College of Water Resources and Civil Engineering,China Argricultural University
National Key Research and Development Plan Projects of China
Control on soil and water leakage is the key to prevent rocky desertification in karst areas, but their loss mechanism and influence factors are still unclear. 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 karst peak-cluster depression were studied through laboratory simulation tests. The results showed that whether the overlying soil layer is broken down or not determines the rate and amount of soil and water leakage. When overlying soil layer was not broken down, the rate of soil and water leakage decreased with time and gradually approached to be steady. Once the soil layer was broken down, water leakage rate increased sharply and then reached its steady state gradually, while soil leakage rate increased sharply to its peak value and then decreased to its steady one. The greater the water pressure was, the greater the soil and water leakage rates were, and the earlier the time that overlying soil layer was broken down and the rate peak of soil leakage occurred was. The greater the fissure width was, the greater the soil leakage rate was, the smaller the needed water pressure that the soil layer was broken down was, and the earlier the rate peak of soil leakage occurred was. The cumulative amounts of water and soil leakage increased with the increased water pressure or fissure width. The rate and accumulative amount of water leakage from soils that particle groups were missed were not affected significantly by soil aggregate size or fissure width, while that of soil leakage decreased with the increase of soil aggregate size. The cumulative soil leakage from small aggregate grounds decreased with the increase of fissure width but increased from large aggregate grounds accordingly. The greater the water pressure and the fissure width were or the smaller the soil aggregates size was, the more easily the soil layer was broken down. The soil layer with missing soil particle groups was more easily broken down than that with whole particle group. The rates and cumulative amounts of soil and water leakage after soil layer was broken down were significantly greater than that of unbroken soil layer. The research results provide a theoretical basis for revealing the mechanism of soil and water leakage and its control measure choice in karst regions.