冻结褐色泥岩非线性加速蠕变西原模型优化

为研究冻结褐色泥岩加速蠕变特性,以陕西某煤矿主井井筒褐色泥岩为研究对象,基于不同的轴压水平,采用WDT-100冻土试验机分别在-5,-10,-15 ℃的负温条件下进行了单轴等载荷蠕变试验。试验结果表明:低轴压水平下的冻结褐色泥岩蠕变呈现出瞬时弹性、减速、稳定3阶段特性,高轴压水平呈现出瞬时弹性、减速、等速、加速4阶段特性,轴压水平因素对冻结褐色泥岩轴向应变增加的影响程度远大于温度因素。基于经典西原模型,串联一个带应变启动的非线性黏滞阻尼器,得到7元件优化西原模型,通过最小二乘法对模型参数进行非线性回归分析,分析结果表明,7元件优化西原模型拟合曲线与试验结果吻合良好,更适合于描述冻结褐色泥岩非线性加速蠕变特性的变化规律,对深井煤矿冻结褐色泥岩的蠕变破坏预报具有参考价值。

An Optimized Nishihara Model for Nonlinear Accelerating Creep of Frozen Brown Mudstone

In the present research,uniaxial creep test was conducted under different axial compression levels at varying freezing temperature (-5℃,-10℃,-15℃) by WTD-100 artificial frozen soil apparatus to investigate the accelerating creep of frozen brown mudstone.The brown mudstone in a coal mine shaft in Shaanxi Province was taken as research object.Test results showed that the frozen brown mudstone experienced three stages of transient elasticity,deceleration and stability under low axial pressure,and four stages of instantaneous elasticity,deceleration,constant velocity,and acceleration under high axial compression level.The influence of axial compression on frozen brown mudstone is much greater than that of temperature.Moreover,by connecting nonlinear viscous dampers with strain start,an optimized Nishihara model with seven elements was established based on classical Nishihara model,and the model parameters are analyzed through nonlinear regression by the least square method.Analysis results showed that the fitting curves of the optimized Nishihara model are in good agreement with the experimental results.The optimized Nishihara model is more specifically suitable for describing the variation rule of nonlinear accelerating creep characteristics of frozen brown mudstone.