Elastic-Viscoplastic Consolidation Analysis Of Saturated Soft Clay Based On The Non-darcy Flow

Saturated soft clay extensively distributed on coastal areas in China,the settlement deformation of soft clay has been an important content of geotechnical engineering research,meanwhile the problem is closely related to the soil consolidation theory.The soft clay consolidation process has obvious rheological and seepage nonlinearity,which is the main reason for the long-term settlement and stability of soft soil foundation and engineering.Based on the two aspects of test and theory,this paper makes a study on the one-dimensional rheological consolidation of saturated soft soil.The main work and achievements are as follows:(1)The elastic-viscoplastic model is introduced to describe the deformation of soil skeleton,and the one-dimensional rheological consolidation equation is derived.A series of one-dimensional rheological consolidation tests were performed for the saturated soft clay,and the influence of reference time on the parameters of elastic-plastic model was studied according to the experimental data.The results shows that the reference time has no influence on the initial coefficient of second consolidation,while it does more influence on the parameters of the reference time line and the reference stress point.In addition,the corresponding model parameters can be used to predict the change of soil vertical strain over time.(2)Considering the influence of non-darcy seepage in the consolidation process of soft clay foundation,the Hansbo seepage model was introduced to rederive the one-dimensional consolidation equation based on the nonlinear rheology of soft clay under the EVP model.The control equation’s numerical analysis is conducted by finite difference,and the numerical solution is calculated using Matlab software programming.Analyzing the influence of Hansbo seepage parameters and EVP model parameters on the consolidation process of the foundation,the following conclusions are obtained: the process of foundation rheological consolidation is delayed when the Hansbo seepage is considered.With the increase of the power exponent or initial hydraulic gradient,the corresponding pore water pressure dissipation and the overall settlement deformation of the foundation are slower.It is found that the initial pore water pressure increased when the EVP model was used to simulate the deformation of foundation soil.Furthermore,the parameters of reference time line parameters,reference points and secondary consolidation coefficients have significant influence on the increase of pore pressure.The effect of instantaneous time line parameters on the dissipation rate of pore water pressure is periodic,and the effect of reference time line parameters and reference points on the pore pressure dissipation rate is monotonicity,while the influence of secondary consolidation coefficients and creep deformation limit value on pore pressure dissipation rate has interval.The development rate of the overall settlement deformation of the foundation increases with the value of instantaneous time line parameters and reference time line parameters,and decreases with the increase of secondary consolidation coefficients and creep deformation limit value.(3)The Hansbo seepage and EVP model were introduced into the radial consolidation analysis of sand well foundation.The following conclusions are obtained through analyzing the distribution and dissipation of pore water pressure,and the change of consolidation degree over time: the greater the value of Hansbo seepage mode and radius ratio,the more obvious the pore pressure dissipation and the delay of the consolidation rate.The phenomenon of pore water pressure increased in the pre-consolidation stage,moreover the elevation value and time of the pore pressure are improved when the Hansbo seepage is taken into account.The effect of instantaneous time line parameters and secondary consolidation coefficient on pore pressure dissipation is similar to that of one-dimensional rheological consolidation.