酸腐蚀条件下石膏岩分数阶蠕变本构模型研究

RESEARCH ON FRACTIONAL DERIVATIVE CREEP CONSTITUTIVE MODEL OF GYPSUM ROCK UNDER ACID CORROSION

为探究地下水对岩石的侵蚀损伤,通过开展酸腐蚀条件下的石膏岩单轴压缩蠕变试验和扫描电镜试验,研究了不同pH条件下石膏岩单轴压缩蠕变特性以及酸腐蚀前后试样的微观变化。结果表明:酸腐蚀加快了试样的蠕变速度,酸性越强,蠕变速率越快;试样主要以劈裂和剪切破坏形式为主,端部出现损伤破坏的现象,酸性越强,损伤破坏越明显。微观上,干燥试样结构完整;而酸腐蚀后的试样,随着酸性增强,孔隙增多、增大,结构疏松。为描述酸腐蚀条件下石膏岩蠕变过程,通过引入酸腐蚀劣化衰减系数β对变系数Abel黏壶进行改造,用改造后的变系数Abel黏壶元件代替西原体中黏塑性体部分的牛顿黏壶,建立了考虑酸腐蚀条件下的分数阶蠕变本构模型。通过试验数据与所建立的模型进行参数拟合,确定了模型中的参数,并对引入的参数β进行了敏感性分析。研究表明,所提出的模型能够很好地反映酸腐蚀条件下石膏岩的蠕变三个阶段,尤其是加速蠕变阶段。

To explore the erosion damage of groundwater on rocks, the uniaxial compression creep properties of gypsum rock under different pH values and the microscopic changes of the specimens before and after acid corrosion were studied by uniaxial compression creep test and scanning electron microscope test. The results showed that the creep rate of specimens was accelerated(the stronger the acid, the faster the creep) by acid corrosion. The specimens are mainly in the form of splitting and shearing failure, and damage and failure appeared at the end(the stronger the acidity, the more obvious the damage failure was). From a microscopic point of view, the structure of the specimens in the dry state was complete, but the structure of the specimens was damaged(with the increase of acidity, increased pores and loosed structure) by acid corrosion. To describe the creep process of gypsum rock under acid corrosion conditions, the variable coefficient Abel dashpot was modified by introducing the acid corrosion degradation attenuation coefficient β, and the modified variable coefficient Abel dashpot was used to replace the Newton dashpot in the viscoplasticity of the Nishihara model, and a fractional creep constitutive model considering acid corrosion was established. The parameters in the model were determined through fitting of the experimental data. The sensitivity of the parameter β is also analyzed.The study found that the fractional derivative creep constitutive model proposed here after considering acid corrosion conditions can better reflect the three stages of creep of gypsum rock under acid corrosion, especially the accelerated creep stage.