等值反磁通瞬变电磁法在公路隧道塌陷区的探测应用

The application of opposing coils transient electromagnetic method to the detection of underground collapse in highway tunnel under construction

某在建公路隧道开挖中发生塌陷,选用等值反磁通瞬变电磁法(OCTEM)进行抢险探测。文中介绍了OCTEM方法原理,针对公路隧道地电结构建立模型,通过正演计算证明了OCTEM具有对地电阻率反映灵敏、分辨率高的特点;将该公路隧道的OCTEM探测结果与高密度电法探测结果进行对比分析,二者异常对应良好,都反映了已知塌陷区。此次抢险探测结果表明,OCTEM设备轻便,施工便捷,作业效率高,适合浅层快速探测,可用于公路隧道塌陷区快速探测。

Collapse occurs during the excavation of a highway tunnel,and hence it is urgent to use geophysical method to detect other potential collapse areas.In view of the large difference of the terrain,the lush surface vegetation and the low resistivity of the surrounding rock,the authors selected the opposing coils transient electromagnetic method(OCTEM)as the equipment of this method which is relatively light and it has high resolution in reflecting the resistivity.Firstly,OCTEM response of underground collapses buried in conductive host was calculated,and the results theoretically proved that OCTEM was sensitive to underground resistivity and had high resolution,and then the OCTEM detection result was compared with the high-density electrometer detection result.It is proved that they correspond well,and both reflect the known collapse area.It is shown that OCTEM can be applied to rapid detection of collapse area in the highway tunnel under construction.