Class A prediction of debris flow impact forces on dual rigid and flexible barriers: MPM modelling

Abstract

Modelling flow-like landslides interacting with barriers poses significant challenges, particularly to predict the impact dynamics. For the design, it is essential to assess the forces exerted by the flow, the depth and velocity of the flow during the impact, the stress and strain distribution in the barrier, and the amount of overflowing material. The direct measurement of these quantities in well-controlled flow-like landslides against monitored barriers serves as a valuable means of understanding the flow-barrier interactions, and it is instrumental in calibrating and validating numerical models. Flume tests were conducted in the Hong Kong University of Science and Technology using the 28-m-long flume for investigating the efficacy of single and dual rigid and flexible barriers. These tests were utilised as part of a “Class A prediction” exercise in May 2022, with the international research community involved. In this context a numerical model based on Material Point Method (MPM) was used to forecast the flow dynamics and the flow-barrier interactions. These predictions were made in advance, without knowledge of the outcomes to be predicted, and were based on limited input quantities such as geometry, barrier setup and material properties. The capabilities and limitations of the employed MPM numerical model are discussed.