| Large deformation of soft rock is influenced by many factors, so there is not unified and rational experience to draw on in support parameter of soft rock tunnel design. Shuangfeng tunnel project on Mu Sui track being the research object, this paper uses finite element analysis software(MIDAS and ANSYS) to conduct optimized research on this tunnel supporting parameters, which bases on the specific soft rock deformation and support structural characteristics DK466 + 565 mileage segment in Shuangfeng tunnel as well as combines with monitoring measurement test in the construction site. The main research contents are as follows:(1) Monitoring measurement test in the construction site. Construction is guided by feedback information from monitoring measurement and the tunnel construction is under dynamic management. Monitoring is strengthened in poor location of weak rock to ensure construction safety.(2) Displacement back analysis of surrounding rock parameters. This paper makes site monitoring measurement data for curve regression based on the principle of least squares with Excel software to predict the final displacement. Then back analysis of surrounding rock mechanics parameters is conducted and its inversion results error is checked according to BP neural network of MATLAB.(3) Support parameter optimization of Shuangfeng tunnel. Combining with construction method and supporting design and using MIDAS-GTS finite element analysis software and stratigraphic-structural model, this paper will analyze the factor that influences stability of surrounding rock and supporting structure. The main optimization includes length set of the feet-lock pipes, grade and thickness of shot concrete and steel arch type and spacing. What’s more, it also uses finite element analysis software-ANSYS and load-structure model to conduct internal force calculation on different thickness of Shuangfeng tunnel’s secondary lining and then optimizes support parameters of Shuangfeng tunnel through numerical simulation results.The results show that: ①The length of the feet-lock pipes is much longer, it is more beneficial for controlling convergence and deformation of surrounding rock and stress of supporting structures. under the consideration of the extent of the improvement effect and force, the feet-lock pipes to take 5.0m. ②The grade and thickness of shot concrete is much higher, the stability of surrounding rock is better and supporting stress is greater, while should be combined with the specific surrounding rock circumstances,the final choice is C30 and 30cm thick shotcrete. ③Steel arch spacing has a significant effect on surrounding rockstability and supporting force. The greater the steel arch type is and smaller the spacing is,control of the surrounding rock convergence is better while the relative supporting stress is greater, finally, i chose 0.6m pitch I22 a steel arch. ④The amount of reserved deformation of tunnel construction is 15 cm,it is determined by convergence displacement values based on the simulation results obtained by the various conditions surrounding rock and monitoring measurement data. ⑤ Secondary lining structure is not so thick and the crack resistance of key parts is poorer, which is difficult to meet the design requirements. So choosing the right thickness 50 cm to meet the requirements of the design and operation. |
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