Engineering Geological Appraisal of Dam Foundation for Gumara Dam, Amhara Region, North Western Ethiopia

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Addis Ababa Universty


Gumara irrigation project is being under taken by the Ministry of Water Resources for the development of the agriculture sector of the country. The project envisages the construction of a zoned earth dam for irrigation purpose. The Gumara Irrigation project is found in Northern Ethiopia, Amhara Regional state, south Gondar Administrative Zone. The present research study was planned to investigate the engineering geological suitability of Gumara dam foundation. The study was aimed to determine the suitability of the dam foundation conditions against seepage, and deformation of the foundation material in response to the loads imposed by the dam. Thus, through the present study an attempt has been made to identify the adverse foundation conditions, which may pose problems during or after the construction stage. Based on the foundation conditions certain remedial measures have been worked out. This contributes towards the safety as well as the economic planning and execution of the Gumara irrigation projects. From the review of the previous investigation reports and the investigations made during the present study through the surface, subsurface investigations and laboratory test results an overall appraisal of foundation condition of Gumara Dam has been made. In order to over come the various problems associated with the dam foundation suitable remedial measures have been worked out. From the evaluation of the foundation condition it has been deduced that the rocks on the abutments and the bed rock in the river section are pervious and needs grouting to improve permeability condition. The left abutment slope is kinametically stable for the present geometric configuration however, it may become unstable during the stripping operations if it is cut at steeper angles. On abutments the rocks are weathered and contain wide open joints these undesirable rocks have to be stripped off before laying the embankment. The most serious problem in the foundation section is the presence of thick organic soil strata, which are about 47m thick. These soils are semi-pervious and highly compressible. In order to improve the permeability condition of these soil strata certain preventive and curative measures are suggested. Further, to overcome the compressibility of organic soils some possible treatments have been suggested.



Gumara Dam