九寨沟震后核心景区崩滑堆积体冲刷启动机制研究

2017年九寨沟震后核心景区广泛发育崩滑堆积体，震后3年间受降雨影响下坡面泥石流频发，严重威胁景区恢复重建。为了研究坡面径流冲刷对崩滑堆积体启动的影响，基于2017－2020年的持续跟踪调查与高分辨率遥感影像解译，利用现场冲刷试验及原位监测，分析了径流冲刷条件下堆积体的渗流响应特征、侵蚀运移过程及冲刷启动机制。结果表明：（1）冲刷过程中坡面物质以下蚀、面蚀、溯源侵蚀及侧蚀为主，湿润锋下移致使坡体内体积含水率与孔隙水压力增大，达到峰值后处于动态稳定状态，而基质吸力则先小幅度波动后不断减小。（2）崩滑堆积体具有坡度陡、土体孔隙间细粒含量多、渗透性良好且抗冲刷能力弱等特征，在强烈的水动力条件下启动演化过程为先期渗透→铲刮滑流→快速堆积→局部饱和侵蚀?稳定。（3）不同饱和状态下堆积体启动的力学分析与现场试验监测结果较为一致，并结合冲刷试验成果认为，土体含水率升高、孔隙水压力急剧增大、基质吸力快速减小与高强度径流冲刷是堆积体启动之机制所在。该研究结果对于震后泥石流活动的长期效应预测与生态治理具有重要意义。

Scour initiation mechanism of deposit in Jiuzhaigou scenic area after earthquake

A magnitude of Ms 7.0 earthquake struck the Jiuzhaigou World Natural Heritage Park, in Jiuzhaigou county, Northwest of Sichuan province on August 8, 2017, and trigged abundant coseismic landslides deposit in the scenic spot. Due to the heave rainfall after earthquake, the slope debris flow occurred frequently, which seriously threatened the restoration and reconstruction in the after three years. In 2017?2020, continuous investigation, remote sensing interpretation and in-situ erosion test were used to research the impact of slope runoff erosion on deposit. The result shows that the seepage response characteristics are significant during the scouring process, and the downward movement of wetting front causes the increase of volumetric water content and pore water pressure, the matrix suction first fluctuates slightly and then decreases. In addition, the material characteristics of deposit provides the prerequisites for initiation. Under strong hydrodynamic conditions, the startup process is "preliminary penetration → scraping slip flow → rapid accumulation → local saturation erosion-stability". And finally, the mechanical analysis of deposit under different saturations is more consistent with the field test monitoring results. It is further believed that the increase of soil moisture content, and pore water pressure, the rapid decrease of matrix suction and the erosion of high-intensity runoff caused the initiation. The research results can have a certain significance for the long-term effects prediction of debris flow and ecological management after the earthquake.