Study on head-cut erosion characteristics of compacted loess check dams

In recent years，water-induced failures of check dams frequently occurred due to short-time heavy rainfalls in Loess Plateau in China. The research foundation on check dam breach simulation is weak，while the erosion characteristics of compacted loess and the head-cut erosion mechanism under the influence of different factors are still unclear. Qualitative and quantitative tests on microscopic pore structures of loess material，and 14 groups of head-cut erosion flume tests of compacted loess have been conducted. In this study，the influences of initial water content and compactness on head-cut erosion process are the main concern，and the influence mechanisms of compacted loess microscopic pore structure on the head-cut erosion mode and rate have been revealed. The model test results show that the water-holding state of compacted loess has an essential impact on head-cut erosion mode and rate. Water molecules change the macroscopic erosion law by affecting the microscopic pore structure of compacted loess. When the soil is in a low water content state，the head-cut is dominated by layered erosion，and the “false cohesion” provided by matrix suction has little impact on the erosion rate. With the increase of water content，the head-cut erosion mode has changed into retrogressive erosion towards upstream accompanied by intermittent instability of blocks. However，the change of compactness does not affect the head-cut erosion mode，but the head-cut erosion rate by adjusting particle skeleton and contact area. The increase of compactness can significantly enhance the erosion resistance of loess. The research results can provide theoretical support for the study of dam breach mechanisms of loess check dams. © 2023 Academia Sinica. All rights reserved.