Abstract:

Twin parallel mined water conveyance tunnels cross underneath existing Wukesong Metro station. The centertocenter distance between the twin tunnels is 94 m and the distance between the crown of the twin water conveyance tunnels and the floor of the Metro station is 3717 m. Therefore, the twin water conveyance tunnels will be excavated in close proximity to the existing Metro station. In the paper, the full course of the excavation of the twin water conveyance tunnels is simulated by means of 3D finite element method, so as to ensure the safety of the existing Metro station and tracks during the excavation of the twin water conveyance tunnels. The analysis on the trend of the displacement of the ground surface and the roof and floor of the existing Metro station demonstrates that the enlarged section of the water conveyance tunnels, the grouting tunnel and the soil mass surrounding the water conveyance tunnels should be reinforced by means of grouting, so as to constrain the displacement of the ground surface and the Metro rails under the specified limits. It is also proposed that symmetrical construction should be carried out on both sides of the Metro station so as to minimize the torque on both sides of the Metro station caused by differential settlement.

Key words: water conveyance tunnel, Metro station, construction in close proximity to existing structure, numerical simulation, mining method, grouting