Analysis On Rheological Consolidation Of A Soft Clay With A Threshold Gradient

Traditional consolidation theory mostly believes that the seepage flow in soil obeys Darcy's law,but theoretical and experimental studies have shown that due to the low permeability of soft clay,the threshold gradient exists in saturated soft clay.Seepage flow occurs only in the soil when the hydraulic gradient is greater than the threshold gradient.At the same time,the rheological properties in soft clay have a crucial influence on the strength of the foundation and post-construction settlement.So far,the soft clay consolidation theory that can simultaneously consider the threshold gradient and rheological properties is still rarely reported in the literature,and the study of its analytical solution is even rarer.Based on the existing research,this paper uses the analytical method to study the rheological consolidation theory of soft clay considering the threshold gradient.The main innovations and research contents include:1.The motion law of the moving boundary and the distribution of excess pore water pressure in soft clay under constant loading are analyzed.The consolidation differential equation is established and the corresponding solution conditions are given.The analytical solution of the model is obtained by Laplace transform.The analytical results of the solution are compared with the results of the difference decomposition,and the rationality and correctness of the solution are verified.On this basis,the influences of the threshold gradient and rheological model parameters on the moving boundary position,the distribution of the excess pore water pressure,the average degree of consolidation of the soil layer and the settlement of the foundation are calculated and analyzed by reasonable parameters.2.Aiming at the slow application of the load in the practical engineering,the motion law of the seepage moving boundary and the distribution of the excess pore water pressure under variable loading are analyzed.The consolidation differential equations under single-stage loading and multi-stage loading conditions are established and the solution conditions under the corresponding conditions are given respectively.The Laplace transform is used to obtain the analytical solution of rheological consolidation considering the threshold gradient under single-stage loading and multi-stage loading.The analytical solution obtained in this paper is compared with the difference decomposition result to verify the correctness of the understanding.Taking the three-steps loading as an example,the influence of the threshold gradient,rheological model parameters and loading time on the consolidation behavior was analyzed by reasonable parameters.Finally,the distribution of the excess pore water pressure and average consolidation degree under transient loading,single-step loading and three-steps loading are compared and analyzed.3.For the case of non-uniform distribution of initial excess pore water pressure due to external factors such as sudden rise and fall of water level in the project or load of building structure,the motion law of the seepage moving boundary and the excess pore water pressure under the condition of linear distribution of initial excess pore water pressure along the depth are analyzed.The consolidation differential equations and the solution conditions for different initial pore pressure distributions are given.The Laplace transform is used to obtain the analytical solution corresponding to the case.The obtained analytical solution is compared with the calculation result of the difference decomposition,and the correctness of the solution is verified.Taking single drainage conditions as an example,the influences of the threshold gradient,rheological model parameters and initial excess pore water pressure distribution on consolidation behavior were calculated and analyzed with reasonable parameters.