Abstract: Debris flows are a critical focus in the prevention of geological disasters in mountainous regions due to their complex solid-liquid interactions and high destructive potential. Flume experiments were conducted to simulate debris flows using spherical particles and glycerol-water mixtures. Triaxial stress sensors, ultrasonic sensors, and high-speed cameras were systematically employed to quantify flow dynamics and substrate stress responses. Results indicate that basal normal and shear stresses exhibit positive correlations with liquid viscosity, slope gradient, particle count, and particle size—with particle size being the dominant factor. Transitions from laminar to turbulent flow amplify particle collisions, increasing stress fluctuations and the erosive capacity of debris flows. Additionally, particle agitation intensity is directly linked to stress fluctuations, thereby governing flow stability and erosion patterns. This work provides new insights into debris flow mechanisms through quantitative analysis of phase interactions.