Landslide dams are composed of wide-graded materials characterized by nonuniform structures that govern breaching mechanisms. However, investigations of the failure characteristics of single-structure dams with different material compositions and inverse grading structure dams remain insufficient. In this study, a series of flume experiments are conducted to investigate the influences of noncohesive dam materials and inverse grading structures on the breaching mechanisms, hydraulic characteristics and residual dam parameters during and after landslide dam failures. The results indicate that the dam breach process is controlled by the material composition and dam structure. A coarse-grained dam remains stable with seepage, a medium-grained dam fails by headcutting and backwards erosion, and a fine-grained dam fails due to layered erosion. An inverse grading dam with coarse-grained overburden features backwards erosion or a combination of sliding and backwards erosion, while a dam with medium-grained overburden fails by headcutting and backwards erosion. The maximum erosion rate occurs at the accelerated breaching stage for single-structure dams and at the initial overtopping or accelerated breaching stage for inverse grading structure dams. Four longitudinal evolution patterns are extracted based on the breach process and erosion characteristics. In addition, the outflow discharge during dam failure can be estimated by measuring the breach width, which is defined as the straight line distance between the ends of the breach crest at the overflow face. Both the peak discharge and residual dam parameters for single-structure dams are sensitive to the median diameter of the material. These parameters of inverse grading structure dams fall within the range of values observed for dams formed by the top layer material and the bottom layer material. The initial overtopping and backwards erosion stages account for 10%–35% and 36%–66% of the total breach duration for single-structure and inverse grading structure dams, respectively. Serious errors in the prediction of breach parameters can occur when top layer materials are considered to characterize the material of inverse grading structure dams.

中文翻译：

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非粘性滑坡坝漫溢破坏的定性分析：材料成分和坝结构对溃口机制的影响


滑坡坝由宽级配材料组成，其特点是控制溃坝机制的不均匀结构。然而，对不同材料成分的单体结构坝和反级配结构坝的破坏特征研究还不够。在本研究中，进行了一系列水槽实验，以研究非粘性坝材料和反级配结构对滑坡坝溃坝期间和之后的溃坝机制、水力特性和剩余坝参数的影响。结果表明，溃坝过程受材料成分和大坝结构的控制。粗粒坝因渗流而保持稳定，中粒坝因切头和向后侵蚀而破坏，细粒坝因分层侵蚀而破坏。粗粒覆盖层的反级配坝具有向后侵蚀或滑动和向后侵蚀相结合的特征，而中等粒覆盖层的坝则以切头和向后侵蚀为特征。最大侵蚀速率出现在单结构坝的加速溃决阶段和反级配结构坝的初始漫溢或加速溃决阶段。根据溃口过程和侵蚀特征，提取出四种纵向演化模式。此外，大坝溃决时的流出流量可以通过测量溃口宽度来估算，溃口宽度定义为溢流面溃口顶部两端之间的直线距离。单结构坝的峰值流量和剩余坝参数均对材料的中值直径敏感。 反级配结构坝的这些参数落入由顶层材料和底层材料形成的坝观察到的值范围内。对于单结构坝和反级配结构坝来说，初始漫溢和反冲阶段分别占总溃决持续时间的10%~35%和36%~66%。当考虑顶层材料来表征反级配结构坝的材料时，溃口参数的预测可能会出现严重错误。