Hydrothermal characteristics of a cold regional tunnel under different climatic scenarios

Abstract

Cold regional tunnels have been encountering numerous frost damages as a result of dynamic changes in hydrothermal conditions of tunnel structural layers. The climate change is recognized as a major contributor for the problems. In this study, the hydrothermal conditions of a high-speed railway tunnel are evaluated under different climate scenarios based on in-situ data and numerical analysis. Subsequently, the effect of different thicknesses of insulation board on hydrothermal conditions inside the tunnel is compared and the reasonable thickness is obtained. The main findings are as follows: 1) the temperature and unfrozen water content gradually decreased and the ice content gradually increased with the service time of the tunnel in the early 15 years. The maximum frozen depth occurs at the tunnel sidewall and it with a depth of 1.64 m within 30 years after the construction. 2) The hydrothermal conditions inside the tunnel are significantly affected by annual mean air temperature (AMAT) and annual range of air temperature (ARAT). The maximum frozen depth decreases with AMAT, but increases with ARAT. 3) After the XPS board with a thickness of 5 cm is laid in tunnel structural layers, the temperature at the most unfavorable position is 0.55 ?C in the cold season, which suggests that frost damages disappeared and this method can be used to protect the tunnel against the frost damages. This paper can provide a basis for heat insulation design of the cold regional tunnels.