煤矿巷道掘进前方含水体的频率域激电响应特征

Frequency domain induced polarization response characteristics of waterbearing body ahead of coal mine tunneling face

  • 摘要:目的】频率域激电法因能观测地质体的频散率和复电阻率等关键电性参数,有效降低电性异常的多解性,已成为煤矿巷道掘进电法超前探水技术的主要发展方向。然而,目前该方法主要沿巷道轴向观测数据,导致对巷道前方地电信息的捕捉能力不足,存在含水异常体方位判识不清等实际难题。因此,探究巷道频率域激电参数的超前响应特征及其各向异性,对于改进数据观测方式,进一步增强含水体判识精度具有重要的理论与实际意义。【方法】首先,结合矿井巷道实际场景,提出了三方向激电视参数观测方式。其次,以全空间无限大板状导电体作为巷道掘进前方含水体模型,推导了三方向激电视参数响应表达式;最后,通过数值计算和理论分析等方法,研究了三方向激电视参数随模型方位角、倾角及其至场源距离等产状参数的变化特征。【结果】结果表明:(1)巷道轴向视频散率和视复电阻率的曲线类型分别为K(低-高-低)型和H(高-低-高)型,基本不受模型参数变化的影响,电性异常始终表现为“低阻高频散”特征。(2)垂直巷道两帮方向的视频散率曲线类型在模型位于巷道正前方时呈现K型,其他为反比例函数型;视复电阻率曲线类型则在模型偏向巷道左、右两侧时分别呈现K型和H型。(3)垂直巷道顶底板方向的视频散率曲线类型在模型处于直立时呈现K型;其他表现为反比例函数型;视复电阻率曲线类型在模型倾向巷道前方和后方时分别呈现K型和H型。(4)三方向激电视参数的异常幅值及其探测极距显著受到模型参数的影响,尤其是异常极值点或阶跃点对应的探测极距,随模型至场源距离的变化而发生显著变化。【结论】三方向激电视参数对板状含水体模型的响应表现出显著的各向异性,其中巷道轴向的激电视参数对模型产状的敏感性差,是导致目前实际探测电性异常方位判识精度偏低的主要原因;垂直巷道两帮的激电视参数对模型方位敏感;垂直巷道顶底板方向的激电视参数对模型倾向敏感。与现有观测方法相比,三方向观测方法能为探测巷道掘进前方含水体提供更为丰富的电性信息,有助于提升含水体的空间定位精度。

     

    Abstract: Objective The frequency-domain induced polarization (FDIP) method has emerged as a pivotal direction in the advancement of water detection technology for coal mines. This is attributed to its capability to measure critical electrical parameters, such as chargeability and complex resistivity of geological bodies, and to mitigate the ambiguity in interpreting electrical anomalies. However, the current implementation of FDIP primarily focuses on data along the tunnel axis, constraining its capacity to capture geoelectric information beyond the tunnel's immediate path. This limitation leads to practical challenges, including the unclear identification of the orientation of water-bearing anomaly bodies. Methods To address these challenges, we propose a three-directional FDIP parameter observation method tailored to the specific conditions of mine tunnels. We modeled an infinite plate-shaped conductor in a full-space to represent a water-bearing fault ahead of the tunnel excavation and derived the response expressions for the threedirectional FDIP parameters. Subsequently, we analyzed the variation characteristics of these parameters with respect to model azimuth, dip angle, and distance from the source using numerical calculations and theoretical analysis. Results Our findings reveal that: (1) the apparent chargeability and apparent complex resistivity curves along the tunnel axis exhibit K-type (low-high-low) and H-type (high-low-high) patterns, respectively, and are largely invariant to model parameter changes, with electrical anomalies consistently displaying 'low resistivity and high chargeability' characteristics; (2) the apparent chargeability curve perpendicular to the tunnel sides is K-type when the model is directly ahead of the tunnel, and inverse function type otherwise, while the apparent complex resistivity curve is Ktype when the model is offset to the left and H-type when offset to the right; (3) for the direction perpendicular to the tunnel ceiling and floor, the apparent chargeability curve is K-type when the model is upright, and inverse function type otherwise, with the apparent complex resistivity curve being K-type when the model is inclined forward and H-type when inclined backward; (4) the anomaly amplitude and detection ranges of the three-directional FDIP parameters are significantly influenced by model parameters, particularly the detection range at extreme or step points, which varies markedly with the model's distance from the field source. Conclusions The three-directional FDIP parameters demonstrate a pronounced anisotropic response to a plate-shaped water-bearing body model. The sensitivity of FDIP parameters along the tunnel axis to the model's attitude is relatively low, contributing to the current challenges in accurately identifying the orientation of electrical anomalies during exploration. In contrast, FDIP parameters perpendicular to the tunnel sides are sensitive to the model's azimuth, and those perpendicular to the tunnel's roof and floor are sensitive to the model's dip. This three-directional observation method provides richer electrical information for detecting water bodies ahead of tunnel excavation compared to existing methods, thereby enhancing the spatial positioning accuracy of water bodies.

     

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