Field test on deformation control of weathered carbonaceous slate tunnel in high geostress

The problems of large deformation often occur in strongly weathered carbonaceous slate tunnels with high geostress. In order to control large deformation in the process of tunnel construction, an advanced drilling measure and an advanced pilot tunnel measure are proposed, then relevant field tests are carried out to verify their results. Compared with conventional support measures, the advanced pilot tunnel measure has a better control effect on horizontal convergence and vault settlement, which are reduced by 29.70% and 75.81%, respectively. In addition, the advanced drilling measure provides more advantages in controlling the maximum surrounding rock stress and the maximum steel frame stress, which are reduced by 77.44% and 23.12%, respectively. The results show that the large deformation of a strongly weathered carbonaceous slate tunnel in high geostress cannot be effectively solved by conventional support measures, but the two advanced stress-control measures can effectively reduce deformation of the surrounding rock of the tunnel and decrease the stress of the tunnel's steel frame and surrounding rock.