Engineering Characteristics of Red Soil: A Case from Western Addis Ababa, Ethiopia
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Date
2017-06
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Addis Ababa Universty
Abstract
The main objective of this research work was to study the engineering characteristics of red soil in the western Addis Ababa.The engineering behavior of residual soils in the area, derived from the in-situ weathering and decomposition of parent rock, is determined by certain physical characteristics designated as engineering properties. For this work both Primary and secondary data from organizations were in use. In this research work, some peculiar geotechnical and physio-chemical characteristics have been investigated on red soils from western Addis Ababa area. Laboratory test results indicate that the reddish brown materials are grouped under silty clayey and clayey soils. The silica to sesquoxide ratio values for two samples of 0.99 and 1.29 indicate that they are true-lateritic soils.The average values of the specific gravity, liquid limit, plasticity index and activity of clay are 2.56, 63%, 18% and 0.37 respectively. They are soils of medium to High plasticity. Free swell result gives an average value of free swell is 52; this indicates medium potential of expansiveness. The direct shear strength test result gives an average value of Cohesion and angle of Friction respectively as 21KN/m2 and 230. Maximum dry density and optimum moisture content values fall between 1.25 to 1.64 g/cm3and 19 to 34% respectively. From the results of UCS average undrained shear strength gives 140Kpa.From Drilled BH data the soil thickness cross section has been produced which clearly shows that the soil thickness in the study area goes up to a maximum depth of 15m.Generally, the soils are classified as A-7-6 to A-7-5 subgroups of the AASHTO classification and according to Unified soil Classification system classify the soil as MH and CL. Finally, based on the general findings of the study, suitable recommendations have been forwarded. Key words: residual soils, physio-chemical characteristics, index tests, mechanical tests and chemical tests.
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Residual soils, Physio-chemical characteristics, Index tests, Mechanical tests and chemical tests