Study on Deformation Response of Surrounding Rock under Different Support Systems of Loess Tunnel

With the mechanization and assembly of tunnels, it is important to explore the support effect of new structures to achieve the “double carbon” target. Based on the new combined structural support system, this paper discussed the flexural performance of the traditional steel frame and π-shaped steel frame by relying on the Daijiazui tunnel. Through field monitoring and numerical simulation, the deformation characteristics and response law of surrounding rock under the traditional support system and new support system were compared and analyzed, and their support effects were defined. The results show that compared with the traditional steel frame, π-type steel frame I_x/I_y is closer to 1, the bending capacity in the horizontal and vertical directions is relatively balanced, and the stability is better. The numerical calculation results are consistent with the settlement trend of field monitoring data. The deformation development of surrounding rock has experienced four stages, and the average errors of the final settlement of vault and the surrounding convergence are 14.85 % and 15.25 %, respectively, which verifies the correctness of the numerical modeling method. A comparative analysis model is established. Compared with the traditional support system, the vault settlement, peripheral convergence and initial support compressive stress under the new combined structure support system are reduced by 53.4%, 61.0% and 35.2%, respectively, and the expansion of plastic zone is effectively controlled. This study can further enrich the support structure selection of loess tunnel and provide reference for the construction of similar projects.