ABSTRACT
It is difficult to understand the mechanism of riverbank failure because of the combined actions of hydrological and geotechnical factors involved. To address problems (e.g., loss of land and agricultural land, and breaches in river levees) caused by such failures, their physical mechanism needs to be examined. A series of bank failure experiments was conducted in a soil tank in this study. Two types of sands were used, and two bank heights (50 cm and 25 cm) and a constant bank slope of 75 degree were considered to explore the major bank failure caused by rise in water level. In these experiments, the compacted sandy soil was eroded by loss of matric suction accompanying the rise in water level; thereafter, collapse occurred because of destabilization. The distinct largest failure event corresponding to rotational slide or cantilever toppling failure was captured using a handheld 3D scanner and particle image velocimetry (PIV) method. Causes of failures were discussed by comparing the relative differences in bank height and matric suction. Cantilever toppling failure was the most frequent failure type, stressing on the importance of modeling a cantilever toppling failure based on tensile strength, incorporating the effect of matric suction. The differences in the amount of failure sediment corresponding to rotational slide and cantilever toppling failure were also revealed through the failure velocity and behavior. These experimental data will be useful for modeling the failure sediment transportation corresponding to each bank failure type.
