Effect of Median Soil–Particle Size Ratio on Water Storage Capacity of Capillary Barrier

Abstract

Capillary barriers are widely used as a cover system to enhance the upper-soil-layer water storage capacity and reduce water infiltrate into the lower soil layer. In this paper, the effects of the median soil–particle size ratio on the water storage capacity of capillary barriers were studied using a series of indoor one-dimensional soil column infiltration tests. The results show that the water storage capacity rises with an increase in the median soil–particle size ratio until it exceeds 10. The variation in the total water storage capacity is related to not only the median soil–particle size ratio but also the particle size of coarse-grained soil or fine-grained soil. When the fine-grained soil-layer particle size is constant, the total water storage first increases, then decreases, and finally remains constant after increasing the median soil–particle size ratio. In contrast, when the coarse-grained soil layer particle size is constant, the relationship between the capillary barrier’s total water storage and median soil–particle size ratio can be defined as a power function. Using the capillary barrier can increase coarse-grained sand by 90% in water storage capacity and can only increase fine-grained sand by 7% in water storage capacity. The breakthrough time increases with the increase in the median soil–particle size ratio. The presence of the coarse and fine-grained soil layer interface in the capillary barrier can affect the fine-grained soil layer infiltration rate.