Construction of new underground infrastructure in dense urban areas presents a significant challenge due to complex ground conditions and the presence of existing building foundations and existing utilities. Selecting an optimal twin tunnel alignment is crucial for minimizing structural damage to surrounding structures. This challenge arises from the surface settlement, where tunnelling activities can potentially damage overlying buildings and utilities within sensitive zones. Accurately determining the magnitude of induced settlements in densely urbanized environments is essential for selecting optimal construction methods and mitigation measures to ensure project success. This study presents a building risk assessment (BRA) based on a vulnerability index in the case of closely spaced twin tunnels of Hanoi pilot metro line N03.