Characterisation of acoustic fields generated by UXO removal Phase 5 quarry trials of ECS low-order technology

This report describes the work undertaken in the project Characterisation of acoustic fields generated by UXO removal: Phase 5. The aim was to investigate the effectiveness of low-order shaped charge technology supplied by ECS to reduce the acoustic output from UXO disposal compared to high-order detonation by conducting controlled experimental trials in a flooded quarry test facility (Limehillock Quarry). This work was funded by the UK Government’s Department for Business, Energy and Industrial Strategy (BEIS) through the Offshore Energy Strategic Environmental Assessment programme (OESEA), Sub-Contract OESEA-22-142. A total of 7 explosive tests were successfully conducted. These comprised two high-order tests on two sizes of surrogate munition (2.5 kg and 5.0 kg), two small shaped charges alone (35 g), and three small shaped charges (35 g) used as low-order deflagration charges against the larger surrogate munitions (two of 5.0 kg, one of 2.5 kg). All charges were detonated successfully and the acoustic radiated noise measured. The results show that the use of the low order technique is beneficial due to the significant reduction of acoustic levels. The results demonstrate that the low order charges used can achieve a reduction in peak sound pressure level of between 14 dB and 19 dB and in Sound Exposure Level of between 14 dB and 22 dB compared to high order detonation for charge sizes of 2.5 kg and 5.0 kg. Post-shot observations and weight measurements suggest that only a modest amount of the surrogate munition charge was consumed during the deflagration shots on the larger surrogates.