INDEX AND ENGINEERING PROPERTIES OF RESIDUAL TROPICAL SOILS OF SOUTHWESTERN ETHIOPIA

Abstract

Civil engineering structures are designed from the knowledge of soil properties at the given site. This research work is for the Investigation of Engineering Properties of Konso town soils. To investigate the engineering properties of Soils found in Konso town, eight test pits were selected based on the expansion potential of the town and the current distribution of the dwellings and buildings according to the municipality of Konso town. The soil samples per pit depth, were collected from pits by direct manual excavation. During field testing, field density and natural moisture content tests were done. The laboratory tests that were carried out include physical properties, index properties, shear strength and consolidation tests. With the aid of these results, analysis were made to determine some characteristics of silty clay soils. To this effect the geotechnical and geo-chemical characteristics of soils sampled from Konso town were investigated. From the results that were obtained for grain size analysis, Atterberg limits and from soil classification systems ), it was found out that the soil dominant in Konso town was found tobe MH .The activity number was below 0.75, which confirmed the soil was inactive. According to the results of this research, Moisture content ranged between 15 - 43%, Plasticity Index between 18.05 – 25.21%, Clay fraction between 33- 57.6, Free swell between 13-43% and Specific Gravity ranges between 2.61-2.86. The shear strength parameters (C, Ф) as determined from UU test ranged between 160.76- 191.34kPa and 10º-12º for saturated sample respectively. Unconfined compression strength (qu) ranged from 245-332 kPa