Karuma Hydropower Project, Uganda: Engineering Geological Analysis and Cost Uncertainty Assessment of Underground Works

Abstract

Karuma Hydropower Project was proposed to stave off prolonged energy shortage in Uganda. The project includes extensive underground works in mostly granitic gneiss bedrock. A first of its kind in the country, the project has suffered persistent funding challenges. A major cost driver for similar projects is uncertainty of engineering geology. In this study, Karuma Hydropower Project?s engineering geology and cost uncertainty arising from it were analysed.From a report of detailed geological investigations for the project; jointing, weakness zones, and distribution and character of rocks were described for each underground component. Thereafter, rock mass quality, rock stresses and their effect on excavation stability, and rock support by Q-method and numerical analysis were evaluated. Possible design improvements and feasibility of using NATM, NMT or TBM tunnelling were also assessed. A sequence for excavation of caverns was proposed as well. Consequently, excavation and rock support costs for the project were estimated; deterministically, and stochastically using Monte Carlo simulation.The study established that the project will be founded in medium quality rock mass (0.1