Flexible barriers have been widely applied in rockfall mitigation in recent years. However, the behavior of flexible barriers under the impact of boulders is still not fully understood. To investigate the interaction between a flexible barrier and a falling boulder, a large-scale physical modeling device has been constructed at a site in Hong Kong. Using this device, large-scale impact tests using boulders with different diameters were conducted. Test results are presented and analyzed in this paper. The motion of the boulder during impact is traced and analyzed. The impact forces on the flexible ring net and the supporting structures are measured and compared. From the comparison, the impact reduction rates (IRR) of boulders with different diameters are calculated. Moreover, a simple approach for estimating the impact loading of a boulder on a flexible barrier is proposed in this study. This approach is calibrated and verified using measured impact forces in the tests. 相似文献
Retention behavior of a flexible barrier in mitigating a granular flow is still an open problem not fully understood, especially due to the complexity of the granular material and the flexible barrier. Understanding the retention mechanism and quantifying the influencing factors of retention efficiency are desirable for optimizing the design and minimizing the maintenance cost of a debris-resisting flexible barrier. In this paper, a numerical model, based on the discrete element method, is presented, calibrated, and validated to analyze the interaction between a granular flow and a flexible net. A full-scale numerical simulation is first performed to compare with a large-scale physical modeling test in the literature and validate the applied parameters in the simulation. The interaction and deposition characteristics of the granular flow interacting with a flexible net are revealed. Afterward, parametric study is performed to investigate the effects of the internal friction angle (φ) of debris material and the relative mesh size of flexible net on the retention efficiency and clogging mechanism of a flexible barrier. The simulation results illustrate that the particle passing ratio (P) increases with increment of the friction angle of particles and enlargement of the mesh size of a flexible net. Both parameters have critical effects on the retention efficiency of a flexible barrier in intercepting a granular flow. Therefore, the friction angle and the particle size distribution characteristics of the debris material are suggested being used for optimization of the mesh size and more efficient design of debris-resisting flexible barriers.