In recent years, heavy rainfall disasters have caused frequent damage to bridge piers due to scouring and have resulted in the fall of bridges in many areas in Japan. The objective of this study was to investigate the effect of local scouring around the downstream of the piers on the local scouring around the center of the river flowing at an angle to the piers. It was found that when the center of the river flows at an angle to the piers, the scouring area becomes wider from the upstream to the downstream of the piers because of the longer inhibition width of the piers positioned perpendicular to the water flow. The downstream scouring depth tends to be smaller than the upstream scouring depth. In addition, the time to the onset of tilting deformation of the piers increases with the inhibition width of the piers positioned perpendicular to the flowing water.

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In recent years, tsunamis caused by earthquakes and flooding associated with heavy rainfall have occurred in Japan. It has often been reported that bridges collapsed because of the outflow of the bridge superstructure and the scouring of the bridge pier resulting from these causes. However, to simulate these phenomena, it is necessary to carry out a coupled analysis of three types of behavior of the structure, ground, and fluid, and the calculation cost is very large. Therefore, the examination of this phenomenon has not currently achieved much progress. The purpose of this research was to perform a fluid-ground-structure simulation (such as for the collapse of a bridge pier because of flooding) at low cost, using a general-purpose physics engine. In this study, the focus was on the simulation of large deformations of the fluid, ground, and structure, and all objects were modeled with particles. First, the parameters that can simulate the behavior of the fluid were set appropriately by using the dam break problem. Subsequently, the flooding phenomenon in a river and the scouring phenomenon on a bridge pier on the ground were simulated using these parameters.

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