Hydration-induced fractures in shale with silt layers: A perspective on slope stability

This study investigates the phenomenon of slope failure in shale, particularly in the context of heavy rainfall events. Despite the critical role that water plays in influencing the stability of shale slopes, the effects of hydrological conditions on their structural integrity remain inadequately understood. To address this gap, the research integrates field observations with controlled laboratory experiments aimed at elucidating the relationship between water infiltration and shale stability under varying boundary conditions. Shale blocks without silt layers (SNSL) and those with horizontal (H-SSL) and vertical (V-SSL) silt layers were considered. Vertical tensile fractures were observed in SNSL blocks, while H-SSL blocks displayed horizontal fractures along the silt layers, particularly at failed corners in the BFC. Fractures along the silt layers and diagonal fractures were more pronounced under the BCC. V-SSL blocks exhibited the formation of vertical rock columns along the silt layers, which were more common in the BFC. Inclined small fractures were commonly observed under the BCC. In a wet environment, shale demonstrates high responsiveness, and its behavior in the presence of water is complex. Water interaction with shale blocks leads to fracture formation, influenced by the clay matrix and silt layers. The introduction of water alters the clay matrix, resulting in tensile fractures. Silt layers act as weak planes, facilitating fracture propagation. Notably, shale is vulnerable under the BCC, with increased vulnerability under the BFC, particularly due to silt layers with outward-facing dips. The study recommends constructing retaining walls and applying polymers to enhance local and regional stability, mitigating the risks associated with slope failure.