ABSTRACT
UAA01 was an underground tunnel contract package connecting Washermanpet, Mannadi, High Court, Chennai Central, Egmore stations, and the May Day Park shaft in Chennai, Tamil Nadu, India. Completed in 2017 as part of Chennai Metro Rail Limited’s Phase 1 Mass Rapid Transit System upgrade, the project aimed to support the rapidly growing Chennai metropolis and its increasing traffic volumes. This was the first use of metro tunnels for this megacity, which has a population of approximately 6.8 million and an average population density of 16,000 people /square kilometer. Approximately 5.5 km of twin bored tunnels were excavated using five 6.6 m diameter Earth Pressure Balance Tunnel Boring Machines through soft, hard, and heterogeneous ground conditions. This paper discusses expected versus observed conditions, focusing on the encountered geology, challenges faced, and an analysis of Tunnel Boring Machine operational parameters along a 1.32 km reach between High Court and Chennai Central.
