CHARACTERIZATION OF EXPANSIVE SOILS UNDER VARIOUS FIELD CONDITIONS OF SODO TOWN, ETHIOPIA

Abstract

Soil characteristics at a particular location are quite important for the development of safe construction and the life of the structure itself. Hence, the engineering properties of the soil in Sodo town are the considered for this study. According to Sodo town's municipality, twelve test pits were chosen based on the town's potential for growth and the present distribution of the structures in order to examine the engineering qualities of the soils discovered there. The soil sample per pit depth was manually excavated directly from the pits. Natural moisture content and field density tests were performed throughout the field-testing. Physical characteristics, index properties, shear strength, and consolidation tests were among the lab tests that were conducted. These findings led to research that helped identify the characteristics of expansive soils. From the test result that was obtained for grain size analysis, Atterberg’s limit, and soil classification system it was found that the soil dominant in Sodo town was found to be CH and soil under group A-7-6. According to the result of this research, the natural moisture content ranges from 31.7% to 42.2%, specific gravity ranges from 2.6 to 2.79 when oven dried, 2.62 to 2.82 when air-dried, free swell ranges ranges from 78 to 90% for air-dried and 73-86% for oven-dried, the liquid limit ranges from 54.2 to 69.6% for air-dried and ranges from 55.8 to 68.6% for oven dried, the plastic limit ranges from 22.9 to 35.6% for air-dried and ranges from 23.4 to 36% for oven-dried, and the plastic index ranges from 23.5 to 38.1% for airdried and ranges from 23.8 to 37.2% for oven-dried, the optimum moisture content and maximum dry density vary from 1.39-1.55 g/cm3 and 35.7-47.4% respectively, the in-situ density ranges from 1.76-1.97g/cm3 for bulk density and 1.30-1.48g/cm3 for dry density, free swell ranges from 78 to 90% for air-dried and 72 to 86%, based on USCS the soil type felt on MH and CH and based on AASHTO classification the soil type felt on A-7-6 and A-7-5, and the compression index value of Cc ranges from 0.033 to 0.213, recompression index Cr ranges from 0.035 to 0.069 and consolidation coefficient Cv value range (1.685 to 10.189)x10-4cm²/sec and permeability of the soil sample vary from 1.1E-08 to 1.5E-08cm/sec and CBR vale ranges from 2.2 to 9.78% indicated that the study area was fine grain soil. In conclusion, soils found in the Sodo town at newly constructed area were presented as weak in bearing capacity that needs to take intensive attentions for design of foundations.