Experimental Investigation of the Effect of Depth of Placement of Six-Legs Elements on Scour at Rectangular Bridge Pier

Pieve scour is one of the most important cause of bridge failure. Covering methods such as using riprap is among techniques which are widely applied for the existing bridges. For those places where the stones of adequate size are not available, use of six-legged elements which is the subject of this, study is a good choice. In this study the effect of placement of a single row six- legged around a rectangular bridge with 100% density in three different cases of above, mid and below the bed under five different Froude numbers of 0.24, 0.22, 0.19, 0.17 and 0.16 have been experimentally investigated. Comparison of the bed topography withmean measure of bed deposit of 0.7 mmof tests with six- legged and tests without elements showed that generally the elements can reduce the scour depth significantly. The elements placed on the mid of bed have shown better performance with maximum reduction of about 57%. The general recommendation is to use these elements with geo-syntactic filter or placed in more rows.