With almost 5km bored already by the first 10m diameter Robbins shield on the Alimineti Madhava Reddy (AMR) water scheme in India, the partly assembled sister TBM is to start excavation in October after land acquisition delays last year.
The first machine was launched in May 2008 and the second was to have been assembled later in the year, but the programme was setback about a half year. In July, assembly of the second shield was nearly half completed for launch in a couple of months from the inlet end of the tunnel.
Contractor Jaiprakash is using the twin machines to drive a 43.5km water transfer tunnel in Andhra Pradesh state. The TBMs were assembled first-time onsite. Geology comprises layered quartzite and shale, and granite.
On a separate water transfer project in the state – the Pula Subbaiah Veligonda scheme – excavation got underway in late June with the second, and larger, TBM on the project. The Robbins machine was originally earmarked to launch around February but was delayed by heavy wet weather and difficulties with site preparation.
The TBM will drive a 19.2km long tunnel that will run parallel to the 7m diameter bore being excavated by a 7.9m diameter Herrenknecht machine (S-370). The first bore has been underway for about a year. Geology along the alignments comprise quartzite, shale and phyllite.
The larger Veligonda tube will be built by a JV of Coastal Projects and Hindustan Construction Co (HCC). The former is part of a separate JV driving the smaller tunnel. The tunnel are to open in 2014.
