Assessment of Microgravimetry for UXO Detection and Discrimination
Abstract
A new capability to model the gravity anomaly field on the ground surface of buried spheroidal-shaped objects is developed. The modeling capability is applicable to predicting the gravity anomalies of objects such as buried UXO (prolate spheroid), land mines (oblate spheroid), underground storage tanks (prolate or oblate), landfills, and other localized features which can be approximated with a spheroidal geometry. The gravity anomaly signatures of ordnance items ranging from 105-mm projectiles to 16-in. projectiles and 2,000-lb bombs are modeled. Average lengths, diameters, masses, bulk density and density contrast are computed for 10 ordnance item types. The density contrasts of the ordnance items are assumed relative to a 2.0 g/cm3 soil, and range from 1.5 g/cm3 for large bombs (e.g., 2,000-lb bomb) to 5 g/cm3 for large projectiles (e.g., 16-in. projectile). Gravity anomaly signatures for these ordnance items are examined for maximum value (magnitude) and spatial wavelength to assess detectability. Relative to a nominal detection threshold (5 micronGal), all the items are detectable at the shallowest depth, i.e., buried horizontally at a depth to center equal to half the diameter or just below the surface. Only five items, 1,000-lb bomb and larger, are detectable at depths 0.5 m or greater, and only the 16-in. projectile is detectable at a depth of 1 m. The gravity anomalies of ordnance items will require measurement spacing of 0.25 to 0.75 m. An optimized survey detection (minimum) threshold (2 micronGal) will approximately double the predicted detection depths for the ordnance items but this minimum detection threshold will be difficult to achieve in the presence of geologic background anomalies. Results of a microgravity survey over a buried 155-mm projectile are presented.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 2000
- Accession Number
- ADA387603
Entities
People
- Dwain K. Butler
Organizations
- Engineer Research and Development Center