Chemical reaction kinetics based models for describing evolution of one-dimensional expansion with time

Two models for describing the evolution of one-dimensional expansion of expansive soils with time are derived based on the second-order chemical reaction kinetic equation, namely, hyperbolic model and Logistic model. The former has two parameters which have clear physical meanings, while the latter has three parameters among which one has an unclear physical meaning. One-dimensional swelling tests on the specimens with different initial water contents and dry densities are conducted to obtain swelling strain-time curves, and the fitting effects using the two models are compared. The results show that both models can accurately describe the swelling strain-time curves. Moreover, the hyperbolic model can also be used to predict the expansion time-history curves of the specimens with different initial water contents and dry densities. The predicted curves have good consistency with the experimental data, and the parameter correction process is simple, which is convenient for engineering applications. The expansion time-history model deduced in this study has important theoretical significance for describing the evolution laws of volume change of expansive soils during the process of water immersion saturation.