顶板离层水地-孔瞬变电磁响应特征及应用

Characteristics and application of groundborehole transient electromagnetic response to coal seam roof separated layer water

开采大深度和巨厚煤层时,由于煤层采掘活动的影响,顶板隔水层破碎,形成高位离层裂隙空间且常聚集大量的地层水,易引起覆岩离层水害,造成淹井事故。为监测研究离层水形成过程,采用数值模拟和现场试验的方法研究了采前、采中和采后离层水的地-孔瞬变电磁响应特征。采前煤层顶板未受采掘活动影响,未产生离层空间,地-孔瞬变电磁特征曲线相对稳定;采中煤层顶板受采动的剧烈影响,产生大体积的离层空间并积水,离层水的地-孔瞬变电磁响应特征明显;采后离层空间逐渐愈合,离层水体积变小,地-孔瞬变电磁响应特征变弱。工作面回采过程和钻孔验证了探测结果,且与实际离层水变化相吻合。

The water-resisting roof layer will be broken due to the influence of mining activities for the extraction of thick coal seam.As a result,the separation fissure space will be formed and a large amount of formation water will be stored in the separation fissure space.Such accumulating formation water could easily cause roadway roof water inrush and mine water disaster.In order to monitor the whole formation procedure of the separated layer water,numerical simulation and field experiments were carried out to study the characteristics of ground-borehole transient electromagnetic response.The results show that the separation layer water is not generated before coal mining and at this stage the ground-borehole transient electromagnetic characteristic curve is relatively stable.In addition,the separation space is generated during the coal mining and the volume reaches the maximum value in the roof.At this moment,the ground-borehole transient electromagnetic characteristic curves exhibit obvious response abnormalities at the depth of the separation layer.With the advance of coal mining,the separation layer gradually closes and both of separation space and water content volume become smaller.In this context,the ground-borehole transient electromagnetic response characteristics at the depth of the separation layer become weaker.The mining process of the working face and boreholes information verify that the detection results are consistent with the actual separation water changes.