不同加载速率下煤岩采动力学响应及破坏机制

研究煤岩在不同加载模式与不同加载速率下采动力学响应及破坏机制对认清煤矿动力灾害本质具有指导意义。基于塔山煤样，先后设计与开展了单轴拉伸与压缩、常规三轴及采动力学试验。获得了不同加载模式下煤样的力学特征参量和变形破坏特性。进一步对比分析了常规三轴试验与采动力学试验煤样变形特征的差异。得到煤样破坏前吸收能量密度随着轴向加载速率的关系，揭示了应力偏量是造成试样破坏强度和吸收能量密度提高的原因，是破坏产生的本质原因，但其受控于围压的临界值，及煤样损伤发生具有的时间效应。建立了采动力学条件下考虑加卸载过程中材料损伤的煤岩黏弹性模型屈服准则，包含有效体积应力的影响、应力差的影响、轴向加载速率的影响及围压卸载速率的影响，新的黏弹性模型屈服准则可以很好地解释加卸载速率引起的材料屈服强度变化。

Failure mechanism and mining-induced mechanical properties of coal under different loading rates

Research on the mining-induced mechanical response and failure mechanism of coal under different loading modes and different loading rates is instructive for recognizing the nature of dynamic disaster in coal mines.Based on the coal samples from Tashan,the uniaxial tension and compression,conventional triaxial compression and mining-induced mechanical test have been conducted.The mechanical parameters and deformation characteristics under different loading modes were obtained.Furthermore,the comparative analysis of coal deformation between conventional triaxial compression and mining-induced mechanical test was studied.The linear relationship between axial loading rate and absorbed energy intensity was obtained.The improved strength and absorbed energy intensity are caused by deviatoric stress,which can explain the time effects of damage.Considering the effective volume stress,the stress difference,the axial loading rate and confining pressure unloading rate,a new viscoelastic model with yield criterion is proposed to describe the material yield strength changes caused by unloading rates.