A semi-empirical swell prediction model formulated from ‘clay mineralogy and unsaturated soil’ properties

• Previous swell related modeling studies have not incorporated the combined effects from soil suction and clay mineralogy attributes to predict swell behavior.
• Eight natural expansive soils were collected and their swell strains were measured under different conditions. Clay mineralogy and soil suction properties of expansive soils were determined.
• A new parameter, mechanical-hydro-chemical parameter (MHCP) is used, that accounts for both matric suction and clay mineralogy characteristic.
• The slope of the path traversed by the soil specimen on a matric suction and void ratio plot (α) is a unique representation of the hydro mechanical change undergoing by the specimen during swelling.
• MHC model accurately predicted swelling behavior of expansive clays for their unique inherent properties.

Swell behavior of expansive clays is an inherent property that can be better explained through its hydro mechanical volume change behavior arising from soil attributes like matric suction and clay mineralogy information. Previous swell related modeling studies have not incorporated these attributes for swell behavior, thereby leading to poor to erroneous characterization practices. Both chemical and hydrological attributes of the soils are targeted in this expansive soil modeling. Eight natural expansive soils were collected and their swell strains were measured under different confining pressure conditions. Soil suction properties of expansive soils as well as soil water characteristic curves (SWCC's) were determined using standard measurement procedures including pressure plate and filter paper techniques. Slope of the paths traversed by the soil specimens in a void ratio — soil matric suction framework are determined and used as mechanical input parameters for the heave modeling. A new parameter, Mechanical Hydro Chemical Parameter (MHCP) is used that accounts for both matric suction and clay mineralogy information. This parameter is correlated with swell property measurements and the correlations developed provided reliable and reasonable swell property predictions. Independent validations with other soils are still needed for further enhancement of the MHCP framework for more reliable predictions.