Abstract: High temperature of surrounding rock will reduce the stability of tunnel lining and worsen the construction environment. It is an effective measure to set up the thermal insulation layer in the tunnel structure. An analytical solution of the temperature distribution is derived by 〖ＪＰ２〗introducing the thirdboundary conditions and the Levy method based on the radial and axial symmetrical twodimensional thermal conduction model of the surrounding rock so as to analyze the influence of the heat insulation layer on the temperature of the lining, and the validation results are consistent with the data of published literatures. The main factors affecting the temperature of the inner and outer surfaces of the lining are analyzed by taking the Gaoligongshan mountaincrossing railway tunnel as an example. The results indicate that: (1) The cooling effect of the different laying methods of the thermal insulation layer on the lining can be easily quantified by using the analytical solution; the relationships between the temperature and temperature gradient of inner and outer surfaces of the lining and the thermal conductivity of the thermal insulation under different convective heat transfer coefficients in the tunnel can also be determined, for example, when the convective heat transfer coefficient is 0.25 W/（m2?℃）,〖ＪＰ〗 the average temperature of the lining with the sandwich insulation layer is about 1.6 ℃ lower than that with the wallmounted insulation layer. (2) When the convective heat transfer coefficient in the tunnel is large, the effect of the thermal conductivity reduction of the insulation layer on the temperature decrease of the inner and outer surfaces of the lining is weakened, which shows that the insulation material with small thermal resistance can also meet the requirements of the insulation when the ventilation condition in the tunnel is good.

Key words: tunnel, thermal insulation layer, lining temperature, analytical solution