堤防管涌声发射采集参数设置研究

为了采集管涌过程具有高信噪比的声发射信号,实现声发射技术在堤防管涌监测预警中的推广运用,开展了变水头作用下的管涌破坏试验。通过相同前放增益设置不同的门槛值,分析环境噪声和电子噪声信号,得到了不同前放增益下的最佳门槛设定值。对管涌破坏过程不同通道的AE信号参数最大幅值和最大峰频值分析,AE通道的前放增益选取40 dB,采样频率1 MHz,门槛值为25 dB。通过波形流的采集方法,采集管涌过程连续的AE信号波形。利用AIC准则对AE信号波形分析,得到了AE定时参数:峰值鉴别时间(PDT)为100μs;撞击鉴别时间(HDT)为900μs。管涌过程中AE信号为突发型信号,时域分布疏密差异。通过对单个撞击间时间间隔的测定,结合采样长度,得到了撞击闭锁时间(HLT)为1 500μs。由对噪声信号和管涌过程AE信号的分析,得到了一套适合堤防管涌过程声发射采集设置参数,研究成果对声发射监测堤防管涌具有重要参考价值。

Study on collection parameters setting of acoustic emission test for dike foundation piping

For collecting a high signal-to-noise ratio AE signals,which can be used in the monitoring and early warning of dike piping,we conduct a piping failure test. By setting different threshold values under the same preamplifier gain and analyzing the environmental noise and the electronic noise signal,the optimal threshold settings under different preamplifier gains are obtained. Analysis of the maximum amplitude and maximum peak frequency of the AE signals in different channels,the preamplifier gain of the AE channel is 40 dB,the sampling frequency is 1 MHz,and the threshold value is 25 dB. The AE signals were collected by the waveform flow method. Using the AIC criterion to analyze the AE signal waveform,the AE timing parameters were obtained: peak discrimination time( PDT) is 100 μs; impact discrimination time( HDT) is 900 μs. The AE signal in the piping process is a burst type signal,and the time domain distribution density difference. Considering the sampling length,the impact lockout time is 1 500 μs by measuring the time interval between individual impacts. Through the analysis of the noise signal and the AE signals of the piping process,a set of setting parameters for the acoustic emission was obtained. The research results have important reference value for acoustic emission monitoring of dikes.