Author(s): Nurudeen Tomiwa Amo, Junji Yagisawa, Norio Tanaka
Linked Author(s): Nurudeen Amo
Keywords: Downstream revet, time of failure, river embankment, overtopping permeability, gradient permeability.
Abstract: Embankment, levee or dyke is one of the oldest and widely used defense structures against river flooding across the globe. Meanwhile this research work looks into the collapse phenomenon in river embankment because of the overtopping events, it has been well known that severe erosion occurs at top of embankment slope. To prevent that severe erosion, it is important to cover the top of embankment slope by some materials. However, it has not been revealed what is a suitable revet length for delaying the time of embankment failure. Therefore, objective of this study is to elucidate the effect of revet length on time of embankment failure by conducting flume experiments. A trapezoidal shaped embankment model (silica sand: d50=0. 3mm) is constructed (by compaction) perpendicular to the river flow in a glass-sided flume with a constant flow discharge upon overtopping of embankment. An acrylic plate (as pavement model) is set at embankment top and revet models with different length are connected to this acrylic plate in each experimental case. Some parameters considered to describe time of failure are overtopping permeability, length of revet on the downstream slope. Phreatic surface (zero pore pressure head) is observed in Case 2 (embankment with 4cm revet) but it rises in Case 3 (6cm revet). Also strong matric suction is observed in Case 2 with the cluster of pore pressure head at the top of downstream slope and embankment layer interface meanwhile Case 3 shows increasingly positive pore pressure (sharp drop in shear strength) at the downstream top of the slope. Therefore, Case 2 highlights the zone of peak shear strength attainable before reduction. In this embankment model, Case 0 (no revet) and Case 3 (6cm revet) saw rapid erosion 60 seconds after overtopping. These two phenomenon should be avoided to prolong embankment lifespan
Year: 2017