Experimental investigation of the behavior of collapsible soil stabilized with calcium carbide residue

Collapsible soils are located in various parts of the world. These soils are characterized by their low values of dry unit weight and natural water content. Collapse and large induced settlements at the saturation state damage the structures built on them. Therefore, measuring the collapse potential of these soils is essential for safe engineering works. This study aims to investigate the collapse index and collapse potential of clayey soil stabilized with calcium carbide residue (CCR). For this purpose, seven different contents of CCR, five curing periods, three different water contents, and two relative compactions were used. The results of tests showed that the CCR contents, relative compaction, and water content during sample preparation were the most key factors in collapsibility measurements. It was observed that CCR contents greatly reduced collapse index and collapse potential of soil and changed the degree of collapse from moderately severe to slight and non-collapsible one. Furthermore, increasing the relative compaction reduces the pore space between the soil particles, leading the denser structure. The denser the soil, the lower the initial void ratios, hence, there is less collapse upon wetting. Finally, the stabilized samples prepared with 2% less than optimum water content have a higher degree of collapse than those with optimum water content and 2% more than optimum water content. The results of this study corroborate the effectiveness of CCR as a by-product material to improve collapsible soils.