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随着煤矿的深部开采,多层积水采空区探测成为煤田水文物探工作的新内容,中心回线瞬变电磁(简称TEM)法因场结构与地层的耦合关系,对低阻层探测有利。但低阻层的屏蔽作用不仅使得探测同样的深度需要更长的观测时间,而且还会减弱下伏地层的异常响应。本文通过直接时域数值模拟和水平分层大地的模型正演,估算了探测目的层所需要的时间长度,根据噪声对观测数据造成的影响,给出了多层积水采空区可分辨的标准。山西大同达子沟煤矿水文勘探中获得的TEM实测曲线,表现了对多层积水采空区的探测能力。在实测曲线的定量反演解释中,利用电测井资料作为初始参数进行定量反演,约束了煤系薄层的等值性。所推断的三层和两层积水采空区,为钻孔所证实。研究结果表明,当观测时间有足够的长度、下伏地层的异常显示大于观测误差,中心回线TEM法探测多层采空区积水是可行性的。
With the deep mining in coal mines, the detection of multi-layer water gob turns into a new content in the hydrological geophysical exploration in coalfields. The coupling of the field loop structure and stratigraphy to the center loop transient electromagnetic (TEM) method is beneficial to the exploration of low resistivity layers . However, the shielding effect of the low resistivity layer not only makes it possible to detect the same depth for longer observation time but also weakened the abnormal response of the underlying formation. In this paper, the time length of the target layer is estimated by direct numerical simulation of time domain and forward modeling of the horizontal stratified earth. According to the influence of noise on the observed data, standard. The TEM observation curve obtained from the hydrological exploration of Datongdaizigou coal mine in Shanxi shows the capability of detecting multi-layer gob water area. In the quantitative inversion interpretation of the measured curve, the quantitative inversion of electrical logging data is used as the initial parameter, which constrains the equivalence of coal-based thin layers. The inferred three-storey and two-storey water gobs were confirmed by drilling. The results show that when the observation time is long enough and the anomalies of the underlying strata are larger than the observed errors, it is feasible to use the central loop TEM method to detect the water accumulation in the multi-layer goaf.