Fundamental framework to design multiple rigid barriers for resisting debris flows

Abstract

Hong Kong, Taiwan and numerous other areas around the world are vulnerable to debris flows. A single rigid barrier is generally installed at the end of a potential flow path to intercept such flows. However, such an approach enables flows to accelerate and increase in volume before impacting a rigid barrier. Thus, large barriers are required to resist higher impact forces. An alternative to a single rigid barrier is series of small rigid barriers installed along a potential flow path. However, no such design codes are available for engineers to design safe and economical multiple barriers. One of the major challenges in designing multiple rigid barriers is determining the appropriate spacing between the barriers to optimise the design of subsequent barriers in the flow channel. A new analytical framework developed to design multiple rigid barriers is presented in this keynote paper. The impact of a debris flow on a barrier is scale dependent; thus, the analytical framework is evaluated by three types of flows impacting dual rigid barriers in two different sized flumes. Physical experiments using dry sand in a 5 m-long flume and water and two-phase flows in a 28 m-long flume are conducted. The validity of the framework is verified and findings are discussed.