Coupled numerical simulation of a flexible barrier impacted by debris flow with boulders in front

Flexible barriers have been widely adopted to mitigate the debris flow disasters. However, the research on the coupled interaction analysis between flexible barriers and debris flows with boulders in front is rarely reported. In this paper, a two-stage coupled modeling technique which can account for the debris mobility, the non-linear behavior of a flexible barrier, and the dynamic interaction between flexible barriers and debris flows is developed firstly based on the Arbitrary Lagrangian-Eulerian (ALE) method using LS-DYNA. The proposed coupling model is verified by a large-scale field test, comparing the flow velocity and flow depth of the debris flow, as well as the internal force and deformation of the flexible barrier. Further, the proposed numerical model is adopted to study the performance of flexible barrier impacted by debris flow with boulders in front. Two practical cases that the debris flow contains a single boulder with a diameter of 2 m and 1 m in front, respectively, are investigated. The impact positions are both the bottom center of the middle functional module of the barrier. The numerical results show that the barrier cannot intercept the debris flow with a boulder of 2 m in diameter. When the flexible barrier is subjected to three 1 m boulders in front of the debris flow, plastic hinges are formed at impact positions of the steel posts. It is recommended that additional protection measurements are required to maintain the structural integrity.