Experimental Research On The Ring-Wing Pier Against Local Scour

The pier local scour is one of the main reasons for washout of bridge. Many scholars and scientists at home and abroad made a large number of theory analysis and model experiments about pier local scour, and made a series of research results. But the hydraulic characteristics around pier and the scouring process and phenomenon are so complex and the influence factors are so much that a good solution is still not put forward to protect the pier against local scour. Therefore it is necessary to continue the research in the area.The flow near the pier include:the diving flow, inrush at upstream face of pier, impact flow in the pier foundation, uprush flow and vortex flow after the pie. And the diving flow is one of the main reasons that result in the pier local scour. The traditional protection methods are mainly to strengthen the pier, and hardly any methods are active to reduce local scour through reducing the diving flow.In light of this, the ring-wing pier was designed which can change the flow pattern of the piers at upstream face. The baffle can stop the diving flow at upstream face of pier and compel flow distributary to weaken the flow scour energy to pier and protect the pier. Velocity variation each section and the scour depth are analyzed to study the influence which the ring-wing pier to reduce the local scour, under the situation of various variable in the experiment,such as velocity, baffle position, baffle size and baffle shape, and compared with the situation that without baffle. The main results are as follows:①The ring-wing pier was designed and it is a new method and design principle to protect the pier local scour to add baffles in the pier.②Compared to the situation without baffle, the ring-wing pier can reduce the local scour significantly.the scour depth can reduced by59%and the near-bottom vertical velocity can reduced by96%.③the optimization combination that can reduce the pier local scour is that the distance between baffle and riverbed is about1/3of water depth, and the baffle size is equal with radius of the pier, and the baffle shape is semicircle.The ring-wing pier can reduce the local scour significantly, which is technically feasible and simple structure and convenient construction. It provided the basic data and reference for further design and construction, and has important practical significance.