Effects of barrier deformability on load reduction and energy dissipation of granular flow impact

Abstract

Granular flows, such as debris flows, are commonly arrested by using deformable barriers, but their designs rely heavily on empiricism. The fundamental impact mechanisms between a granular flow and a deformable barrier have yet to be elucidated. Thus, estimating the impact load on deformable barriers remains a key scientific and engineering challenge. In this paper, the material point method (MPM), with the Drucker-Prager yield criterion associated with a linear elastic model is calibrated against physical model tests. The effects of barrier deformability on the impact force induced by a granular flow are examined. For simplicity, a vertical and deformable cantilever barrier with different flexural rigidity is simulated. The dissipation of energy of a frictional granular assembly subjected to shear is considered in the simulation. A threshold 3EI/H3norm = 6.3 × 10−5 (normalized by the stiffness of a typical 1-m thick reinforced concrete cantilever barrier) is identified in this study to demarcate between rigid and deformable barriers. A maximum deformation of only 3% of the total barrier height and corresponding reduced relative velocity are enough to attenuate the peak impact load by 40% compared to a rigid barrier. Around 85% of the dissipated energy occurs during the pile-up process, the interaction between the incoming flow and deposited material along the slip interface is effective in dissipating flow kinetic energy.