Telangana

Anjanagiri Reservoir to be first with GW bund

A view of the earthen bund of Anjanagiri Reservoir of Palamuru-Rangareddy project under construction near Narlapur village of Kollapur mandal in Nagarkurnool district.

A view of the earthen bund of Anjanagiri Reservoir of Palamuru-Rangareddy project under construction near Narlapur village of Kollapur mandal in Nagarkurnool district.   | Photo Credit: Nagara Gopal

Other option was to transport soils over 25 km to reservoir site

When completed, Anjanagiri Reservoir of the Palamuru-Rangareddy project would become, according to engineers, the first water storage facility in the country to have been constructed with a technology that is not tried and tested here.

The reservoir’s earthen bund is being formed with well-graded gravel (GW) instead of the regular well-graded silty clayey gravel (GWC) due to non-availability of suitable casing soils in the vicinity, Executive Engineer (Div. I) of the project K. Vijay Kumar said. “The nearest point where the suitable soils are available is about 25 km to 28 km away and transporting over 100 crore cubic meters of soil from such a distance is not only a costly affair but filled with other challenges too since the vehicles carrying the material would have to cross four villages to reach the reservoir site,” he explained.

The project engineers were left with no choice but to look for alternative material as they have identified the problem during the planning stage itself. “As per the American Civil Engineering Code use of GW soils is allowed, although it has not been used so far in India,” he noted.

Concrete bunds

The options of cement-concrete and rock-fill bunds were ruled out as constructing about 6.5 km length of bund with such material would have jacked up the reservoir cost very high. Besides, transporting such huge quantity of soil would have taken at least two years at the rate of 100 dumper-trips everyday with required trips estimated to be about 6.67 lakh.

However, they had to get the available GW soil, excavated from the reservoir bed by using controlled blasting, tested for its strength when used for construction of a major reservoir bund. Accordingly, they approached the Central Soil and Materials Research Station (CSMRS) in New Delhi and the material was cleared for use. Later, the technology was also vetted by the experts from Tehri dam in Uttarakhand.

No seepage

“Use of the material has already proven its strength as there has been no damage to the bund during the rainy season and there’s no seepage of water too since four-five meters deep rainwater is already logged towards the major portion of the bund,” site engineers and work agency engineers stated.

During a visit to the project works recently, Mr. Vijay Kumar told The Hindu that a level (design) flaw was also detected in time, before the commencement of works, wherein it was noticed that there was a variation of 10 metres to 12 meters in the alignment starting with Anjanagiri reservoir after a 10-metre contour was overlooked by mistake in the toposheets. “Had the mistake been not noticed, alignment of all structures in the project would have gone wrong and failed to serve the desired purpose,” he stated.

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Printable version | Mar 31, 2020 2:17:42 AM | https://www.thehindu.com/news/national/telangana/anjanagiri-reservoir-to-be-first-with-gw-bund/article30676877.ece

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