Flume investigation of debris flow entrained boulders with cylindrical baffles and a rigid barrier

Abstract

Large boulders entrained by debris flow can generate destructive impact force and cause significant damage to a rigid barrier located downstream. Baffle arrays can be installed in front of the rigid barrier to reduce the potential damage from large boulders by dissipating flow energy with filtering boulders from the debris flows. In this study, to investigate the effect of baffle arrays on the flow behavior and the dynamic impact force of debris flows acting on the terminal barrier, small-scale flume experiments were performed with various baffle configurations. After the experiments, the dynamic flow behavior with boulders, impact forces, and travel distances of boulders, were analyzed with transverse blockage ratios and numbers of baffle rows. As a result, entrained boulders in debris flows significantly increased impact force about six times. With the installations of baffle arrays, however, peak impact force decreased by an average of 70 % and by up to 94 %. In addition, increasing the number of rows of baffles from one to two led to an average reduction of 50 % in impact force for each transverse blockage ratio. However, in the case of one row of baffles, the impact force reduction for high s/δ values proved to be less effective compared to the other baffle configurations. Finally, the results of this study can provide appropriate ranges for the baffle spacing and the number of baffle rows in the baffle design to estimate the load attenuation due to boulder filtration.