深部煤体非线性蠕变本构模型及实验研究

Research on experimental and nonlinear creep constitutive model of coal at depth

深部煤体蠕变规律研究对控制巷道围岩变形,预防煤与瓦斯突出及改善瓦斯抽采效果具有重要意义。基于分数阶导数流变模型,推导出煤体三维应力条件下非线性蠕变本构方程。考虑深部煤体赋存的高应力环境及应力变化路径,进行了三向应力状态下轴压恒定、分级卸围压的煤体蠕变实验。实验结果表明:在三向高应力状态下,试件的轴向和环向应变表现为初始蠕变和稳态蠕变,最终出现加速蠕变阶段;在相同差应力条件下,煤体蠕变变形随围压增大而减小。利用煤体卸围压蠕变实验数据对文中蠕变本构方程的参数进行拟合,结果表明:该蠕变本构方程能很好地描述煤体蠕变三阶段,特别是加速阶段。在蠕变本构方程参数确定的前提下,分析了应力水平、分数阶导数阶数及黏性系数对煤体蠕变特性的影响规律。

The study of creep law in deep coal is important to control the deformation of surrounding rock,prevent coal and gas outburst and improve the effect of gas extraction. Based on the rheological model of fractional derivative,the nonlinear creep constitutive equation of coal under three-dimensional stress is deduced. Considering the occurrence of high stress environment and stress variation path of coal at depth,the creep test of coal under constant stress and multistage unloading confining pressure in three direction stress state is carried out. The experimental results show that in the three dimensional high stress state,the axial and circumferential creep strains of specimens are characterized as initial and steady state,and finally occur to accelerated creep stage; under the condition of same differential stress,the creep deformation of the coal decreases with the confining pressure increasing.The parameters of the creep constitutive equation are fitted by the experimental data of unloading confining pressure of coal. The results show that the creep constitutive equation can well describe the three stage of creep of coal,especially the accelerated stage. Furthermore,the influence of stress level,fractional derivative order and viscosity coefficient on creep characteristics of coal is analyzed under the premise of determining the parameters of the creep constitutive equation.