Model and experimental study on surface wettabilities of weathered red-bed mudstone particles

A visualized test platform based on high-speed cameras was independently built to observe the diffusion process of droplets impacting on the surface of coarse red-bed mudstone particles. Based on the principle of energy conservation, the prediction model of the maximum diffusion factor βmax on the surface of coarse red-bed mudstone was established, and the correctness of the model was verified by the droplet wetting test. Through the prediction model, the energy distribution of the infiltration process was analyzed. The results show that the wetting behavior of droplets can be divided into two modes, i. e. oscillation mode and buffer mode, which have the characteristics of fast spreading speed and strong capillary effect. The infiltration characteristics of the coarse mudstone surface depend on the relative relationship of kinetic energy, matrix potential and viscosity dissipation. With the increase of the initial velocity, the kinetic energy increases while the capillary effect decreases, and more droplets tend to diffuse on the surface. With the increase of diameter, droplet kinetic energy, surface free energy and matrix potential are almost unchanged. With the increase of the contact angle, especially when the contact angle is more than 60°, the capillary effect is significantly weakened and prevents water penetration. This model can improve the understanding of the surface wetting phenomenon of coarse mudstone in red bed and can provide a basis for finding a reasonable scheme to limit water infiltration. © 2023 Central South University of Technology. All rights reserved.