Undrained cyclic behavior of under-consolidated soft marine clay with different degrees of consolidation

Abstract

In certain land reclamation projects, soft marine clay with various consolidation degrees (U) under a foundation exhibits different mechanical properties when subjected to cyclic loadings. Compared with normally consolidated soft marine clay, under-consolidated soft marine clay has poor engineering properties and exhibits a larger deformation when it is subjected to cyclic loadings. Therefore, the cyclic behavior of soft marine clay with different consolidation degrees needs to be examined. In this study, a series of triaxial tests were conducted to investigate the cyclic behavior of soft marine clay with various consolidation degrees. The undrained shear strength, permanent strain, and stress-strain hysteretic loops were analyzed. Some useful conclusions were obtained. First, the undrained shear strength of the specimen decreased, and the permanent strain increased with a decreasing consolidation degree. Second, compared with the normal consolidated sample (U = 1), the stress-strain hysteretic loops of the under-consolidated specimen (U < 1) had a larger envelope area, indicating that the deformation behavior of the under-consolidated soil exhibited more distinctive viscoelastic and hysteretic characteristics. Finally, in the low consolidation range (U = 0.5–0.85), the deformation resistance of the clay rapidly increased as the consolidation degree increased. By contrast, in the near-normal consolidation range (U = 0.85–1), the deformation resistance of the clay did not significantly increase. Based on these results, the critical consolidation degree for soft marine clay was found to be 0.85, which can be used as a standard reference, considering the need for rapid construction in actual projects.