煤层冲击倾向性评价的新指标体系

New index of coal seam impact tendencies

基于煤岩微元强度的韦伯分布假设和连续介质损伤力学理论,建立单轴压缩下考虑残余强度的损伤统计本构模型,修正了动态损伤应变计算式,结合损伤因子、损伤速率和损伤加速度研究了煤样的损伤演化规律和煤层冲击倾向性的评价指标,并利用最小二乘法对实验数据进行反演得到反映实验曲线的本构方程,且验证了其正确性。结果表明:考虑残余强度的损伤统计本构模型能较好地反映煤岩峰值强度后的应力-应变曲线的变化趋势和残余强度特征点,并可得到损伤速率的最大值;修正后的动态损伤应变在间接表征冲击倾向性实验的动态破坏时间时可不再受加载方式的限制;提出的盈余能指数变化率指标可综合衡量盈余能、峰后破坏过程损耗的应变能、动态破坏时间的变化情况,衡量煤层冲击倾向性;以最大损伤速率、修正后的动态损伤应变和盈余能指数变化率构成的指标体系可作为评价煤层冲击倾向性的新方法。

Based on the assumption of weibull distribution of coal-rock micro-strength and continuum damage mechanics theory,a damage statistic constitutive model considering residual strength under uniaxial compression is established,and the dynamic damage strain calculation formula is modified.The damage evolution rule and the evaluation index of coal seam impact tendency are studied with damage factor,damage rate and damage acceleration.Further,by using the least squares method,the experimental data are retrieved to reflect the constitutive equation of the experimental curve,and the correctness of the model is verified.The results show that the damage statistic constitutive model considering residual strength can well reflect the change trend of stress-strain curve and the characteristic point of residual strength after the peak strength of coal and rock,and the maximum value of the damage rate can be obtained.The modified dynamic damage strain can no longer be restricted by the loading mode when it indirectly characterizes the dynamic failure time of the impact tendency experiment.The proposed change rate index of surplus energy index can be used to measure the change of surplus energy,the strain energy and the dynamic damage time of post-peak damage process.It can also measure the impact tendency of coal seam.The index system composed of maximal damage rate,modified dynamic damage strain and surplus energy index change rate can be regarded as a new method to evaluate the impact tendency of coal seam.