Effect of gravity on transport of particles in saturated porous media

Saturated soil column experiments are conducted to explore the influence of gravity on the transport of particles in saturated porous media. The experimental schemes include two series (seepages flow from top to bottom and from bottom to top), and 5 seepage velocities are conducted in each series. The studies show that when the seepages flow from top to bottom, the peak value of effluent curve is greater and the travel time for the peak value of effluent curve is shorter than those in the opposite seepage direction. The peak values of effluent curves are lower with the lower flow rate when the seepages flow in the same direction. Besides, the dispersivity of particles decreases with the increase of the seepage velocity when the seepages flow from top to bottom, but the seepage velocity has little influence on the dispersivity when the seepages flow in the opposite direction. The deposition rate decreases and the recovery rate increases with the increase of the seepage velocity. When the seepages flow from top to bottom, the deposition rate is larger than that in the opposite direction. Overall, the study highlights the importance of gravity and seepage velocity on transport of particles in saturated porous media, and the gravity plays an even greater role in low seepage velocity conditions.