EVALUATING THE SWELLING BEHAVIOUR OF EXPANSIVE SOILS OF SODO TOWN

Abstract

In this country, many studies have been conducted on the mapping and characterization of expansive soils in a number of towns. On the other hand, some studies were carried out in Addis Ababa and other parts of Ethiopia on expansive soils to determine the unsaturated shear strength behavior of expansive soils. The present study examines the swelling behavior of Sodo town's expansive soils. A laboratory testing program was designed and implemented in the town to assess particle size analysis, consistency limits, specific gravity, free swell, compaction, unconfined compression, and swelling pressure on both disturbed and undisturbed soil samples collected from eight distinct locations. The laboratory test results revealed that the liquid limit ranges from 67.00 to 113.80 percent; the plastic limit ranges from 29.74 to 72.50 percent; the plasticity index ranges from 24.4 to 60.47 percent; the linear shrinkage limit ranges from 9.21 to 12.17 percent; the shrinkage index from 56.76 to 104.19 percent; free swell from 70 to 130 percent; specific gravity from 2.62 to 2.72 percent; swelling pressure from 89 to 475 kPa; swelling potential from 1.21 to 3.50 percent; maximum dry density from 1.21 to 1.59 g/cc; optimum moisture content from 22 to 38 percent; unconfined compression strength from 64.08 to 257.68 kPa, and the soils are classified according to soil classification systems. The measured swelling pressures and the geotechnical parameters determined from identification tests are used to assess the validity of already developed expressions by various review literatures to the site under study, and new models that relate swelling pressure and swelling potential with index and physical properties are developed using Microsoft Excel for Windows. In this work, tests were carried out on one undisturbed, potentially expansive soil sample collected from the truck station area at a depth of 3.0 m. One of the tests was on saturated soils and the other one was on unsaturated soils. The results from CU triaxial test carried out with a modified triaxial equipment on undisturbed samples setting nil matric suction for varying an effective confining pressure of 100 kPa, 200 kPa, and 300 kPa during saturated case and varying matric suction to be 100 kPa, 150 kPa, and 200 kPa for constant an effective consolidation pressure of 200 kPa for unsaturated case. The maximum deviator stress was found to increase from 115.82 kPa to 298.75 kPa, indicating that the unsaturated condition yielded higher shear strength than the saturated one. The maximal deviator stress increased as the matric suction increased, but the stress strain diagram's form remained identical.