TEM apparent longitudinal conductance interpretation in tunnel geological forecast
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摘要: 瞬变电磁隧道超前地质预报最常用到的成果解释图为视电阻率等值线图，但由于视纵向电导相对于视电阻率等值线图具有更好的电性界面识别特征，因此，研究隧道超前地质预报中的瞬变电磁视纵向电导解释方法就显得很有意义。通过建立在全空间条件下的等效导电平面法来计算视纵向电导参数，并且详细阐述了视纵向电导曲线及其一次、二次微分曲线之间的关系。然后，通过建立隧道正演夹层模型和实际应用实例对视纵向电导的解释特点和效果进行较为全面的分析研究，并深入讨论了视电阻率等值线图与视纵向电导二次微分成像联合解释方法。最后，总结和归纳出视纵向电导在瞬变电磁超前地质预报解释中的一些方法特点和规律，以此指导瞬变电磁法在隧道内的超前地质预报工作，不断提高瞬变电磁隧道超前地质预报的精度及准确度Abstract: The most common result interpretation map of transient electromagnetic tunnel geological forecast is the apparent resistivity contour map. However, compared with the apparent resistivity contour map, the apparent longitudinal conductance has better electrical characteristics of the interface identification. Study on transient electromagnetic apparent longitudinal conductance interpretation methods in the tunnel geological forecast is important. The apparent longitudinal conductance parameter is calculated by use of the equivalent conductive plane method based on the whole space theory, and the relationship among the curves of the apparent longitudinal conductance including its first derivative and quadratic differential ones is described. Then, through the establishment of the tunnel forward layered model and the example of the practical application of transient electromagnetic tunnel geological forecast, comprehensive analyses and studies on the interpretation characteristics as well as effect of the apparent longitudinal conductance are made, and the interpretation method which combines the apparent resistivity contour map the longitudinal conductance second differential imaging is discussed. Finally, some characteristics and laws of transient electromagnetic apparent longitudinal conductance in the tunnel geological forecast are summarized . It will guide the tunnel geological prediction of transient electromagnetic methods and continuously improve the accuracy of transient electromagnetic tunnel geological forecast.
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