Buried and displaced: moving characteristics of building fragments in debris flows

Abstract. Buildings can be destroyed and displaced from their original position in large-scale debris flows and flow-type landslides. Accurate prediction of the relocated position of buildings within debris-flow deposits is urgently needed for emergency rescue. This has been proven to be challenging due to the intricate nature of physical processes. In this study, an elucidation of the complicated physical mechanisms associated with the movement of building fragments within debris flows is provided. Well-controlled flume experiments are conducted to verify the theoretical predictions, and an inertial measurement unit is embedded within the model of the building block to monitor the block's movement mode. An analytical model considering the hydrodynamic drag force, earth pressure, and basal friction is further established. Dimensionless parameters are derived to clarify the underlying physical mechanisms. The results demonstrate that the deposition position of building fragments is predominantly governed by the basal sliding velocity of debris flow. The dimensionless parameter αFr² informs optimal model selection to enhance predictive accuracy within this framework. These findings provide actionable guidance for post-disaster emergency rescue by enabling precise positioning of buried structures.