Experimental investigation uses of slot at pier for control of scouring

The purpose of this study was to investigate the effect of the use of slot in the pier of a rectangular bridge to control scour. For this purpose, four shape of pier, trapezoidal, invers trapezoidal, triangular and invers triangular, with the same cross-sectional area, were placed in three levels on bed, 1.5 cm and 3 cm above the bed, in four Froude number 0.3 and 0.27, 0.24 and 0.19 were tested. The experiments of present study, were carried out in a laboratory flume in Tehran's Soil Conservation and Watershed Management Institute. The results show that increasing the level of the slot from the bed, increased the scour depth upwards of the piers. Also topography changes along the canal and the dimensions of the cavity also increase. So that in all Froude numbers, the slots placed on the bed, reduced the depth of scouring about, 15.5-51.81 percent for invers triangular, 21.16-62.18 percent for invers trapezoidal, 26.67-65.28 percent for triangular and 38.83-73.58 percent for trapezoidal slots has best performance compared to the two other levels.