# Deformation Analysis of the Rock Surrounding a Tunnel Excavated through a Gently Dipping Bed
## 4 Engineering Application
### Comparison of Measurements and Simulation Results
As shown in Figure 13, (1) for the settlement of the vault, the minimum accumulated deformation point was located on the construction entrance face, and the maximum accumulated deformation point was located 1 m away from the construction entrance face in the direction of the construction exit face. (2) When the dip angle of the bedding plane was \(30^{\circ}\), in the case of an inverse layer, the cumulative deformation outside the hole diameter of the construction exit side, which was 0.5 times that of the construction entrance side, was essentially the same; that is, the influence range of the construction entrance side on the construction exit side was about 0.5 times the hole diameter. (3) When the dip angle of the bedding plane was \(-30^{\circ}\), in the case of layering, the cumulative deformation outside of the hole diameter, which was one time the hole diameter from the construction exit side to the construction entrance side, was essentially the same; that is, the influence range of the construction entrance side on the construction exit side was about one time the hole diameter. (4) By comparing the cumulative settlement curves for a vault that is 0.5 times the tunnel diameter (5 m rock pillars) through the upper bench and that of a tunnel excavated  
Figure 12: Schematic diagram of the excavation from 5 m rock pillars left on the construction entrance side to tunnel penetration. Figure 13: Y = 50 m, cumulative vault settlement of the tunnel: (**a**) Retained rock mass pillar and (**b**) excavated rock mass pillar. completely penetrated, it was found that the deformation of the exit side with rock pillars retained during the tunneling was reduced by 20-25%. Figure 14 shows the cumulative uplift of the tunnel invert when the rock mass pillar was retained or excavated. The rock mass pillar was 5 m, which is about 0.5 times the tunnel span. As shown in Figure 14, (1) for uplift of the tunnel invert, the minimum accumulated deformation point was located on the construction entrance face, and the maximum accumulated deformation point was located 1 m away from the construction entrance face in the direction of the construction exit face. (2) When the dip angle of the bedding plane was \(30^{\circ}\), in the case of an inverse layer, the cumulative deformation outside of the hole diameter on the construction exit side, which was one time the hole diameter of the construction entrance side, was essentially the same; that is, the influence range of the construction entrance side on the construction exit side was about one times the hole diameter. (3) When the dip angle of the bedding plane was \(-30^{\circ}\), the cumulative deformation outside the hole diameter on the construction exit side was 0.5 times that of the construction entrance side and was essentially the same; that is, the impact of the construction entrance side on the construction exit side was about 0.5 times the hole diameter. (4) By comparing the cumulative uplift curve of the tunnel invert, we found that when the upper bench was connected by a span 0.5 times the tunnel diameter (5 m rock pillars) and the tunnel was completely connected, the deformation of the tunnel invert with rock pillars was 30-33% lower than that without rock pillars. Through comprehensive comparison of Figures 13 and 14, the following conclusions were obtained: (1) From the cumulative settlement of the vault when the upper bench was 0.5 times the diameter of the tunnel and the tunnel was complete, the degree of disturbance to the construction exit side caused by the excavation of the construction entrance side was very significant, which also indicated that the temporary support on the construction exit side should be strengthened when a joint-through construction scheme is adopted. (2) The final cumulative settlement of the vault was about 2-3 cm smaller than that of the tunnel with pillars and 0.5 times the tunnel diameter from the upper bench. The final cumulative value of the uplift of the tunnel invert was about 5-6 cm smaller.