Mumbai's biggest TBMs prepare for tunnel work

ANI Mumbai's proposed Coastal Road extension through the western suburbs has moved a step closer, with two massive tunnel boring machines (TBMs) being prepared to excavate twin underground road tunnels between Kandivli and Malad. The machines, which will bore through hard basalt rock nearly 40 metres below the surface, are undergoing testing at a manufacturing facility in Chennai before being transported to Mumbai. The 3.9-km twin tunnels will form a crucial part of the Brihanmumbai Municipal Corporation's (BMC) ambitious Versova-Dahisar Link Road (VDLR), also known as Coastal Road (North). Once completed, the four-lane tunnels in each direction are expected to provide a faster route for motorists travelling through Mumbai's western suburbs and reduce dependence on the congested Western Express Highway. With cutterhead diameters of 15.6 metres, the two TBMs are among the largest machines of their kind to be deployed for a road tunnel project in India. The machines are being assembled and tested at the Herrenknecht India Private Limited facility in Chennai, where a team of BMC officials recently conducted a factory acceptance test (FAT) on one of them, according to a report by TOI. Read more - Passengers climbing through train windows, some travelling in toilets, others waiting 12 hours in queues: Railway stations witness unprecedented Diwali-Chhath chaos Mumbai Coastal Road: What is the 22-km Versova-Dahisar Link Road project? The Coastal Road (North), or Versova-Dahisar Link Road, is a proposed 22-km transport corridor connecting Versova and Dahisar. The project will comprise a combination of ground-level roads, elevated stretches, roads on stilts, a cable-stayed bridge and a cut-and-cover tunnel beneath a creek. The twin underground tunnels between Mindspace in Malad and Charkop Creek are among the most significant components of the project. They are being constructed under two separate packages, C and D, each covering a 3.9-km stretch. Live Events Package C will accommodate the northbound tunnel from Mindspace, Malad, towards Charkop Creek, while Package D will cover the southbound tunnel from Charkop Creek to Mindspace. Together, the tunnels will provide four lanes of underground road connectivity in each direction, forming part of the proposed signal-free Versova-Dahisar corridor. Mumbai's 15.6-metre TBMs undergo factory acceptance tests in Chennai The two tunnel boring machines will undertake the challenging task of excavating the underground stretches. With a cutterhead diameter of 15.6 metres, they are among the largest TBMs being deployed for a road tunnel project in India. A team of BMC officials recently visited the Herrenknecht India Private Limited plant in Chennai to conduct a factory acceptance test on one of the machines. The inspection covered several critical components and operating systems, including the cutterhead rotation, shield mechanism, grouting system, pressure levels and thrust jacks responsible for pushing the machine forward. Officials also examined the segment-lifting mechanism and the machine's mechanical and electrical systems. "We inspected all the machine parameters, including the rotation of the cutterhead, functioning of the shield, grouting system, pressure levels and thrust jacks that propel the TBM forward, as well as the segment-lifting mechanism," a civic official told TOI. The team also checked the ventilation arrangements, air pressure systems, operator cabins and control cabin, which monitors pressure levels across the machine. TBM machines to be transported from Chennai to Mumbai on 100 trailers The massive machines were manufactured in Germany, with their components shipped to Chennai for assembly at the factory. Each fully assembled TBM measures approximately 87 metres in length. However, transporting the equipment to Mumbai will involve a separate logistical exercise. The machines will be dismantled and moved in parts on an estimated 95 to 100 trailers. Their components will be transported in phases, in coordination with the progress of excavation work at the tunnel-launching site. The BMC faces space constraints along the project alignment, leaving limited room to store the large components before they are assembled at the construction site. "There is little space to store the machines' large components along the alignment. This differs from the south Coastal Road project, where reclaimed land provided some room to handle and store construction material," a BMC official told TOI. The logistical challenge is further complicated by the alignment passing through creek and mangrove areas, where limited working space and difficult ground conditions have added to construction complexities. Mumbai Coastal Road tunnel construction: TBM launch scheduled for May 2027 Preparatory work for the underground tunnels is already under way at Charkop, where construction of the launching shaft began in August. The shaft covers an area of approximately 31 metres by 120 metres and will serve as the starting point for the TBMs. The machines are scheduled to begin tunnel boring in May 2027. Before excavation starts, they will undergo another round of site acceptance tests after being transported to Mumbai. Unlike factory testing, these checks will assess the machines under actual ground and operating conditions, which cannot be fully replicated at the manufacturing facility. Each tunnel will have a finished internal diameter of 14.2 metres. Of the total 3.9-km stretch, approximately 3 km will be excavated using TBMs, while the remaining 900 metres will be constructed through the rectangular cut-and-cover method. The excavation will be particularly challenging because of the geological conditions beneath Mumbai's western suburbs. Hard basalt rock poses challenge for Mumbai's underground road tunnels The tunnel alignment passes through Mumbai's Deccan Trap geological formation, which largely comprises basalt, a dense volcanic rock created by the cooling of ancient lava flows. Basalt can be extremely hard and abrasive, making excavation a demanding process. Variations in the rock's composition, hardness and degree of weathering could further influence the speed and complexity of tunnel boring. The presence of creek and mangrove areas along parts of the alignment adds another layer of difficulty for engineers. Space constraints and the possibility of encountering unexpected geological conditions will also need to be addressed during construction. The BMC has appointed Megha Engineering & Infrastructures Ltd (MEIL) as the contractor for this stretch of the project. Will Mumbai Coastal Road extension reduce traffic on Western Express Highway? The proposed Versova-Dahisar corridor is expected to improve connectivity across Mumbai's western suburbs and provide motorists with an alternative to some of the city's busiest roads. Dhaval Shah of the Lokhandwala Oshiwara Citizens Association said the project could reduce travel time and ease congestion on the Western Express Highway. However, the proposed infrastructure has also raised environmental concerns, particularly over its impact on mangrove cover along the alignment. Environmentalist Mili Shetty has flagged the potential loss of mangroves in the project's influence zone. Of the approximately 60,000 mangroves in the area, around 45,000 are expected to be impacted, while approximately 9,000 are likely to be permanently felled. She has expressed concerns that the loss of green cover could result in increased noise and air pollution in surrounding areas. Civic officials, meanwhile, have said compensatory afforestation will be undertaken in Bhayander and Chandrapur, near the Tadoba forest area. Inputs from TOI Add as a Reliable and Trusted News Source Add Now! (You can now subscribe to our Economic Times WhatsApp channel ) Read More News on Mumbai Coastal Road project Versova Dahisar Link Road Mumbai twin tunnel project Mumbai TBM