Laboratory investigation of dam-break flow of a mixture of water and granular matter

Some preliminary experimental results concerning the velocity of the snout of a debris flow originating from the instantaneous opening of a sluice-gate (dam-break) in a rectangular flume are presented. The measurements have been performed by varying the slope and roughness of the channel bed and the amount of cohesionless solid material (gravel) mixed with water stored in a tank above the sluice-gate at the beginning of the test. It has been observed that the bed roughness does not immediately affect the evolution of the debris flow and its effects are seen only after a certain time from the opening of the sluice-gate. This observation provides a way to evaluate the time scale of the resistance force in the debris flow. Moreover, sometimes the dam-break wave evolves into a fully developed flow, allowing a quantitative description of the steady motion of a debris flow.