煤岩破裂过程电荷信号时-频域特性及降噪研究

为了拓展电荷信号综合分析手段,进一步提高电荷感应方法的煤岩体冲击地压预测准确性,将室内物理试验和理论分析相结合开展煤岩受载破坏电荷信号监测试验,基于煤岩破裂电荷信号产生机制和傅里叶变换方法获得了不同受载阶段电荷信号时-频域特征及其变化规律,并设计数字滤波器进行电荷信号降噪处理。研究结果表明:电荷时-频域信号幅值与煤岩受载变化具有良好的一致性;非接触式感应电荷信号监测装置工频白噪信号组成频率较固定,白噪时-频域信号幅值随采样频率升高明显提高;煤岩受载过程中时域信号特点为弹性后期小幅值振发型,强化损伤阶段高幅值振发型,峰后破坏阶段高幅值连续型;频域变换得出电荷信号为主频率范围1~100 Hz的甚低频率信号,且该范围内的频域信号幅值随时域信号幅值升高而显著增加,此试验结果是区别电荷信号与高频率电磁辐射信号的主要标志,基于研究结果设计了数字低通滤波器,较好的剔除了工频白噪信号同时又不失真的保留了有益信号;基于电荷信号的时-频域特性可将工频干扰信号与有益信号区分有效提高信号监测准确性,达到预测预警冲击地压发生的目的。

Investigation on charge signal time-frequency domain characteristics in coal failure process and noise reduction

In order to expend the means of charge induction comprehensive analysis,improve the accuracy of rock burst forecast based on charge induction method,combining the physical test and the theoretical analysis,a test of charge monitoring in coal failure process was carried out,the characteristic and law of charge time-frequency domain signal in coal different failure processes were investigated based on the charge induction mechanism and Fourier transform method,and noise reduction was carried out by a digital filter designed.The results show that there was a good consistency between the amplitude of charge time-frequency domain signal and the loading variations.It was fixed that the main frequency spectrum information of white noise,which produced by the non-contact type inductive charge signal monitoring device,the amplitude of white noise time-frequency domain increased with sampling frequency improved.There had different signal characteristics at different loading stages,the late of elastic stage was minor amplitude intermittency type,nonlinear stage was major amplitude intermittency type,post-peak phase was major amplitude continuous type.The charge signal was a kind of very low frequency dispersed signal that main vibration frequency in the 1-100 Hz range and its frequency amplitude obviously increased with loading,this feature could be used as a major indicator of distinguishing between charge signal and electromagnetic radiation,the white noise was removed and the useful signal reserved with no distortion used the digital filter designed.The time-frequency domain characteristics of charge signal could distinguish between beneficial signals and interference signals,that could improve monitoring accuracy effectively,achieve the purpose of forecast and early warning rock burst.