基于应变空间的盐岩蠕变全过程变形规律及演化模型研究

The deformation law of salt rock creep has an important effect on the long-term stability of salt cavern storage , and it’s related with the security of the national energy strategic reserve . Considering the deformation properties of salt rock , this project studies the elasto-plastic constitutive relation of salt rock by strain space , and then establish nonlinear characteristic creep evolution model of describing the creep acceleration phase .Combining experimental analysis with theoretical research , this project studies characteristics and associated relationships of the post-failure phase in softening and the different creep deformation stages of the complete stress-strain curve based on strain theory , the cut-off points of whole-process creep evolution in different stages of rock salt were determined .The relationship between the start and end and the failure characteristics under different stress conditions with the complete stress-strain curve of creep deformation of rock salt is obtained . Concrete forms of hardening function were determined by strain space theory . The elastoplastic constitutive relations strain space representation was established . Damage parameter and damage evolution equation was introduced in the creep acceleration phase based on the rock rheologic theory and the damage theory .3-dimensional viscoelasto-plastic creep basic equation of strain space was established based on K-B model’s .More reliable theoretical was provided for the long-running rheological analysis of salt cavern underground storage.

盐岩蠕变变形规律对盐穴储库长期稳定性具有重要影响，同时关系到盐穴储库的安全运营。考虑盐岩变形特点，引入应变空间方法研究盐岩弹塑性关系，进而建立可描述蠕变加速阶段非线性特征的蠕变演化模型。项目采用理论研究与实验分析相结合的方法。依据变形理论，研究全应力应变曲线的软化后破坏阶段、蠕变过程不同变形阶段的特征及其关联，并确定盐岩蠕变全过程各阶段的分界点。得到盐岩全应力应变曲线与盐岩蠕变变形起始、终结的对应关系，及其与不同应力状态下盐岩蠕变破坏特征的对应关系。基于应变空间理论确定硬化函数具体形式，建立盐岩的弹塑性本构关系的应变空间表述。根据岩石流变学及损伤理论，在盐岩蠕变加速阶段引入损伤参数与损伤演化方程，借助西原模型的结构形式建立应变空间盐岩的三维黏弹塑性蠕变基本方程。为盐穴地下储库长期流变分析提供可靠的理论支撑。

研究基于应变角度分析了盐岩蠕变变形机理并结合应变空间理论建立蠕变本构模型。主要研究成果包括：通过不同围压作用的盐岩压缩试验，统计盐岩力学特征对围压有很强的相关性。盐岩压缩全应力应变曲线呈现弹性，硬化，软化三个阶段，采用非线性强度准则建立盐岩软化本构模型。并且依据应变空间理论，采用统一硬化函数更简便、准确地描述了盐岩硬化软化特性。结合蠕变全过程试验结果，借助蠕变终止轨迹线的概念确定了蠕变加速阶段的粘弹塑性损伤率及蠕变加速起始条件。并通过构建的应变空间弹塑性本构方程确定该蠕变加速条件（应变阈值），进而在西原模型的基础上，串联应变阈值开关元件，基于应变阈值来控制蠕变方程形式，建立了一种可描述加速蠕变的七元件蠕变本构模型。最后与盐岩压缩试验及蠕变试验进行了模型参数辨识与验证，结果表明该模型能够很好地吻合试验结果。研究结果可预测蠕变破坏关键参数，进而大大降低蠕变实验时间成本,对盐穴地下储库长期稳定性的评价具有广泛的应用前景。