Further Modified Duncan-Chang Constitutive Model Considering Intermediate Principal Stress with Lateral Unloading for Silty Clay

Abstract

Duncan-Chang model describes the soil stress-strain relationship more accurately when the soil will be loaded. However, it will be inaccurate when the soil is in the unloading process, such as the pit excavation. In order to dispose of properly the Duncan-Chang constitutive model describing accurately the stress-strain relationship of the silty clay under the unloading condition so as to achieve the purpose of engineering application. This paper developed a further modified Duncan-Chang model, which consider intermediate principal stress, lateral unloading process, the parameter λ was introduced to the model; The result by taking the true triaxial test data of a typical silty clay shows that when λ=0.45, a new modified unload Duncan-Chang model for silty clay is effective in solving the problem of descripting unload stress-strain relationship test curves of the silty clay. And for the results further showed it is not suitable for using the sum of the intermediate principal stress σ2 and third principal stress σ3 is equal to 0.5 instead of the intermediate principal stress σ2 through the finite element calculation to the silty clay pit excavation.