Protecting river banks from erosion by spur dikes is one of the traditional methods in river engineering. Directing the flow toward river axis, spur dikes prevent strong currents in river banks, thus guarding them against erosion. Installation of spur dikes in the flow path results in local scour and topographical changes in the spur dike. The results of this research showed that by increasing Froude number of the flow, the relative distance between spur dikes, and their relative lengths, the maximum relative scour depth at the spur dike entrance increases. Scour around spur dikes in bent paths is one of the main reasons for the destruction of spur dikes. In the present study, the experiments were performed in a laboratory Plexiglas flume of rectangular section with a 180° bend to evaluate the effect of the relative distance between two spur dikes in the bend on scour. To that end, two spur dikes were installed at relative distances of 2, 3, 4, and 5 times the length of the spur dikes and in four different relative lengths in the first half of a 180° bend to study scour around the spur dikes. All experiments were performed in four different discharges and a constant flow depth in clear water. According to the results, by increasing the relative distance between spur dikes, the relative maximum scour depth at the opening of the spur dikes in-creases.The results of this study showed that there is a direct relationship between the maximum relative depth of scour and the relative length of the spur dikes, the relative distance between the spur dikes, and Froude number. By increasing the relative distance, the relative length and Froude number of the maximum relative depth of scour in the nose of the spur dikes increase. By measuring the depth of scour based on experimental observation, an empirical relation is developed with a high regression coefficient of 96%.
展开▼
