Effect Of Clay Structure Degradation On Settlement Of Embankment

Due to the degradation of initial structures, soft clays can experience significant settlement without much change of pore pressure. Such a phenomenon has recently been observed at a fully instrumented trial highway embankment near the town of Ballina (New South Wales, Australia). In contrast, the displacements in saturated soils without structure (such as a fully remoulded clay) are always associated with the dissipation of excess pore pressure through the effective stress principle. This paper demonstrates the effects of clay structure degradation on the settlement of embankments, through numerical analysis of a trial embankment on soft clay. A constitutive model that accounts for destructuration of soils is used to characterise the behaviour of the soft clay. The material parameters are derived from conventional oedometer and triaxial tests for the structured constitutive model. It is shown that the settlement and the dissipation of excess pore pressure during construction of the embankment are closely related with the destructuration of the soft clay. With appropriate choice of the constitutive model and material parameters, the lag between the settlement and pore pressure dissipation can be well predicted by the coupled finite element method based on the effective stress principle and consolidation theory.