Study on horizontal diffusion of agent solutions in underground unsaturated soil: Experiments and model simulations

Abstract

Solute transport or water transport in unsaturated soil plays an important theoretical guiding role in remediation engineering. In order to study the diffusion of agent solutions in practical remediation engineering, the soil column experiments of unsaturated soil were carried out using the self-made laboratory test device. The effects of injection rate and soil pressure (confining pressure) on the solute diffusion in soil were studied. The experimental results show that the injection velocity has a great influence on the solute diffusion in soil, and the change in the diffusion rate is not proportional to the injection velocity. The effect of confining pressure on solute diffusion was first promoted and then suppressed. The fractal Richards equation (FRE) model was used to fit the water content curves. The results show that the FRE model has a fine fitting effect on this series of experiments, proving that it can provide model support for the simulation of solute diffusion in underground unsaturated soil. At the same time, the physical significance reflected by the fitting parameters can be used to analyze the mechanism of the experimental phenomena.