Towards rational use of baffle arrays on sloped and horizontal terrain for filtering boulders

Baffle arrays are used to filter boulders from granular flows, such that the impact load exerted on barriers is reduced. However, current guidelines provide limited recommendations on baffle design. In this study, a calibrated Discrete Element Method modelled boulders entrained in a bulk granular assembly interacting with baffles and a terminal rigid barrier. Different baffle spacings relative to the boulder diameter (1 < s/δ < 4) were considered. A ratio of s/δ=1 is recommended for reducing the impact load by up to 80%, whilst s/δ = 4 renders an array of baffles inadequate for filtration. The optimum configuration is a staggered array with three rows of baffles on a horizontal plane in front of a barrier. This layout reduces the peak discharge by up to four times more than a similar array on sloping terrain, compared to channels without baffles. Furthermore, the transition from sloping terrain to a horizontal plane works together with the array of baffles to dissipate flow kinetic energy. On the horizontal plane, baffles attenuate the flow velocity more as the Froude number Fr increases, implying that baffles should be used if high Fr are anticipated. Finally, guidance is provided on estimating load attenuation from boulder filtration.

Computational investigation of baffle configuration on impedance of channelized debris flow

Channelized debris flows surge downslope in mountainous regions and have large impact forces. Arrays of debris flow baffles are frequently positioned in front of rigid barriers to engage torrents and attenuate flow energy. They are regularly designed on empirical and prescriptive basis because their interaction mechanism is not well understood. Numerical back-analysis of flume experiments using the discrete element method (DEM) is conducted to provide insight on flow interaction with an array of baffles. Varying configurations of baffle height, a second staggered row, and spacing between successive rows are examined. Upstream and downstream kinematics are monitored to capture and compare the Froude number, kinetic energy, and discharge resulting from each baffle configuration. Results from this study reveal that the height of baffles can be categorized relative to the initial approach flow depth (h), namely tall baffles (1.5h) and short baffles (0.75h). Tall baffles are characterized by the development of upstream subcritical flow conditions, whereas short baffles exhibit supercritical upstream conditions. Furthermore, tall baffles facilitate the suppression of overflow, and short baffles lead to excessive overflow that is supercritical in nature. Less flow attenuation occurs as the distance increases both upstream and downstream from each array of baffles. A second staggered row of short staggered baffles is ineffective in reducing debris kinetic energy, whereas tall baffles should be positioned as close as possible.