sand lining
1.The geological conditions are very complicated in Hejiazhai tunnel which is located in Guizhou Shuibo railway, this tunnel is named "mashed tunnel" with the most difficult geological conditions such as the high dense gas and developed karst and gushing water assembled together, the geological hazards like the gushing water and sand, the collapse of tunnel, surface subsidence and slide, cracking of tunnel lining were often happened during construction period.
