In engineering projects such as tunnels, dams, foundations, and slope stability, the strength and... more In engineering projects such as tunnels, dams, foundations, and slope stability, the strength and elastic properties of the intact rock affect both the project design and the construction operation. Geological, geophysical and geotechnical study have been carried out for construction of multipurpose hydroelectric power plant at Genale-Dawa (GD-3) on the Genale River with the goal of generating 254 MW of hydroelectric power and providing irrigation water for downstream agriculture. The dam site is located on massive pegmatoidal granites with minimal foundation excavations and minimal grouting requirements. Weathering at the dam site is generally less than about 5 m. In general the Lugeon tests have shown that the rock mass at the dam site is generally tight below 6 m but this could extend to 10 m or possibly more in places. In the power house area weathering extends to about 15 m on the ridge and about 9 m in proximity to the river. This deeper weathering is probably due to the presence of schists within the granites as the foliated schists with significant mica content are more prone to weathering. Point load test, laboratory UCS tests and correlation of P-wave velocity with UCS is considered in assigning the reliable value of rock strength. Combined three input parameters RMR, Q system and RMi system were used for the assessment of the rock mass strength of tunnel and dam foundation. The tunnel will be excavated largely in the pegmatoidal granites with a Rock Mass Classification of ''Very Good'' to ''Good'' This is largely due to the massive, relatively un-jointed rock mass of high strength. There is a section of headrace tunnel, of uncertain length and at the surge shaft in proximity to the outlet portal, where significant proportions of the pegmatoidal granites contain remnants of feldspathic and biotite schists, the Rock Mass Classification of this unit is ''Fair'' to ''Good''. The proposed hydropower project is situated in a geologically favorable environment with very suitable foundation and tunneling conditions. The study lists recommendations in relation to testing and rock classification procedures, which are indirectly related to the safety and quality of the hydropower infrastructure.
In engineering projects such as tunnels, dams, foundations, and slope stability, the strength and... more In engineering projects such as tunnels, dams, foundations, and slope stability, the strength and elastic properties of the intact rock affect both the project design and the construction operation. Geological, geophysical and geotechnical study have been carried out for construction of multipurpose hydroelectric power plant at Genale-Dawa (GD-3) on the Genale River with the goal of generating 254 MW of hydroelectric power and providing irrigation water for downstream agriculture. The dam site is located on massive pegmatoidal granites with minimal foundation excavations and minimal grouting requirements. Weathering at the dam site is generally less than about 5 m. In general the Lugeon tests have shown that the rock mass at the dam site is generally tight below 6 m but this could extend to 10 m or possibly more in places. In the power house area weathering extends to about 15 m on the ridge and about 9 m in proximity to the river. This deeper weathering is probably due to the presence of schists within the granites as the foliated schists with significant mica content are more prone to weathering. Point load test, laboratory UCS tests and correlation of P-wave velocity with UCS is considered in assigning the reliable value of rock strength. Combined three input parameters RMR, Q system and RMi system were used for the assessment of the rock mass strength of tunnel and dam foundation. The tunnel will be excavated largely in the pegmatoidal granites with a Rock Mass Classification of ''Very Good'' to ''Good'' This is largely due to the massive, relatively un-jointed rock mass of high strength. There is a section of headrace tunnel, of uncertain length and at the surge shaft in proximity to the outlet portal, where significant proportions of the pegmatoidal granites contain remnants of feldspathic and biotite schists, the Rock Mass Classification of this unit is ''Fair'' to ''Good''. The proposed hydropower project is situated in a geologically favorable environment with very suitable foundation and tunneling conditions. The study lists recommendations in relation to testing and rock classification procedures, which are indirectly related to the safety and quality of the hydropower infrastructure.
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