Thesis (Ph.D.) - Cairo University - Faculty of Engineering - Department of Civil Engineering

Swelling pressures and strains are induced when expansive soils swell vertically and laterally as their moisture content increases damaging structures and roadways. The main purpose of this research is to study the effect of polystyrene geofoam in reducing vertical swelling pressure and strain. Three synthetic expansive soils were used. Expanded polystyrene EPS beads and extruded polystyrene XPS geofoam were utilized in the study. Three treatment techniques were used in the study which were inserting cylindrical cores of XPS within the expansive soil mass, filling holes with EPS beads and mixing EPS beads with the expansive soil. The XPS core insertions and the holes filled with EPS beads are newly proposed approaches. The diameters of the XPS cores and the holes filled with beads were 5, 10 and 15 mm while the mixing contents of EPS beads were 0.1, 0.2 and 0.3%. Small and large oedometer were used in testing. Results of XPS inserts showed a reduction in vertical swelling pressure and strain of up to 40.8 and 50.2%, respectively, while the holes filled with beads reduced the vertical swelling pressure and strain by 66.2% and 79.0% respectively. The EPS beads-soil mixtures achieved a reduction of 100% for both parameters

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