APPLICATION OF EH4 ELECTROMAGNETIC IMAGE SYSTEM IN SURVEY OF DEEPLY-BURIED LONG TUNNELS FOR EXPRESSWAYS

EH4 electromagnetic image system is a set of dual-power electromagnetic auto collecting and processing geophysical exploration system. It is a combination of CSAMT and MT.The paper describes principles,characteristics,procedures and data analysis of EH4 using a case study in survey and investigation of the deeply-buried long tunnel in Expressway in Yunnan.EH4 successfully located soft and weak layer,underground water and broken fractures with assistance of other technical methods,which provides additional information needed for classification of surrounding rocks of the tunnel.This method also provides a new method for survey of deeply-buried long highway tunnels.