瞬变电磁法对隧道含水不良地质体的探测规律

Regularity of Transient Electromagnetic Methods for Detecting Hydrous Unfavorable Geological Body in Tunnel

瞬变电磁法是一种对水体较为敏感的预报方法,为探索瞬变电磁法对探测隧道含水不良地质体的探测规律,通过现场大量瞬变电磁法探测实例,总结其对涌水通道、含水溶洞、含水裂隙的反应规律,以及后方低阻体对探测的干扰影响。结果表明,当探测前方存在含水通道时,视电阻率等值线会在其含水通道所在区域明显降低,且呈条带状分布,条带宽度与管道分布有关;当探测前方存在含水溶洞时,视电阻率等值线会在溶洞所在区域发生弯曲甚至闭合,且视电阻率值较其他区域明显降低;当探测前方内存在多处含水裂隙(溶隙)时,视电阻率等值线会在含水裂隙区域发生小范围的闭合,且视电阻率值降低;当掌子面附近后方存在金属低阻体及大量地面积水时,可能出现假异常"低阻闭合环"。并提出在瞬变电磁法探测预报过程中强调重视两点,一是探测环境,二是地质分析与成果图件相结合的解释方法。

Transient Electromagnetic Method is a good method of detecting underground water.For finding detection regularity of unfavorable geological body containing underground water in tunnel,the paper generalizes the transient electromagnetic response regularity of run-off pipe with water,solution cavity containing underground water,fracture with underground water,and response characters of low electric resistance body disturb transient electromagnetic field by field typical cases.The results indicate that apparent resistivity contour plays down obviously with ribbon and contact with pipe distributing,when run-off pipe containing water appears in front of detection workface;apparent resistivity contour can play down obviously and format flexual or closed curve when hydrous cavity appears in front of detection workface;apparent resistivity contour can play down slowly and format smally closed curve when hydrous cracks appear in front of detection workface;apparent resistivity contour chart will display fake abnormal phenomenon that is the closed loop of low electric resistance,when lots of metal support and abundant surface water appear in back of workface.It accentuate two points about transient electromagnetic method detecting,one is environment of detecting,and the other is interpretation method of combine geology with charts.