Left: Breakthrough underway
Tunnelling is below historical structures in the densely
populated city. Geology is mainly sand, silt and clay, with some weathered rock. The TBMs have versatile mixed-ground dome-style
cutterheads. The tunnel lining is concrete rings (5+1) of 275mm-thick segments. The works also include construction of diaphragm
walls and entry and exit structures at four locations – Madhavaram Milk Colony, Murari Hospital, Ayanavaram, and Purasawalkam High Road. The project also includes building launch and retrieval shafts at the stations. Over recent months, the Terratec TBMs have achieved
a series of breakthroughs, on the lot: TBMs S98 & S99 bored parallel tunnels from Madhavaram Milk Colony to Venugopal Nagar shaft, slightly to the north; and, TBMs S96 & S97 bored from Madhavaram Milk Colony in the opposite direction, south to Madhavaram High Road.
● In June, TBM S98 (named ‘Anaimalai’) arrived at Venugopal Nagar shaft after a relatively short, 415m-long northbound drive from Madhavaram Milk Colony, starting in February.
● In August, TBM S96 (‘Nilgiri’) holed through at Madhavaram High Road after launch at Madhavaram Milk Colony in October 2022 to drive 1.4km.
● In September, TBM S99 (‘Servarayan’) completed the parallel tunnel to S98, to hole through at Venugopal Nagar after launch in May.
Most recently, in early November, Tata Projects Ltd achieved breakthrough with TBM S97 (‘Podhigai’) at Madhavaram High Road, after a parallel drive to TBM S96. North-to-south, parallel tunnels are complete from Venugopal Nagar shaft via Madhavaram Milk Colony to Madhavaram High Road. Including the length of stations that is 2.5km of the route constructed.
MITHI RIVER IMPROVEMENT MOVES After prior sewerage work in Mumbai, Terratec’s 3.14m-diameter
EPBM moved on to work in the same sector elsewhere in the city, this time on the Mithi River water quality improvement project where through last year its tunnelling work advanced well. Mithi River is part of the oldest river systems in the country but
passing through both industrial and residential zones it is effectively an open sewer for waste. The water quality improvement project is aims to introduce more underground drainage to help reduce pollution load into the river. The refurbished and upgraded TBM (S80) has been driving progressive stages of the sewerage zone of the project, passing through geology comprising mixed ground and basalt. When launched, just over a year ago, it was then currently the smallest hard rock EPBM operating in India. Designed with a fully active articulation system to accommodate a minimum curve radius of 250m, the small diameter EPBM’s cutterhead is equipped with 25 x 17” rear-replaceable cutter discs, and a high torque, high speed hydraulic main drive – chosen due to size constraints, and the installation of a full hyperbaric manlock. The TBM has been erected 1000mm-long precast reinforced concrete rings (4+1 universal) with 200mm-thick segments. The
segments are transported, and muck removal performed, using rolling stock and battery-powered locos also supplied by Terratec. The TBM was previously used on the Mumbai Sewer Disposal
Project (MSDP) Stage 2 Priority Works. It was refurbished and upgraded to undertake the tunnel boring on the Mithi River project, Lot Package IV, where the client is Municipal Corporation of Greater Mumbai. The contractor is a JV of J Kumar Infraprojects and Michigan Engineers Private Ltd (MEPL).
Above: Small diameter rock tunnel EPBM for Mithi River project, Mumbai
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