不同节理夹角煤单轴压缩力学和声发射响应及影响机制

Response characteristics and influence mechanism of uniaxial compression mechanics and AE of coal with different joint angles

煤岩的力学特性和声发射响应规律对冲击地压监测预警至关重要,为研究加载方向与节理面夹角(α)对煤样力学特性、裂纹扩展方式及声发射响应的影响,对不同加载方向与节理面夹角的煤样进行单轴压缩试验,并分析了力学和声发射信号响应规律。结果表明:加载方向与节理面夹角对煤样力学特性和声发射响应规律有显著影响。随α增大,峰值载荷和破坏时间均呈先微降后增大的趋势,峰后破坏时间从0°到30°出现陡降趋势。α≤45°煤样的应力-应变在峰值或峰值后出现震荡起伏现象,单轴抗压强度和应变量均小于α>45°的煤样。α>45°煤样的应力-应变曲线在峰值或峰值后无震荡起伏现象;α≤45°的煤样受力以平行节理面应力分量为主,更容易产生沿节理面的滑移破坏,振铃累计值陡增和大能量声发射信号主要集中在峰后阶段,声发射信号与应力降具有很高的相关性。α>45°的煤样受力以垂直节理面应力分量为主,更容易产生挤压摩擦破坏,在应力稳定上升阶段就伴随着大量的声发射信号,大能量声发射信号主要集中在峰前阶段;随α增大,煤样表现出的冲击倾向性越强,声发射信号以45°为界表现出不同的峰前峰后特征。因此,鉴定煤冲击倾向性和利用声发射进行冲击地压监测预警时,需充分考虑煤层节理面与现场受力情况。

The mechanical properties of coal and rock and the AE response law are very important for the moni-toring and early warning of rock burst.In order to study the influence of the angle(α)between the loading direction and the joint surface on the mechanical properties,crack propagation mode and acoustic emission(AE)response of coal samples,some uniaxial compression tests were carried out on coal samples with differentα,and the characteristic response laws of mechanical and AE signals were analyzed.The results show that the angle between the loading direction and the joint surface has a significant effect on the mechanical properties and AE signals.With the increase ofα,the peak load and failure time both show a trend of decreasing first and then increasing,from 0°to 30°,the failure time after the peak tends to drop sharply.The stress-strain curve of coal samples withα≤45°fluctuates after the peak value or at peak value,and the uniaxial compressive strength and strain are less than that of coal samples withα>45°.The stress-strain curve of coal sample withα>45°does not fluctuate after the peak value or at peak value.The coal samples withα≤45°is mainly the stress component of the parallel joint surface,and it is more likely to slip along the joint surface.The accumulated sharp increase of AE pulse and the high-energy AE signal are mainly concentrated in the post-peak stage,and the AE signal has a high correlation with the stress drop.For the samples withα>45°,the stress component of the vertical joint surface is the main stress component,and the main failure mode is extrusion friction.The accumulated value of pulse increases steadily before the peak point,and the high-energy AE signals are mainly concentrated in the pre-peak phase.Withαincreasing,the stronger the impact tendency of coal samples is,and the size of AE early warning parameters is different.Therefore,when identifying the coal impact tendency and using AE to monitor and warn the impact,it is necessary to take full account of the coal seam joint surface and the field stress.