Oblique Runup and Impact Load of Debris Flow on Deflection Barriers

Deflection barriers are a critical mitigation measure for redirecting debris flows away from high-risk zones. However, their design is complicated by the oblique shock dynamics that occur upon impact, leading to complex runup and loading patterns that are not fully characterized. To address this gap, this study develops and validates an analytical model for predicting the runup height and impact loads generated by oblique debris-flow shocks. The theoretical model, derived from momentum conservation principles, explicitly links the runup height and peak impact load to the incoming flow conditions, notably the Froude number. A series of scaled flume experiments were designed to test the model's validity. By systematically varying the channel slope and gate opening height, we generated a range of supercritical flows to quantify the influence of incoming kinetic energy on shock phenomena. Results demonstrate the theoretical predictions show excellent agreement with experimental measurements across all tested scenarios. Furthermore, analysis confirms that the normal shock condition serves as a conservative upper bound for oblique shock impacts, providing a valuable simplified criterion for preliminary design. Importantly, we identify a key limitation: the model's accuracy decreases in flows where pronounced dead zones form downstream of the barrier, as the assumed shock geometry no longer holds.