重力对饱和多孔介质中颗粒输运特性的影响

Effect of gravity on transport of particles in saturated porous media

利用室内土柱试验研究重力对饱和多孔介质中颗粒输运特性的影响,包括渗流方向自上向下和自下向上两种不同的试验系列,每个系列中进行了5种不同渗流速度的试验。研究结果表明,渗流方向自上向下时的流出液中颗粒的浓度峰值要大于自下向上时的浓度峰值,并且前者的浓度峰值出现的也快。同一渗流方向条件下,渗流速度越大,流出液中颗粒的浓度峰值越大。其次,渗流自上向下时,随着渗流速度的增加,弥散度的值随之减小,但在渗流自下向上时,渗流速度的变化对弥散度的影响很小。另外,同一渗流方向中,随渗流速度增大,沉积系数逐渐减小,回收率逐渐增大,并且沉积系数在渗流自下向上时较渗流自上向下时的要大。可见,重力和渗流速度是影响饱和多孔介质中颗粒输运的重要因素,渗流速度越小,重力的作用越明显。

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.