Effect of Slope on the Stability of Riverbanks with a Mobile Bed: An Experimental Study

The interaction of the river flow and riverbank wall particles leads to riverbank erosion and collapse in the long term. In the parts where riverbanks have fine-grained sediments and are subject to erosion and changes in water level, the possibility of bank collapse increases, and the creation of riprap or heavy protective structures might cause the riverbank to become more unstable. This research investigates the effect of changing the wall slope on the riverbank stability in mobile bed conditions. To this end, ۲۱ experiments were conducted on three different slopes (۲۰, ۲۵ and ۳۰ degrees) on river sediments at different stream depths. The results showed that the riverbank with a slope of ۲۰ degrees is destroyed later than the other two slopes (۲۵ and ۳۰ degrees). As the Froude number increases to ۰.۲, all riverbank slopes reach instability. However, this instability occurs later for the bank with a lower slope than for the bank with a higher slope in terms of the time parameter. Besides, with the increase in the Froude number of particles Frd and the flow depth, the collapse time Tf decreased due to going farther from the incipient motion of the bed and wall particles. As the test are done under live bed condition the destruction is started faster than in clear water.

Keywords:

Mobile bed , Bank slope , Froude number of particles , Incipient motion