This project will address the need to predict depth of burial of unexploded ordnance (UXO) in estuary and offshore environments where the water depth is less than 35m. In these scenarios existing methodologies must be modified to more realistically predict impact on the sediment surface, where velocities may be relatively high and interface effects may produce highly non-linear trajectories. To meet this need, this project will deliver a comprehensive penetration model to compute the depth of burial of munitions in saturated soils with water overlays, to be called UnUxOIMPACT (for underwater UXO impact burial analysis). The new model builds on two existing models for water and sediment penetration, both of which resulted from previous SERDP projects (MR19-1073 for water entry and MR19-1277 for sediment penetration). The new UnUXO comprehensive model will realistically and accurately predict depth of burial in estuary and offshore environments and will predict the trajectory of a projectile from non-normal impact and penetration in water, and the subsequent impact and terminal embedment in the sediment. It will enable Underwater Munitions Expert System (UnMES) to carry out stochastic predictions based on distribution functions for ballistic variables, water depth, and sediment properties.
New experimental techniques will be developed and implemented at New York University/Manhattan College to measure projectile motion, including rotation, for penetration of water, soil, and interfaces. This will involve a vertical ballistic range, photon Doppler velocimeter measurements, synthetic refractive index-matched transparent soils, and centrifuge tests. Meanwhile, existing multi-degrees of freedom (DoF) codes developed at Naval Postgraduate School will be built out to include higher velocities and cavitation effects in water and sediments. The multi-DoF model will improve and update methods developed as part of SERDP MR19-1073 for water impact and entry. Sediment penetration predictions will be improved using the GeoPoncelet framework developed as part of SERDP MR19-1277. The parameters of the new comprehensive model, referred to as UnUxO, will be determined using experiments, and will be verified in laboratory tests with water and sediments. UnUxO will then be formulated in terms of geotechnical parameters and implemented in UnMES.
At the conclusion of this project, SERDP will have a means of making site-specific depth of burial predictions for shallow water environments. This capability will be integrated into UnMES where it will improve the predictions of initial impact burial. The model may also be used without UnMES where for estuaries the main problem may be total depth of burial (related to remediation) instead of migration.