INVESTIGATION OF THE COLLAPSE POTENTIAL OF GYPSUM SAND SOIL IN UNSATURATION CONDITIONS USING A MODIFIED OEDOMETER

Abstract

This study examines the impact of varying soaking durations on collapse potential (CP) within gypsum sand soil containing 29% gypsum content. It explores the enhancement of CP through the addition of CKD (Cement Kiln Dust) in concentrations ranging from 1% to 5%, employing a modified oedometer apparatus. The oedometer provides accurate measurements of soil compressibility, consolidation properties, and settlement behaviour under realistic load conditions, which are crucial for foundation design and long-term stability predictions. It also aids in assessing soil-structure interaction and validating soil behaviour models, enhancing the accuracy of geotechnical analyses. The oedometer is preferable over other available devices because it is specifically designed for consolidation and collapse studies, making it ideal for testing how additives like CKD affect the soil's collapse potential under controlled soaking conditions. This study categorized specimens into seven groups based on saturation and unsaturation conditions, varying soaking durations of one, two, and three weeks to investigate CP. The findings revealed that the CP under saturation conditions without matric suction for a one-week soaking period exceeded CP under the same conditions with zero matric suction (ψ = 0) by 16%. Additionally, CP increased by 16%, 41%, and 136% when specimens were tested under ψ = 0 after one, two, and three weeks of soaking, respectively, compared to the one-week soaking period. Furthermore, under matric suction of 40 kPa (indicating reduced moisture content), CP results increased by 55% and 228% for two and three-week soaking periods, respectively, compared to the unsaturation state at 40 kPa matric suction with a one-week soaking period. The optimal CKD addition percentage for improving CP ranged from 2% to 3%, contingent upon the specific case study.