Abstract: The process of natural and binary riverbank collapse is simulated with compound plastic sand of different particle sizes (adding adhesive of appropriate proportion to the upper layer) through indoor generalized model tests. Test results reveal that the collapse process can be divided into five phases in general: the slope toe is scoured and steepened, and then cracks develop on the shoal surface, in subsequence, slope surface is progressively eroded, followed by riverbank collapse, and equilibrium of riverbank erosion and deposition. During the collapse, sands in the lower layers were scoured and the bank was steepened, then the upper sands collapsed in different types under various conditions. In the presence of equal water discharge, the bank stability during water level drawdown obviously decreased than that during water level raise. This research finding provides theoretical support for the harnessing of embankment collapse, flood protection and disaster reduction.

Key words: binary riverbank, generalized model test, collapse, compound plastic sand