Investigation into Noncontact Protective Strategy of Ancient Bridge Foundations against Scour Risk: An Experimental Study

Scour is a natural hazard caused by water flow on erodible beds and has been identified as one of the key problems leading to the failures of bridges. Unlike those built in recent decades, ancient bridges have served hundreds of years and have been confronted with unpredictable natural hazards and anthropogenic disasters. Meanwhile, considering their historical and cultural value, it is not recommended that ancient bridges be repaired and reconstructed using the same strategies and techniques as modern bridges usually adopt. This study presents experiments investigating the scour mechanism and protective strategies, namely foundation reinforcement and noncontact pathways. An ancient bridge built in the year 1119 AD, named Buying Bridge, is used as the prototype. Results indicate that the scour process is related to the interaction between coming flow and corners, which appear commonly in the piers and foundations of ancient bridges due to the techniques used at that time. The strategy to reinforce the ancient bridges and make the foundation a larger shape, which is used for repair and protection in the current, cannot effectively reduce the scour depth in the long term. Due to the comparisons, installing stepping stones upstream of the bridge can reduce the scour and relieve the pressure on the ancient bridges.