INVESTIGATION ON SOME OF THE ENGINEERING AND INDEX PROPERTIES OF TROPICAL RESIDUAL SOIL IN SOUTHERN ETHIOPIA (THE CASE STUDY OF SAWLA TOWN

Abstract

ABSTRACT Tropical Residual soils are formed from rock or accumulate organic material &remain at the place where they are formed, it usually formed chemical or physical weathering& eventually cover parent rocks can have characteristics that are quit distinctively different from those of transported soils in which the conventional concept of soil mechanics is not applicable to many tropical residual soils as it consists of aggregates or crystals of weathered mineral matter that break down and become progressively finer under continuous manipulation. In this thesis work both index and engineering properties of tropical residual soil have been investigated on the soil specimen by the test procedures recommended for tropical residual soils. Generally it was found that sample pre-test treatment and energy application alter the result of SAWLA town soil. Comparison between the moisture content determined using air drying (or alternatively 500C oven drying temperature) and that of 1050 C oven drying temperature indicate that there no significant of structural water. Analysis of specific gravities of the soils using varios pretreatment and testing procedure showed that, increase in drying temperature reduces specific gravity of the soils In the analysis of Atterberg Lmits, the majority of the soils difference was observed between the Atterberg Limits obtained from test on the specimen mixed for 5min and that of 30 min, this indicates that the cementation of the clay particles is to be disaggregate with higher mixing time.. One-dimensional consolidation test showed that the area under investigation is over consolidated and almost normally consolidated in its natural state, have compression index ranging from 0.201-0.278, re compression index ranging from 0.0325-0.