Viscoelastic Constitutive Model and Large Deformation Control Technology of Carbonaceous Slate with High Ground Stress

In order to solve the problems such as long deformation time period, large deformation amount and insufficient support strength of carbonaceous slate tunnel with high ground stress. The viscoelastic constitutive model and large deformation control technique of carbonaceous slate are studied by laboratory experiment, numerical calculation and field test. The results show that: (1) The peak strength of the carbonaceous slate is greatly affected by the bedding inclination, exhibiting a U-shaped trend with increasing inclination, and the strength of the rocks with the bedding inclination of 45° is the weakest. (2) The unsteady Burgers creep constitutive model was constructed, and the creep parameters of the constitutive model were determined according to the triaxial creep test. (3) Six supporting conditions were established by using the creep constitutive model constructed. Considering safety and economy comprehensively, the supporting parameters of the large deformation control test section were defined in case 3 (HW175 steel frame, 0.6 m/pin, 4 m long anchor bolt set at the arch, 6m long anchor bolt set at the side wall, spacing 1.2 m×0.8 (ring × longitudinal)). (4) Through the test section, HW175 steel frame and 4 m arch top + 6 m side wall long anchor rod are used. The average arch top settlement and side wall convergence are 18.1 mm and 79.72 mm, respectively, meeting the purpose of controlling large deformation. The research results can provide reference for similar projects.