Developing Correlation Between the Index Properties and Swelling Potential of the Expansive Soils Found in Ambo Town

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Addis Ababa University


A large surface area of Ambo town is covered by expansive soils which has a tendency to undergo volume change due to change in water content with seasonal moisture variation. Civil engineering structure constructed on such soils shows damage due to uneven movement caused by swelling and shrinking of the soil. The focus of this study is to develop correlation between index properties and swelling potential of the expansive soils found in Ambo town. Conducting swelling pressure and swelling potential tests are time taking and expensive when one compare with a simple index property tests. Therefore, it is very important and has engineering implication to develop correlation formulas for estimating the swelling potential from simple index properties tests. The thesis investigated the feasibility of single linear regression analysis and multiple linear regression analysis in correlating swelling potential with soil index properties. Hence, a total of 20 disturbed and 20 undisturbed samples were collected from different parts of Ambo town and the necessary laboratory tests were conducted in order to develop the empirical correlations. In this research regression analysis is used to explore the significance of individual independent (index) soil variables. The empirical correlation is given in the form of an equation of swelling potential as a function of natural moisture content, dry density, grain size analysis, Atterberg Limits by considering the effect of an individual soil index properties and effect of a combination of soil index properties on the swelling potential results. The new empirical correlation using single regression analysis results in a good determination coefficient of R-square (R 2) = 0.5258 and mean confidence level of (CL) =99.99%, whereas multiple regression analysis gave comparatively a better correlation with determination coefficient of R-square (R 2) = 0.6401 with mean confidence level of (CL) =99.73%. Results of the validity of the newly developed correlation with control test results shows that, the correlation of swelling potential value with soil index properties is valid only for preliminary design purposes and estimation of swelling potential of soils.



Geotechnical Engineering