Experimental and numerical study on the load and deformation mechanism of a flexible net barrier under debris flow impact

High-strength flexible net barriers have achieved a certain effect in mountainous debris flow prevention, but research on the mechanism of structural stress and deformation is still developing. This study first presents an analytical model based on the quasi-static mechanical equilibrium to evaluate the geometric nonlinearity and the load performance of the structure and then conducts a flume experiment to reveal the load mechanism of the structure. Then, a full-scale simulation is performed to investigate the deformation and failure of the flexible net barrier impacted by the debris flow via PFC3D software. The results show that the deformation of the flexible net barrier occurs not only in the direction of flow but also in other directions to make the structure force balanced under debris flow impact. The load impacting on the barrier is far less than the total impact force exerted by debris flow. The flexible barrier has an obvious effect to block a coarse debris flow, and the blocking capacity is related to the volume of debris flow and the slope gradient of the flume. The displacement patterns of loaded cable in the experiment and the simulation are different, but the cable under non-debris flow impact is only dragged by the mesh rope showing a regular parabolic shape, and the tension inside the flexible mesh is far less than that of the transverse cable. In addition, the model shows the failure characteristics of flexible barrier under large-scale debris flow, which plays a guiding role in practical engineering design of the structure.