低围压煤样破裂过程次声波响应特征研究

Infrasonic wave response characteristics of coal samples in fracture process under low confining pressure

为实现次声波监测煤矿井下地质灾害,利用煤岩蠕变-渗流加载、声发射采集、次声波采集系统监测低围压煤样破裂失稳过程,对比分析围压缸内油体耦合的第1路次声波信号与围压缸外与空气耦合的第2路信号,第1路信号在破坏前响应特征明显,与应力-应变曲线、声发射信号一致性较好,弹性阶段前无明显变化,且优于第2路信号,塑性阶段后期信号异常,声压增大。研究结果表明:煤样破坏引起宽频带现象,频率较低信号强度较大,1 Hz处强度最大;可将异常次声波特征作为煤体破坏判定依据之一。

In order to monitor underground geological disasters in mines by using infrasound,creepseepage loading system,acoustic emission acquisition system and infrasound wave acquisition system were used to monitor fracture and destabilization of coal samples under low confining pressure.Then,contrastive analyses were conducted between first channel infrasound signal coupled with oil body in confining pressure cylinder and second channel infrasound signal coupled with air outside the cylinder.The first signal had obvious response characteristics before fracture and conformed fairly well with stress-strain curve and acoustic emission signal with no significant changes before elastic stage.It was superior to the second signal and witnessed abnormal signals at late plastic stage,and its sound pressure gradually increased.The results show that coal sample failure causes wide-band phenomenon,and signal strength is larger as frequency is lower,with maximum strength at 1 Hz.Characteristics of abnormal infrasound waves can be regarded as one of the bases for coal failure determination.