Bearing Capacity of Shallow Footing on Compacted Dune Sand Underlain Iraqi Collapsible Soil


Gypsies Soils are disturbed in many regions in the world including Iraq, which cover about (30 %) of the surface area of the country (Al-Dulaimi, 2004). Existence of these soils, sometimes with high gypsum content, caused difficult problems to the buildings and strategic projects due to dissolution and leaching of gypsum by the action of water flow through soil mass. In this research, a new technique is adopted to investigate the performance of replacement and geosynthetic reinforcement materials to improve the gypseous soils behavior through experimental set up manufactured locally specially for this work. A series of tests including dry and wet tests were carried out using steel container (600×600×500) mm. A square footing (100×100) mm was placed at the center of the top surface of the bed soil. The results showed that the most effective thickness for dune sand layer with geotextile at the interface, within the tested range, was found to be almost equal to the width of foundation. Therefore, under this depth, the soil was reinforced with geogrid and geotextile. The bearing capacity increases to (1.5-2.0) time under concentric loads and (2.5-3.0) under eccentric loads after replacement and reinforcement of gypseous soil.