Abstract:Research purposes:The problem of frost damage faced by shallow buried tunnels in alpine regions threatens the long-term safe operation of tunnels. In order to explore the mechanical response of the non-uniform frost heave deformation of surrounding rock under the frost heave mode with unfrozen interlayer, a typical frost heave model of the shallow buried section of the tunnel in cold region was established. The stress deformation and frost heaving force distribution evolution of tunnel lining and surrounding rock were studied by finite element numerical software. Furthermore, the frost resistance design of shallow buried tunnels in alpine regions was optimized according to the research results. Research conclusions:(1) The outer diameter of the surrounding rock freezing circle and the non-uniform frost heave coefficient k are the key factors affecting the frost heaving force level in the shallow buried section of the tunnel. The larger the outer diameter and k of the surrounding rock freezing circle, the greater the average frost heaving force of the lining. The maximum tensile stress and compressive stress of the lining structure are located at the waist and the vault, respectively. When the thickness of the unfrozen interlayer is small, the local stress of the waist and the vault exceeds the standard strength of concrete. (2) Under the non-uniform frost heave of the surrounding rock, the maximum displacement of the surrounding rock freezing circle, lining and surface layer shows a decreasing trend as the thickness of the unfrozen interlayer increases, and the larger the surrounding rock freezing circle radius is, the higher the maximum displacement is. (3) The unfrozen surrounding rock interlayer has a significant influence on the spatial distribution and evolution of the frost heaving force of the alpine tunnel. With the increase of the thickness of the unfrozen interlayer, the non-uniformity of the tunnel frost heaving force gradually decreases. (4) The frost heaving force distribution and lining mechanical response of shallow buried tunnels in cold regions revealed in this paper can provide theoretical guidance for frost resistance design of similar tunnel projects.
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