The influence of matric suction on the compressibility of unsaturated gypseous sand soil under various loading conditions is investigated in this research. The gypseous percentage of the soil samples from Al- Najaf, Iraq, was 14 percent, 22 percent, and 29 percent. In a modified triaxial cell, these substances were subjected to loading-path, which occurs when a structure is built on these soils at a certain saturation level (specific matric suction). With two distinct confining stresses of 100 kPa and 200 kPa, four matric suctions were used: 100, 60, 30, and zero percentages of initial matric suction. Under the confining loads, two saturation tests (CD; Consolidated-Drained) were also conducted. The volumetric strains were found to be increased when the matric suction was reduced, and the gypseous content was increased. This type of soil experiences high volume variations during the wetting process, which can result in significant soil strain as a result of substructure damage. Also, the shear strength parameters are decreased by increasing the matric suction.

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