DEM investigation of the interaction between rapid dry granular flow and dual-slit structures

Granular flow are considered as the one of the most hazardous geological disasters in mountainous area. Multi-slit structure including one or more slits could partially block the granular flow and thus allow downstream flow at a reduced rate, have played a vital role in granular flow geohazard mitigation. This study conducted a series of discrete element method (DEM) models to investigate the interaction between dry granular flow and multi-slit structures (dual-slit structures in this study), and characterize the regulation functions of multi-slit structures. The dynamics process of flow-slit structure interaction and the effects of granular arches in multi-slit structures has been explicitly analyzed. Based on the analyses, a further modified Beverloo law considering the contraction behaviors is proposed to quantify the relationship between the mass outflow rate and relative slit size. The simulation findings show that both the slit size, slit numbers and slit separation have a significant impact on the regulating functions, such as pile-up height, mass outflow rate, and grain-trapping efficiency. In addition, it was found that, the shearing effect of the particles between the two nearby slits, the forming of the granular arches and the Froude characteristics might together influence the flow-slit interaction process, a key value of 4 for relative slit separation under a lower Froude number (5.86, in this study) was found to offer a reference for multi-slit structure scientific optimization design.