The Coupled Creep Damaged Constitutive Model For Deep Frozen Clay And Its Engineering Application

The artificially freezing clay shaft excavation unloading mechanical process of the deep alluvium were simulated in this paper by consolidation, low temperature freezing and unloading triaxial shear test method. Obtained by the experiment:the stress-strain of frozen soil showed a straight line when the deviatoric stress level was not large, the stress-strain was obviously nonlinear when the deviatoric stress was larger, the frozen soil was a plastic body. The artificially frozen soils meet the Zienkiewicz-Pande parabolic yield criterion under high confining pressure unloading path; the shear yield surface of the frozen soil in low confining pressure unloading path can choose Mohr-Coulomb yield function.The unloading triaxial creep tests results of the frozen clay showed that:when deviatoric stress levels were low, only the I and II stages of creep deformation occurred and the creep deformation occupied the total deformation more than 70%; when the deviatoric stress was higher than a critical value, the III creep stage emerged, and a large plastic flow happened, experienced a short time to destroy, usually 3 to 5 hours or so, and the creep deformation occurred the total deformation more than 80%; and the critical value of the creep stage III could be described by the improved Zienkiewicz-Pande parabolic yield criterion.Based on the artificially frozen soil creep and triaxial shear test results, using the viscoelastic-plastic mechanics, thermodynamics, geotechnical damage mechanics,derived the viscoelastic-plastic damage coupled variable and the damage evolution law of the frozen soil, used the improved Zienkiewicz-Pande parabolic yield criterion instead of the Linear Newtonian, got the artificially frozen soil viscoelastic-plastic damage coupled constitutive model under unloading stress paths, and derived the calculate the instantaneous elastic compliance matrix, viscoelastic and viscoplastic damage coupling compliance matrix. The artificial ice constitutive finite element programs were compiled in the Compaq Visual Fortran6.6A environment, and embedded into the non-linear finite element software ADINA through the user subroutine. By the numerical simulation and experiments we obtained the creep tests and the numerical simulation values of the artificially frozen soil in unloading stress paths agreed well, and the maximum difference was 4.8%. The results showed that it was reasonable to take the viscoelastic-plastic damage coupled constitutive model which expressed by the non-linear Newtonian structure parabolic yield criterion to describe the frozen soil creep.The artificially frozen soil creep in unloading stress paths, including transient strain components, viscoelastic strain components and viscoplastic strain components these three parts, the frozen wall was divided into Damage regional, viscoelastic regional and viscoplastic region these 3 regional. And assuming frozen wall damaged area to meet the Mohr-Coulomb yield criterion, viscoelastic-plastic frozen wall using Laplace transform theory to solve deep freeze wall stress and displacement field from theory. The measured displacement and calculated frozen wall changes were exactly the same, show that the calculated frozen wall stress field and displacement field using the viscoelastic-plastic damage theory is reasonable.The temperature, the internal forces and the displacement of the shaft wall excavation process in the deep alluvium freezing sinking were site measured and obtained the corresponding laws. According to the project conditions to determine the frozen wall temperature field, using the artificial ice damage coupled constitutive viscoelastic-plastic model, taking into account the dynamic construction mechanics of the shaft excavation process, using the nonlinear finite element analysis software ADINA coupling analyzed the deep frozen wall temperature field, the stress field and displacement field, the work-face displacement distribution and the stress field distribution of the frozen shaft excavation process were obtained, and they in accordance with the actual laws.The artificially frozen soil creep constitutive model which was based on statistical damage theory, overcame the defects that the component model can only describe the linear creep characteristics. The calculated parameters could be getting through the constitutive model by simply tests and the model had few parameters, easy to calculate and other advantages. The constitutive equation provided effective approaches for the further study of the mechanical behavior of the field frozen structures, and had practical significance for the long-term stability analysis and prediction of the frozen soil structure. Figure [62] Table [15] Reference [108]...