Research on the Frost Resistance Safety of Tunnel Lining Structure of Plateau Railway

Research purposes: A plateau railway is located in Chengdu Plain of Sichuan Basin, which crosses the Hengduan Mountains to Lhasa Plain of Qinghai-Tibet Plateau. The average elevation of the plateau railway is more than 3 000 meters. According to the bad environment characteristics of tunnel in high altitude and cold area of plateau railway, this paper takes the typical tunnel of plateau railway as the basis, adopts the quantitative criteria and classification method of surrounding rock frost heave considering the factors of surrounding rock grade, lithology, groundwater recharge condition, freeze-thaw degradation law, and the calculation method of frost heave force considering the effect of uneven frost heave on tunnel lining, and studies the evaluation of tunnel surrounding rock frost heave, calculation of frost heave force and safety analysis of lining structure. Research conclusions:(1) The frost heaving of the surrounding rock at the entrance of the typical tunnel on the Yalin line of plateau railway under the most unfavorable conditions is evaluated. The results show that the surrounding rock at the entrance and exit of the tunnel with a depth of 1.25 km has frost heaving, while the surrounding rock has no frost heaving when the depth exceeds 1.25 km. (2) The frost heaving force of the surrounding rock of the typical tunnel on Yalin line of plateau railway is calculated. The results show that the maximum frost heaving force of the tunnel is 1.40 MPa, and the minimum frost heaving force is 0.12 MPa. (3) The safety factor of secondary lining at the most unfavorable section of typical tunnel on Yalin line of plateau railway is calculated. The safety factor of the most dangerous condition of grade V surrounding rock is 2.02, and the safety factor of the most dangerous condition of grade IV surrounding rock is 2.58, which are greater than the safety factor of Code for Design of Railway Tunnel. It can be considered that the anti-freezing safety of the structure meets the requirements under the condition of considering the frost heaving force.(4)The research results can provide reference for the design of frost heave force of lining structures in similar projects of plateau railway tunnels. © 2021, Editorial Department of Journal of Railway Engineering Society. All right reserved.