Effect of Clay Content Percentage and Compaction Energy on Pier Bridge Scour in Erosive Bed and in the vicinity of Abutmnet

Bridge failures are fortunately rare, but every year a number of bridge collapse that has occurred somewhere in the world. In many cases these collapses could have been avoided by an adequate bridge management regime that included good inspection, assessment and maintenance procedures. One specific type of failure that from time to time causes sudden catastrophic collapse of bridges is the undermining of foundations due to bed scour. Bed scour is the transport of bed material by the flow of water and is present to some degree where the river bed is formed of granular material. Scour increases as flow rates increase and therefore the actual collapse of structures due to scour often occurs during periods of extreme flow due to flooding. Of course, this is exactly the time that direct observation of the foundations of a structure is not possible and therefore a collapse may be put down to an ‘act of God’. A good inspection regime that includes bed measurement and engineering analysis can find indications of developing scour before the situation becomes critical. If this is followed up with well-designed remedial works, undermining of the structure, even in extreme conditions, may be prevented. The formation of scour holes around bridge piers or abutment is one of the main causes of bridge foundation collapse. Local scour at bridge piers and abutment may be defined as a local lowering of the bed elevation. This lowering is mainly caused by the horseshoe vortex combined with the downflow in front of the pier and abutment, the vortex shedding at the back of the pier, abutment and the flow contraction. Bridge failure due to the effects of local scour associated with the structure of the local flow field around piers and abutment involves a considerable interest in scour prediction and scour protection measures. Two basic procedures may reduce the scour depth. The first consists in enhancing the ability of the bed material to withstand erosion. This is generally done by placing an armoring device on the bed, such as riprap. The riprap provides a physical obstacle that resists the erosive power of the flow. The second procedure consists in reducing the downflow in front of the pier and the horseshoe vortex scouring the bed material. The local scour around bridge pier and abutment in recent years has been widely studied by different authors. They proposed different methods to control the scouring depth. The most dominant concern about bridges stability is the occurrence of local scour around foundations. The local scour around bridge piers and abutments has been widely studied by different authors in recent years. They proposed different methods to control the scour depth. In order to reduce scouring around bridge piers and abutments one of the methods is the soil compaction. Compaction rise the relative density and soil resistance which mitigates scour and produce a time delay in scour hole development process. This paper focuses on the effect of clay content percentage and compaction ratio on scour reduction around bridge piers. Hence, 5%, 10%, and 15% clay was added to soil and then compacted. According to the experimental results, when 15% clay was added to non-cohesive sediment materials in saturated bed conditions with a relative density of 70%, the scour process was completely controlled after 24 hours around the bridge pier.