Browsing by Author "Alemayehu, Bisrat"
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Item Evaluation of Weathered Rock Material for Embankment Dam Construction (The Case of Zarema May Day Dam)(Addis Ababa University, 2016-03) Alemayehu, Bisrat; Tadesse, Samuel (PhD)In the construction of many embankment dams rock materials plays a vital role. These rock materials exist at every parts of the world at different stages of weathering which is from residual soil up to fresh intact rock. GW soils (well graded gravels) are the best free draining shell material. Nevertheless, several problems associated with these materials when they are found at highly weathered condition which creates more fines. The most common problems due to these are pore water development in the dam body, shear strength decrement and failure of the shoulder section of the dam. In this thesis, evaluation has been conducted on weathered rock materials at different level using several laboratory tests to determine their suitability for use in embankment dam construction. The laboratory test includes grain size analysis, Atterberg limits, permeability, compaction, specific gravity, Los-Angeles abrasion test and direct shear test. Also field Schmidt hammer test had been conducted. The test result on several samples indicate that as the weathered rock samples produce more fines, the permeability and shear strength of rock decreases. But in recent embankment dam engineering technology there is an approach to design and construct the dam based on the available material on the site without extensive processing. This means accommodating easily accessible materials surrounding the site based on the strength of materials. Also provide technical procedures to following appropriate construction and techniques starting from quarrying up to placement of the material. From samples collected SN-10 is desirable for core of the dam. And SN-1, SN-2 and SN-3 are best to be inner shell and transition filter from the core to the outer shell. Sample no SN-6 and SN-8 are best to be outer shell because they have high hydraulic conductivity (greater than 10-4 cm/s) and helps to stabilize the dam by dissipating pore water pressure. As well as SN-4, SN-7 and SN-9 are better material for inner shell.Item An Examination of the Link Between Tax Administration and Value Added Tax Compliance in Ethiopia(Addis Ababa University, 2010-05) Alemayehu, Bisrat; Chanie, Paulos (PhD)