Engineering geological investigations of surge pool and pump house (5 X 130 MW) area of Pranahitha - Chevella Sujala Sravanthi Lift Irrigation Scheme- 08, Karimnagar district, Andhra Pradesh

Underground surge poll (350 L x 20 W x 54 m H) and pump house (150 L x 25 W x 60 m H) of Pranahitha-Chevella Sujala Sravanthi Lift Irrigation Scheme-8 is proposed to lift the water into Mothevagu reservoir. The surge pool and pump house area was investigated through detailed engineering geological traverse mapping, exploratory drilling and laboratory testing. The rock mass properties, i.e. joint sets, weathering grade, RQD, RMR etc. of the rock masses to be encountered during the excavation of surge pool and pump house have been analyzed in detail. Core samples from the exploratory drill holes drilled at the surge pool and pump house area were tested for physico-mechanical properties of rocks in the laboratory. The mapping details indicated that surge pool and pump house will be excavated through fresh, coarse to very coarse grained, hard and jointed granites. Classification of rock mass using Rock Mass Rating (RMR) of Bieniawski (1989) and Tunnelling Quality Index ‘Q’ of Barton, et.al. (1974) was attempted. On the basis of detailed investigations and laboratory testing, inferences and recommendations have been made which will be helpful during the construction of these underground cavities.