煤层顶板致灾水体井上下双磁源瞬变电磁响应及应用

煤层顶板隐蔽致灾水体是矿井水害之一,矿井瞬变电磁法是探测矿井灾害水源的主要方法之一。由于矿井瞬变电磁法采用多匝小回线装置,发射磁距小,其探测深度不能满足大深度矿井对煤层顶板探测的要求。基于此,提出了井上下双磁源对煤层顶板进行立体探测的新方法。利用有限差分数值模拟技术,对井上(地面)激发,井下巷道接收和井上下双磁源激发,井下接收2种装置瞬变电磁响应进行了对比,结果表明:当顶板含有富水体和不含有富水体时,瞬变电磁响应特征均有明显的差异,主要表现为:在感应电位衰减曲线交叉点左侧,顶板存在含水体时曲线幅值相对较小,而在交叉点右侧幅值相对较大,表明该曲线特征与顶板富水性密切相关。分别采用井上下双磁源激发、巷道接收和井下磁源激发、巷道内接收2种工作方式在某矿进行煤层顶板含水体实际探测,探测结果表明:当煤层顶板富水性较强时,井上下双磁源激发、井下接收与井下激发、井下接收的瞬变电磁响应特征与数值模拟结果一致,交叉点左侧井下单磁源激发的视电阻率值明显低于井上下双磁源激发视电阻率值,而在交叉点右侧情况正好相反;当顶板富水性较弱时,2种情况所测的视电阻率曲线趋势基本一致,实际探测结果与钻孔资料吻合良好,对大深度矿井顶板隐蔽致灾水体的探测提供了一种新的有效探测方法。

Transient electromagnetic response of double magnetic source in coal seam roof disaster caused by water and its application

The concealed water body in the coal seam roof is one of mine water disasters and the mine transient electromagnetic method is one of main methods to detect the source of mine disaster water.However,it cannot meet the requirement from the coal mine with great depth due to its small transmitting magnetic moment.Based on above consideration,a new method is proposed to use double magnetic sources,one located in the coal mine roadway and the other one located at the surface,to detect coal seam roof from two directions.Besides,the numerical simulation method is used to simulate the different geo electrical model by using finite difference method and comparison between the result of magnetic source transmitting on the ground surface and receiving information in the roadway and the result of double magnetic sources located on the ground surface and in the coal mine roadway and the receivers located in the roadway.As a result,the modeling results show that there are existing great difference of electromagnetic responses for two different geo electrical models,one with good water abundance and the other one with poor water abundance.The amplitude of induced potential decay curve of geo electrical model with good water abundance is smaller than that with poor water abundance on the left of cross point,inversely,the amplitude of induced potential decay curve of geo electrical model with good water abundance is relatively larger than that with poor water abundance on the right of cross point.Hence,these characters of the curve are related with the water abundance of the coal seam roof.Besides,The authors measure the data of different typical mine hydrogeological structures and the detecting results show that the characters of curves are similar with numerical simulation.Therefore,this study provides a new method for the detection of concealed and damaging water bodies in the coal seam roof for great depth coal mine and it has certain theoretical significance and practical value.