Lowering of two further TBMs into the launch boxes at the Delhi metro last month has taken the total number of machines getting underway on Phase 2 of the project to four, and a further two are due in the ground next month.

Later this year another eight machines are to be launched on the latest stage of the metro project, and excavations by all 14 TBMs are due to be completed by or during 2009, T&TI was told by client Delhi Metro Rail Corp (DMRC).

Last month, the first two of four shields to be used on contract BC-16 between Udyog Bhavan to Green Park were lowered. The two 6.54m diameter Herrenknecht EPBMs (S-411, S-412) were lowered at the INA box and will drive twin 2km long bores.

Next month, two EPBMs from Robbins and Mitsubishi Heavy Industries (MHI) are due to be lowered at the site to drive a pair of tunnels of the same length in the opposite direction. All four machines were built in China.

Geology along alignment comprise sandy silt, silty sand and gravels. The groundwater level ranges from the surface to a depth of 20m. The cover to the tunnels is about 15m, and the EPBMs are to work under 3 bar pressure. The segmental lining (5+1) has two internal diameters – 5.7m and 5.8m.

The contractor on BC-16 is a joint venture of Taiwanese firm Continental Engineering Corp (CEC) and local company Soma Enterprises. Just over a year ago, the JV was awarded a 40 month contract to design and construct the tunnels. In addition, the contractor is to build four stations – Race Course, Jor Bagh, INA and AIIMS – each 318m long.

For contract BC-18 (Hauz Khas-Malviya Nagar), which is being undertaken by Metro Tunnelling Group (MTG), two TBMs were launched last December. Driving from Malviya Nagar, the 6.46m diameter Herrenknecht machines (S-403 and S-404) that were previously used in Phase 1 of Delhi metro will now excavate twin 3km long tunnels.

MTG is a Dywidag International-led JV and it was awarded its 38 month contract in early 2007. The JV members previously worked together on Phase 1 of the metro.

Machines to be launched later this year are: four TBMs on BC-24 by the JV of Ital Thai Developments (ITD) and ITD CEM; two TBMs on AMEL-C1 by the JV of Alpine, Hindustan Construction (HCC) and Samsung; and, two TBMs on AMEL-C5 by the JV of Shanghai Urban Construction (Group) Corp and Larsen & Toubro (L&T).


Two more TBMs were lowered at the Delhi Metro in February TBM assembly at Delhi metro