One-dimensional Consolidation Analysis Of Saturated Soft Clay Based On Fractional Non-Darcy Flow

In our country,soft clay is widely distributed in coastal and inland plain areas.It has rheological properties,non-Darcy properties,low permeability and other properties,which result in the consolidation settlement of soft clay is often much slower than that of other types of soil.If the engineering design and construction personnel do not consider these factors,it may lead to instability and damage to the buildings.Therefore,it has become an important problem to analyze and predict the consolidation of soft clay foundations accurately in the field of civil engineering.In order to simplify the actual situation and facilitate consolidation analysis,Terzaghi deduced the one-dimensional consolidation theory of saturated soil based on six assumptions.The proposal of this theory filled the blank of human consolidation theory and provided a solid theoretical basis for the research of later scholars.However,due to the complexity and uncertainty of practical engineering,the classical consolidation theory has some limitations.Based on Terzaghi’s one-dimensional consolidation theory,the rheological properties of soft clay,non-Darcy characteristics,and permeability coefficient changes during the consolidation process are considered in this thesis,and one-dimensional consolidation of saturated soft clay is further studied to better predict the consolidation of saturated soft clay.The specific work is as follows:1.Under the condition of uniform constant load and only top surface permeability,the fractional Merchant model which can characterize the time accumulation effect in the process of soil consolidation is used to describe the solid phase of saturated soft clay,and the fractional non-Newtonian exponential seepage model which can characterize the global spatial scale characteristics in the process of soil consolidation is used to describe the liquid phase of saturated soft clay.A new one-dimensional consolidation equation for saturated soft clay is derived by modifying the solid-liquid two-phase equation,and its numerical solution is obtained by discretization using the finite difference method.2.The results based on the fractional order theory in this thesis are reduced to integer order,and the results are compared with the integer order theory results to verify the accuracy of the solution in this thesis.At the same time,the relevant model parameters are obtained by parameter fitting based on the existing test data,and the applicability of the model in this thesis is verified by comparing with the test data and the integer order theoretical results.In addition,the consolidation mechanism is further explained by analyzing the parameters of the model.3.Based on the fractional-order constitutive equation and fractional-order non-Darcy flow equation,the influence of permeability variation in the consolidation process is considered.By using the permeability coefficient change equation proposed by Taylor,the fractional-order flow equation considering the coupling effect of variable permeability coefficient and non-Darcy characteristics is obtained.On this basis,the numerical solution of the one-dimensional consolidation of soft clay is solved.By comparing with the experimental data and the consolidation theory results under the constant permeability coefficient,the superiority of the fractional order model under the variable permeability coefficient is verified.Finally,the sensitivity analysis of the related parameters is carried out.