Robbins Slurry TBM ramps up for Mumbai Metro Line 3

First of two mixed ground machines will begin boring this autumn.

• A Robbins Slurry TBM measuring 6.65 m (21.8 ft) in diameter underwent factory acceptance on September 4, 2017.
• The rebuilt Slurry machine is one of two such machines that will bore contract UGC03 on the Mumbai Metro Line 3 for the Dogus-Soma JV.
• The machines will bore through basalt rock and breccia at water pressures of up to 3 bar using robust cutterheads and slurry piping fitted with abrasion-resistant plating.
• The 33.5 km (20.8 mi) long Line 3 of Mumbai Metro will consist of 26 underground stations and one at-grade station to reduce heavy traffic and rail congestion. 

The first of two Slurry TBMs, a rebuilt 6.65 m (21.8 ft) diameter machine, passed its factory acceptance on September 4, 2017 in Singapore. The machine, fitted with a Robbins cutterhead and outer shields, is destined for the Mumbai Metro Line-3 under contract UGC03 for the Dogus-Soma JV (DSJV), and will begin excavation in late 2017.  The factory acceptance for a second 6.65 m (21.8 ft) diameter Slurry TBM will be conducted by the end of 2017.
The on-time delivery of the first machine is just the beginning of partnership that will span years.  “There are few companies in the international arena that are as professional as Robbins. Robbins has been very helpful to DSJV since the inception of the project and will be our partners until the end of the contract. Robbins’ presence in India including field service crews will be a great help for us in future,” said DV Raju, Senior Vice President, SOMA.
   
The two machines will excavate parallel 3.5 km (2.2 mi) long tunnels between Mumbai Central and Worli station sites, passing through three intermediate cut and cover stations on the way. Ground conditions consist of fresh to weathered basalt and breccia up to 100 MPa UCS with water pressures up to 3 bar. 

The JV selected Slurry machines for their contract due to the challenging ground conditions expected. “I have worked with Slurry TBMs on similar geology globally. Slurry TBMs have real power and will suit the hard rock geology of our Mumbai Metro contract 3. The water table and variable geology, especially basalt of higher hardness, can be easily tackled by Slurry TBMs,” said Tamay Sayin, Project Manager, DSJV. The cutterheads of the machines are fitted with wear protection, wear detection bits, and Robbins 17-inch disc cutters for the conditions. Grizzly bars will limit the size of boulders that can enter the cutterhead to 250 mm (9.8 in). The slurry systems includes rock crushers as well as abrasion-resistant plating in high-wear areas.

The two TBMs are the first of a total of four machines being provided by Robbins for the Mumbai Metro Line-3. Another two 6.65 m (21.8 ft) diameter Crossover XRE machines will bore parallel 2.8 km (1.7 mi) tunnels on a separate contract in 2018. “Mumbai Metro is one of the most prestigious metro works in the country, and Robbins’ involvement in providing suitable machines and associated services is an honor,” said Kapil Bhati, Managing Director, Robbins India.

The 33.5 km (20.8 mi) long Line-3 of Mumbai Metro being constructed by the Mumbai Metro Rail Corporation (MMRC) will consist of 26 underground stations and one at-grade station that will reduce heavy traffic and rail congestion between Bandra and Churchgate areas of the city. A total of 17 TBMs are being procured to bore various sections of the tunnels, which will be excavated at average depths of 15 to 25 m below the city. The entire line is expected to be operational by 2021.