Experimental study of the viscoplastic dambreak wave dynamics and the impact force exerted on rigid structures

Surface sediment-laden flows, such as landslides, Debris, and mud flows or hyperconcentrated fast floods, are gravity-driven transient processes, usually moving over steep slopes, with high solid concentrations and complex non-Newtonian behavior. These geophysical flows involve the mobilization of large masses of water, sediments, and solid materials. Better risk evaluation tools and more effective protection measures are required to mitigate their destructive potential for facilities and population. In this sense, reliable experimental data are essential to validate those models. This work presents a novel set of non-intrusive laboratory measurements for a viscoplastic dambreak wave moving over an inclined slope and impacting on an obstacle. The force exerted on the obstacle, the transient flow depth, and the free surface velocity are provided for five different experiments of increasing fluid mass in the reservoir. The measured data allowed us to relate the force signal evolution to the flow dynamics around the obstacle. For low mass experiments, a force signal with two peaks, P1 and P2, respectively, was measured. As the involved fluid mass increased, a sharp third force peak P3 appeared and became as high as P1 and P2. The first force peak P1 was related to the momentum dissipation, whereas the second P2 and the third P3 peaks were induced by the fluid pressure upstream of the obstacle. Moreover, for high mass experiments, a sudden force drop was observed between the peaks P2 and P3, caused by the appearance of marked non-hydrostatic pressures upstream of the obstacle. This experimental dataset provides enough temporal–spatial resolution to characterize properly the impact of non-Newtonian shock waves on structures and can work as a reliable benchmark test for computational models.