Under-consolidation characteristics of an offshore marine clay from Yellow Sea, China

Consolidation characteristics of marine soils are crucially important to ocean reclamation, pile foundation design and construction, etc. A series of oedometer tests were conducted on samples from three different depths in north Yellow Sea, China, to disclose the consolidation properties of the marine soil. Intact and reconstituted samples, under seawater or freshwater condition, were tested in loading, unloading and reloading processes. The pre-consolidation pressure was determined by double logarithmic method, and the consolidation coefficients were evaluated by Taylor’s method. Results show that the compressibility of the tested marine clay is much lower than other reported marine soils, with low liquid limit (w_L = 35.34∼42.22 %), low water content (w = 23.08∼25.91 %) and low permeability (k = 0.82∼1.57 × 10^-7cm/s). The consolidation coefficient is of 10^-4cm²/s and can be increased up to 416 % when the sample processes reloading after undergoing unloading. The intact sample is lower in compression index and higher in consolidation coefficient than reconstituted samples. Besides, in tests of reconstituted samples with seawater, the compression index of marine sample can be reduced and the consolidation coefficient can be improved. The determined pre-consolidation pressure indicates that the marine samples from different depths are all under-consolidated, which was verified by CPTU tests and explained by Gibson’s theory for clay sedimentation under water.