Deep-seated landslides are among the most devastating natural hazards on earth, usually involving a rigid rock mass sliding over a weak, clayey shear band rich in phyllosilicates. The mechanical response of this shear band to the loading of the overburden is, therefore, critical for the stability and the evolution of a landslide. We hereby show that this mechanical response is strongly associated with mineralogy and microstructure of clay minerals forming the shear band, and vice versa. By presenting a detailed mineralogical, textural, and mechanical characterization of a shear band of an active deep-seated landslide, we attempt to shed light on processes determining the failure mechanism of a large deep-seated landslide. The case study chosen is the El Forn landslide located in Andorra Principality (Eastern Pyrenees). Its shear band is formed of black shales of the Silurian period. Using core samples of this landslide, we have performed mineralogical and microstructural analyses (XRPD, SEM-EDS, and MicroCT), combined with mechanical tests (liquid limit, plastic limit) to study the interplay between the internal texture of the material of the shear band and its mechanical response. Our results show that the highest mechanical alteration of the material occurs at the center of the shear band, where the phyllosilicates are perfectly aligned parallel to the shearing direction. The alignment of the crystals and their face-to-face contact increases the plasticity index of the material and reduces its porosity. Hence, the shearing movement rearranges the contacts of the phyllosilicate grains inside the shear band, reducing the resistance of the material and promoting the slip of the overburden.

中文翻译：

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层状硅酸盐结构与深部滑坡力学响应之间的相互作用。El Forn de Canillo 滑坡案例（安道尔）

深层滑坡是地球上最具破坏性的自然灾害之一，通常涉及刚性岩体滑过富含页硅酸盐的弱粘土剪切带。因此，该剪切带对上覆地层载荷的机械响应对于滑坡的稳定性和演化至关重要。我们在此表明​​，这种机械响应与形成剪切带的粘土矿物的矿物学和微观结构密切相关，反之亦然。通过呈现活动性深层滑坡剪切带的详细矿物学、结构和力学特征，我们试图阐明确定大型深层滑坡破坏机制的过程。选择的案例研究是位于安道尔公国（东比利牛斯）的 El Forn 滑坡。它的剪切带由志留纪的黑色页岩形成。使用该滑坡的岩心样本，我们进行了矿物学和微观结构分析（XRPD、SEM-EDS 和 MicroCT），并结合力学测试（液限、塑限）来研究剪切材料内部结构之间的相互作用带及其机械响应。我们的结果表明，材料的最高机械改变发生在剪切带的中心，其中页硅酸盐完全平行于剪切方向排列。晶体的排列和它们面对面的接触增加了材料的塑性指数并降低了其孔隙率。因此，剪切运动重新排列了剪切带内层状硅酸盐颗粒的接触，