Collapse and Volume Change of Unsaturated Gypseous Soil: A Model Study

The collapsible soil is a particular form of unsaturated soil, which is susceptible to loss of their strength due to a decrease in total volume upon wetting. Gypseous soils are considered to be problematic soils that are directly affected by wetting. Increasing the water content in soil samples can increase the degree of deterioration in the physical, chemical, and mineralogical properties of soil samples depending on the gypsum content. The purpose of this research is to better understand how gypseous soil behaves by examining the impact of beginning circumstances on suction, collapse potential, and vertical stress. The impact of gypsum content on capillary rise and water volume penetration amount per time are also investigated in this study. Three varieties of gypseous soil, including sandy soil from various locations in Iraq, have been utilized. A large-scale model with box dimensions (700 × 700 × 600) mm was used to obtain the effect of wetting on the gypseous soil. To measure the suction, gypsum porous block sensors attached to special data logger were used in this study which are considered the applicable device to be used in large-scale models and field conditions. It was shown that the compressibility of gypseous soil is low when loaded under unsaturated condition. With the increase of initial dry unit weight, the collapse potential reduced by 11–27% depending on the gypsum content within the soil. The increase of initial water content decreases the collapse potential for all used soil samples. The initial void ratio plays an essential role in the value of specific collapse; the higher the void ratio, the higher the collapse potential.