*4.1. Variations of SSCs in the Overlying Water*

During the initial period of the 7 cm height wave loading, the initial SSCs increased rapidly due to wave disturbance. This was similar with the SSC variation in the wave flume experiment conducted by Tzang et al. (2009). Under wave loads, the vertical distribution of pore pressure had depth gradients with a maximum value at a certain depth in sediment [37,38]. Once the sediment liquefaction initiated, pore pressure generally amplified in both shallow fluidized soil layers and near below the fluidized layer [23]. Thus, fine particles and pore water at this depth transported upwards from the interior of sediment under the "pumping" effect of pore water pressure [22,39], and caused higher initial rises of SSCs. After 30 min of wave loads, the depth of liquefaction interface reached a maximum value and began to move upwards (Figure 4a). Meanwhile, the SSCs increased slightly afterwards.

### *J. Mar. Sci. Eng.* **2019**, *7*, 449

During Stage III, the sediment liquefaction interface essentially remained at a stable level. In this stage, the structure of the sediment was continuously strengthened as a result of gravitational consolidation and drainage of pore water in sediments, and the sediment particles became more compact [25]. Thus, liquefaction was not observed in this post-liquefied sediment [40]. Since the upward transport of fine particles from the liquefied soil layer gradually decreased and sediment deposition rate was larger than the resuspension rate [39], the SSCs in the overlying water gradually reduced.
