Browsing by Author "Samuel Tadesse (PhD)"

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    Improving The Characteristic of Collapsible Soil Using Pumice
    (Addis Ababa University, 2022) Yehamleshet Bekele; Samuel Tadesse (PhD)
    Collapsible soils, which are sometimes referred to as metastable soils, are unsaturated soils that undergo a large change in volume upon saturation with or without loading which pose problem to civil engineering structure. Many researches have been done and variety of methods and techniques have been proposed for improving the engineering property of this soil to make suitable for civil engineering structure built on it. Some techniques used for improving collapsible soils are partial excavation and replacement with compacted fill, dynamic compaction and chemical stabilization. Alternatively, use of other local abundant available pumice material as a means improving is one method which reduce damages on structure. This study was undertaken on collapsible soil sample taken from Ziway-Adamitulu Woreda. The change in engineering properties of this soil investigated with addition of increasing percentage of pumice. Pumice is the most locally abundant available material around the aforementioned area. The preliminary investigation of the soil to be improved initially characterized and classified based on indicative tests and found to be A-4 according to AASHTO and SM class of soil according to USCS systems. Compaction, direct shear, CBR and collapsible potential tests were used to evaluate engineering properties the improved soil. Field density tests also conducted to determine the in-situ densities of the soil. Analysis of the results shows that the collapse index of natural and compacted untreated soil 6.720% with moderate severe disorder soil at bulk and 2.235% with moderate disorder soil at OMC respectively. Treating this soil with pumice reduce collapsible index from moderate disorder soil (2.235%) to slight disorder soil (0.329) % at optimum content of 25 % pumice according to ASTM D5333. Similarly, MDD decrease and CBR, Shear strength and OMC values increased as pumice content is increased. Curing has significant effect on the geotechnical properties of pumice-stabilized soil. Therefore, this experimental result contributes in solving the problems of soil collapse by treating to enhance its resistance.
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    Relationship between Water Content Ratio and Undrained Shear Strength of Fine Grained Soil
    (Addis Ababa University, 2023-07) Tigist Gemechu; Samuel Tadesse (PhD)
    Undrained shear strength of clay soil is a very important feature in geotechnical engineering. Obtaining undisturbed samples and testing them is a tough and time- consuming procedure; any experiment aimed at obtaining correlations between shear strength and consistency limits would be extremely beneficial. In this thesis, efforts have been made to obtain valid correlations between undrained shear strength and Water content ratio (WCR) for saturated soil samples and for unsaturated soil samples suction values were obtained from previous proposed mode of SWCC then suction value and undrained shear strength were correlate. For this purpose, Red clay soil samples collected from different sites in Addis Ababa city at the depth of 3m were used. In addition to collected soil samples secondary data were used. And for each samples Atterberg limits, Specific gravity, Sieve and hydrometer analysis, Compaction tests were conducted beside that by remolding these samples Unconfined Compressive Strength (UCS) tests were conducted. The best fit line, correlation, regression analysis, and comparison were performed using EXCEL. The findings are expected to have a wide range of applications in construction, making it easier for designers to produce a solid, cost-effective, and dependable design.