Sensitivity analysis of a built environment exposed to the synthetic monophasic viscous debris flow impacts with 3-D numerical simulations

Abstract

Abstract. The characteristics of exposed built environments have a significant effect on debris flow impacts on buildings, but knowledge about their interactions is still limited. This paper presents a sensitivity analysis on the peak impact forces on a whole building resulting from the built environment parameters, including the orientation, opening scale of the target building, and azimuthal angle and distance of surrounding buildings. The impact forces were obtained from the monophasic viscous debris flow with a synthetic and simplified hydrograph using the FLOW-3D model, a computational fluid dynamics approach, verified through the physical modeling results. The results show that the surrounding buildings' properties have significant roles in determining the peak impact forces. A shielding effect or canalization effect, which reduces or increases impact forces, respectively, can be produced by changing the azimuth angle. A deflection wall for building protection is recommended according to the shielding effect. A narrowed flow path, determined by both the azimuth angle and distance, has a significant effect on the variation in impact forces. In addition, it is concluded that a splitting wedge should be designed following a criterion of avoiding the highest flow depth – the maximum approaching angle – appearing near the longest wall element. The protruding parts caused by changing the building's orientation contribute to increasing impact loads within a shielding area. A limited opening scale effect is observed on the whole building if there is sufficient time for material intrusion. The insights gained contribute to a better understanding of building vulnerability indicators and local migration design against debris flow hazard.