Application of the high-resolution EM method in the investigation of B Tunnel

A successful case history of exploring for concealed structure using the high-resolution EM method in the investigation of the West-East Gas Pipeline Project's B Tunnel is presented in this paper. The high frequency electromagnetic image system named STRATAGEM EH4, operating at frequencies rang...

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Bibliographic Details
Published in:Applied geophysics 2005-09, Vol.2 (3), p.140-144
Main Authors: He, Lanfang, He, Zhanxiang, Wang, Xuben, Zhang, Xizhe, Yang, Lunkai
Format: Article
Language:English
Subjects:
Data acquisition
Electromagnetic fields
Geological engineering
Geological structures
Geophysics
Magnetic fields
Pipelines
Seismology
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Summary:A successful case history of exploring for concealed structure using the high-resolution EM method in the investigation of the West-East Gas Pipeline Project's B Tunnel is presented in this paper. The high frequency electromagnetic image system named STRATAGEM EH4, operating at frequencies ranging from 90 KHz to lHz, was used for data acquisition. The orthogonal components of the electromagnetic field were measured during the field acquisition and the relevant electromagnetic attributes of the object body were extracted from the electromagnetic data. Hybrid sources, consisting of natural and full tensor-controlled sources, were utilized to produce high-quality electromagnetic field data. B Tunnel lies in the western part of Hubei province, at depths of less than 200 m. The geologic setting of B tunnel is very complex. Following an initial geologic investigation, an outcrop considered to be a bedrock interface by investigators, collapsed during tunneling operations. A second investigation applied high-resolution EM and seismic refraction methods to reveal a more complex geologic structure along the tunnel route. The predicted rock classes and fault were encountered during the subsequent tunneling operations.[PUBLICATION ABSTRACT]
ISSN:1672-7975
1993-0658
DOI:10.1007/s11770-005-0016-6