DEVELOPING MATHEMATICAL MODEL TO PREDICT SWELLING POTENTIAL OF THE EXPANSIVE SOILS USING INDEX PROPERTIES: A CASE OF HOLTE TOWN

Abstract

Expansive soils are clay soils with high plasticity and expand when wet, shrink when dry out, and typically containing clay minerals constituent. These soils, considered as problematic soils thereby performance of clay minerals constituent, which makes them, exhibit the shrink-swell behaviors. This thesis aims to develop mathematical model to predict swelling potential of the expansive soils using index properties: a case of Holte town. To achieve these thesis objectives, twenty disturbed and undisturbed test samples were collected from ten test pits with a depth of 1.5 to 3 m in the various location of the town. Laboratory tests were conducted for natural moisture content, in-situ dry density, specific gravity, grain size analysis, atterberg’s limits, free swell, standard compaction, and consolidation tests as per the specified practices of the American Society for Testing and Materials Procedures. After collection and testing of the soil samples, compositions of the soil factors, such as plasticity index, liquid limit, percentage finer than 0.002 mm, plastic limit, percentage finer than 0.075 mm, liquidity index and in-situ dry density, in-situ moisture content from its placement conditions were used as input parameters in Statistical Package for Social Sciences. This thesis study revealed that, the natural moisture content, in-situ dry density, and bulk unit weight ranges from 31.21-40.93%, 1.21-1.30 g/cm3, and 1.65-1.73 g/cm3 respectively. Liquid limit, plastic limit, plasticity index, liquidity index, activity ranges from 58.15-76.92%, 25.63-32.94%, 27.64-45.14%, 0.00-0.35%, 0.55-0.85 respectively. From grading test, gravel, sand, silt, clay ranges from 0.10-3.31%, 1.26-6.21%, 36.13%-46.82%, and 50.01-58.51% respectively. And also the swelling potential, swelling pressure, optimum moisture content, maximum dry density, free swell, and specific gravity ranges from 2.40-6.73%, 40-180 kpa, 27.46-35.50%, 1.219-1.325 g/cm3, 70-105%, and 2.66-2.75 respectively. As per USC system the study area dominant on inorganic clays of high plasticity, CH and as per AASHTO classification scheme the soil of the Holte town fall under A-7-5 and A-7-6, group these imply silt-clay materials. Finally, this study provide a statistical mathematical modeling that can be used to obtain an indirect estimation of swelling potential thereby index properties, in-situ dry density and plasticity index with multiple soil index of 6.808𝛾𝑑+0.174PI-10.38 from multiple linear regression analysis with 84.3% of the points were fall within the regression line and a mean confidence level of 98%.