Research on surrounding rock phase change effect to the initial supporting in cold region tunnels

In order to study the influence of surrounding rock temperature phase change to the initial supporting force, temperature sensors, pressure box, steel force meter were used to monitor the tunnel environment temperature, surrounding rock temperature, pressure between surrounding rock and shotcrete layer, steel stress etc. The results show that the average environment temperature remain about 9 degrees C, surrounding rock temperature increased with the exposure time, the melting depth is 1m when exposure time is 7d; the change of pressure between spray layer and supporting was small; constructing insulation layer in time can protect the surrounding rock and improve initial supporting force obviously, the research results can provide basis for tunnel construction in cold region.