坑道直流电阻率法超前探测的快速反演

The fast inversion for advanced detection using DC resistivity in tunnel

在坑道电阻率超前探测工作中,视电阻率异常极值位置与异常体位置、厚度、电性以及产状相关.设计有效的反演方法对异常体的各种参数综合反演是非常必要的.首先利用有限元数值模拟技术分析并消除坑道空腔对视电阻率的影响,并将坑道超前探测视电阻率曲线转化为全空间视电阻率曲线.然后采用最小二乘法对超前探测视电阻率曲线进行快速反演.反演结果可准确反映围岩电阻率、异常体的电性、位置和产状;而由于同层等值现象,反演结果只能确定异常体的厚度和电阻率的组合值.

The place of the anomalous extremum of apparent resistivity curve is related to the position, thickness, resistivity and occurrence of geologic bodies ahead of the tunnel. It＇s indispensable to design an effective method to invert for multiple parameters of the geologic body synthetically. Firstly, we make numerical modeling analysis with finite element method and eliminate the effect of tunnel-cavity, translate the apparent resistivity curve of advanced detection in tunnel into the curve in full space. Then inversion of the advanced detection is caried out by least square method. The result shows that the electric property and position and occurrence of anomalous body, the resistivity of bed rock, can be obtained correctly; however only the composite value of resistivity and thickness of anomalous body can be determined because of equivalence.