Investigation On Some Of The Engineering Properties Of Soils Found In Wolenchity Town, Ethiopia

Abstract

Investigation of soil properties at site is a basic prerequisite to economical design of the substructural elements and provides sufficient information for feasibility and economic studies of proposed structures. The causes of failure of engineering structures built on soils are mostly related to misunderstanding of the engineering properties of soil prior to construction. The objective of this research is to investigate the engineering property of soil found in Wolenchity town in order to understand clearly the nature of soils by collecting samples from eight test pits at different parts of the town and laboratory tests were done on the collected samples. The natural moisture content and specific gravity of the studied soils are ranging from 11.72 – 33.58% and 2.60 to 2.70 respectively. The grain size analysis test result showed that the dominant proportion of soil of the research area is sandy and silty soil, which has a fraction of clay 0.92 – 18.54%, silt 3.08 – 59.14%, sand 31.4 – 78.9% and gravel 0.3 – 28.8%. The LL: 25 – 49%, PL: NP – 34.85% and PI: NP –15%. The studied soils are non-swelling soil with free swell with 0 – 25%. According to USCS, four soil types were identified in the study area: ML, SM, SW and SP. The AASHTO Classification System shows that soils of the town are A-2-4, A-3, A4, A-6, A-7-5 and A-7-6. The maximum dry density and optimum moisture content ranges from 1.3 to 1.7 g/cm3 and 17.5 to 31% respectively. The values of shear strength parameters, cohesion (C) and internal friction angle (ф) ranges from 1.41 - 15.95kPa and 21.5 - 30.7º, respectively. Finally one-dimensional consolidation test showed that; the soil under investigation is over consolidated in its natural state, have compression index ranging from 0.17 - 0.22, coefficient of consolidation ranging from 0.023 to 0.132 cm2/min and coefficient of permeability ranging from 0.15x10-8 to 18.16x10-8 cm/sec.