PROPOSAL FOR A METHOD TO PREDICT THE LOCAL SCOUR DAMAGE OF RIVER BRIDGES AND TO EVALUATE THE RESIDUAL BEARING CAPACITY AFTER SCOUR

<p> In recent years, heavy rains and typhoons have become increasingly severe due to climate change, resulting in accelerated scour of river-crossing bridges supported by shallow foundations. Local scour causes the soil on the upstream side of the pier to be excavated and washed away by the river flow, destabilizing the foundation, and causing it to settle and slope upstream. Therefore, there is a need to improve the accuracy of predicting the extent of scouring damage in advance and the evaluating of bearing capacity after the damage. In this study, we conducted model tests using aluminum rods ground model, through a series of processes from scouring phenomena to bearing capacity tests. The purpose of this study is to propose two methods. The first is to estimate the scour scale that leads to large-scale damage that causes piers to collapse in terms of the bearing capacity of the ground. The other is a method to evaluate the residual bearing capacity after medium-scale damage where residual settlement and tilting have occurred without collapse. As a result, it was shown that the extent of scouring leading to large-scale damage can be quantitatively evaluated in terms of the relationship between the width of the foundation perpendicular to the bridge axis and the height of the center of gravity of the piers, and it was also shown that it is possible to quickly restore the functionality of the bridge (i.e., resume its use) by simple emergency repair of the damaged foundations if the residual eccentricity ratio estimated from the residual inclination angle after medium-scale damage is within 1/10.</p>