The high water content of soft soil leads to complex sedimentation, consolidation, and permeability characteristics, posing challenges to engineering design and construction. Although existing research has made progress in the field of consolidation and settlement characteristics, discussions on the low stress stage are still insufficient, and there is a lack of appropriate mathematical models to describe it. At the same time, the correlation and differences between the degree of consolidation used for settlement calculation and the degree of consolidation used for pore water pressure calculation have not been fully clarified. This study improves the measurement method for permeability coefficients and optimizes consolidation equipment, conducting research on the permeability and consolidation characteristics of soft soil with high water content. The research results show that soft soil with high water content exhibits significant consolidation settlement under low stress, and the incremental settlement decreases with the increase of consolidation stress. The void ratio and compression coefficient undergo drastic changes during consolidation, with a difference of 2 to 4 orders of magnitude, especially significant during the low-pressure stage. This study indicates the existence of a critical stress of about 4 kPa and proposes a segmented method to describe the consolidation and permeability characteristics of soft soil with high water content, establishing an e-lg sigma-lgk relationship model, which can effectively reflect the consolidation behavior of super-high water content soft soil. At the same time, the study also finds that in practical engineering applications, the degree of consolidation used for settlement calculation and the degree of consolidation used for pore water pressure calculation should be considered comprehensively to more accurately predict the consolidation process and guide construction.

This study first invents a novel oedometer apparatus for clay slurry, featuring a lightweight acrylic loading cap, a noncontact laser displacement sensor, and a 1:1 dead-weight loading system to improve traditional consolidation devices. The novel apparatus is then used to examine two clays: Hong Kong Marine Deposit and Kaolin clay. The loading with a minimum stress of 0.025 kPa is applied on samples with a maximum initial water content exceeding 9 times the liquid limit. Results demonstrate the S shape compression curves influenced by initial water contents, and the power-type relationships between permeability coefficient and void ratio. Empirical equations are obtained to determine the yield stress point based on initial water content and liquid limit. Higher initial water contents increase compression parameters (e.g., recompression index, Cr; compression index, Cc; and creep index, C alpha), though Cr/Cc and C alpha/Cc are almost in the normal range. The Cc of Kaolin clay with initial water contents above 3.5 times the liquid limit is significantly relevant to effective stress. Finally, a nonlinear creep model is enhanced and integrated into the finite strain consolidation equations, effectively simulating the oedometer tests and a self-weight consolidation test of clay slurry with nonlinear consolidation characteristics.