Author(s): Rhythm Bhattarai; Umesh Singh; Pawan Bhattarai

Linked Author(s): Pawan K Bhattarai

Keywords: Bridge failure. River bed erosion; Bridge scour; Abutment scour; Delft3D

Abstract: Pier and abutment scour caused by changes in river morphology is a significant problem globally, especially in alluvial river reaches can cause bridge failures. The collapse of an under-construction bridge over the Triyuga River in Gaighat region of Udayapur District, Nepal, resulting from scour-induced subsidence of specific piers at vicinity of right abutment, is one such example of a bridge failure in an alluvium reach. This study investigates potential reach-scale hydraulic and morphological phenomena causing the failure of the bridge. Satellite image analysis and 2D morphological modeling were used in the study. The morphological evolution during the construction of the bridge showed that the approach flow to the bridge axis shifted from the left bank to the right bank, mainly caused by the natural phenomena. The numerical model results revealed that the concentration of the approach flow and deflection at the abutment at the right bank resulted in high river bed erosion at the piers located at the right bank causing their subsidence. The study suggests that streamlined approach flow is essential for bridge opening and the presence of a guide bund/ embankment can prevent high river bed erosion at the bridge. The study also shows how a process-based modeling tool can assess flow and morphological impacts on bridge scour and inform the design and construction of future bridges in the region to ensure their longevity. In alluvial reaches, reach-scale numerical simulations are suggested to predict the morphological behaviors of river during design process of bridges.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p1331-cd

Year: 2023