Abstract
The nonlinear constitutive relations of clay are investigated considering different initial conditions. Highly compressible clay is selected as the test sample. Two groups of tri-axial compression tests are performed, respectively, afterK0consolidation and isotropic consolidation. On the basis of the framework ofE~vmodel, a uniform nonlinear constitutive model is proposed by fitting the test data. With the average slope of the unloading-reloading curve selected as the unloading modulus, the unloading function is constructed as the loading-unloading criterion. Moreover, a comparison between the experimental stress-strain curves and the results predicted by the constitutive model is made. It is shown that the prediction is reasonable, which can reflect the stress-strain behavior of the soil under theK0consolidation and isotropic consolidation conditions. The maximum relative error of the two series of curves is not remarkable, less than 6%.
Highlights
In geotechnical engineering, the nonlinearity nature of soil is influenced by a stress path and has a close relationship with a load and a loading method
A unified nonlinear constitutive model was proposed for clay under different initial conditions
It is shown that the model can reflect the stress-strain behavior of the soil under the K0 consolidation and isotropic consolidation conditions
Summary
The nonlinearity nature of soil is influenced by a stress path and has a close relationship with a load and a loading method. The hyperbolic model has been a widely used nonlinear constitutive relationship for clay because of its simple model structure and accessible parameters [4] This constitutive model was based on the data of tri-axial shear tests [5] under regular loading path. To consider the soil structural damage during loading, the concept of damage rate was introduced to modify Duncan-Chang model [18, 19] In these modified models, the initial stress state was assumed to be isotropic. The anisotropic initial stress and strain states result in different strength and deformation characteristics, and the constitutive relationship was different from that of isotropic stress states [21] To overcome these differences, a unified nonlinear constitutive model was proposed for clay under different initial conditions. It is shown that the model can reflect the stress-strain behavior of the soil under the K0 consolidation and isotropic consolidation conditions
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