Water Volume Change Due to Wetting of Unsaturated Gypseous Sand Using Modified Oedometer

Abstract

This paper investigates the water volume changes in gypseous sand soils within the change in matric suction and under different stress levels. The present research aims to examine water entry into the soil with different matric suction under different levels of constant net normal stress (221, 442, and 885 kPa). The soil sample is collected from Al-Najaf city, Iraq The main soil of the city is sand with different percentages of gypsum at different locations and depths. These experiments revealed a clear relationship between decreasing the matric suction (wetting) and changing the gypseous soil structure, i.e., increasing the void ratio, and this behavior also depends on the net stress level. With the demolition of the voids under high-stress levels, there is a decrease in water volume change at zero matric suction (saturation). A comparison is made between the predicted soil water characteristics curve (SWCC) for the soil with the investigated values. The results show a shifting, which may be due to the accuracy of the curve fitting or/and the effect of the loading and gypsum content. This new understanding should help improve predictions of the impact of the load, gypsum content, and time.