Ubiquitous and complex avalanche–substrate interactions during rock avalanche emplacement have attracted widespread attention in recent years and are regarded as vital processes influencing mobility and damage potential through rapid changes in avalanche mechanical properties. However, the fundamental interaction mechanisms of avalanche mass on substrate and the resultant effect on mobility have yet to be elucidated for natural events. To better understand the mechanics of avalanche–substrate interactions, we present a detailed study on the spectacular synsedimentary deformation structures at the bottom of the gigantic Iymek rock avalanche deposit, including undulose structures, flame structures, mixed textures, clastic dikes, and cracked gravels. The cracked gravels demonstrate that the overriding avalanche mass exited high-energy shearing on the avalanche–substrate interface, where the stress in substrate far exceeded the overburden from the avalanche mass during the avalanche–substrate interaction. Along with high-energy shearing, two different interaction modes with the change of substrate materials are identified, i.e., the Kelvin–Helmholtz instability (KHI) characterized by undulose-to-flame structure transitions, and the Raleigh–Taylor instability (RTI) characterized by the formation of clastic dikes. The KHI is interpreted as a result of the growth of shear instabilities induced by high-energy shearing along the avalanche–substrate interface. The RTI is associated with local liquefaction of the water-bearing sandy substrate and was mainly induced by the high-frequency ground vibrations generated by high-energy shearing. Therefore, we propose that the overriding avalanche mass exited high-energy shearing on the substrate during the avalanche–substrate interaction, which motivated two predominant physical processes of the KHI and RTI along the avalanche–substrate interface. The shear-induced KHI is a potential mechanism of erosion and entrainment in rock avalanches and is responsible for promoting the incorporation of substrate materials into moving avalanche mass. These results not only yield profound insights into the interaction behaviours between rock avalanches and substrates but also provide a fundamental geological prototype to motivate further modelling work to elucidate rock avalanche dynamics.

中文翻译：

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伊梅克岩石雪崩沉积物中雪崩与基质相互作用的观察：可能的成因机制


近年来，岩石雪崩就位过程中普遍存在且复杂的雪崩-基质相互作用引起了广泛关注，并被认为是通过雪崩力学特性的快速变化影响流动性和潜在损坏的重要过程。然而，对于自然事件，雪崩质量在基底上的基本相互作用机制以及由此对迁移率产生的影响尚未阐明。为了更好地了解雪崩与基质相互作用的机制，我们对巨大的 Iymek 岩石雪崩矿床底部壮观的同沉积变形结构进行了详细研究，包括波状结构、火焰结构、混合纹理、碎屑岩脉和裂隙砾石。破裂的砾石表明，压倒性的雪崩块在雪崩-基底界面上产生了高能剪切，在雪崩-基底相互作用期间，基底中的应力远远超过了雪崩块的覆盖层。除了高能剪切之外，还确定了两种不同的与基底材料变化的相互作用模式，即以波状到火焰结构转变为特征的开尔文 - 亥姆霍兹不稳定性（KHI）和以波状到火焰结构转变为特征的罗利 - 泰勒不稳定性（RTI）通过碎屑岩堤的形成。 KHI 被解释为沿雪崩-基底界面高能剪切引起的剪切不稳定性增长的结果。 RTI与含水砂质基质的局部液化有关，主要是由高能剪切产生的高频地面振动引起的。 因此，我们提出，在雪崩-衬底相互作用期间，最重要的雪崩质量在衬底上退出了高能剪切，这激发了沿着雪崩-衬底界面的 KHI 和 RTI 两个主要物理过程。剪切引起的 KHI 是岩石雪崩中侵蚀和夹带的潜在机制，负责促进基质材料融入移动的雪崩体中。这些结果不仅对岩石雪崩和基质之间的相互作用行为产生了深刻的见解，而且还提供了一个基本的地质原型，以激发进一步的建模工作，以阐明岩石雪崩动力学。