Abstract Swelling potential (SP) has long been used as a terminology to describe a soil's expansibility. It is commonly defined in terms of pressure or deformation under certain constraints. However, fundamentally, SP originates from the soil‐water interactions in the interlayer space of expansive minerals and should not depend on displacement or force constraints. Here, the writers propose a SP based on the concepts of soil sorptive potential, unitary definition of matric potential, and water retention hysteresis. Water retention hysteresis in low matric potential is the result of interlayer hydration against the interlayer energy barrier. This energy barrier prevents water from entering the interlayer space. SSP synthesizes all the known sources of water adsorption, which provides the energy for soil swelling and can be determined under the unified definition of matric potential. The SP is defined as the energy hysteresis of interlayer hydration during wetting and drying. It is a function of relative humidity and can be calculated solely from the soil water isotherm (SWI). The SWI data of a wide variety of fine‐grained soils are used to determine and assess the proposed SP. For validation, the SP index (SPI), defined as the maximum energy consumed to overcome the energy barrier during wetting, is used. The SPI compares well with several expansive soil classification systems, confirming the validity of the SP. This study provides a scientific basis for linking soil water potential and energy used for swelling and understanding the volumetric behavior of expansive soil under varying humidity environments.
Wang et al. (Thu,) studied this question.