The Deformation Mechanism And Nonlinear Creep Constitutive Model Of Bedded Salt Rock

Salt rock is recognized as an ideal medium for energy storage or high radioactive wastes permanent disposal because salt rock have especial characteristic such as well creep deformation, low permeability and damage recovery. Bedded salt rock in China has the unique characteristics, "many layers of salt rock, the thin single-layer , salt rock in general contains many sandwich(mudstone, etc.) ", energy storage in the bedded salt rock will be more complex than abroad. This paper mainly considers the current two issues concerned widespreadly for bedded salt rock: the layered, heterogeneous lithology and differential deformation, creep between individual layers. In connection with sedimentary characteristics of salt rock in Yincheng city, HuBei , the mechanical properties of bedded salt rock, deformation mechanism, constitutive model and key mechanical issues in energy storage are studied, the main work are included as follows:1. Experimental study for the mechanical properties of bedded salt rock: uniaxial-triaxial compression test, uniaxial-triaxial creep test are performed to obtain the corresponding mechanical parameters, Comparison about stress and strain characteristics, the strength parameter and creep mechanical properties under uniaxial-triaxial compression between Yincheng salt rock and Jintan salt rock are presented, the microscopic analysis and the interface role of bedded salt rock are carried out.2. The deformation problem of bedded salt rock due to elastic parameters mismatch are studied: with the help of numerical experiment, the mechanics and deformation properties of bedded salt rock are analyzed with the finite element software ABAQUS, the micro-stress and displacement, stress concentration problems and the interaction mechanism are studied in the bedded salt rock with different thickness and different mechanical parameters under uniaxial-triaxial compressive loadings.3. The deformation problem of bedded salt rock due to creep rate mismatch are studied: creep mechanical response for bedded salt rock with different content interlayers under uniaxial compression and triaxial compression with low confining pressure with the finite element method are calculated, stress relaxation, stress redistribution and evolution of stress and strain are analyzed in the bedded salt rock, the interaction and nonlinear creep properties of bedded salt rock are studied, and then the effect of different content mudstone on creep mechanical properties of bedded salt rock are studied.4. The anisotropic nonlinear incremental creep constitutive model of bedded salt rock is established: based on the micromechanical method and strain compatibility principle, considering the elastic behavior of mudstone interlayers, elastic and creep behavior of salt rock, an anisotropic incremental nonlinear composite creep constitutive model of bedded salt rock is derived, the new model is rewritten to be a subroutine with fortran language and incremental-substituting algorithm, and then the model is introduced into finite element software ABAQUS, as a example, a simple bedded salt rock sample is modeled to verify the composite model, the result is agreed with the experiment.5. Long term stability analysis for bedded salt rock cavern: the above proposed anisotropic nonlinear creep constitutive model of bedded salt rock is applied to analyze the stability of the oil, gas storage cavern in the bedded salt rock in Hubei yunying city in this section, stress distribution, displacement vector image of bedded salt rock cavern are analyzed under different pressure and different creep time, these will give the reference for the building and operation of bedded salt rock cavern.