Author(s): Peyman Modaber Dabbagh; Mojtaba Saneie; Mohammad Rostami; Mohammad Mehdi Razmi
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Keywords: Local scour; Bridge lateral abutment; Non-submerged pile; River engineering
Abstract: Scour around hydraulic structures is an inevitable phenomenon. Recognizing this phenomenon and dealing with it is an issue upon which the plan’s success is warranted. Local scour at the abutments is reported as the most significant cause of bridge failures. Bridge abutment cause contraction in the river channel and deflect the path of flow. Because of single-span in the river, high concentration of velocities, bed shear stresses, vortices, and turbulence occur in the upstream abutment nose. These entire factors lead to erosion of materials around the abutment and expansion of a ravine hole. Protecting the abutments from local scour is one of the requirements in designing structures built in rivers. Utilizing submerged and non-submerged piles are one of the scour countermeasure methods. Non-submerged piles are rarely used in investigating the amount of scour. In the present study, the results obtained from a series of tests performed with diverse flow rates (3 flow rate), with different arrangements (9 type) of non-submerged piles, at the bridge lateral abutment, are presented. The tests have been carried out in clear water conditions and in a flume with 14 meters length, 60 centimeters wide, and 60 centimeters height. The findings show that the best arrangement of locating piles is when that located in a line with 7 piles and with two times an abutment length (40 cm). Using piles result in scour volume reduction from 50% to 76% as well as maximum scour depth reduction from 25% to 58% . The high figures are related to type 1 in which 7 piles are used in linear form. The last figures are related to type 5 where 7 piles are used with the arrangement of L shape. (In all of the tests, piles distance of abutment is two times an abutment length and it is fixed).
Year: 2013