Research purposes: The piston wind will be generated when the train passes through the tunnel and the piston wind will bring the cold air into tunnel, resulting in the changes of temperature field in tunnel. If the understanding of the impacts is improper, the unreasonable fortification measures will be taken and the freezing damages will occur, which have serious impacts on the safety of train operation. In view of such circumstances, the impacting mechanism of train piston wind on temperature field in tunnel was analyzed by theoretical analysis and numerical simulation, and the impacting law of train piston wind on temperature field in tunnel in cold regions was studied, which provided a technical support for the anti-freezing design of tunnel in cold region.
Research conclusions: (1) The piston wind will cause the significant changes of temperature field in tunnel instantly while the train passes through the tunnel in winter. The continuously impacting of train piston wind on the temperature field in tunnel is shorter. After the train passes, the temperature field inside the tunnel will gradually recover, especially when the frequency of the train is small, it can basically return to the state under natural ventilation conditions. (2) The frequency of driving causes an increase or decrease in the longitudinal negative temperature length inside the tunnel, with a rate of about 1%. With increasing of surrounding rock temperature, the longitudinal negative temperature length in tunnel significantly decreases. The higher the surrounding rock temperature is, the weaker the impacts of piston wind direction on the temperature field in tunnel becomes. (3) Considering the impacts of piston wind on the cold and frost resistances of tunnel in cold regions, the impacts on anti-freezing of ditches at both sides of tunnel shall be focused. Due to the occurrence of alternating freeze-thaw phenomena in local lining, the durability of the lining should be taken into consideration in the design of tunnel structures. (4) The research results can be used as references for the construction of extra-long railway tunnel in cold region, especially for the anti-freezing design of railway tunnel under the condition of unidirectional natural wind.