Seismic shaking-enhanced impact effect of granular flow challenges the barrier design strategy

Abstract

Barrier design considering the coupling effect of flow impact and seismic shaking is challenged and has not been covered in previous researches, thus we performed numerical simulations to obtain fundamental insights on this matter. The influence and mechanism of the effects of shaking direction and magnitude on the impact processes of dry granular flow are investigated using a range of slope angles. Slope-normal shaking exhibits the most significant influence on flow mobility. Under 0.99 g, the maximum velocity is enhanced by 10.23% and the accumulative kinetic energy increases by 8.12%, which is caused by the coupled effect of reduced frictional resistance and energy supplement, where the latter dominates. Slope-longitudinal shaking exerts a more significant effect on the impact force, showing that the overall peak force increases by 42.14% under 0.99 g shaking, which implies that the enhanced mobility is not the main cause of enhanced impact effect but the evolution of dead zone, whose stability is altered by seismic shaking bringing and leads the barrier design load to largely exceed the value required by traditional design strategies. The influence of shaking on granular flow impact dynamics is substantially more significant when the flow conditions are gentle: the normalized force discrepancy is reduced from 77.05% to 41.36% when the slope angle is increased from 25° to 40° under 0.99 g slope-longitudinal shaking. In addition, the limitations of current models and direction for future work are discussed, including the effect of the fluid phase in debris flow, real seismic ground motion, and barrier types.