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.

Smooth blasting is a commonly used blasting technique for the excavation of ultra-long mountain tunnels. This paper takes the construction of the Dongge section tunnel in Shenzhen City as the engineering background. It investigates the effect of relevant blasting parameters on the smooth blasting effect. Numerical models with different linear charge densities were established. Through analysis of the numerical simulation results, the optimal linear charge density suitable for this blasting project was determined. The results indicate that: The length of the main cracks in the smooth blasting layer on both sides of the blast holes and in the surrounding rock mass increases with the increase of linear charge density. At a linear charge density of 0.08 kg/m, the effect of crack penetration along the blast hole alignment is not good, with partial under-excavation observed. When the linear charge density is 0.12 kg/m, the crack length during the blasting process is the longest, resulting in greater damage to the surrounding rock mass. Through multiple analyses and calculations using numerical simulation, it was determined that a linear charge density of 0.10 kg/m yields better blasting effects. The outline of the smooth blasting is neater, and the half-hole rate is higher. Theoretical derivation and calculation results can provide reference for similar engineering projects.