Abstract
Features of finger flows in fine sand and quartz sand were investigated experimentally and the effect of types of finger flows on the leaching characteristics were analyzed. The average particle size of fine sand was 0.18mm and that of quartz sand was 0.64mm. Salt was mixed uniformly as far as possible in the amount of 1.65g per 100g air-dry sand. Three different initial water content (air-dry, 1%, 2%) and two different rainfall flux (30 mm/h, 180 mm/h) were applied as the experimental conditions. Transducerized tensiometers were installed in the sand through the panel by which the changes of suction within fingers were measured.
The results show that the shapes of wetting fronts were classified into four types, low-swell finger, high-swell finger, wavy front, and plane front. The values of suction gradients inside low-swell fingers were almost 0, suggesting that water movement inside them were mainly conducted by gravimetrical gradients. The changes of suction in low-swell fingers and in high-swell fingers were remarkably different. These differences were attributed to the differences of water content distributions within these two types of fingers.
Leaching characteristics of sands were significantly influenced by the types of wetting fronts. Especially in the air-dry conditions, where low-swell fingers were generated, their leaching efficiencies were very small (20%-67%) compared with those of other types.
