Key Points and Large Deformation Control in Construction of Tunnel in Carbonaceous Slate

In order to prevent collapse and control deformation of Luza inclined shaft of Muzhailing Tunnel on Lanzhou-Chongqing Railway located in carbonaceous slate,the author analyzes the behavior and deformation mechanisms of the carbonaceous slate,as well as countermeasures to control the deformation.The conclusions drawn are as follows: the carbonaceous slate is a kind of soft ground subject to softening when water is encountered;collapse is subject to occurring after excavation in water-bearing sections,therefore advance reinforcement and pre-grouting are needed;tunnels located in high-stressed carbonaceous slate are subject to long convergence period and large deformation;countermeasures such as installing invert to form a closed ring,long rock bolts,radial grouting and protection arch can be taken to control the deformation.