IMPACT OF THE WINTER ENVIRONMENT ON INTRUSION DETECTION SYSTEMS BURIED IN SOIL OR GRAVEL

Buried intrusion detection systems (IDSs) are commonly emplaced in soil or gravel, with perhaps a layer of sand surrounding the IDS. The detection capabilities of ground-motion IDSs, such as optical fiber systems, and ported coaxial cable IDSs depend on the elastic properties and unfrozen moisture content of the burial media, respectively, which in turn depend on the frozen-unfrozen status of the media. Results of controlled intrusions against ported coaxial cable and optical fiber IDSs are presented to show the magnitude of changes in detection capability associated with the freezeup of the burial media. Numerical simulations of heat transfer and freeze—thaw penetration in soil, done for several moisture contents, show that the presence of a sand layer surrounding the sensor cable is beneficial for ported coaxial cable IDSs. Optical fiber IDSs have better and more consistent detection capability year-round when buried in gravel than in soil.