Effects of nano-clay on the geotechnical properties of gypseous soil

Abstract Gypseous soils suffer from sudden settlement when subjected to water flow due to dissolving of gypsum salts, so all structures constructed on gypseous soil undergo significant deformations due to the soil’s ability to collapse. Around the world, specifically in the arid and semi-arid regions gypseous soils are mostly found also, and can be found in the west desert of Iraq and even in the southern regions, amounting about between 30 and 35% of the country’s total area. There are several techniques to improve the geotechnical properties of collapsible soils, but one of the most recent techniques is using the nano technology. Five different proportions of nano-clay (NC) were incorporated into a gypseous soil containing 80% gypsum in order to enhance its chemical and geotechnical characteristics (1, 2, 3, 4, and 5%). The tests findings (chemical, physical, and mechanical tests) demonstrated that the addition of nano-clay to gypseous soil has a significant impact on the geotechnical properties of soil where it leads to decrease the gypsum content of soil, pH value, maximium dry density, specific gravity, and collapse index. On the other hand, the utilized of nano clay material causes to increase shear strength parameters (c and φ), optimum water content and liquid limit. Adding 4% of nano-clay results in a significant decrease of 53% in the collapse index and an increase of 311% in soil cohesion and 30% in the angle of internal friction.