Experimental Study On Local Scour Around A Multistage Circular Pier Bridge

The depth of local scour at bridge pier is one of the important bases of bridge design. There are very important practical significances to study convenient and suitable method to calculate the depth of local scour of bridge pier for improving the reliability of bridge design and ensuring safe operation of existing line and construct of new line. Considering the scour formula of right bridge is ripe, the scour calculation of skew bridge in mountain area is emphases and difficulty in the current research because of its special region characteristics.A lot of domestic and international scholar and Scientists and Technologists have carried out plenty of research about pier scour, such as indoor model test, the observation of open country and value calculation, and they have put forward many experience and half-experience of formula about scour depth calculation. But so far, the erode mechanism knowledge and theoretically study are very limited, just because the pier-erosion phenomenon is very complex, and has numerous influencing factor. So, the further research is necessary.In order to study the influence of bridge security about the multistage scour of altitude highway downstream bridge, summarizing a suit of account method for scouring depth in actual and in different frusta location collocation of the downstream bridge, providing references for design. This essay systematically summarize the results accomplishment about pier scour for many years, establishing four bridge site scheme about double downstream piers in the base of the experimental study on circling single pier, and studying the local scour of bridge in different current condition.We use the vectrino to measure the velocity around a circular pier in a rectangle flume, so the longitudinal, lateral and vertical 3D mean velocity around a pier are presented. It has drawn up the plane 2D mean velocity vector field distribution, summarization for the lateral mean velocity and analyzed the variety of the vertical velocity in the typical section.Consequently, we have established the connection with the fluid state of the circular cylinder and local scour at bridge pier. On the basis of them, this paper studied the characteristics of water movement around pier and sediment movement by flume scour experimentation of double downstream mass piles bridge piers, taking pier scour of natural Sandy River as prototype. In the test, we have used IH optical fiber liquid interfacial measuring instrument to measure the change of the local scour depth in the front of the pier with time in different bridge site. And we gained the functional relation formulas about the front row piers'local scour depth changes as time with different bridge site. Simultaneity, we get the double rows piers'local scour depths have strong correlativity between the back row piers'and the front piers'in different current condition. Also infers the relation formula of the front and back row piers'local scour depth with the 90 degree bridge site. We supplied scientific gist for engineering design.At last, this paper combined the analysis of theory with the test of model observation dates, utilized the angle of energy balance and the dimension concord theory to deduce the new theory formula, from the measured dates to get the parameters, the formulas, for scour depth around the bridge piers under different riverbed surface conditions, were derived. We verify these new formulas by in common use 65-2 modify formula. The result has much practicality value for bridge design especially for double rows downstream bridge site in mountain area.