THE DEPARTMENT OF CIVIL ENGINEERING, INSTITUTE OF TECHNOLOGY, SCHOOL OF GRADUATE STUDIES, ARBA MINCH UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE GEOTECHNICAL ENGINEERINg

Abstract

Finote Selam is located in western Ethiopia and it could be classified as warm-cool commonly called "weinadega" climate conditions. The topography of the city is flat to rolling terrain with red, brownish-red, and yellowish red color was covered. Classification, identification, and prediction of the soil type and their behavior, besides the determination of consolidation parameters, undrained shear strength, compaction parameters, and geotechnical index properties were made. Specimens of disturbed and undisturbed soil specimens were collected from twelve test pits. The location sample area was based on well representative soil found in Finote Selam town. The disturbed specimens used were especially the moisture content, specific gravity, grain size distribution, atterbereg limit, and compaction tests while undisturbed specimens were conducted like Insitu density one-dimensional consolidation and unconfined compressive strength test. From the index properties and engineering behavior the study attribute that the moisture content range from 34.5 % to 48 % the insitu density 1.63 g/ to 1.9 g/ its dry density is 1.22- 1.38 g/cm3 the specific gravity 2.62 to 2.85 the grain size analysis the gravel 0-14.0%, Sand 8.4-25.6% Silt 11.9%-49.2% and Clay in between 28.6% to 67.6%. Hence the dominant type of soil in Finote Selam town was silt and clay with a minimum of 57.2 % the soil was finer than 0.075mm sieve so that the soils were classified as fine-grained. The liquid limit range from 54.9 to 66 %, plastic limit, 18.3 to 47.7 %, plasticity index12.7 to 42.3%, liquidity index, 0.3 to 1.2 %, flow index 2.2 to 90.2 %, and toughness index 0.31 to 1.93 %. According to a unified classification system the soil was classified as CH (clay with high plasticity) and MH (soil of high plasticity silts), in other cases the AASHTO classification system, the soil was classified as A-7-5 and A-7-6. Hence the soil is named clayey soils with poor subgrade strength as per the recommendation of AASHTO the suitability of subgrade streng material. The unconfined compressive strength test value from 127 kpa to 220 kpa ,the value of cohesion varies from 64 kpa to 210 kpa and the remolding sample varies from 125.4 to 132kpa with the soil are stiff and very stiff consistence’s. The one-dimensional consolidation test result shows the compression index range from 0.27 to 0.46, swelling index from, 0.038 to 0.079, the preconsolidation pressure range from 65 kpa to 140 kpa coefficient of consolidation lays between 0.23 to 1.48 and coefficient of permeability range from 0.45 to 3.84 . The various linear regression analyses were made between atterberg limit and compression index was done, the linear regression shows that the mathematical correlation between liquid limit and compression index was strongly correlated hence the correlation coefficient was 0.6244 other than plastic limit with compression index with correlation coefficient 0.1786, plasticity index with compression index with correlation coefficient 0.1899 and liquidity index correlation coefficient of 0.13.