Debris flows usually cause great destruction to the environment and human fatalities around the world. In recent decades, multiple flexible barriers have been recognized as an efficient approach to mitigate debris flow for densely populated areas with the the advantages of easy construction and cost-effectiveness. However, due to the complex deformation during flow-barrier interaction, the impact dynamics of debris flow against flexible barriers are not well understood, thereby hindering the effective design of engineering measures for debris flow mitigation.

In this research, centrifuge modelling was conducted to study the interaction between granular flow with different particle sizes and barriers with different stiffnesses under the prototype stress state. A newly developed test setu...[ Read more ]

Debris flows usually cause great destruction to the environment and human fatalities around the world. In recent decades, multiple flexible barriers have been recognized as an efficient approach to mitigate debris flow for densely populated areas with the the advantages of easy construction and cost-effectiveness. However, due to the complex deformation during flow-barrier interaction, the impact dynamics of debris flow against flexible barriers are not well understood, thereby hindering the effective design of engineering measures for debris flow mitigation.

In this research, centrifuge modelling was conducted to study the interaction between granular flow with different particle sizes and barriers with different stiffnesses under the prototype stress state. A newly developed test setup is used to measure the impact force and barrier displacement simultaneously. The coupled Discrete Element and Finite Element Method (DEM-FEM) was calibrated against the experimental data and further utilized to study the discrete loading on the flexible plate-type and net-type barriers. In addition, in order to model a broader range of flow types, like the viscous flow and frictional flow with small particle sizes, Material Point Method (MPM) is utilized to investigate the interaction process between flow and deformable structures.

The experimental study fully replicate the interaction process under the prototype stress state. It is found that the change in barrier stiffness has a significant influence on the impact dynamics. Around 10% barrier deformation can lead to nearly 40% reduction of impact force. Maximum barrier deformation occurs at the bottom of the barrier, and the lower half bears about 60% of the impact loading.

Granular flow dissipates most of its kinetic energy through internal shearing. Around 85% of the dissipated energy occurs during the pile-up process, and the interaction between the incoming flow and deposited material along the slip interface is effective in dissipating flow kinetic energy. A flexible barrier only absorbs less than 10% of flow energy, while facilitates longer shearing interface during the pile-up process, thereby dissipating more energy compared to that of rigid barriers. This study suggests to use the normalized particle diameter δ/h_f > 0.4 as a criterion to estimate if the peak impact loading is dominated by the impulsive loading of large particles.

The influence of frist flexible barrier on the dual barrier system performance is investigated. The deformation of flexible barrier can redirect the flow to roll back and reduce the runup height by around 30%. As a result, the landing distance can be reduced by the flexible barrier and more flow volume is retained by the flexible barrier.