In the Indian metropolis of Mumbai, a new metro line is currently under construction. It is aimed to improve traffic and rail congestion of the city. In this giant project, The Robbins Company has been entrusted with parts of the tunnel boring work. To do the job, Robbins relies once again on Liebherr‘s proven main bearings.
Starting in June 2018, the twin Robbins Crossover TBMs began to bore parallel 2.8 km (1.7 mi) long tunnels. The twin 6.65 m (21.8 ft) machines combine features of a hard rock single shield TBM and an earth pressure balance machine and are ideal for application in mixed geology. They are able not only to bore in hard rock, but also operate in soft ground, using a screw conveyor at each machine’s centerline with a bulkhead gate and discharge gate. The mixed grounds in Mumbai consist of basalt, shale, tuff and breccia, as well as possible water pressures of up to 2 bar. Such mixed geology pose particular challenges to both machines and material. This, in turn, places high demands also on the components in the tunnel boring machines.
Liebherr main bearings are specially designed for high continuous loads and reliable, fail-safe drilling. “Liebherr is more than a supplier, Liebherr is a partner we can depend on to supply the most critical components on our machine”, says Mike Kolenich, Director of Supply Chain at Robbins.
The three-row roller bearing with a diameter of 2,640 mm (114 in.) ensure an even rotation and a stable load transmission on the cutter shields to achieve highest bore quality. Also, the ring gear was supplied by Liebherr for the project, measuring the diameter of 1,924 mm (76 in.).
“In general, Liebherr has provided an excellent product within the schedule restrictions given by the customer. We visited Liebherr facilities in Germany and remained impressed with the overall organization of the production line, the clean and efficient working environment and the customer service provided,” explains Matias Iovine, Project Manager Mumbai Metro at Robbins.
The most recent breakthroughs for the two Crossover machines were on Oct. 3 and Oct. 22, 2019, when they completed 499 m of tunneling between Vidhan Bhavan and Churchgate stations. Starting from Jan. 25 and Feb. 15, 2020, respectively, the machines are now boring their third drive and are expected to break through in May 2020 on a 700 m drive.
The project is expected to be fully operational in December 2021.