Preliminary Analysis using Surface Wave Methods to Detect Shallow Manmade Tunnels

Abstract

Multi-channel Rayleigh wave data were acquired across a 1m diameter spillway tunnel along three parallel traverses with surface to tunnel separations of 0.90 m, 2.15 m, and 3.13 m, respectively. The data were acquired by placing a 24-channel array across the tunnel (perpendicular to the center-line of the spillway tunnel) and walking the sledge hammer source through the array starting with a far-offset of 10 m. The 4.5 Hz geophone array spacing was at 0.5 m intervals. Single shot data were analyzed to visually locate and to highlight attenuation effects associated with the tunnel. The field records were then velocity filtered in order to enhance back-scattered Rayleigh wave energy thereby allowing for visual identification of the tunnel location. The same single shot data were analyzed using the Attenuation Analysis of Rayleigh Waves (AARW) method. The intent was to demonstrate the utility of these approaches to tunnel delineation at a site where the geometry of the target and the nature of the encompassing soil was known. Electrical resistivity data was also acquired along the traverses for comparison purposes.

Meeting Name

21st Symposium on the Application of Geophysics to Engineering and Environmental Problems (2008: Apr. 6-10, Philadelphia, PA)

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Attenuation Effect; Back-scattered; Electrical Resistivity; Field Record; Geophone Array; Multi-channel; Preliminary Analysis; Single Shots; Sledge Hammers; Spillway Tunnels; Visual Identification; Electric Conductivity; Geophysics; Rayleigh Waves; Spillways; Surface Waves; Wave Energy Conversion; Data Visualization

International Standard Book Number (ISBN)

978-1605603001

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2008 Environmental and Engineering Geophysical Society (EEGS), All rights reserved.

Publication Date

01 Apr 2008

Link to Full Text

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