Abstract: In view of the problems such as slow construction speed and difficult processing of temporary supports existing in the construction of long-span highway tunnels when the sub-excavation method is adopted, based on the tunnel of Qingshuiyi-Fujiayao Highway of G312 Line,the curved middle partition was replaced by the vertical middle partition,andthe numerical difference between these two partition walls was compared and analyzed using MIDAS GTS. Combining the on-site measured data, the numerical simulation results were verified, following the comparative of the deformation and stress effects of the partition walls of the same structure with different material strengths on the construction of large-span tunnels. The results show that: (1) Both kinds of middle partition support can meet the requirement of construction stability, in which the vertical stress of the vertical middle partition wall is increased by 97.16% compared with that of the curved middle partition wall, and the displacement and deformation of the tunnel surrounding rock and the middle partition wall adopting the vertical middle partition wall are smaller than that of the curved middle partition wall; (2) Comparing two different types of vertical middle partition walls, i.e. I18 and I22b, respectively, in the construction of long-span tunnels, it is found that the maximum stress energy generated by the middle partition wall using I22b steel frame can be reduced by 23.09%.

Key words: tunnel engineering, large section tunnel, temporary support, numerical simulation