Multi-scale flume investigation of the influence of cylindrical baffles on the mobility of landslide debris

Debris flows travel downslope at high speed and often cause damage to the infrastructure of societies around the world. With increasing extreme rainfall events and urbanization in mountainous regions, effective structural countermeasures are in increasing demand. Over recent years, engineers have proposed the installation of an array of cylindrical columns, called baffles, to reduce the velocity of debris flows in catchments. However, existing design methods are highly empirical in nature, so it is unclear whether they are adequate or over designed, and appropriate specifications and arrangement of cylindrical baffles have still not been suggested. Moreover, previous experimental studies have predominantly modeled debris flows as dry granular flows at a laboratory scale. In this study, to investigate the effect of cylindrical baffles on the dynamic characteristics of debris flow, a series of small-scale flume tests was conducted using a flume equipped with devices to measure the flow interaction between baffles and the dynamic loads of debris flow. In addition, to investigate the scale effect of debris flows and cylindrical baffles on flow characteristics, large-scale tests were also performed according to different numbers of rows of baffles for similar baffle configurations confirmed by small-scale tests. Using the small- and large-scale test results, this study analyzed the energy dissipation and dynamic impact characteristics according to the height and number of rows of baffles. The analysis results showed that the use of baffles increased the energy dissipation of debris flows, and an additional row of baffles produced greater effects on the energy dissipation in the debris flows. Based on the test results, the average dynamic pressure coefficient for cylindrical baffles was 0.31. •The use of baffles reduces the frontal velocity and flow energy of debris flow.•Downstream flow velocity and energy can be reduced by increasing the row numbers and height of baffles.•The small-scale and large-scale test show similar trend for the dynamic flow characteristics.•Based on the test results, the average dynamic pressure coefficient for cylindrical baffles is 0.31.