Research on excavation stability of large-section and small-clearance tunnel with bias pressure

Abstract

Due to the limitation of terrain conditions in southwest China, the construction of tunnels needs to pass through complex geological environments, so double-track tunnels are often constructed in the form of small clear distances. Since the distance between the two faces of the small clear distance tunnel will have a certain influence on the disturbance of the double-hole excavation, if the disturbance is strong, the bearing capacity of the middle rock column will be weakened, thereby affecting the safety and stability of the tunnel. Therefore, in this paper, FLAC3D technology is used to study the effect of different face spacing, and it is concluded that under the condition of grade V surrounding rock when the back hole is excavated 6 m, the optimal excavation face spacing of the first hole is 12 m, and the excavation stress of the back hole is 12 m. The influence range is within 6 m behind the palm face. With the increase of the step distance, the surface subsidence decreases, and the plastic zone of the tunnel face of the back hole and the vertical displacement above the middle rock column increase. too much impact.