Local scour at abutment under vertical and side suction seepage

The present laboratory study is done to understand the effect of suction seepage flow on the scour geometry around an abutment placed on non-cohesive bed materials. The experimental data revealed that suction seepage through the channel side and bed affects the scour depth and deposition height. Under the present experimental conditions, it is found that the maximum reduction of scour depth under vertical suction, side suction and combined suction are 37%, 19% and 21% respectively. The results further demonstrate that the reduction of scour depth at the upstream outer nose of the abutment is more under vertical suction, whereas under side suction, the main influence area is closer to the side wall. However, under combined suction seepage, it is found that the reduction of scour depth is in between vertical suction seepage and side suction seepage. Another important finding is that scour reduction increases with increase in seepage rate.