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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 kind of forecasting method which is more sensitive to water. In order to explore the detection law of transient electromagnetic method for detection of water-poor geological body in tunnels, a large number of transient electromagnetic methods are used to probe the examples and summarizes its application to water gully, , The reaction rules of water-bearing fractures, and the influence of the rear low-resistivity body on the detection. The results show that the apparent resistivity contour decreases obviously in the area where the water channel is located when the water channel exists in front of the channel, and the strip width distribution is related to the pipeline distribution. When there is a water hole in front of the channel, The apparent resistivity contour will bend or even close in the area where the cave is located, and the apparent resistivity value is significantly lower than that in other areas. When the presence of multiple water-bearing fractures (sags) exists in the front of the cave, the apparent resistivity contour will change from A small area of water-fractured area closes and the apparent resistivity decreases. Fake anomaly “low-resistance closed loop” may occur when metal low-resistivity body and a large amount of surface water exist near the back of the face. And put forward two points emphasis on transient electromagnetic method detection and forecasting, one is to detect the environment, the second is the method of interpretation of the combination of geological analysis and results map.