Experimental investigation of the properties of collapsible soil stabilized by colloidal silica

Collapsible soils pose significant geotechnical challenges due to their tendency to exhibit high strength under natural moisture conditions but undergo substantial settlement upon wetting. To address this issue, various stabilizing agents, including lime, cement, silicates, resins, and acids, have been explored. This study investigates the effectiveness of colloidal silica (CS), a low-viscosity solution capable of forming a gel, as a stabilizing agent. Its unique properties enable it to be injected into or mixed directly with soil, offering versatility in application. The behavior of CS-stabilized collapsible soil was evaluated through collapse potential and unconfined compressive strength (UCS) tests. Scanning electron microscopy (SEM) was also conducted to analyze microstructural changes in untreated and CS-treated soils. Colloidal silica was added at concentrations of 3, 5, 7, and 10% by weight of dry soil, with curing times of one, 7, 14, and 28 days. Collapse potential tests were performed at relative compactions of 80 and 85%, while UCS tests used a relative compaction of 95%. Results indicated that colloidal silica significantly reduced soil collapsibility while enhancing stiffness and UCS without inducing brittleness. A 5% CS concentration was optimal, reducing collapsibility from severe to negligible. Increased relative compaction (80 to 85%) further decreased collapsibility, whereas higher inundation stress increased it. These improvements are attributed to pore filling by colloidal silica, which enhances inter-particle bonding and structural integrity.