COMPARATIVE STUDY OF SOLID AND PERMEABLE SPURS

Abstract

Spurs are the most widely used structures to train river course along a desired alignment , to protect river bank and to advance the bank towards riverside. They may be solid or permeable depending on the type of construction materials used. They may be used single or in series. The important aspects of their performance are the scour, deposition and length of bank protection u/s and d/s. While solid spurs, single or in series, attracted the attention of many investigators in the past, very little information is available on permeable spurs, single or in series. The present investigation included permeable spurs, single and in series. For a comparison , solid spurs , single and in series were studied. Holding blockage ratio of, the spurs and their angle of inclination with the bank same, the permeability and the spacing of the spurs were varied between 0 and about 50 % and 4 to 8 times the spur length, respectively. The experiments were carried out in 0.6m wide, 0.5m deep and 8m long tilting flume at a slope of 1 in 1000. A sediment of 0.525mm median size and 1.18 standard deviation was used in the test section of the flume bed under live bed condition of approach flow. Sediment was supplied manually into the flume at the transport capacity of the flow. The flow conditions were varied over a narrow range. The predictor proposed by Ramu(21) for scour depth due to single solid spur has been further tested with all the data available in literature and recommended for use. Considering this as the most basic case, the scour depth in all other arrangements of spurs has been expressed as a ratio of that of the basic case. The ratio is believed to be independent of blockage ratio and flow parameters.