This study looks into the influence of matric suction on the volume change of gypsum sand soil in unsaturated conditions. The specimens were collected from Al-Najaf, Iraq, and included 14-percent and 29-percent gypsum. Three series of initial stress of laboratory tests were utilized in a modified Oedometer device. For each gypsum contents, twelve remolded specimens were examined in unsaturated circumstances with the initial stress and applied stress using four matric suctions (30 KPa, 18 KPa, 9 KPa and saturated state). Three tests were performed for each matric suctions with initial stresses, no initial load, 56 KPa and 112 KPa, respectively. The findings exhibits a clear pattern of increasing in vertical strain as gypsum content rises and matric suction reduces under a variety of situations. The wetting process softens the gypsum components which are significantly resulting in an increase in vertical strains.

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