浅埋采空区瞬变电磁法响应特征试验研究

Experimental study on response characteristics of transient electromagnetic method in shallow gob

为了查明浅埋深采空区的瞬变电磁法响应特征,在鄂尔多斯矿区选取有代表性的已知浅埋深采空区,进行不同线框尺寸、发射电流、发射频率、增益等参数条件下单支曲线电磁响应特征的分析,并在典型剖面中进行已知采空区与正常煤层视电阻率对比,总结浅埋深采空区的判识标志。研究结果表明:对埋深小于150 m的采空区,选择发射线框不宜大于180 m、发射电流宜大于12 A、频率不宜小于25 Hz、24～26左右增益的参数组合,采集的试验数据信噪比高。将参数优化结果应用到实际探测中,采空区附近测点归一化电位曲线与正常岩层相比有明显差异,采空区附近测点归一化电位衰减更快,表现在视电阻率断面图上,采空区边界误差不超过10 m,可实现浅埋深采空区精细探测。

This paper presented the results of an experimental study on response characteristics of transient electromagnetic method in shallow gob.Representative shallow gobs with known depth in Ordos mining area were chosen to perform the experiments.Single curve analysis of electromagnetic response characteristics was conducted under different wire frame sizes,emission currents,emission frequencies,and gains.The apparent resistivity of the known goaf and the normal coal seam was compared with the typical electromagnetic response profile to develop the identifying criteria for shallow gobs.The experimental results showed that for gob below 150 m depth,under the combinations of these conditions,the collect data had a high signal to noise ratio-emission frame below 180 m,emission current over 12 A,frequency above 25 Hz,and gain around 24~26.Applying the optimized parameters to field detections,the normalized potential curve near the gob was significantly different from that of the normal rock formation,the normalized potential decayed faster near the gob.From the apparent resistivity profile,the detection error of gob boundary was less than 10 m,which proved that the shallow gob could be accurately detected.