Study on one-dimensional nonlinear consolidation behavior for saturated soils with threshold gradient

In reduced coordinates, a one-dimensional finite strain consolidation equation for saturated soils is derived with threshold gradient. The new equation shows that threshold gradient and variation of permeability coefficient with void ratio should be considered. Using the two empirical relations proposed by Mesri, a new governing equation is obtained. Then three examples are analyzed by applying the partial differential finite element software FlexPDE. The results show that excess pore water pressure slightly increases at the beginning of consolidation progress and then dissipates. This phenomenon is similar to the Mandel-Cryer effect. It will be more significant if threshold gradient is greater or location of soil is deeper. Even though the maximum excess pore water pressure increases when threshold gradient increases, the increment is very small. It is too difficult for us to observe the tiny increments in laboratory and practical engineerings. Therefore, there is no need to consider threshold gradient in vast majority of actual projects. In other words, classical Darcy's law is applicable. This research shows that it is very important to consider threshold gradient, geometric nonlinearity and material nonlinearity in studying the Mandel-Cryer effect so as to further understand the consolidation properties of saturated soils.