On the compression behaviors and microstructural characteristics of marine clays along the coastal China

Compared with typical onshore clays, coastal marine sediments exhibit higher compressibility, larger void ratios, and looser microstructures owing to their distinctive depositional environments and biogenic components. This study systematically investigates the physical properties, compression and consolidation behavior, and microstructural characteristics of marine clays from the Yellow Sea, Bohai Sea, East China Sea, and South China Sea, and clarifies their regional variability and controlling mechanisms. The results show distinct spatial differences along the Chinese coast. South China Sea clays are characterized by higher natural water content, lower density, larger void ratio, higher Atterberg limits, and greater compressibility. One-dimensional oedometer tests on intact and remolded samples indicate clear structural yielding: intact samples deform slightly before yielding and compress rapidly after structural collapse, with their compression curves gradually approaching those of remolded samples under increasing stress. Based on experimental and published data, three patterns of consolidation coefficient evolution with stress are identified: monotonic decrease, decrease followed by increase, and monotonic increase. Scanning electron microscopy observations reveal that open flocculated fabrics, biogenic debris, and inter-particle or intra-particle pores largely explain the high water retention and compressibility of South China Sea clays. These findings provide geotechnical guidance for settlement evaluation and offshore foundation design in coastal China.