STABILIZATION OF DISPERSIVE SOIL WITH LIME FOR IMPROVING SUB-GRADE OF ROAD, CASE STUDY OF WOZEKA-GIDOLE ROAD PROJECT, ARBAMINCH

Abstract

The soils that are highly susceptible to erosion and containing high percentage of exchangeable sodium ions are called Dispersive soils. Dispersive soils give rise to major problems that need due attention in geotechnical investigations. These are because easily erodible and segregate due to variation in moisture content and exchangeable sodium. These problematic dispersive soils, therefore, when encountered as sub-grade should be avoided or treated properly. The main objective of this paper presents a study on identification and improving engineering properties of dispersive soil in subgrade of Wozeka-Gidole road when stabilized by hydrated lime in varying quantities from (3%-9%). A series of tests such as grain size analysis, Double hydrometer, crump, chemical analysis, liquid limit, plastic limit and plasticity index, specific gravity, dry density, moisture content relationship, unconfined compression strength and California Bearing Ratio test were conducted before and after adding lime in (3%, 5%, 7% and 9%) percentage by weight of dispersive soil at curing periods of 5,7 and 14 days. The results show that the lime provides better index properties in term of liquid limit, plastic limit, plasticity index and reduce sodium cation and dispersivity properties, California Bearing Ratio and unconfined compression value increased as lime content increased with 3%, 5%, 7% and 9% at curing periods of 5, 7, and 14 days. Also the lime decreased dispersivity from 69.2% at 7day curing period to 33.2% at 14 day curing period and sodium cation from 6.21% of at 7day curing period to 3.89% at 14 day curing period. The finding of this thesis outlined that the sub-grade soil of untreated sample was classified as A-7-5 by the AASHTO and MH, CH per USCS systems which is consider as poor subgrade quality. The findings suggest that the grain size of particles of subgrade soil was changed to GC and GM groups of soil after different percentage of lime treatment for the first 7days and 14days curing periods. Therefore, it can be concluded that lime can improve the engineering properties of dispersive soils. Practically, the effective lime content should be blended with 9% lime which provide high strength, optimize optimum moisture content and provide high quality of subgrade pavement rating.