Protecting Secure Facilities from Underground Intrusion Using Seismic/Acoustic Sensor Arrays [open pdf - 3MB]
"The necessity to detect tunnels that penetrate secure facilities such as detention centers, government offices, borders, or forward operating bases (FOBs) has developed from the need to deter or counter underground exploitation along the southern United States border, Iraq, and other facilities. The United States Army has been in the tunnel detection business for many years, to include providing support to other government agencies in locating tunnels along our southwest border. Iraq became an issue with the nearly successful escape from a tunnel constructed over several months by detainees in an Iraqi center. A team of researchers was sent to Iraq to investigate the utility of several technologies that perhaps could detect voids as small as 1 meter in diameter. A third technology investigated was a passive seismic/acoustic array. The team built a 7-meter-deep tunnel at the same depth as the escape tunnel. The array was tested around the camp to garner the seismic and acoustic characteristics of the typical vehicles and machinery and their interactions with the soil and each other. The in-tunnel tests were conducted using typical digging tools available to the detainees. All of these signals were then used to 'train' the computer algorithms. Plans were laid for a larger study and more detailed sediment and mineral studies. There is a definite requirement to thoroughly understand the interactions between sound propagation and the local geology and geochemistry of the sediments."
Maneuver Support Center of Excellence: http://www.wood.army.mil/wood_cms/
Engineer (May-August 2009)