芒硝蠕变特性及本构模型研究

利用RLW-2000岩石流变试验机对芒硝开展了三轴压缩蠕变试验。试验结果显示，同一围压下，随轴向应力增大，芒硝蠕变变形量和稳态蠕变率均随之增加，而各级荷载加载过程中芒硝变形模量不断减小；芒硝蠕变过程具有非线性特征，且随蠕变时间延长，芒硝屈服强度逐渐降低。以分数阶粘滞体代替广义Kelvin模型中的经典粘滞体，建立了分数阶广义Kelvin模型；针对其蠕变方程形式复杂、应用不便的缺点对其进行了简化，将简化后的分数阶广义Kelvin模型与Heard稳态蠕变模型相结合，构建了一种新的非线性蠕变本构模型，并利用芒硝蠕变试验结果反演了模型参数。结果表明，拟合曲线和试验结果吻合良好，说明该模型能够较好的描述芒硝的蠕变特性。

Study on creep properties and constitutive model of thenardite

Triaxial compression creep tests to thenardite specimens are carried out on the RLW-2000 rock rheology testing machine. The test results indicate that the creep strain and steady creep rate of thenardite increase gradually with the increasing of axial stress under a same confining pressure, while the deformation modulus of which in loading process decreases gradually. The creep process of thenardite has a nonlinear characteristic, and the yield strength of which decreases gradually with creep time increasing. The fractional generalized Kelvin model is established by replacing the classical viscous body in the conventional generalized Kelvin model with a fractional viscous body, however, the creep equation of which is very complex, and not convenient for using. To overcome this shortcoming, the creep equation of the fractional generalized Kelvin model is simplified. Then, a new nonlinear creep constitutive model for thenardite is constructed by combining the simplified fractional generalized Kelvin model with the Heard steady creep model, and the parameters of which is inversed using the creep test data of thenardite. Fitting curves and test curves conform very well to each other, which illustrates the new nonlinear creep model can well reflect the creep properties of thenardite.