The damage mechanism of loessial soils was studied by the statistical theory.Based on the characteristics strength of loessial soils micro-unit with Weibull distribution, and parameters that described by distribution variable of Drucker-Prager creterion are used, loessial soils damage constitutive model considering damage threshold is established to reflect the full process of loessial soils failure. Conventional triaxial consolidation undrained shear test results of loessial soils are taken as example to verify the model. By comparing theoretical calculation results with test results, it is showed that the statistical damage constitutive model considering damage threshold is reasonable.
A linear viscoelastic plastic creep model of mica-quartzose schist is established by using the method of establishing combined-linear-component model based on triaxial creep test. The micro-structural changes of mica-quartzose schist during triaxial creep process are observed by using the scanning electron microscope test, based on that, the relation of macro-stress and macro-strain with porosity and damage variable are established through statistical damage theory and simplified mechanical model respectively, the creep damage variable is obtained by further derivation on the basis of above study. The creep damage variable is simplified according to the whole creep process curve, substitutes the simplified creep damage to the estabilished linear viscoelastic plastic creep model of mica-quartzose schist, considering the change of modulus and viscosity during creep process, a viscoelastic plastic damage model of mica-quartzose schist is established. The model parameters are got by segment fitting, the good consistency of the test curves and the fitted curves shows the right and reasonable of the creep model, it also shows that the model can well describe the nonlinear accelerated creep stage. Sensitivity analysis shows that parameter m has greater influence on the accelerated creep deformation than parameter a.
Firstly, the creep curves of mica-quartzose schist are obtained through the triaxial creep test, the triaxial creep characteristics are found out by analyzing the creep curves. Secondly, a linear viscoelastic model is established by using model theory, a viscoplastic model is established by using empirical formula, added the above two model, a non–linear viscous elastic-plastic creep model of mica-quartzose schist is obtained. Lastly, the creep model parameters are got by data fitting, the good consistency of the test curves and the theoretical curves show the right and reasonable of the creep model. The non–linear viscous elastic-plastic creep model established can well describe the accelerated creep of mica-quartzose schist.
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