ABSTRACT
Tunnelling operations in urban infrastructure projects within towns and cities filled with dilapidated, aged structures present unimaginable complexities during execution. The modernization of the old city of Mumbai, through the construction of an underground Metro Project amidst narrow, congested streets and deteriorated residential, commercial, and heritage buildings, posed significant challenges. These difficulties were successfully mitigated through appropriate preparedness and strategic measures. This paper discusses the complications faced and the solutions implemented, leading to the project’s successful completion. The UGC02 Project of Mumbai Metro Line 3 involved the construction of twin tube bored tunnels, Vaitarna-1 (4059m) and Vaitarna-2 (4072m), extending from Chhatrapati Shivaji Terminus (CST) to Mumbai Central, with four intermediary Metro stations situated among high-rises, dilapidated structures, heritage buildings, and important places of worship. A comprehensive geotechnical investigation conducted prior to the project’s commencement enabled an accurate assessment of the geological conditions. An exhaustive evaluation of the 1004 structures within the project’s Zone of Influence proved invaluable in warding off frivolous claims from residents regarding construction-induced damages. Challenges included TBM-induced settlements in a football ground that lacked initial geotechnical investigations due to space constraints, construction-induced vibrations in a subway located in a shallow cover zone, and impacts on various dilapidated structures. Additionally, monitoring water levels in holy wells at a 180-year-old heritage site and addressing related litigations in superior courts were crucial. These issues, along with various frivolous claims and litigations concerning construction-induced damages to dilapidated structures, were tactfully resolved through an extensive Pre-Construction Building Condition Survey, structural audits, and a comprehensive Instrumentation and Monitoring regime. This paper details these occurrences and their timely and effective resolutions.
