Experimental investigation the effect of T-shape spur dike's angel on rip rap stability to bank protection of navigation river in 90 degree bend

One of the most important topics in river engineering is protection of banks. Because of change in flow characteristics the banks of rivers will be remove that it is very sever. Use of spur dikes is one of the common methods for protection of banks but there is a problem in this field that is protection of spur dikes which there isn’t many research about it. Because the spur dikes are very useful in the bends therefore this research carried out in the 90 degree bends. In this research the goal is investigation of the of spur dikes angel on stability if riprap. For achievement of this goal use three length of nose of spur dike (50%, 75% and 100% of body length of spur dike) and three diameter of rip rap (1.51cm, 1.12cm, 0.72cm). The results showed that in all of the experiments increase in angel of nose cause decrees in Froude number of flow, densimetric froud number of sediment in failure of riprap and then decrees of riprap stability