Research status and progress of tunnel frost damage

The problems of frost damage in cold region tunnels have been systematically analyzed and studied by local and foreign scholars. A series of important achievements has been proposed. In this paper, the research results on mechanism of frost damage, analysis of temperature field, classification of frost damage levels, and frost prevention technologies are summarized. The principles and limitations of the three major theories of frost damage mechanism are elaborated, and the importance of structural damage research on shotcrete in cold region tunnels is emphasized. Two major defects of current research on temperature field are concluded. The present situation of research on frost damage classification of cold region tunnels is discussed. The directions of further studies for tunnel temperature field and frost damage classification are proposed. The prevention technologies for tunnel frost damage in foreign countries, and the advantages and disadvantages of the four major prevention technologies in China and their applicable conditions, are concluded and analyzed. Meanwhile, the importance of frost damage classification is highlighted. Therefore, the local and foreign research results for cold region tunnels are systematically concluded, the defects of the researches are comprehensively analyzed, and the directions of further study are proposed. They are significant to solve the problems of tunnel frost damage in the future.