Dynamic Response Characteristics of Soft Clay Under the Coupling Action of Graded Loading and Wave Loading

Abstract:

Taking the mudflat enclosure project， located behind the Changxing submerged breakwater in the Yangtze Estuary， as the research object， indoor dynamic triaxial tests of the silty soft clay were conducted at different confining pressures and different combinations of dynamic and static stress based on the soil samples of the dam foundation and the actual load stress path. Besides， the strain and pore pressure properties and strength weakening characteristics were explored under the coupling effect of wave force and vertical hierarchical construction action. The research results show that the stress-strain curves in the coupling stress path appear to have the properties of strain softening and strength weakening. Moreover， the strain increment and pore pressure increment decrease on account of the graded loading effect. The strain increment， the pore pressure increment， and the strength weakening after cyclic loading are related to the confining pressure， the static deviatoric stress ratio， and the dynamic deviatoric stress ratio. Corresponding to the same deviatoric stress ratio， when the soil layer is shallow， the confining pressure is smaller， on the contrary the static deviatoric stress ratio is larger， hence the greater the strain increment and pore pressure increment will be， along with the more obvious static strength attenuation. With the increase of dynamic deviatoric stress ratio， the strain increment， the pore pressure increment， and the degradation of strength after cyclic loading increase， with a more obvious deviation of different depths. Based on the results，the degradation of strength β， the generalized shear strain γgs and the generalized composite pore pressure increment ratio Δu/σ3 were quantified respectively. Furthermore the relation between (β-γgs) and (β-Δu/σ3) were explored. The research results have certain reference value for guiding specific engineering practice.

Key words:coupling stress state;soft clay;shear strain;pore pressure increment ratio;degradation of strength