Enhancing system kinetics through size segregation in granular materials

The segregation process is a remarkable phenomenon in granular materials found in nature, occasionally accompanied by interlayer slippage. However, their impacts on system kinetic energy remain unclear. This study aims to quantitatively analyze the relationships between interlayer slippage, kinetic energy fluctuations, and fluidity during the segregation process of granular materials using three-dimensional Discrete Element Method simulations. The simulation parameters include size ratios (Sr: 0.5-1.0), volume ratios (Vr: 0.2-0.8), and inclination slopes (delta: 10 degrees-30 degrees). The results show that interlayer slippage at the top significantly reduces the degree of segregation, while slippage at the bottom has a smaller effect. A positive correlation is observed between kinetic energy and the degree of segregation, with the correlation being more pronounced on steeper slopes. Moreover, minimal vertical kinetic energy fluctuations induced by segregation significantly enhance granular fluidity, whereas interlayer slippage can reduce system kinetic energy by at least 50 %. These findings indicate that the widespread segregation process observed in long-runout landslides may promote their extreme mobility and destructive power by enhancing granular fluidity. This study may provide insights into granular system dynamics and practical guidance for landslide disaster prevention and mitigation.