Distribution rules and key features for the lining surface temperature of road tunnels in cold regions

Abstract

Temperature distribution rules are the basis for researching on freezing damage in tunnels. But temperature fluctuations in the daily period has been neglected. Three tunnels with different lengths in the WuShaoling Tunnel Group are chosen for temperature measurement. About 160,000 pieces of data are collected by 5500 h of continuous monitoring in 31 test sections. The results show that the longitudinal temperature curves of tunnels present four shapes: an oblique straight line, a parabola, a hook, and a lying S. The daily temperature range is largest in freeze-thaw seasons, followed by the warm season. There is a zone in tunnels with length of 4905 m where the daily temperature range is less than 2 °C. Besides, the daily period fluctuation is a key feature of tunnel temperature fields, which causes freeze-thaw cycles on the lining. The number of freeze-thaw cycles shows a declining trend with the increasing distance from entrances. For tunnels with lengths between 500 m and 1000 m, the whole secondary lining can go through more than dozens of freeze-thaw cycles in an observation period. For tunnels with lengths between 1000 m and 3000 m, freeze-thaw cycles may happen everywhere in the longitudinal direction. And for tunnels longer than 3000 m, the freeze-thaw zone can grow to a limited length and not spread to the whole tunnel. It is hoped that those distributions can provide some references for freezing damage prevention.