Three-dimensional modeling of the impact behavior of debris flows in areas affected by earthquakes

The 2008 Wenchuan earthquake triggered many landslides and caused high volumes of loose solid material to collect in gully drainage areas; over time, this material eroded and became the source material for multiple debris flows. On August 13, 2010, a heavy rainstorm struck the areas that were impacted by the Wenchuan earthquake. The resulting debris flows caused more than 2000 deaths and destroyed numerous buildings, bridges, and traffic facilities. To mitigate and/or prevent the negative consequences of such disasters in the future, it is important to have reliable and effective methods for predicting the impact behavior of these debris flows. In this study, we investigated the impact behavior of debris flows in post-earthquake areas using a three-dimensional model that is based on the particle flow code PFC3D. We verified our model by simulating a granular flow model test in a laboratory. We quantified the flow process and the impact force of the granular material; by comparing our model data to the test data, we found that the PFC3D model was capable of accurately simulating the dynamic behavior of the granular flows. We then used our model to estimate the propagation processes and the impact forces exerted on check dams by two large debris flows that occurred in the Wenchuan earthquake area. The results agreed with data collected during field surveys, and the PFC3D model can reproduce the dynamic behavior of debris flows in areas that had recently experienced significant seismic activity.