An instrumented flume to investigate the initiation mechanism of the post-earthquake huge debris flow in the southwest of China

The 2008 Wenchuan Earthquake in SW China in the Sichuan Province generated many co-seismic landslides, which delivered a huge amount of loose co-seismic landslide deposits. It caused a dramatic increase in debris flow occurrence in the subsequent years. The mechanism of these runoff debris flows has not been completely understood. The study of the complexity of the phenomenon, such as runoff-induced erosion in initially unsaturated granular deposits, and damming and breaching effects caused by instability in gully banks due to erosion, requires the use of a well-equipped flume. To this aim, an instrumented flume was built at Chengdu University of Technology for the study of the initiation mechanism. Advanced equipment such as the 3D laser scanner was used to monitor the change in tomography of the slope during the test. And some sensors for unsaturated soils such as TDR and tensiometers were installed to capture the change of hydraulic properties of soil. Especially, the erosion was analyzed quantitatively by collecting the washing-out material every 20 s. The preliminary experimental results are very encouraging for investigating the initial mechanism of debris flow. The erosion curve was obtained, and the damming and breaching effect was found to be of key importance to the initiation process.