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Bull Eng Geol Environ (2013) 72:339352 DOI 10.1007/s10064-013-0480-9
ORIGINAL PAPER
Geological challenges in constructing the proposed Geba dam site, northern Ethiopia
Gebremedhin Berhane Kristine Walraevens
Received: 28 February 2012 / Accepted: 26 April 2012 / Published online: 6 October 2013 Springer-Verlag Berlin Heidelberg 2013
Abstract It is proposed to construct a dam across the Geba River, Ethiopia. The paper reports the engineering geological investigations undertaken, including mapping, discontinuity surveys, core drilling, water absorption testing and sampling for laboratory tests. The complexity of the site, with limestones and interbedded limestone-shale horizons, is indicated by the variability of the RQD and Lugeon values. Of the 63 tests undertaken, some two-thirds had Lugeon values implying grouting was necessary. Following removal and replacement of the alluvial deposits in the central area, a grout curtain including two to three rows of grouting holes was recommended to a depth of 100 m for the left abutment, 35 m for the central foundation and 60 m for the right abutment.
Keywords Dam site Engineering geological
mapping Geba River Lugeon test Northern
Ethiopia
Rsum La construction dun barrage sur le euve Geba, en Ethiopie, est projete. Larticle prsente les reconnaissances gologiques et gotechniques ralises, comprenant une cartographie, des levers de discontinuits, des carottages, des essais dabsorption deau et des chantillonnages pour les essais de laboratoire. La complexit du site, avec des formations calcaires et des alternances de schistes et
calcaires, se traduit par des valeurs de RQD et des rsultats dessais Lugeon trs divers. Sur les 63 essais Lugeon raliss, environ les deux tiers prsentent des valeurs impliquant des travaux dinjection. Aprs lenlvement et le remplacement des dpts alluviaux dans la zone centrale de la fondation, un cran dinjection constitu de deux trois ranges de forages dinjection a t recommand jusqu une profondeur de 100 m pour lappui de rive gauche, 35 m pour la partie centrale de la fondation et 60 m pour lappui de rive droite.
Mots cls Site de barrage Cartographie de gologie
de lingnieur Rivire Geba Essai Lugeon Ethiopie
du Nord
Introduction
One of the most important environmental issues faced by various countries is the lack of an adequate water supply. It has been estimated that nearly two-thirds of nations worldwide will experience water shortages by the year 2025...