Freezing Deformation Law and Mechanical Response of Frost-Shrinkage Surrounding Rock in Cold Region Tunnels

To investigate the freezing pressure in tunnels subjected to the frost deformation of frost-shrinkage surrounding rock and lining in cold regions, laboratory tests were conducted to determine the frost deformation behavior of water-saturated rocks and their frost-shrinkage linear strain at various temperatures. The elastic solution for frost-shrinkage pressure of the surrounding rock was derived analytically. Case analysis and numerical comparison validation were performed, and the control variable method was used to analyze the effects of different parameters. The research shows that: Water-saturated tuff and sandstone exhibit overall frost-shrinkage deformation under different freezing temperature conditions. Notably, water-saturated sandstone demonstrates some frost-heave recovery during the freezing and shrinking process, with porosity being the key factor influencing this recovery. The results of theoretical calculations and numerical simulations for surrounding rock pressure in cold region tunnels in various types of rock and under low-temperature concrete frost deformation are consistent, demonstrating the reliability of the theoretical solution. The frost-shrinkage surrounding rock pressure in cold region tunnels increases exponentially with the maximum freezing depth of the surrounding rock and increases linearly with the increase of the frost-shrinkage linear strain of the surrounding rock and the ratio of the elastic modulus of the frozen rock to the unfrozen rock. The proposed frost-shrinkage surrounding rock pressure solution in cold regions of tunnels can provide certain theoretical guidance for the frost resistance design of similar tunnels in cold regions.