Research Article
Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia
Kirubel Molla Bazezew
,
Wahaj Khan,
Belay Sitotaw Goshu*
Issue:
Volume 1, Issue 2, June 2026
Pages:
110-131
Received:
5 February 2026
Accepted:
24 February 2026
Published:
5 March 2026
Abstract: The Legeoda Dam project, proposed in eastern Ethiopia’s Dire Dawa region on the Halo Busa Lege Odamirga watershed, aims to provide irrigation water for downstream agricultural development. This geotechnical feasibility study addresses foundation challenges associated with deep tropical weathering of Oligocene flood basalts overlain by uniform alluvial deposits. Twelve boreholes along the 520 m dam axis, supported by extensive laboratory testing (index properties, shear strength, compressibility, permeability) and in-situ SPT, revealed a consistent stratigraphic sequence: 1.5 m topsoil, 2.5 m clay, 4.0 m sandy silt, 7.0 m highly weathered basalt, 10.0 m fractured basalt, and sound basalt below ~25 m depth. Key findings include uniform overburden thickness (39.9–40.1 m), progressive strength increase with depth (SPT N = 5.5–78.8), high untreated settlement potential (6251 mm), and significant seepage risk through fractured basalt. Seepage, stability, and settlement analyses confirmed technical viability following targeted foundation treatment. Novel contributions include quantitative risk-based treatment optimization and cost-benefit evaluation specific to Ethiopian basalt terrains, demonstrating benefit-cost ratios exceeding 3.0 for integrated cutoff and grouting measures. The study concludes that the site is highly suitable for a zoned earth-rock embankment dam with standard foundation improvements. Recommendations emphasize deep cutoff penetration into sound basalt, selective grouting, and comprehensive instrumentation. This work advances sustainable dam development on flood basalt foundations in rift-margin settings.
Abstract: The Legeoda Dam project, proposed in eastern Ethiopia’s Dire Dawa region on the Halo Busa Lege Odamirga watershed, aims to provide irrigation water for downstream agricultural development. This geotechnical feasibility study addresses foundation challenges associated with deep tropical weathering of Oligocene flood basalts overlain by uniform alluv...
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Research Article
Geological and Geochemical Characteristics of
Quartz-Feldspar Pegmatites in Southern Ethiopia
Mitiku Tamene*
Issue:
Volume 1, Issue 2, June 2026
Pages:
132-141
Received:
16 January 2026
Accepted:
24 February 2026
Published:
14 March 2026
DOI:
10.11648/j.sdenv.20260102.12
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Abstract: The Kenticha pegmatite field, located within the Neoproterozoic Adola Belt of Southern Ethiopia, represents one of the most significant rare-element mineral provinces in the East African Orogeny. Tantalum was exploited from weathered regolith before and also produced the huge reserves of feldspar, quartz and lithium from underlying hard-rock bodies. This study presents the geology properties and evaluating economic potential of five major veins (No. 1-5) through a multi-disciplinary approach including field geological mapping, core logging, and geochemical characterization. Major and trace element concentrations were determined using X-ray Fluorescence (XRF) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), while mineralization phases were defined by X-ray Diffraction (XRD). Geochemical analysis demonstrates that the pegmatites are classified as the Lithium-Cesium-Tantalum (LCT) family and the spodumene subtype, and characterized by extreme magmatic fractionation. Fractionation indices, notably the K/Rb ratio, exhibit a systematic decline from approximately 36 in the granitic wall zones to 19–20 in the highly evolved spodumene-rich upper intermediate zones. Quantitative assessments of industrial mineral quality reveal SiO2 averages of 67.3% and Al2O3 contents of 17.2%, with subsurface Fe2O3 levels consistently below 0.1%. These values comply with ISO 13006 Group BIa standards for the international glass and porcelain industries. Economic reserve estimations, calculated based on the 1:5000 geological map and strike tracing, assumption 2.7 million tons of high-grade feldspar and 7.2 million tons of quartz. Additionally, the discovery of 87.7 million tonnes of lithium ore at 0.78% Li2O underscores the deposit's strategic importance. The report concludes with recommendations for an integrated multi-mineral extraction strategy to drive Ethiopia’s industrialization and green energy supply chain.
Abstract: The Kenticha pegmatite field, located within the Neoproterozoic Adola Belt of Southern Ethiopia, represents one of the most significant rare-element mineral provinces in the East African Orogeny. Tantalum was exploited from weathered regolith before and also produced the huge reserves of feldspar, quartz and lithium from underlying hard-rock bodies...
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