STUDY ON TUNNELING FOR UNDERGROUND METRO RAIL SYSTEM IN DHAKA CITY

In this research, the prospect of tunneling by cut and cover and New Austrian Tunneling Method (NATM) for underground metro rail system in Dhaka city was evaluated. Both conventional analysis and 2D finite element analysis using an elasto-plastic constitutive model named as subloading tij considering plane strain drained condition were performed. A comparison was made between results obtained from conventional analysis and numerical analysis for braced cuts. The behavior of different types of soil layers are simulated. Effects of different loading conditions and presence of water table have been considered for both cut and cover and NATM excavation method. Comparing the results of different foundation types, it has been found that for shallow foundation the surface settlement at the position of the foundation is larger than that for pile foundation. From analyses, it was revealed that for greenfield like Tongi to Uttara along the MRT-4, cut and cover is more appropriate considering its simplicity in execution and NATM is preferable at flyover junction points in Cantonment and structurally obstructed places.