a spring rain, followed by the rise of tunnel construction. As everyone knows, the construction of tunnel is a huge project considering of complicated geological conditions, so the research of stability of tunnel surrounding rock in the process of construction is very necessary. Guanshan tunnel’s length is15.6km, and Guanshan mountains geological conditions are very complicated experienced the long term complex evolution, Bad geological conditions develop, construction’s difficulty are high, it is urgent to solve related technical problems.In this paper, I take the Guanshan tunnel as the engineering background, and investigated the engineering geological conditions including geological characteristics of landform, strata lithology, geologic structure, hydrologic, had a preliminary judgment according to a clear understanding of the tunnel surrounding rock classification, the tunnel mainly cross the Variscan intrusive rocks diorite, which is quite broken, and the buried depth of tunnel is large, so it is tend to happen accident such as block collapse. The angle between maximum principal stress and the tectonic stress is smaller, therefore we can ignore the impact of tectonic stress on the stability of the tunnel. Tunnel may exist water inrush when it through the secondary water rich section, so it is necessary to strengthen geological forecast in construction.According to the analysis of the comprehensive advanced geological forecast technology tunnel construction used and the final excavation results, it indicates that the integrated forecast system is goodworking, In view of the bad geological condition for effective prediction which guaranteed the successfully construction.In this paper, I tend to analysis the original data by mathematical regression. Building exponential function, logarithmic function and hyperbolic function by the least square method with Excel built-in function formula, then selecting the optimal function to predict the final value of tunnel crown displacement and the horizontal convergence, results show that the absolute value of correlation coefficient of the exponential function is closest to1, indicating that the index function has the closest datas comparing the original datas.Using the finite difference software FLAC3D I made a two-dimensional simulation about the three steps tunnel construction method with the temporary inverted arch, analysing the regularity of stress and strain of rock and the support, in order to pay more attention to the dangerous section, in the same time one step and two step method is also simulated in order to compare with three step method, the results show that the three step construction method has a better control on the deformation of tunnel surrounding rock, and the phenomenon of stress concentration is worse than the other two kinds of methods, Tunnel plastic zone range is minimal,which is conducive to the stability of rock mass and supporting structure.Also made a3D simulation about the three step temporary inverted arch tunnel construction methods using the FLAC3D software, analysed the performance of rock stress and strain after every step excavation, found out the stress concentration phenomenon is obvious on both sides and the front after each step excavation, which belong to the dangerous area, we must strengthen the monitoring during construction and adjust supporting parameters appropriately. Vault subsidence and horizontal convergence performance severe when excavating in its part,so we should be careful in construction.Weak interlayer region’s deformation is obvious in the process of excavation, collapse phenomenon is easy to occur in construction, we should pay more attention to it. Finally the simulation results and monitoring datas were compared, the laws demonstrated through the data are similar,proved the validity of the simulation.Research content of this paper could provide technical guidance in the analysis of stability of tunnel rock and provide technical reference to tunnels of similar engineering geological conditions in design and construction. |
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