Symmetrical Rock Fractures Based on Valley Evolution

During preliminary reconnaissance at a hydropower station site in Southwestern China, a unique phenomenon of deep-seated fractures was identified within the slopes, which were symmetrically developed on both banks. These features occur within unloading zones and manifest as tensile fractures with deep-seated fractures exhibiting unloading characteristics. This study systematically analyzes the spatial distribution, developed patterns, and structural attributes of these deep fractures. Through numerical model of stress field dynamics during valley evolution, we investigate the relationship between stress states and deep fracture formation. Research demonstrates that these fractures result from energy release through unloading at stress-concentration zones in slope interiors, driven by rapid valley incision under high in situ stress conditions. This process is further conditioned by specific slope geometries, rock mass structures, and geomorphic settings. Crucially, river incision rate governs fracture depth, while the number of incision cycles significantly controls fracture aperture. These findings provide a theory for understanding deep-seated slope failure mechanisms and engineering mitigation in analogous geological environments.