Foundation Assessment: a Case in Megech Dam Project, North-Western Ethiopia
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Date
2020-06-06
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Addis Ababa University
Abstract
Dams are civil engineering structures built to impound large volume of water for different purpose and are built in different sizes, shapes and types. Geotechnical and Engineering geological assessments play a great role in deciding size, shape, type, location and ensure safe performance of dams. The present study was carried out at Megech dam project which is an earth –rock fill embankment type dam with central clay core and is 76m high from the river bed. The study area is located in Amhara National Regional State, in Northwestern Ethiopia about 740 km from Addis Ababa. The main objective of the present study was to carry out geotechnical and engineering geological investigations to address Rock mass quality, permeability and deformability of the rock mass in the dam foundation. Besides, bearing capacity and settlement potential of piles under the intake and conduit outlet works of the dam foundation was also assessed. In addition, effect of groundwater chemistry on submerged piles was also studied.
For the present study systematic investigation was made to address the geological and geotechnical conditions prevailed in the dam foundation. Primary and secondary data was utilized to know the rock mass properties and to classify the rock mass through rock mass rating system. Further, the strength and deformability characteristics of the rock mass were estimated through empirical relations using rock mass rating system (RMR). Rock mass classification, deformability and strength results of the rock mass at dam foundation suggests low quality rock mass on left abutment as compared to the right abutment. In addition permeability of rock mass in dam foundation was assessed based on lugeon test results which indicated necessity of (improvement) grouting in the dam foundation with extensive grouting in the left abutment. The bearing capacity and settlement assessment for piles under conduit and intake structure suggests relatively high allowable bearing capacity for the right abutment as compared to the left abutment. Further, the study also suggests that the piles submerged in water under the intake and conduit outlet works will safely serve their design period without any deterioration resulted from the ground water aggressiveness.
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Rock Mass Rating, Foundation, Bearing Capacity, Permeability, Settlement