International Journal of Engineering and Technology

Using impermeable groin is a protective method of rivers bank erosion which, in the case of accurate design and implementation, in addition to bank erosion control, leads to recovery and restoration of valuable lands in the rivers’ margin. Local scour of the groin nose is one of the design issues in such structures which happens due to narrowing the flow section and existence of the strong vortexes. Due to narrowing of the nose section and occurrence of the downward rotatory flow, local increase of flow velocity leads to the formation of the scour holes of which advancement endangers strength of the structure.VelocityIn this study, the T-shaped breakdown length effect on the riprap stability around the groin in the river was investigated using CCHE2D model.The results were compared with the measured values in the physical model. Results indicated that with the increase of the Froude number, the flow velocity and the shear stress in the groin nose has increased leading to the rise of the index (Nc) and consequently the stability reduction of rip raps. Also, the increase of riprap particles diameter from 9.5 mm to 12.7 mm leads to a 13.5% index (Nc) reduction indicating the increase of ripraps stability with diameter increase. As the groin length increases, there will be no sensible change in the riprap stability but as the length of the groin wing increases, rip raps stability will increase. Results of simulations are very close to the physical model and their average difference is 1.17%. This comparison shows well that CCHE2D software can be used for simulation of the groin and rip raps stability with high precision.