Author(s): Sepehr Karimi; Amir Reza Zarrati; S. Amin Salamatian
Keywords: Scour; Bridge abutment; Bridge constriction; Scour extension
Abstract: Scouring is an important phenomenon caused by construction of various river structures in stream ways. Scouring undermines the structures which this may cause serious damages. Therefore, studying scouring is an important part in designing hydraulic and river structures. In the present work, scouring around bridge abutments is studied. A flume 12m long and 0. 75m wide was used for the experiments. Abutments with different lengths were installed in 7m distance from the flume entrance. Bed scour topography at the vicinity of the abutments was measured at different flow shear stresses in clear water condition by a laser meter. Using the measured data, some relationships were developed for calculating scour hole side slopes at different directions around the abutments. Extension of the scour hole upstream of the abutments and at the bridge section can be estimated by knowing the maximum scour depth and the scour hole slopes calculated from these relationships. Maximum scour depth can be calculated from one of existing empirical equations. An advantage of the present model is that if a pier is built in the vicinity of the abutment, bed scour at the pier due to the extension of the abutment scour hole can be calculated. The flow condition at which the scour holes of the two abutments reach each other and the bridge section experiences a full degradation can also be predicted.