149 / 2024-02-21 10:05:32

EXPERIMENTAL STUDY ON COUNTERMEASURES WITH GUIDE PILES AGAINST LOCAL SCOURING AROUND A BRIDGE PIER

Countermeasures,Gude Piles,Horseshoe Vortex,Local Scouring,Bridge Pier

In recent years, rivers in Japan have been suffering from increased flood flows due to torrential rains at the end of the rainy season and heavy rains caused by typhoons, resulting in the loss of bridges and the failure of levees due to flooding, as occurs every year.

In addition, the construction of erosion-control dams and the extraction of gravel in river channels to improve river discharge capacity have reduced the supply of sediment from upstream, resulting in a general decline in the riverbed. Under these conditions, localized scour around structures such as bridge piers, bed stops, and intake weirs in the river channel becomes more pronounced.

Countermeasures against local scour of bridge piers include protection against riverbed scour or control of horseshoe eddies with strong downstream currents. In Japan, the former is often adopted as a countermeasure for localized scour, and there have been research cases in which permeable rubble piers and impermeable protection piers with concrete blocks have been applied around piers. In the latter, there have been cases where the shape of the piers has been improved to streamline or vanes or piles are installed upstream of the piers, but these have not been studied under systematic conditions, and there have been many unknown points.

In this study, we focused on the latter, which has a smaller environmental impact, and installed flow guiding piles directly upstream of the piers to suppress the horseshoe vortex around the piers and the downstream flow in front of the piers to reduce scouring around the piers.

In many previous studies, the suppression effect of countermeasures on local scour of piers was examined only in terms of the maximum scour depth, but in this study, the volume of flow-conducting piles and scour pits around piers were also considered in consideration of the stability of piers.

The experimental results showed that the maximum scour depth around the piers was reduced by about 50% and the volume of scour holes was reduced by about 20% when the flow-conducting piles was installed compared to no countermeasure.