Design recommendations for single and dual rigid debris flow barriers with and without basal clearance

Abstract

Debris flows pose threats to sustainable development in many countries worldwide, including China, Japan, Switzerland and USA. To mitigate these flows, rigid and flexible barriers are commonly installed along the predicted flow paths. To arrest large volumes of debris flow, several barriers may be installed in series to create a cascading effect to progressively decelerate and retain the debris. Barriers may even be designed with a basal clearance to allow small discharges to pass underneath the barrier to reduce the peak impact force. Despite the importance of barriers as life-saving assets, their design remains essentially empirical because of the highly heterogeneous and scale-dependent nature of debris flow. These features of debris flow have hindered an understanding of their fundamental impact mechanisms, thereby hampering the development of scientific design guidelines to enable robust and cost-effective barriers. This forum paper presents a collection of physical experiments modelling the impact mechanisms of the two extreme cases of water and dry granular flows, and two-phase debris flows against single and dual rigid barriers, and a single flexible barrier. Furthermore, the effects of a basal clearance on the impact dynamics of dry granular flow against a single rigid barrier are examined. Experiments were conducted at two different scales, including 5 m-long and 28 m-long flumes. Based on the observed impact mechanisms and measured data, a newly developed analytical framework for designing multiple rigid barriers was evaluated. Recommendations and procedures are provided for the design of single and multiple rigid barriers with and without a basal clearance.