锚固条件下矿用锚索中纵向导波传播特性的实验研究

Tests for propagation characteristics of longitudinal guided waves in an anchored mining anchorage cable

实验研究了矿用锚索的锚固段长度对纵向超声导波L(0,1)模态的衰减与群速度的影响。首先,通过简化为细直杆的钢丝中纵向超声导波的频散曲线分析了无锚固矿用锚索中该模态的传播特性。然后采用厚度振动型压电陶瓷片在水泥锚固条件下的矿用锚索中进行穿透法的实验,得出频段20-500 kHz内L(0,1)模态的幅值,确定了该压电陶瓷片对水泥锚固条件下的锚固矿用锚索的最佳导波检测频率为280 kHz。在此基础上,研究了280 kHz附近频率点下L(0,1)模态的幅值与群速度随水泥锚固段长度增加的变化规律。最后,对矿用树脂锚固条件下的矿用锚索进行了穿透法的实验,该实验结果与水泥锚固条件下的锚固矿用锚索的实验结果相符合。这些实验为利用纵向超声导波测量锚固条件下矿用锚索的长度奠定了基础。

The effect of anchored length of a mining anchorage cable on amplitude attenuation and group velocity of ultrasonic longitudinal guided wave mode L（ 0,1） was investigated experimentally. Firstly,the propagation characteristics of ultrasonic longitudinal guided wave in a mining anchorage cable unanchored were analyzed with the dispersion curves of a steel wire simplified as a rod. Then,a piezoelectric element of thickness vibration type was used to perform a throughtransmission test in a mining anchorage cable anchored with cement,and the amplitudes of L（ 0,1） mode were acquired in the frequency range of 20-500 kHz. The piezoelectric element＇s most suitable monitoring frequency for guided wave in the mining anchorage cable anchored with cement was 280 kHz. Based on this result,the amplitude attenuation and group velocity variation characteristics of L（ 0,1） mode at several frequencies near 280 kHz were studied in the mining anchorage cable with increase in anchored length. Finally,the through-transmission tests were performed in a mining anchorage cable anchored with resin,the test results coincided with those obtained in the mining anchorage cable anchored with cement. These tests provided a basis for the length measurement of anchored mining anchorage cables by using ultrasonic longitudinal guided waves.