Delhi Metro Phase III completes TBM excavation 09 Feb 2017

Fig 1. Extent of the Delhi Metro network to date

With the construction of the Delhi Metro Phase III project in India, the Delhi Metro Rail Corporation (DMRC) is ending TBM excavation on one of the largest urban tunnelling projects in the world currently. With more than double the amount of tunnelling of Phases I and II combined, a total of 30 TBMs were used to bore the 80km of running tunnels needed for the Phase III expansion.

Among the machines applied on the project, eight Terratec EPBMs completed 20 drives, for a total length of 18km and for four separate contracts. In addition to providing the largest number of new machines for Phase III, Terratec also provided comprehensive services on site to support the operation and maintenance of the equipment, assisting the contractors in their achievements.

Table 1. Scope of each of the Phases of expansion

Two of these TBMs made a historic double breakthrough, marking the end of tunnelling works on the 58.6km Phase III Pink Line (Line 7) (Fig 1 and Table 1). Indian contractor J Kumar Infraprojects Ltd, working with China Railway Third Group (CRTG), achieved the breakthroughs on Contract CC-24 having completed the final 970m long running tunnel drives between Vinobapuri and Ashram Stations. The 6.61m diameter EPBM shields featured 900kW VFD electric driven cutterheads with a versatile configuration of cutting tools and 17in disc cutters that enabled excavation through mixed face conditions of soil and hard rock. Both TBMs also feature active articulation and two-component grout backfilling systems.

Two 6.61m diameter mixed rock/EPB shields were used on the Contract CC-07 Violet Line (Line 6) Extension by JV Metrostroy of Russia and local firm ERA Infrastructure. The machines encountered unexpected amounts of full face very hard (up to 200MPa) and highly abrasive quartzite, and sections of highly variable mixed faced conditions with numerous large diameter boulders. The Terratec TBMs successfully completed four drives between Jama Masjid and Kashmere Gate Stations.

Earlier in 2015, another two 6.61m diameter mixed rock/EPB shields completed 2.2km of tunnels from Mayapuri to Delhi Cantt on the second Pink Line (Line 7) contract (CC-20) for the J Kumar/CRTG JV.

The final contract (CC-34) on the Magenta Line (Line 8), which was the first Line to be completed in full, was delivered by the Hindustan Construction Company (HCC) and the South Korea Samsung Engineering and Construction Group JV and forms the most westerly section of the new line between Janakpuri and Palam Station. The contractor selected Terratec to design and manufacture two 6.52m diameter EPBMs with a traditional soil configuration, equipped with a spoke-type cutterhead with a 57% opening ratio.

20 Phase III TBM breakthroughs for Terretec in Delhi

The geology along the 3.6km alignment comprised very wet silty clay and dry sandy soil. Both TBMs passed underneath residential areas and came within close proximity to a number of sensitive structures, such as the foundation piles of existing elevated metro stations and a highway flyover. Protecting these structures required accurate settlement control measures.

The performance of the machines was recognised at the breakthrough ceremony. “We are thankful to all our sub-contractors and equipment suppliers. Terratec in particular supplied TBMs that have excavated very smoothly, which has helped to complete the works ahead the planned schedule,” said Raman Kapil, Project Director of the HCC-Samsung JV.