CMRL TBM breakthrough and launch: tunnelling risk notes for metro engineers
Reviewed by Tom Sullivan
First reported on Tunnels & Tunnelling International – News
30 Second Briefing
TBM Mullai has broken through into Kolathur Station North shaft after a 246 m drive from Kolathur Ramp, negotiating just 1.8 m overburden, a -3.8% gradient and ground protection works beneath heavy traffic. Simultaneously, TBM Kurinji has been launched from Kolathur South shaft to excavate a 1,060 m tunnel to Srinivasa Nagar station through Grade 4–5 rock and a 230 m curve, a first in India for a same-station launch and breakthrough. The works form part of Chennai Metro Phase 2 Corridor 5, a 47 km line with 5.8 km underground and 41.2 km elevated, using four TBMs.
Technical Brief
- Ground protection beneath heavy surface traffic implies pre-support and strict settlement control at station approaches.
- Simultaneous TBM launch and breakthrough in one station shaft demands tight shaft logistics and sequencing.
- Grade 4–5 rock along Kurinji’s alignment will require higher cutter wear management and frequent tool changes.
Our Take
With only 5.8 km of the 47 km Corridor 5 alignment underground, CMRL and Tata Projects Ltd are effectively concentrating complex TBM risk into a relatively short but technically demanding stretch, which often drives disproportionate schedule and cost contingency on metro builds in our database.
The combination of very low overburden (1.8 m) and a -3.8% gradient on this Chennai section is at the more challenging end of urban TBM work seen in recent Infrastructure coverage, suggesting heightened emphasis on settlement control and real-time ground monitoring near surface structures.
Deploying four TBMs on this Corridor 5 section aligns with a pattern in other large Asian metro projects in our database, where multiple smaller drives are favoured over fewer long drives to manage interface risks at stations and ramps and to keep overall programme duration in check.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
Related Articles
Related Industries & Products
Tunnelling
Specialised solutions for tunnelling projects including grout mix design, hydrogeological analysis, and quality control.
Mining
Geotechnical software solutions for mining operations including CMRR analysis, hydrogeological testing, and data management.
QCDB-io
Comprehensive quality control database for manufacturing, tunnelling, and civil construction with UCS testing, PSD analysis, and grout mix design management.