Tunnel Analysis of Dhaka Subway using PLAXIS 2D Considering Different Groundwater Level Conditions

Abstract

Dhaka subway, which will be an underground structure is being considered to combat the rising congestion in the city. As the city is very congested special consideration must be given to ground movement and surface settlement during the planning of the subway. Also, the rise in water level as the city moves away from groundwater for its water supply must also be taken into consideration for the long-term design of the tunnel. In this study, 2D finite element analysis was carried out using Plaxis 2D. Different soil profile representing different areas of the Dhaka city was considered and the surface settlement due to tunnel excavation was investigated. It was found that as the depth of the tunnel excavation increases the surface settlement decreases and the settlement trough becomes wider. Also, the volume loss and the grouting pressure required for a specific surface settlement after the tunnel was constructed was also studied and it was found that both volume loss and grouting pressure required increases with the depth of the tunnel. And also, the lining stresses of the tunnel considering different groundwater conditions was analyzed. It was found that as depth of tunnel increases the axial forces experienced by the tunnel lining increases. Also, the axial forces, bending moments and shear forces mostly increases as the ground water level increases in the future.