Quantification of Wave-Induced Liquefaction in Small-Scale Surf Zone Sandbar

This study quantitatively measures wave-induced liquefaction within a small-scale sandbar under different compaction conditions. An artificial sandbar of 2 m cross-shore length was positioned on the surf zone of a 17-m-long wave flume. An array of pressure transducers, wave gauges, and a grid system were installed to observe the pore pressure, wave height, and erosion depth of sandbar, respectively. A total of eight wave scenarios were tested under loose and medium-dense compaction conditions of the sandbar. The experimental results revealed that the liquefaction index decreases with an increase in sediment depth because the excess pore pressure decreases with increasing sediment depth. During the same wave height, the decreasing tendency of the liquefaction thickness with increasing wave period was observed. Furthermore, a reduction in wave height resulted in a reduction in the liquefaction thickness. A strong correlation (R2 = 0.96) was established between liquefaction thickness and wave steepness. During the 10 min of wave action, an average of 16.5% of the liquefied thickness was eroded in loose compaction conditions, whereas 6.3% of the liquefied thickness was eroded in medium-dense compaction conditions. These findings emphasize the necessity for an in-depth field study of wave-induced liquefaction.