| At present, our country strives to develop the passenger special line projects in the southwest area, where is situated the Yunnan Guizhou Plateau, full of high mountains and steep slopes, for which reason tunnels account for a large proportion in the line design, almost 70% in our Yunnan Guizhou project. In the tunneling site area, with complicated geology and varied land, there exist geological hazards at the tunnel entrance and exit zone, such as shallow burial, biased loads, weak rock and soft foundation etc. Using the technology of high pressure jet grouting pile, the roof and the foundation have been reinforced at the tunnel opening and the safety of tunnel construction and cut and cover construction is guaranteed, and especially, for the soft foundation in the cut and cover tunnel part, early preventive measures can be taken against sinking, mud pumping, springy soil and other engineering diseases that may seriously hazard the operation safety. |