Locating and Characterizing Unexploded Ordnance Using Time Domain Electromagnetic Induction
BRITISH COLUMBIA UNIV VANCOUVER DEPT OF EARTH AND OCEAN SCIENCES
Pagination or Media Count:
An assumption is made that the Time Domain Electromagnetic TEM response of a buried axisymmetric metallic object can be modeled as the sum of two dipoles centered at the midpoint of the body. The strength of the dipoles depends upon the relative orientation between the object of the source field and also upon the shape and physical properties of the body. Upon termination of the source field, each dipole is assumed to decay as Kappatalphasup -Betaeexp -1gamma. The parameters Kappa, Alpha, Beta, and Gamma depend upon the conductivity, permeability, size, and shape of the object, and these can be extracted from the measurements by using a nonlinear parametric inversion algorithm. Investigations carried out using an analytic solution for a sphere and laboratory measurements of steel and aluminum rectangular prisms suggest the following two-step methodology 1 The value of is first used as a diagnostic to assess whether the metallic object is nonmagnetic or magnetic, 2 the ratios of Kappa 1Kappa 2 and Beta 1Beta 2 are then diagnostic indicators as to whether the geometry is plate-like uninteresting or rod-like a high candidate for being an unexploded ordnance UXO. Results from the application of this algorithm to a TEM field data set acquired at the U.S. Army Engineer Research and Development Center ERDC UXO Test Site have successfully identified a UXO to be magnetic and rod-like.
- Ammunition and Explosives
- Electricity and Magnetism