Erosion dynamics in loess with artificial joints: An experimental approach

Subsurface erosion induced by water seepage is a critical mechanism triggering geological disasters in loess regions, characterized by their unique joint structures. This study systematically investigates the influence of key factors, including seepage velocity, soil properties (dry density and initial moisture content), and joint characteristics (aperture, roughness, shape, and orientation of micro-convex body), on the subsurface erosion dynamics of jointed loess. By utilizing a self-developed visualization apparatus for specimens with artificial joints, a series of seepage-erosion tests on jointed loess were conducted. Experimental results demonstrate that inflow velocity is the primary factor controlling the erosion rate, with higher velocities leading to greater erosion mass. Loess dry density exhibits a strong negative correlation with erosion mass, and samples with a dry density of 1.4 g/cm³ show enhanced erosion resistance. When the initial moisture content of the jointed specimens reaches 15%, the erosion resistance of the specimens drops significantly. Joint characteristics play a critical role: larger joint apertures increase erosion, while an appropriate micro-convex body density (D_m = 10) improves resistance. Triangular joints cause more intense erosion than rectangular joints. In vertical joints, when flow is perpendicular to surface micro-features, the synergistic effect of gravity and hydraulic erosion is enhanced, resulting in significantly higher erosion in vertical compared to horizontal joints. Furthermore, a strong linear correlation exists between the joint-to-sample volume ratio and cumulative erosion mass. The morphological evolution of joints during erosion progresses through four distinct stages: capillary-permeability dominance, channel generation, channel expansion, structural instability, and ultimately culminating in sample failure.