Failure Patterns of Protective Flexible Mattresses on a Riverbank under Water Flow Scouring. I: Physical Mechanisms

Riverbank erosion presents significant risks to infrastructure stability and flood management. This study introduces a representative physical model combined with distributed optical fiber sensing technology and a numerical finite element model to investigate the failure mechanisms of protective flexible mattresses deployed on the riverbanks. The study reveals that flexible mattresses exhibit distinct patterns of deformation and failure driven by the interaction between water-induced scouring and the mattress-sediment system. Two major deformation mechanisms are revealed: (1) shallow slips, induced by surface sediment erosion; and (2) sliding collapses. Topography changes and finite element analysis further elucidated the stress redistribution in the riverbank material under water flow-induced scouring, revealing that sliding collapse is triggered by a continuous increase in maximum shear stress along the potential sliding surface with increasing scour depth. The study provides new insights in the physical mechanisms governing the failure of protective riverbank structures and offers physically justified guidelines for the design and implementation of flexible mattress systems for riverbank erosion control.