Terratec machines achieve four more breakthroughs, this time on Contracts CC-24 and CC-34 of the Delhi Metro Phase III project. Twelve more, for a total of 18 including two already achieved earlier in the year, are scheduled to take place in the coming weeks and months. A total of 20 TBMs, eight of which are being supplied by Terratec, are being used across the whole alignment, which spans 41km underground.
For contract CC-34 between the launch shaft at Vikaspuri Station and Palam Station, via three stations in between, the Hindustan Construction Company (HCC)/Samsung JV is using a total of four machines (two from Terratec) to complete eight drives in total.
After launching in August (2014), a Terratec 6.52m diameter EPBM (S37) machine completed the 675m drive on the down line from Vikaspuri to the cut-and-cover shaft near Janakpuri West Station on September 8. Its sister machine (S36) completed the parallel drive early last month (7 October 2014). The machines will now complete parallel 1,250m drives between Dashrathpuri Station and Palam Station.
The S36 and S37 EPBMs both feature a classic soil configuration and are equipped with a spoke-type cutterhead with a 58% opening ratio designed to minimise clogging. The cutterhead features soft ground tools, but is designed to allow for switch out to 17in roller disc cutters for excavation through D-walls and any unexpected and unmapped underground infrastructure such as old wells or foundations.
For contract CC-24, held by the J. Kumar Infraprojects/China Railway Third Group JV, Terratec has deployed a pair of 6.61m diameter EPBMs (S28 and S26) optimised for mixed conditions that are expected to include some sections of hard rock. This design of machine has been successfully used in earlier phases of the Delhi Metro where quartz rock with a UCS of over 200 MPa has been encountered.
On 30 September (2014) the S28 machine accomplished breakthrough after completing the drive between the Nizzamudin and Ashram stations. The TBM successfully advanced 1,652m without stopping to change cutting tools, following in the footsteps of its sister machine (S25) which completed the parallel drive on August 2 (2014). On 19 October (2014) the S26 TBM working on a different section of Contract CC-24 completed excavation on the down line from the Lajpat Nagar Station to the Vinoba Puri Station, advancing a total of 833m – again without needing any stoppages to change cutting tools.
The latest breakthroughs for Terratec machines follow successful completion of the down line from Jama Masjid Station to Lai Quila Station under Contract CC-07, held by the Metrostroy OS (Russia)/ERA Infra (India) JV, and brings the number of successful breakthroughs for the Australian-based TBM manufacturer on Delhi Metro Phase III, to six.