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The Design and Construction of an Acoustic Imaging System for Imaging Underground Facilities | ||
رادار | ||
Article 5, Volume 9, Issue 1 - Serial Number 25, September 2021, Pages 45-55 PDF (2.27 M) | ||
Document Type: Original Article | ||
Authors | ||
Masoud Ardini* 1; Ali Tamimi2; Hamid Reza Khodadadi3; Abbas Bashiri2; Yahya Bayrami2 | ||
1M.Sc., Hossein University, Tehran, Iran | ||
2M.Sc., Imam Hossein University, Tehran, Iran | ||
3Assistant Professor, Imam Hossein University, Tehran, Iran | ||
Receive Date: 07 April 2021, Revise Date: 13 October 2021, Accept Date: 14 December 2021 | ||
Abstract | ||
As underground hidden facilities are used for various applications, imaging systems are required for the detection and recognition of these facilities. In this paper, imaging by mechanical wave propagation in the soil is investigated. Most underground facilities can be considered as air chambers located in the middle of the soil. Air and soil have a large difference in acoustic impedance, so underground facilities can produce a large reflective signal because the amplitude of the reflected signal depends on the difference in impedance of the two materials. Seismic and non-destructive concrete testing systems also use the process of propagation of mechanical waves in the material. Although seismic systems have been successful in the detection issue, they require several meters of space for equipment layout, and transportation complexity is also one of their problems. They are unsuitable for urban space because they are inherently designed to detect water sources at depths of several hundred meters. On the other hand, while the non-destructive concrete testing system equipment have suitable dimensions, they have low penetration depth which is impractical for this purpose. Seismic and non-destructive testing systems of concrete operate in the range of subsonic and ultrasonic waves, respectively. This research project proposes the idea that by choosing an operating frequency between the two mentioned ranges, it is possible to obtain equipment with the appropriate dimensions for imaging underground facilities. In this project we managed to image an underground constructed cylindrical cavity with the diameter of 1 meter and the depth of 4 meters. The accuracy of this method depends on the sound propagation speed in the material. Since there are accurate relationships for the propagation speed of sound in air, the diameter of the cylinder was estimated with an accuracy of about 4%, but with the measurement of propagation speed being infeasible in this project, leading to the ambiguity in the value of propagation speed of sound in soil, the values cited in several reference sites were used, giving the accuracy of 4 to 20%. | ||
Keywords | ||
Acoustic Impedance; Acoustic Imaging; Correlation Function | ||
References | ||
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