Chennai Metro Creates Historic Same Day Dual Tunnel Boring Milestone at Kolathur

Chennai Metro Rail Limited has created a significant moment in India’s urban infrastructure story with a rare engineering achievement at Kolathur. On 29 November, the team successfully completed the breakthrough of Tunnel Boring Machine Mullai at the Kolathur North Shaft after an extremely demanding 246 metre drive. What followed made the event truly historic. Within minutes of Mullai’s completion, the second machine named Kurinji was launched from the very same spot, marking an unprecedented same day dual tunnel operation.

TBM Mullai’s journey was particularly challenging due to the complex geological conditions in the area. The machine had to navigate through a low overburden of just 1.8 metres and manage a steep gradient of 3.8 percent. The site was also surrounded by continuous vehicular movement. Despite these pressures, the team achieved the breakthrough without disrupting public traffic or daily life in the neighbourhood. This accomplishment reflects the precision, planning, and coordination handled by the Chennai Metro Rail engineers and workers.

Immediately after Mullai’s success, TBM Kurinji began its task. Kurinji is designed to tunnel through 1.06 kilometres of hard rocky ground and will pass through a curve stretching around 230 metres. Launching a second machine on the same day and at the same shaft has never happened before in tunnelling projects in India and is rarely reported globally. This remarkable milestone highlights the speed and efficiency with which Phase II works are moving.

These tunnelling activities form an essential part of Chennai Metro Phase II Corridor 5 that stretches over 47 kilometres. The corridor will improve connectivity across important residential and commercial pockets of the city once completed. With such engineering advances, Chennai Metro continues to strengthen its position as one of the most progressive and technologically driven metro rail systems in the country.

This dual TBM milestone is expected to accelerate upcoming tunnelling tasks and stands as a proud moment for Chennai’s urban development journey.