Improved Duncan-Chang Model Based on Mechanical Properties of Coarse-grained Soil Filling of Embankment

To study the influence of dynamics and moisture content on the mechanical properties of embankment filling with coarse-grained soil, samples of coarse-grained soil under different moisture contents w were prepared. Dynamic stress with different frequencies f was applied to the samples, and then static triaxial compression tests were performed. The σ0-ϵ1 curves of the different samples were analyzed. According to the Janbu formula, the correlation between the dynamic deviator stress σd, moisture content w, load frequency f, and parameters n and K were explored. The fitting formulas for the initial deformation modulus Ei, ultimate deviator stress (σ0)ult, and controlled variables were established. An improved Duncan-Chang model was proposed for coarse-grained soil considering the influence of the dynamics and moisture content. Finally, verification tests were conducted to analyze the effectiveness of the revised model. The results show that the deformation of the samples changes from elastic to plastic when ϵ1>0.5%. Under different controlled factors, the σ0-ϵ1 curves of the samples change significantly in the range of 0.5%<ϵ1<2.0%. The tangent deformation modulus Et also changes considerably within this range; the reduction rate reaches 58%-76%. When ϵ1>2%, the change in Et gradually decelerates and stabilizes. The samples exhibit strain-hardening characteristics during loading. As the moisture content, dynamic deviator stress, and load frequency increase, the deviator stress decreases when it reaches the same axial strain in the static triaxial tests. The initial elastic modulus Ei of the coarse-grained soil was related to the third principal stress σ3. A linear relationship exists between lg(Ei/Pa) and lg(σ3/Pa). The parameter n in the Janbu formula is not sensitive to controlled factors. In these tests, the value of n is stable at 0.78-0.80. The relationship between σd, w, f, and parameter K is nonlinear. Parameter K decreases with an increase in σd and w, while f shows an opposite trend. The power function can be used to establish the relationship between Et and controlled factors, the relationship between (σ0)ult and controlled factors is the same. Validation tests show that the improved constitutive model in this study can effectively predict the σ0-ϵ1 curve of the coarse-grained soil filling of embankments with different σd, w, and f. © 2023 Xi'an Highway University. All rights reserved.