Improvement Of Geotechnical Properties Of Expansive Soil Using Stone Dust And Coal Ash (The Case Of Olonkomi Town, Ambo Area)

Abstract

Nearly 40% of land area in Ethiopia is covered with Expansive soil. This soil possesses low shear strength and high plasticity causing damage to foundation of light weight buildings and pavements. To improve the shear strength, plasticity and swelling properties of expansive soil, stabilization technique is one of the known techniques used worldwide in construction Industry. In the present study expansive soil (ES) and Stone dust (SD) were collected from Olonkomi Town, Oromia Region. The coal ash (CA) was collected from Ayka Addis textile and investment group, Alemgena, Oromia Region to meet the desired objectives. The experimental program is carried out with a batch of three material mix (Expansive Soil-Stone Dust-Coal ash). The laboratory tests have been carried out for Index and Engineering tests. The moisture-density relationship is studied for different moisture contents. The maximum dry density for optimum mix decreases from 13.4 kN/m3 to 12.3kN/m3 to that of the expansive clay soil. The optimum moisture content of the optimum mix increase from 31% to 35% to that of the clay soil. Based on the maximum UCS value the percent of the optimum mix of clay soil, Stone dust and coal ash are 85% ,5% and 10% respectively (ES+5SD+10CA). The UCS value for expansive soil and optimum mix are 158 kN/m2 and 237 kN/m2 respectively. Based on free swell index test result the optimum percentages of blended soil changed from highly expansive to medium or marginal. The results of CBR test shows that the CBR value increases from 3.54% to 5.31% from clay soil to stabilized soil. Finally, the cost comparison was made between stabilized soil and selected material and it was concluded that the expansive soil stabilized with stone dust and coal ash are better than replacing the soil with selected material.