Experimental investigation of scour around semi-conical piers under steady current action

In this paper, the experimental results of scour around semi-conical piers are presented to show the effect of their lateral slopes on the scour depth under steady current. Piers with different side slope angles (i.e. 0°, 2.5°, 5°, 7.5°, 10°, 12.5° and 15°) and two cross-sections (circular and elliptical) were tested in the experiments. The angles are defined with respect to the vertical axis. A number of tests were carried out under clear water condition for this research study. It was found that the piers with even small side slopes decrease the scour depth at the upstream and downstream of the piers. The scour depth of the pier with circular section with the largest lateral slope angle is reduced about 36 and 53% at the upstream and downstream sides of the pier in comparison with those of the circular cylinder, respectively.