Abstract: By lots of creep test researches, artificial frozen clay shows an obvious creep behavior under high deviatoric stress. When artificial frozen clay in low stress level, a viscoelastic creep deformation presents. While in high stress level, viscoplastic creep deformation presents. On the basis of Nishihara model, parabolic viscoelasto-plastic creep constitutive model is constructed by adding a viscoelastic element and parabolic yield function instead of plastic yield. The modified Nishihara model can describe the shear creep characteristics of artificial frozen soil well. Based on niche technology, genetic algorithm and viscoelasto-plastic theory, the model of viscoelasto-plastic displacement back analysis for artificial frozen soil has been set up by finite element program generator (FEPG). With the measured data, displacement back analysis is conducted during the excavation of deep freezing shaft. And the obtained parameters of mechanical model for frozen soil agree with the test results. The deviation between numerical calculation results and measured data is less than 6%; so the inversion results verify the feasibility of the model. The constitutive model parameters, which obtained by displacement back analysis for artificial frozen soil, can reflect the average of frozen wall construction process and effective freezing range. So it has wide representation and important engineering significance for frozen wall stress field, displacement field and stability prediction.

Key words: genetic algorithm, displacement back analysis, artificial frozen soil, viscoelasto-plastic constitutive model, FEPG