Nonlinear Large Strain Consolidation Analysis Of Nature Structured Soft Clay Subgrade

The majority of natural sedimentary clays,distributed widely in the coastal regions of China,generally have certain structural characteristics.The differential settlement and large strains of foundation after construction can be induced in the clay layer due to the structure and high compressibility during the construction of these areas.Hence,it is imperative to take the structural characteristics of nature soft soil into consideration in the calculation of natural sedimentary soft soil consolidation deformation.Meanwhile,it is necessary to adopt large strain geometric assumption to predict the settlement,owing to the large strain value of natural soft soil under external load.However,there seems to be few studies on the comprehensive consideration of large strain assumption,structural of nature soft soil,nonlinear variation of permeability coefficient and compressibility coefficient during the process of consolidation.Therefore,it is of great theoretical and engineering significance to study the large strain nonlinear consolidation theory for structured soft soils.In this paper,the structural characteristics of natural soil,nonlinear variation of structural yield stress,permeability coefficient and compressibility coefficient,time-dependent loading as well as high strain characteristics of the foundation are taken into account simultaneously,based on which the large strain nonlinear consolidation models were established under the assumption of seepage in clay obey Darcy flow law and non-Darcy flow law,respectively.The finite difference method is adopted to obtain numerical solution.The main research contents are summarized as follows:?1?Based on the Darcy flow law,the large strain nonlinear consolidation model of naturally deposited soft soil under time-dependent loading is established by considering the structural characteristics and nonlinear compressive permeability of natural soil and introducing the large strain geometric assumption.The solutions are obtained via the finite difference method,on the basis of verifying the reliability of the solutions,the influence of the structural property,the time-dependent loading,the self-weight stress as well as other factors on the consolidation behavior has been analyzed;The differences in consolidation behavior under different geometric assumptions of large and small strain have been analyzed;?2?The one-dimensional large strain nonlinear consolidation equation,based on the Hansbo non-Darcy flow model,was established considering the nonlinear variation of self-weight stress during the progress of consolidation,nonlinear variation of structural yield stress,permeability coefficient and compressibility coefficient,as well as time-dependent loading and other parameters.The solution conditions were deduced from the boundary conditions and initial conditions,the solutions were obtained via the finite difference method.On this basis,the influence of structural property,time-dependent loading,parameters m,i₁ as well as the nonlinear variation of soil parameters on the consolidation behavior were specially analyzed;The differences in consolidation behavior under different geometric assumptions of large and small strain have been analyzed.?3?The one-dimensional large strain nonlinear consolidation equation with threshold hydraulic gradient non-Darcy flow model was established,considering the structural characteristics,nonlinear variation of permeability coefficient and compressibility coefficient during the progress of consolidation.The solutions were obtained via the finite difference method.Based on the verification of these solutions,the influences of the structural yield stress,time-dependent loading,threshold hydraulic gradient i₀ on the consolidation behavior of the structural soft soil have been analyzed;The differences in consolidation behavior under different geometric assumptions of large and small strain have been analyzed;The effect of low threshold hydraulic gradient on the calculation results of consolidation deformation has been analyzed.