TERRATEC’s 3.14m Rock EPB TBM successfully navigates sharp 87m radius curve—a first in India.

TERRATEC has achieved an engineering milestone in India’s infrastructure development with the successful completion of a sharp 87-meter radius curve using its 3.14m Rock EPB Tunnel Boring Machine (TBM S116). This engineering feat was accomplished on the 4.6km-long Priority Sewer Tunnel-Phase 2, part of the Mumbai Sewage Disposal Project, between Goregaon Pumping Station and New Malad IPS, setting new standards for urban tunnelling in constrained environments.

The project posed a significant engineering challenge: to drive a tunnel through a sharp 90-degree curve beneath a busy road junction—without the use of a shaft. The TBM had to maintain millimetre-level precision while navigating just 2.3 meters of clearance between active metro foundation pillars, all during live train operations. It also passed through a section with minimal overburden, encountering highly variable ground conditions, including 95MPa basalt, large boulders, and mixed soils. Additionally, the TBM excavated approximately 500 metres directly beneath a creek and mangrove wetland, managing the substantial risks associated with tunnelling through an environmentally sensitive area with very low overburden.

This achievement was made possible by deploying a purpose-built TERRATEC spherical articulation TBM, supported by a suite of innovative engineering solutions tailored specifically for the project. The team introduced a dual-segment lining system—660mm rings for the sharp-radius curve and 1000mm segments for the straight sections. The excavation of this tight-radius section marks a first for tunnelling projects in India. Key modifications included cutter disc adjustments to enable controlled overcutting, customized rolling stock to accommodate reduced clearances, and a purpose-designed conveyor system engineered to navigate the sharp curvature.

The tight-radius solution offered significant advantages over conventional methods by eliminating the need for Shaft S10 at a congested road intersection near a shopping mall and metro station. This approach prevented major traffic disruptions and resulted in substantial savings in both construction time and cost by removing the requirement for an additional launch shaft.

TERRATEC 3.14m diameter Rock EPB TBM (S116) shares the same design as its sister machine, TBM S80, which previously worked on the MSDP Stage-II Priority Works and is now tunnelling for the Mithi River Water Quality Improvement project. Both TBMs have maintained impressive productivity, averaging 300 rings—or approximately 360 meters—of tunnel advancement per month.

The Mumbai Priority Sewer Tunnel represents a critical component of the city’s wastewater management upgrade, designed to significantly reduce pollution in the Mithi and Oshiwara rivers while enabling advanced water recycling processes. TERRATEC continues to reinforce its leadership in India’s tunnelling sector, building on successful deployments in major metro projects across Delhi, Lucknow, Pune, and Mumbai. This latest achievement underscores the company’s commitment to delivering innovative, customized solutions for India’s unique infrastructure challenges.

source: TERRATEC press release.