Gabion baskets are the preferred rockfall mitigation method from an economic, environmental, and maintenance perspective due to their low cost to build, more natural appearance, ability to be covered with landscaping, and ease of repair by maintenance crews. However, there is considerable risk and liability issues in deploying gabion barriers owning to the general inability to characterize the serviceability and efficacy post-impact. Due to the fact that performing full-scale physical impact tests on gabion barriers is not economically feasible, these gabion barriers are currently designed for the static loads associated with soil retention. Clearly, this design approach may lead to the barriers being over- or under-designed. Therefore, numerical modeling of the impact loads on gabion rockfall barriers are conducted in this study to explore the behavior of the barriers during extreme rockfall impacts and the subsequent possible failure modes. Specifically, a numerical approach based on the discrete element method is developed in this study to address the issue involving transient dynamic rockfall impacts. The model proposed focuses on reproducing the behaviors of the gabion baskets under sequential impacts.

1. INTRODUCTION

Gabion baskets are large, multi-modulus, welded wire or wire mesh boxes filled with manmade gravels to resist lateral earth pressure and rockfall impacts (Schuster, 1974). This structure has been widely used along road corridors in mountainous areas to protect the infrastructures and the pavements, as shown in Figure 1. Though Oregon Department of Transportation (ODOT) frequently uses gabion baskets as rockfall barriers, this mitigation method currently lacks design standards and industrial design methods, presenting considerable liability and safety concerns to ODOT in the event that the gabions are pushed into the roadway by a large rockfall event or otherwise fail under the high kinetic energy (Chau et al., 2002) of such an event (Figure 2). In addition, there is no generally accepted approach to assess the life cycle of these systems, particularly after a rockfall event. This is partially due to the fact that experimental study of these impact loads would be burdensome, both in terms of complexity and cost. For many rock slopes along ODOT corridors, gabion baskets are the preferred rockfall mitigation method from an economic, environmental, and maintenance perspective due to their low-cost to build, more natural appearance, ability to be covered with landscaping, and ease of repair by maintenance crews, but there is considerable risk in using them without design criteria to support their use and assess their continued efficacy post-impact. Clearly, a systematic approach for design and life cycle assessment is needed, particularly, to evaluate the remaining strength of these baskets after severe rockfall impacts.

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