Abstract
The progressive failure of earthen check dams triggered by upstream flow is common in loess gullies on the Loess Plateau of China. However, studies on the formation mechanism of progressive failure are still unclear. To investigate the failure modes and progressive failure process of earthen check dams, a physical model test on an earthen dam influenced by upstream flow was conducted by monitoring and analyzing hydrologic and mechanical parameters, including water content, pore water pressure, soil stress, and displacement. The test results indicate that the progressive failure process of earthen dams is induced by seepage water discharged on the downstream slope, including slope slide and overtopping. Continuous seepage results in the occurrence of creep at the toe, gradually driving the deformation and sliding of the dam slope. The progressive failure begins in the downstream slopes, and this study focuses on analyzing the initiation mechanism of slope slide. The slope failure presents retrogressive sliding, including four repeated slip failures, and each sliding presents a long-time progressive process. This physical model test reproduces the entire life cycle of earthen check dams and reveals the traction sliding mechanism of dams, which is consistent with field observation. The aforementioned results provide an important reference for understanding the failure mechanism of earthen check dams triggered by upstream flow.
Highlights
The Chinese Loess Plateau is the most severely eroded area in the world (Hessel, 2006; Fu et al, 2017), and check dams are important and effective measures for erosion control in plateau catchments that experience torrents (Romero et al, 2012; Conesa and Lenzi, 2013; Zhao et al, 2017)
The toe of the downstream slope begins to creep, generating tension cracks in the middle part of the downstream slope extending to both sides (Figure 5B)
This model test revealed the whole life cycle of the check dam satisfactorily and showed that the complex failure process of an earthen dam consists of seepage on the downstream slope, sliding of the downstream slope, and overtopping, which are consistent with the aforementioned field observations, especially for the progressive multi-stage slope sliding
Summary
The Chinese Loess Plateau is the most severely eroded area in the world (Hessel, 2006; Fu et al, 2017), and check dams are important and effective measures for erosion control in plateau catchments that experience torrents (Romero et al, 2012; Conesa and Lenzi, 2013; Zhao et al, 2017). Up to 2020, nearly 163,000 check dams have been built, mainly on tributary channels under the project “Gully Land Consolidation” (GLC) (Jin et al, 2019). Because of low design standards, most check dams built without flood discharge facilities or spillways had relatively short lives as they rapidly filled with sediment or were breached by extreme flood events (Zhao et al, 2017; Fang et al, 2019). 516 check dams in Yan’An city, China, were damaged by the “7.26” extreme rainstorm on July 26, 2017 (Yang et al, 2020). Understanding check dam failure is crucial for risk assessment and decision-making.
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