Delhi Metro has reached a significant milestone in its Phase IV expansion with the successful breakthrough of an underground tunnel on the Aerocity-Tughlaqabad corridor, also referred to as the Golden Line. The tunnel connecting Maa Anandmayee Marg and Tughlaqabad railway colony station was completed early Saturday morning, marking the excavation of a 0.79-kilometre stretch using an advanced tunnel boring machine (TBM).
The breakthrough was achieved by deploying a colossal 96-metre-long TBM designed to bore two parallel circular tunnels facilitating seamless up and down metro movement. While this first tunnel has been completed, the parallel tunnel is projected to reach breakthrough by July 2025, continuing the robust expansion of the metro network in the national capital region. This underground infrastructure was constructed at an average depth of approximately 18 metres below the surface. Throughout the tunnel’s length, about 566 precast concrete rings were meticulously installed, forming an inner diameter of 5.8 metres. These precast rings were manufactured in a state-of-the-art, fully mechanised casting yard in Mundka, employing a steam curing system that ensures early strength and durability. The tunnel itself was constructed using the earth pressure balancing (EPB) technique, a technology well-regarded for its ability to maintain ground stability and protect existing urban infrastructure.
Safety and structural integrity remained paramount throughout the project. According to senior officials overseeing the construction, sophisticated monitoring instruments were installed on neighbouring buildings to detect any potential ground movement. The continuous data confirmed that there was no settlement or structural disturbance during tunnelling, an achievement critical in densely populated urban zones. Phase IV of the Delhi Metro development involves the construction of over 40 kilometres of underground lines. The Aerocity-Tughlaqabad corridor alone comprises nearly 19.34 kilometres of subterranean rail, highlighting the extensive scale and complexity of this project. The corridor promises to enhance connectivity significantly, providing commuters with improved access to key commercial and residential hubs while easing surface traffic congestion.
Tunnel boring machines have transformed urban rail infrastructure projects worldwide by enabling the excavation of tunnels beneath cities with minimal surface disruption. TBMs are capable of traversing a variety of soil and rock strata, from soft alluvium to hard rock, making them indispensable in complex metropolitan tunnelling projects. For a city as densely populated as Delhi, TBMs offer a sustainable and eco-friendly alternative to traditional open-cut excavation, preserving urban landscapes and reducing carbon emissions associated with construction activities. Delhi Metro Rail Corporation (DMRC) has been a pioneer in adopting this technology since Phase I of the metro’s inception. During Phase III, approximately 50 kilometres of underground lines were constructed with the deployment of nearly 30 TBMs. This continued utilisation underscores DMRC’s commitment to sustainable urban transit infrastructure, leveraging technology that minimises environmental impact while maximising construction efficiency.
The expansion of the metro network is integral to Delhi’s vision of becoming a zero-net-carbon city, where public transport plays a crucial role in reducing vehicular emissions and urban pollution. The underground corridor developments not only expand mass rapid transit options but also contribute to equitable urban mobility by connecting diverse neighbourhoods and improving accessibility for all demographics, regardless of gender or economic status. Experts involved in the project emphasise that such infrastructure developments must balance engineering excellence with social and environmental responsibility. The continued use of TBMs reflects an approach aligned with eco-friendly construction practices, including reduced noise pollution and less surface disruption, critical to maintaining the city’s livability during expansive infrastructure projects.
Looking ahead, the successful breakthrough on the Aerocity corridor signifies strong progress in the overall Phase IV rollout. Once completed, this corridor is expected to alleviate congestion on existing lines and provide a seamless travel experience to millions of daily commuters, supporting Delhi’s ambitions of sustainable urban growth and carbon neutrality.
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