Numerical Assessment of Soil Dispersivity Based on Inter-Particle Energy Dynamics

Journal article, 2025

Dispersive soils disintegrate into individual grains when exposed to water, often leading to structural failures in dams, embankments, roads, and canals. This phenomenon arises from the dominance of repulsive forces, primarily due to the hydration of adsorbed monovalent cations, over attractive van der Waals forces. This study develops a theoretical model to quantify soil dispersivity based on energy dynamics between repulsive (hydration forces) and attractive (van der Waals) forces. Dispersivity is defined as the net energy release (D = R.E + A.E), where repulsive energy is derived from osmotic swelling pressure and attractive energy through mathematical integration of van der Waals interactions. Experimental validation was performed on three soils—(local dispersive soil, black cotton soil, red soil)—treated with KOH, NaOH, and LiOH to alter dispersivity. Results indicate that repulsive energy increased with treatments, correlating well with elevated liquid limits. The model-derived dispersivity also strongly aligns with double hydrometer trends and other geotechnical indicators. Conventional shrinkage limit and unconfined compressive strength tests may produce consistent outcomes, but they remain unreliable as stand-alone dispersivity indicators because of their exclusive reliance on soil structure. The model is presented as a fundamental, physics-based alternative to existing methods, eliminating dependence on dispersing agents and resolving issues such as negative values from conventional tests.