Smart Surrogate Munitions for Nearshore Unexploded Ordnance Mobility/Burial Studies

Abstract

Unexploded ordnance (UXO, also referred to as munitions) are located in nearshore and other underwater environments as a result of military activities. UXO have been found in the surf zone and on populated beaches. This paper describes the development and evaluation of instrumented UXO surrogates for observing munitions migration and burial. Surrogates were designed and fabricated to match mass properties for a variety of common munitions (81-mm Mortar, BLU-61 Cluster Bomb, M151-70 Hydra Rocket, M107 155-mm). Surrogates housed suites of self-logging sensors. Sensor suites that could record up to 7–12 h included various combinations of inertial motion units (IMUs), pressure transducers, shock recorders, and photocells. Instrumented surrogates were then exposed to prototype scale wave conditions over a mobile bed at the Littoral Warfare Environment at the Aberdeen Test Center, Aberdeen, MD, USA. Surrogates were deployed in the swash and breaker zones. IMUs and shock recorders provided congruent acceleration measurements of swash impact. IMUs accurately resolved heading and orientation during periods of low-frequency motion. Photocells resolved surrogate roll consistent with IMU as well as surrogate burial. However, in the breaker zone, the large presence of suspended sediment and surface foam make photocell data more difficult to interpret. Surrogate mobility and forcing conditions measurements can provide data to improve modeling of munitions burial and migration in the nearshore environment.