隧道掌子面前方低阻夹层的瞬变电磁探测研究

 实践表明，隧道掌子面前方含水、充泥等不良地质体对隧道施工构成潜在的危险和障碍，严重影响隧道施工速度。由于瞬变电磁法对低阻体反应灵敏，在进行瞬变电磁隧道超前地质预报时，这些含水、充泥等不良地质体通常又可以近似当成一种低阻夹层来处理，因此，利用瞬变电磁法对掌子面前方低阻夹层的探测研究就显得很有意义。采用建立在全空间理论上的瞬变电磁等效导电平面法，利用遗传算法进行计算，并结合视纵向电导及其微分成像对隧道掌子面前方低阻夹层展开相应的正演模拟及应用研究，重点讨论视纵向电导微分成像的电性界面响应特点及其与视电阻率断面等值线联合解释方法，总结出相应的结论和规律，以此来指导瞬变电磁法在隧道内的超前地质预报工作，不断提高瞬变电磁探测的精度及准确度。

RESEARCH ON DETECTION OF LOW RESISTIVITY INTERBED IN FRONT OF TUNNEL FACE BY MEANS OF TRANSIENT ELECTROMAGNETIC METHOD

Practices show that the unfavorable geological body with water or mud in front of the tunnel face is great dangerous to the tunnel construction. If these unfavorable geologic bodies can not be detected，which will effect the tunnel construction progress；moreover，some engineering accidents and casualties may happen. As the transient electromagnetic method(TEM) is sensitive to the low resistivity body，and the unfavorable geological bodies usually can be equal to a low resistivity interbed，the study of the detection of the low resistivity interbed in front of the tunnel face becomes very meaningful. The TEM-equivalent conductive plane method based on the whole space theory and the apparent longitudinal conductance and its differential coefficient imaging will be used to have a forward modeling and application research on the detection of the low resistivity interbed in front of the tunnel face. Besides，a discussion on the electricity interface response character of the apparent longitudinal conductance is presented with differential coefficient imaging and the interpretation combined with apparent resistivity section contours. At last，some characteristics and laws of the detection are summed up so as to guide the actual TEM tunnel geological forecast and improve TEM detection accuracy and precision.