The Hindu : Andhra Pradesh News : All set for work on mammoth irrigation tunnel

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Monday, Mar 24, 2008
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Andhra Pradesh

Andhra Pradesh

All set for work on mammoth irrigation tunnel

N. Rahul

The 135-metre-long Tunnel Boring Machine will excavate world’s longest end-to-end tunnel

PHOTO: P. V. SIVAKUMAR

Gigantic: People gather to have a look at the Tunnel Boring Machine at the Srisailam Left Bank Canal Tunnel Scheme at Mannevaripalli mandal of Achampet in Mahabubnagar district on Sunday.

DEVARAKONDA (Nalgonda dt.): Finishing touches are being given for the kick-start of a mammoth 135-metre-long machine to excavate the world’s longest end-to-end irrigation tunnel through rocky terrain of the Rajiv Gandhi Tiger Reserve near Mannevaripalli village on the Nalgonda-Mahabubnagar border here.

The Tunnel Boring Machine (TBM), as it is called, has been designed and manufactured by The Robbins Company of US who are pioneers in this type of technology. The machine was assembled at one end of the tunnel for the past several months with parts imported from different countries.

Chief Minister Y.S. Rajasekhara Reddy was supposed to formally launch the TBM on Sunday but he postponed his visit to Monday due to incessant rain. It would inch its way slowly on rails to cut the through the rock after final inspection of all components in a few days.

A similar TBM at the other end of the tunnel would move in another seven to eight months. The machines from either ends would excavate 44 km of tunnel in as many months. Each of them costs Rs. 260 crore.

67 cutters

At the head of the machine is a huge circular plate which is fitted with 67 cutters. It will rotate to chisel the rock with a 9.2 metre diameter and proceed ahead. The overburden, including cut pieces of rock and the residue, would be shifted backwards to a dumping point through a conveyor belt. The lining of the caved in area would be taken up with pre-cast segments, said R. Prabhakar Reddy, chief engineer (projects) Mahabubnagar and Anil A. Kamath, senior vice-president, Jaiprakash Associates Ltd, the contracting firm.

3 lakh acres

The 44 km tunnel would be the first part of the Srisailam Left Bank Canal tunnel scheme of Alimineti Madhava Reddy project to irrigate three lakh areas in the drought prone areas of Nalgonda district. This one and another tunnel of seven km carry 4,000 cusecs of water through gravity from the foreshore of Srisailam reservoir.

No disturbance

Since Tunnel I would be crossing the wildlife sanctuary and the tiger reserve, it was proposed to be executed with TBM technology to avoid disturbance to animals. The noises of TBM would get muffled and were non-perceptible on ground.

Tunnel II which passed through plains would be executed with the conventional drilling method.

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