Geological and geotechnical investigations of Loharinag-Pala Hydroelectric Project,Garhwal Himalaya,Uttarakhand |
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| Authors: | Ajay K Naithani A K Bhatt K S Krishna Murthy |
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| Institution: | (1) National Institute of Rock Mechanics, Kolar Gold Fields, 563 117, India;(2) Water and Power Consultancy Services (I) Ltd., Gurgaon, India;(3) 928, 22nd Main Road, IV T Block, Jayanagar, Bangalore, 560 041, India |
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| Abstract: | The project area, forming a part of Bhagirathi valley, exposed rocks classed as central Himalayan crystallines and are medium
to high grade metamorphics. The rock types exposed are feldspathic gneisses, quartz-biotite schists, garnet-biotite schist,
biotite gneisses, migmatites and amphibolites. To design the rock support for the underground structures of desilting chambers,
HRT, surge shaft, pressure shafts, power house, TRT and for the foundations of barrage and intake of desilting chambers, rock
mass classifications was attempted following the methods of Bieniawski Rock Mass Rating (RMR) Classification and Tunnelling
Quality Index (Q) of Barton et al. RMR technique involves collection of data on rock strength, RQD (%), spacing of discontinuities,
condition of discontinuities and groundwater condition, while the ‘Q’ involves collection of data on RQD (%), joint set numbers
(Jn), joint roughness number (Jr), joint alternation number (Ja), joint water reduction factor (Jw) and stress reduction factors
(SRF). The permeability test in the overburden was done by the constant head method, while in the bed rock portion conducted
by packer test. The result indicates that the rock masses of the area fall under the good, fair and poor rock quality. Augen
gneiss of power house area is coming under the category of moderately strong rock as proved by deformability characteristics
and strength parameter. On the basis of above study recommendations have been made for the proper and safe construction of
the project components. |
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| Keywords: | Hydroelectric Rock Mass Classification Tunnel Quality Index Garhwal Himalaya Uttarakhand |
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