Movement of submerged unexploded ordnance due to ocean waves

The movement of submerged unexploded ordnance (UXO) due to ocean waves is a problem at Formerly Used Defense Sites (FUDS) near coastal areas containing either dumped or placed UXO or where ordnance was test fired into coastal waters. In some cases, UXO has washed up on beaches causing public safety concerns. In other cases, UXO has been dredged and pumped onshore as part of beach nourishment activities. Research was conducted to characterize submerged UXO and unrestrained cylinder movement mechanisms to help understand how submerged UXO/cylinders respond to wave forces and to develop predictive techniques so that areas containing UXO can be cleared to a degree that any remaining UXO are not likely to be mobilized into a previously cleared area.; Laboratory experiments were conducted in a wave flume to measure wave conditions (height, period and kinematics) that caused movement of submerged UXO/cylinders. Laboratory results were analyzed and two empirical theories were developed for predicting movement based on wave conditions and UXO/cylinder characteristics. One theory employed a modified Shields parameter approach, which compared UXO/cylinder parameters with a wave Shields parameter to identify critical regimes for UXO/cylinder movement. The second theory employed a Keulegan-Carpenter number (KC) approach which compares the ratio of maximum orbital velocity at the UXO/cylinder surface and UXO/cylinder diameter with relative water depth. Evaluation of these two approaches with the laboratory data indicated that the best predictive technique appeared to be the modified Shields parameter approach. A field deployment of two drogue cylinders instrumented with acoustic pingers was conducted to further investigate UXO movement using acoustic tracking procedures. Measured wave conditions and cylinder characteristics were used in the modified Shields parameter approach and indicated that the cylinders would be mobile. The field deployment of two cylinders verified the prediction results showing net movements of 15 m and 13 m, respectively.