Dynamic variations in the drainage water retention curves of unsaturated soils due to acoustic vibrations

This study examines the differences between the static water retention curve and dynamic water retention curve using a sand box test. It also examins how various frequencies of sound waves (0 Hz, 75 Hz, 100 Hz, 125 Hz and 150 Hz) of sound wave would affect the dynamic water retention curve during the drainage process. The results show that the differences in the curves for the relationship between saturation and time, and the changes in saturation due to the acoustic waves under stable pumping rate are not significant. It can be assumed that acoustic vibration does not affect the curve of the relationship between the saturation and time, and the desaturation rates. This means that the acoustic waves affect the dynamic behavior of capillary tension and the dynamic coefficients. The experimental results showed that dynamic coefficients with acoustic shocks are smaller than those without acoustic shocks. Moreover, the minimum value of the dynamic coefficient is t₁₅₀. Using the van Genuchten model (VG model) to fit the relationship between the shape factor a and frequency, the results show that acoustic shocks affect the shape factor a, with the smallest effect seen for the 100 Hz sound wave, and the greatest effect for the 150 Hz sound waves. The results mean that the entry pressure (P_d) of the water retention curve is changed following the change in acoustic wave frequency, and that the P_d of the water retention curve is the lowest with a sound wave of 150 Hz. The results also show that an acoustic shock allows air to penetrate the porous media more easily.