Abstract:

During   tunnel excavation processes,some geological diseases such as  water-filled or mud filled cracks and other geological faults, often occur  in front of the working face, which usually exist in a form of the water interlayer. By means of apparent longitudinal conductance quadratic differential coefficient imaging  based on the equivalent conductive plane method,the response characteristics  and the identify method of the apparent longitudinal conductance quadratic differential coefficient imaging were obtained  through the “H”type geoelectricity model. Then,  the effect of water interbed advance detection  was analyzed by way of apparent longitudinal conductance quadratic differential coefficient imaging. The conclusions can be used to direct the transient electromagnetic method in  tunnel geological forecast and to  improve the accuracy of TEM detection.

Key words: transient electromagnetic; water interbed; apparent longitudinal conductance; advanced detection