Sinkholes in Earth Dam Kota Barrage [India]

Abstract

Kota Barrage is the lowermost hydraulic structure amongst the series of four dams built across the river Chambal, a tributary of the river Yamuna in the Ganga Basin. It is situated near the Kota City, Rajasthan in India and is in operation since November, 1960 with an irrigation potential of 679 thousand ha in two adjoining states of Rajasthan and Madhya Pradesh. It comprises of a composite structure consisting of a 268.2m long earth and rockfill dam and a 304.8m long masonry spillway, the total length being 573.0m The earth/rockfill dam abuts in the right against a hillock over which a very old Garh Complex exists and two fort walls intervened in between the spillway and the abutment have divided the dam into three distinct reaches having different foundation sub-strata. The spillway rests on hard quartzitic sand stone with high rock face in the left flank and is provided with 19-radial gates (12 2m x 12.2m each) and 2-under-sluices (2. 7m x 3.3m) to discharge 21240 cumecs at MWL 260.9m. Heavy leakage of water through the bed rock crevices in the adjacent right abutment resting on hillock stope wet spots on downstream edge alongwith repeated settlements and formation of sinkholes on top of the dam has led to a great concern about safety of the dam. Geo-technical investigations carried out recently revealed some lenses/zones with low density soilmass and higher permeability at places in the embankment

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