基于化学酸碱度表征的页岩蠕变模型

Shale creep equation based on chemical pH value characterization

  • 摘要: 以山东唐口煤矿页岩为研究对象,采用三轴蠕变试验机进行不同化学pH值条件下的蠕变特性试验研究。针对化学酸碱度对页岩蠕变关键特征参数的影响,结合蠕变过程中化学腐蚀效应,提出了一种新的化学腐蚀流变元件; 通过对幂指数蠕变经验方程与Burgers模型中的黏塑性二元件的黏性系数进行非线性处理,建立了不同pH值条件下页岩蠕变方程; 通过对试验结果分析,运用最小二乘法确定蠕变方程参数,并得到化学pH值对页岩蠕变关键参数的影响规律; 通过对方程的关键参数进行敏感性分析,探索出弹性模量、黏性系数等关键参数对页岩蠕变特性的影响规律。模型理论曲线与试验曲线在蠕变的3个阶段吻合较好,说明构建基于不同化学pH值的页岩蠕变本构模型可以对页岩蠕变过程进行准确表征,尤其是第3蠕变阶段; 化学酸碱性越强,与页岩材料性质有关的参数值β越大,其蠕变的稳态阶段越短,越易发生非稳定蠕变直至岩石失稳破裂,而且页岩在pH=3时的酸性条件比pH=10时的碱性条件下的影响更为强烈。通过对蠕变试验结果拟合分析得到的模型关键参数随化学pH值的变化曲线,可得出不同化学pH值(酸碱性)对页岩蠕变关键参数的影响趋势。研究结果为地下岩石工程在地下水腐蚀环境中的长期稳定性评价提供了参考和依据。

     

    Abstract: Taking the shale sample in Tangkou coal mine in Shandong province, China, the creep characteristics of different chemical pH values are tested with a triaxial creep tester.Aiming at the influence of chemical pH on the key characteristic parameters of shale creep and combined with the force-chemical coupling effect in creep process, a new force-chemical coupling rheological element is proposed.The creep equation of shale under different pH values is established by nonlinear processing of the creep empirical equation of power exponential and the viscosity coefficient of the viscoplastic body in Burgers model.By analyzing the test results and using the least squares method, the creep equation parameters are determined and the influence law of chemical pH value on the key parameters of shale creep is obtained.Through the sensitivity analysis of the key parameters of the equation, the influence law of the key parameters (including elastic modulus, viscosity coefficient etc.) on the creep characteristics of shale is explored.The model theory curve is in accord with experiment curve in three phases, which indicates that creep equation based on chemical pH value characterization proposed above is capable to describe the whole creep process of corrosion shale, especially the third creep phase.The stronger the chemical acid base is, the larger the exponent β which is related to the properties of shale materials is, the shorter the steady phase of creep is, and the more prone to unstable creep until the rock is unstable and fractured.The acidic condition at pH=3 is stronger than the alkaline condition at pH=10.Based on the fitting analysis of creep test results, the change curve of key parameters of the model with chemical pH value is obtained, and the influence trend of different chemical pH values (acidity and alkalinity) on the key parameters of shale creep is obtained.The results provide a reference and basis for the long-term stability evaluation of rock engineering in underground water corrosive environment in coal mines.

     

/

返回文章
返回
Baidu
map