Serious flood setback for TBM project in India
  • Herrenknecht
Serious flood setback for TBM project in India Oct 2009
Shani Wallis, TunnelTalk
Assembly of the TBM was complete and launch was just a week away when disaster struck. An overtopping of the cofferdam completely flooded the inlet portal working site of the AMR tunnelling project near Hyderabad in India. Exceptionally heavy rainstorms charged the levels in the chain of Srisalem Reservoirs leading to rises in water levels by up to 3m in a short period of time.
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    • Pumping out of the flooded cofferdam slowly reveals the submerged TBM

Although at the end of the rainy season in India, the rainfall was unprecedented and called for emergency management of the water levels in the reservoirs. Opening release gates to control levels in an up stream dam contributed to extra charging of the downstream reservoir and overtopping of the tunnel site cofferdam submerging the full site, the TBM and all to be seen to the top of the site's gantry cranes.
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    • The inlet site and starter tunnel before assembly of the TBM and the flooding storms

There was a flood at the outlet working site as well but with less serious consequences. The machine working from the outlet is well into its long drive and the 1.5m of water flooded the TBM launch pit and working site. The site office and workshops at the outlet portal were also flooded and everything was covered in think red silty mud when the water subsided. Access to the job site was cut off for a few days because a river to be crossed on the access road was impassable.
The two 10m Robbins TBMs are driving the 43.5km long water deliver tunnel as part of the vast AMR water supply and irrigation project in the normally drought stricken Andhra Pradesh State of central India.
Pic 3a

Assembled TBM ready to start

The storms occurred on Wednesday September 30. Since then the upstream site inside the cofferdam has been pumped out and the work of cleaning the mud off the wrecked TBM has started. At the outlet portal, once flooded electrics and the working area were restored, TMB production was underway again to take the shielded rock TBM and its precast concrete lining beyond the 5km mark.
News confirms that the outlet TBM is going well with the TBM now 5,150m into the drive and working through hard quality rock. Launch of the TBM at the upstream portal was delayed by late delivery of the access road to the TBM assembly and working site. The flood is an added serious setback. Along with cleanup and recovery of the upstream TBM, communications start with the insurance companies.
TunnelTalk made a visit to the project last year but didn't get to travel to the far inlet portal site. Access through the region is difficult and this is a hard blow for large scale project in such a remote location.
References
Robbins reintroduces TBM advantages to India at AMR - TunnelTalk, Jan 2009

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