Surface Settlement Induced by Excavation of Double-Line Shield Tunnel

Abstract

AbstractIn the construction of the Harbin Metro Line 3 twin-bore tunnel project, the ABAQUS numerical simulation method was employed to investigate the impact of various grouting thicknesses, burial depth ratios, tunnel spacing, and excavation pressures on the geological conditions of the project. Corresponding construction control measures were proposed. The study revealed: (1) Grouting thickness is inversely proportional to ground settlement, with an optimal thickness of 0.3 m; (2) Lateral ground settlement increases with an increasing depth ratio, showing an initial increase followed by a decrease, closely related to soil arching effects; (3) As the distance (L) between two parallel tunnels increases, the peak ground settlement of the left and right tunnels decreases. Smaller tunnel spacing leads to stronger mutual interactions, resulting in a “V”-shaped settlement deformation within the overlapping disturbance zone. When the tunnel spacing is sufficiently large, the mutual interference between the two tunnels diminishes, and the ground settlement deformation is considered the superimposition of two independent tunnel settlements, forming a “W”-shaped settlement trench; (4) Excavation pressure exceeds the static soil pressure, causing soil disturbance, leading to an uplift of the soil in front of the tunnel face and an expansion of the plastic zone in the surrounding soil, ultimately resulting in increased subsequent surface settlement.