Author(s): Wenjun Zhang; Colin Rennie; Ioan Nistor; Husham Almansour
Keywords: Dynamic debris jam; Temporal scour; Hydraulic head
Abstract: woody debris from the local landscape moving with water flow causes new problems and challenges to the safety of infrastructures like river bridges and coastal area structures. Woody debris trapped by the bridge pier forms a debris jam in front of the bridge pier, and the presence of debris jam enhances the pier scour and induces hydraulic head. Previous studies considered the debris jam as a stable and static structure that cannot represent the natural formation of debris in practice. This study thinks the debris jam is a dynamic and unstable process, and we consider the whole life-scale of debris jam including initiation, growth and failure stages through a longer timescale. The influences of dynamic debris jam on bridge pier scour and induced hydraulic head are focused, and the results show the dynamic debris jam has non-linear relation to scour depth and behaves much more complicatedly than static debris jam. In addition, a formula is derived to quantify the influence of the debris jam on debris induced hydraulic head.