Sediment characteristic of landslide accumulation body in earthquake zone of Wenchuan under artificial rainfall simulation condition

Abstract: Scientific management of soil and water loss on landslide deposits is meaningful and important in Wenchuan earthquake area. This study aimed to investigate the sediment characteristics of landslide accumulation body in earthquake zone of Wenchuan under artificial rainfall simulation condition. On the basis of field surveying, the soil-rock ratio was designed as 1:1, 1:2 and 1:4. The rainfall intensities of 1.0, 1.5 and 2.0 mm/min simulated the precipitation often occurring in Wenchuan landslide deposit. Under the combination of different rainfall intensity and soil-rock ratio, the sediment yield and sediment concentration in runoff were measured. The results showed that: 1) the soil-rock ratio and rainfall intensity were the influence factors of the sediment yield and the sediment concentration of landslide deposit. The correlation between mean sediment yield rate and soil-rock ratio was higher than that with rain intensities. Runoff was not found in the treatment of soil-rock ratio of 1:4 under all the conditions and in the soil-rock ratio of 1:2 under the rain intensity of 1.0 mm/min. It indicated that a critical value might be between the soil-rock ratio of 1:2 and 1:4. Above the critical value, rainfall infiltration was large and runoff could not be yielded; 2) The sediment rate presented a upward-to-stable trend during the erosion. The mean sediment yield rate, the values under the stable condition, and cumulative sediment amount increased with increasing rainfall intensity. The fluctuation of soil-rock ratio 1:1 was higher than that with soil-rock ratio of 1:2. The latter change was more stable; 3) Sediment in runoff increased with increasing soil-rock ratios and also with increasing rainfall intensity; and 4) Cumulative sediment amount increased with cumulative runoff but the sediment yield happed after the runoff. The sediment characteristic of landslide deposit with different soil-rock ratio under different rainfall intensity in earthquake zone was quite different. In the landslide deposit, gravels accounted for more than 50%. The sediment yield characteristic of the landslide deposit was different from that of the pure soils. With prolonged precipitation, the soil runoff happened first. After a while, the sediment yield rate became smaller. The sediment yield depended on the soil-rock ratio. If the ratio was above the critical value, runoff didn't occur. The result may lay the foundation for the establishment of process-based model of soil erosion caused by landslide accumulation body in earthquake zone, and provide a scientific guidance for comprehensive control of soil and water loss in the Wenchuan earthquake zone, China.