An experimental investigation on the effect of thixotropic aging on primary and secondary compression of reconstituted dredged clays

Dredged clay is often undesirable as a foundation soil layer since it undergoes large deformation with time. In addition, the space constraint due to ever-growing population might require to utilize the dredged-fill reclaimed lands. As such, an effort has been taken in this study to characterize the deformation behavior of dredged clay. To this end, the one-dimensional incremental load oedometer tests were administered on three reconstituted dredged clays. Samples were prepared at a moisture content ranging from 0.54-1.27 times the corresponding liquid limits. To observe the effect of thixotropic aging, prepared samples were subjected to three aging periods, such as 10 days, 30 days and 90 days. At a particular moisture content, with the increase of aging period, yield stress was observed to be increased. A unique relationship was established between yield stress ratio and initial moisture content incorporating the aging time. Compression index, Cc increases linearly as the void ratio at yield stress increases. However, Cc decreases as the yield stress increases, the decrease being rapid when the yield stress is below 7.5 kPa. Secondary compression index, Cα increases as the consolidation pressure increases, reaches a peak value and decreases thereafter. At higher initial moisture content, the secondary compressibility of dredged clays increases. Irrespective of the type of the clay, the relationship between Cα and Cc is linear in the considered stress range and time. The slope of the linear relationship (Cα/Cc) is higher for thixotropically aged clays compared to the unaged ones, indicating high secondary compressibility due to thixotropic effects.