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Mixed ground success for Terratec in Delhi19 Aug 2014

TunnelTalk reporting

Terratec completes the first two of 18 breakthroughs scheduled to be accomplished by its machines in the coming weeks and months on the Delhi Metro Phase III Project.

Second breakthrough for Terratec at Ashram Station
Second breakthrough for Terratec at Ashram Station

The Australian-based TBM manufacturer has supplied eight of the more than 20 machines for the project, with the first S23 machine completing excavation of the down line from Jama Masjid Station to Lai Quila Station (Contract CC-07). The breakthrough ceremony was held in the presence of contractor representatives from the joint venture between Metrostroy OS of Russia and ERA Infra of India, together with representatives of the client, DMRC.

Three days later, on August 2, the S25 TBM working on Contract CC-24 (held by the J. Kumar Infraprojects (India)/China Railway Third Group (China) JV) accomplished breakthrough at Ashram Station at the end of a 1,665m drive from Hazarat Nizamuddin Station. That machine will now advance from Ashram Station to Vinoba Puri Station.

The S23 and S25 EPBMs are 6.61m in diameter and feature a 900 KW VFD electric-driven cutterhead. They are of a versatile design designed to cope with a predicted geology of soft ground, as well as sections of mixed ground/rock. Both machines can be fitted with up to 33 x 17in roller disc cutters for rock sections, and both have active type articulation and two-component grout backfilling systems.

450mm boulders on CC-07 drive
450mm boulders on CC-07 drive

Geology encountered to date on the CC-07 contract includes large quantities of very hard (up to 200 MPa) and very abrasive quartzite. In addition to sections with a full face of rock, there have also been encountered sections with very variable mixed ground conditions with numerous large diameter boulders.

Work will continue through 2014 for scheduled completion in 2015. Two more Terratec machines, operating on behalf of the Hindustan Construction Company (HCC, India)/Samsung (Korea) Joint Venture (Contract CC-34), have just launched on parallel 675m drives between a launch shaft at the end of the underground section of the Phase III alignment, back towards Janakpuri Station. Upon completion these machines will then be transported further down the CC-34 contract section to complete further parallel tunnels of 1,250m between Dashrathpuri and Palam stations.

Some 41km of the 140km Phase III works run underground, and unlike Phases I and II, Phase III concentrates on the outer lying areas of the city and on connecting the long radial lines created by the earlier phases of works.

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