| Popis: |
[Objective] Soil and water loss control is the key to the prevention and control of rocky desertification in karst areas, so the mechanism of soil and water loss and its influencing factors are explored. [Methods] The effects of water pressure (0.3, 1.3, 2.3, and 5.5 m water head height), karst fissure width (0.25, 0.5, 0.75, and 1.0 cm), and soil aggregate size (0～1.0, 1.0～2.0, 2.0～5.0, and 0～5.0 mm) on the process of soil and water leakage in the karst peak-cluster depression were studied through laboratory simulation experiment. [Results] The greater the water pressure and the fissure width were, the smaller the soil aggregate size was, or the absence of certain soil particle groups, the more easily the overlying soil layer was broken down taking approximately 2 to 20 minutes. After the soil layer was broken down, the water leakage rate surged rapidly before stabilizing, while the soil leakage rate peaked and then settled. The rates and cumulative amounts of soil and water leakage from the disrupted soil layer were significantly greater than that of the unbroken one. The cumulative amounts of water and soil leakage increased with the increased water pressure or fissure width. When fissure width was 0.25, 0.50, 0.75, and 1.00 cm, the cumulative amount of water leakage at 1.3 to 5.5 m water pressures was 1.2 to 13.2, 2.4 to 131.0, 2.1 to 167.3, and 75.8 to 141.9 times greater than that at 0.3 m one, respectively. The cumulative soil leakage diminished notably with larger soil aggregate sizes. The absence of larger aggregates led to the decrease of soil leakage with the increase of fissure width but the opposite was true for soils lacking smaller aggregates. When fissure width was 0.25, 0.50, 0.75, and 1.00 cm, the cumulative amounts of soil leakage from 1.0 to 2.0 and 2.0 to 5.0 mm aggregate particle groups were decreased by 98.4% and 99.1%, 46.3% and 83.7%, 43.2% and 74.0% as well as 41.1% and 27.1%, respectively, compared with that of 0 to 1.0 mm one. [Conclusion] The stability of the overlying soil layer plays a pivotal role on the process of soil and water loss in peak-cluster depression, and hydraulic conditions, soil properties, and the degree of karst fissure development critically influence this stability. |
