The influence of the slit size and spacing on the impact dynamics of dry granular flows on slit dams

Slit dams play a crucial role in mitigating natural granular flows in the form of geophysical mass movements. The accurate estimation of the maximum force experienced by slit dams is a vital consideration in their design. However, understanding of the coupled influence of the incoming flow conditions and dam geometry, specifically the slit size and spacing, on the granular flow impact characteristics and forces remain incomplete. In this research, the Discrete Element Method (DEM) is used to simulate the interaction process between gravity-driven granular flows and slit dams with varying slit sizes and slit spacing. Impact characteristics are evaluated from the forces and pressures experienced by the barrier that falls between two slits, here called the divider. For a constant divider size, increasing the slit size amplifies the maximum impact force. However, once it exceeds a threshold size, enlarging the slit size diminishes the force due to a restriction from run-up height. Conversely, maintaining a constant slit size while increasing the divider size weakens the force. The influence of the slit and divider size and incoming flow conditions on the maximum force are summarized by a scaling relationship that captures the linear dependence of the impact force on the ratio of slit and divider size. Pressure distribution models are further proposed based on this scaling relationship. These outcomes provide new insights for the design of effective flow-resisting slit dams.