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In-depth Investigation into Engineering Characteristics of Jimma Soils

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dc.contributor.advisor Teferra, Alemayehu (Professor)
dc.contributor.author Jibril, Jemal
dc.date.accessioned 2018-06-26T08:30:48Z
dc.date.available 2018-06-26T08:30:48Z
dc.date.issued 2014-10
dc.identifier.uri http://localhost:80/xmlui/handle/123456789/3626
dc.description.abstract Jimma is located in south-west Ethiopia and is classified as “Weyna Dega” with high degree of humidity. The topography is predominantly flat and rolling terrain. It is mainly covered with black, gray and red colored plastic clay soils. Identification of soils type, classification of soils, and determination of compression parameters and estimation of the soils shear strength is done. Samples of 16 disturbed and 12 undisturbed soils are collected from 8 different test pits. The locations of the test pits are selected so that they can well represent soils found in Jimma town. Disturbed samples are used for grain size analysis, index property, free swell, geochemical and compaction tests whereas undisturbed samples are used for consolidation and undrained shear strength tests. The study shows that the natural moisture content varies from 37% to 68%. The specific gravity varies from 2.58 to 2.82. The soils are categorized as fine-grained soils from which more than 90% of the particle sizes are smaller than 0.075mm. The liquid limits range from 53% to 108% and plastic limits vary from 27% to 41%. According to the Unified Soil Classification System, the soils are categorized as CH-clay with high plasticity (fat clay) with a potential of expansion. And as per AASHTO classification system these soils classified as plastic clay which are unfavorable for subgrade construction. The soil in the study area consists of expansive and lateritic residual soils. From geochemical tests, the silica sesquioxide ratio varies from 1.2 to 1.79 which proves that the presence of lateritic soils. Their Atterberg limits are considerably affected by sample preparation methods for air dried and oven dried and testing procedures such as for 5 minute and 30 minutes mixing time. For black and gray soils their Atterberg limits, free swell and consolidation tests indicate that these soils are expansive. The free swell ranges from 80% to 130% and Swelling pressures vary from 135kPa to 260kPa. The activities of the soils fall within range of 0.58 to 1.43. From different classification schemes, the expansive soils of the area are rated medium to high to very high in their degree of expansiveness. The maximum dry unit weight and optimum moisture content of the studied soils, from compaction test, range from 12.7 to 14.00kN/m3 and from 30% to 37% respectively. For lateritic soils, pre-test drying temperature and test procedures also affect the result of the maximum dry densities and optimum moisture contents. Compression parameters such as coefficient of compressibility extends from 106x10-4 to 241x10-4 m2/kN, compression index ranges from 0.238 to 0.399, swelling index varies from XII 0.0393 to 0.0947, preconsolidation pressure varies from 230 to 300kPa and the OCR is much greater than 2. The coefficient of consolidation extends from 7.24x10-2 to 1.15x10-1cm2/min and coefficient of permeability ranges from 3.64x10-7to 8.24x10-7cm/min. The undrained shear strength of the studied soils ranges from 54 to 157kPa for undisturbed samples, 26 to 90kPa for disturbed samples. The sensitivity of the soils is less than 2, indicating that the soils are less sensitive to disturbance. Tangent modulus and secant modulus of deformation varies from 3750 to19000kPa and 2160 to 6300kPa respectively. Comparison is made for expansive and lateritic soils investigated in this study with previously done researches in other parts of Ethiopia. The comparison shows that the engineering properties of these soils from the study area lie within the range given by different researchers in the other part of the country. en_US
dc.description.sponsorship Addis Ababa University en_US
dc.language.iso en en_US
dc.publisher Addis Ababa University en_US
dc.subject Civil Engineering en_US
dc.title In-depth Investigation into Engineering Characteristics of Jimma Soils en_US
dc.type Thesis en_US

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