Scour at Sooyung Seawall caused by wave reflection and liquefaction

A serious scour problem has been reported near the rubble-mound Sooyung Seawall, Korea. The present paper concerns numerical modelling work to reproduce the scour around the wall. Two numerical models were involved in the work. The first model was for wave-reflection and the resulting seabed profile change. The model solved the intra-wave-period mild-slope wave equation system. The model reproduced wave reflection, and pattern of nodes and anti-nodes in front of the wall. The model included the erosion mechanism as well, so that the seabed levels were allowed to change. The calculated scour profile in front of the wall was found to agree reasonably well with field measurements. The second model was used to examine the possibility of liquefaction at the site. The model solved the velocity potential function and the elastic movement of soil in a two-dimensional vertical domain. The model results show that liquefaction can occur around the structure, if the coefficients involved are assumed to be correct. The model results suggest that both wave reflection and liquefaction have contributed to the scour at the site.