Numerical Simulation Research on Optimization of Large Deformation Control Parameters in Layered Slate Tunnel

Abstract

In order to explore the deformation characteristics of layered slate tunnels under different dip angles of rock formations, a numerical simulation research method for optimization of large deformation control parameters of layered slate tunnels is proposed. The plane deviation, plane deformation, and DP parameters of the structure are obtained through the calculation mode. When studying the effect of overlapping rock masses on the stability of thick tunnels, the incidence angle of the rock structure is assumed to be zero. The estimated thicknesses of the dolomite limestone surrounding the tunnel are 0.3 m, 0.4 m, 0.5 m, 0.6 m, 0.7 m, 0.8 m, and 0.9 m, respectively. Select the vertical displacement to be analyzed as the result of the calculation. In order to study the influence of the structural slope on the tunnel stability, the thickness of the rock layer was 0.6 m, and the structural slopes of 5°, 15°, 30°, 45°, 60°, 75°, and 85° were used for simulation calculations. During on-site construction, focus on monitoring the tunnel section deformation before the secondary lining construction. Every 10-20 m, when the surrounding rock changes, the observation section of the enclosure convergence and vault settlement is arranged, and the peripheral displacement rate and the vault settlement rate are calculated according to the observed deformation. The results show that the vertical displacement of the top of the tunnel is generally in a “V” shape, that is, the maximum settlement in the tunnel; when the layer thickness is 0.3 m, the maximum vertical displacement of the rock layer is 7.2 mm, and the total settlement in the lining support tunnel is 8.23 mm. When the layer thickness is 0.9 m, the vertical displacement of the rock layer is 5.14 mm, and the total settlement in the lining support tunnel is 5.22 mm2; when the layer thickness was changed from 0.9 m to 0.3 m, the maximum vertical displacement of the rock layer increased by 140%, and the settlement at the vault increased by 158%. At this time, the focus of tunnel support is on both sides of the lining structure and the vault with large vertical settlement. The phenomenon that the section of YK51+032 first decreases and then increases due to the sudden appearance of mud in the surrounding YK51+040, resulting in increased short-term deformation. Only the ZK49+356 section at the entrance of the left line has a large deformation due to the thin overlying stratum, and other sections are relatively consistent, indicating the reliability of the calculation results.