Multiple debris-resisting barriers with basal clearance: A study on impact force

Optimising debris-resisting barriers is of paramount importance on constructing cost-effective and eco-friendly mitigation works. Multiple barriers with basal clearance can potentially serve as an optimal approach because they can facilitate flow energy dissipation, reduce the impact force on each barrier, ease the maintenance and resist a large flow volume. However, the design impact force of multiple barriers with basal clearance remains empirical. In this study, physical model tests were carried out to investigate the impact force of idealised dry granular flow against dual rigid barriers with basal clearance using a 5-m-long flume model. Measured impact forces show that basal clearance attenuates the impact force exerted on the second barrier by apportioning the impact forces from basal discharge and overflow. Basal discharge dissipates the kinetic energy of landing flow and reduces the impact force of overflow. A rational design of basal clearance serves as an efficient measure for optimising the design of multiple barriers.