From geotechnical and engineering geology points of view collapsible soils are classified as a problematic soils. The existence of collapsible soils has been reported in all of the world continents. In Iraq, gypseous soil is consider as collapsible soil. Existence of these soils, sometimes with high gypsum content, caused difficult problems to the buildings and strategic projects due to dissolution and leaching of the gypsum slates by the action of water flow through soil mass. The gypseous soil used was brought from Tikrit city, (Al- Qadissia district), from depth ranging (1.5-2.0) m. The gypsum content was more than (40 %). A dune sand, which used to replace gypseous soil was brought from Baiji in Salah AL-Deen Governorate from different depths to reduce the collapse that occurs during soaking. A series of model loading tests was conducted on gypseous soil improved by replacement with dune sand and using geogrid and geotextile under different values of eccentricities under condition of soaking. Tests was conducted on homogenous soil partially replaced gypseous soil with dune sand reinforced with geotextile reinforcement layer at the interface. Bearing capacity increases to (2.5-3.0) time after replacement and reinforcement of gypseous soil.
ISSN: 1792-9040 (Print)