A Study Of Frozen Soil Elastoplastic Constitutive Relationship Model With Triaxial Shear Characteristics

In recent years, with the rapid development of industry and agriculture in cold region and the promotion and application of freezing method in engineering, the importance of the research of frozen soil stands out more clearly. At present, the freeze method has been widely used in digging well engineering in unstable stratum In our country. However, with the increase in depth of frozen shaft in unstable stratum there come some new challenges. Engineering circles increasingly realize that it becomes imperative to grasp the mechanics properties of artificial frozen soil to solve the problem, in particular to focus on the constitutive relations of frozen soil. Based on this, the paper obtained a double yield surface model of frozen soil by study on triaxial shear properties of Artificial frozen clay. The research results have important reference value both in theory and in engineering applications.This main research work includes:1. Take mechanic test of the frozen clay under different conditions, including triaxial compressive strength test under different temperature and different confining pressure, by W3Z-200Electro-hydraulic servo triaxial testing machine developed by freezing soil research institution of Anhui University of Science and Technology, then analysis the test results. The tests show that the shapes of stress-strain curves under different conditions are almost the same. As the axis strain keep increases, the deviator stress increase rapidly when the axis strain ε≤(1.0%～4.5%), and in this phase the curve are approximately linear and Show the elastic properties to a certain extent, that indicate the frozen soil is elastic body. The stress-strain of frozen soil has a strong nonlinear relation when the deviator stress becomes larger, the frozen soil present plastic body. Within the confining pressure this paper test, the value of q increases linearly as the value of p increased, therefore we can description this characteristics by Mohr-Coulomb criterion.2. Suppose that the value of p, q and e of normally consolidated clay have a unique relationship In the process of loading, namely the volume state of soil is irrelevant to the stress path. Based on the modified Cambridge model, put forward a Single surface constitutive model theory compliant with frozen clay, and verify the model by the results of Triaxial compression test, then obtained the corresponding test fitting curve.3. Considered that the single yield surface model of frozen clay limited by the traditional plastic potential theory and not fully consider shear deformation, add a shear yield surface that With plastic shear strain as hardening parameter. Based on this, put forward a modified double yield surface constitutive model of frozen clay. Through simulate multiple sets of test results by computer indicate that this model has a high prediction skill and widespread applicability.Finally, discuss about further research briefly.