A STUDY OF THE AMAGING EFFECTS OF ACOUSTIC SHOCK WAVES FROM A "CONTROLLED" EXPLOSION ON NEARBY BUILDINGS

On 23rd May 2019, an unexploded World War II era bomb was discovered on a building site in Kingston-upon-Thames, approximately just 50 metres away from the back of Kingston University’s Penrhyn Road campus. The bomb was believed to contain around 250kg of high explosive material, resulting in Police evacuating the University campus, and all homes in a radius of 400m of the bomb, temporarily displacing approximately 3000 residents. A bomb disposal team from the Royal Engineers’ Carver Barracks came the site, packing around 350 tonnes of sand around the bomb, before performing a controlled explosion around 4:15pm on 24th May. Local residents described this as a "very loud blast and reverberations were felt", adding "All the birds flew out the trees, followed by loud cheers and celebrations heard afterward!". The blast was heard as far away as New Malden, some 2.5km (2.2 miles) away. This was despite the bomb – a type commonly dropped by Junkers Ju 87 “Stuka” diver bombers – not being one of the heaviest or most powerful conventional bombs used either in World War II or more recently. A spokesperson for the Metropolitan police was quoted as saying “So far, limited damage has been discovered with a 50 metre radius of the detonation.” However, several cars were damaged on the adjacent Fassett Road and in the nearby car park of Kingston University, and quite a number of windows were broken in houses on Fassett Road. After they event, we logged the pattern of damage to houses and University buildings, finding an interesting pattern of damaged and undamaged houses, indicative of blast waves undergoing multiple specular reflections off plane walls on alternate sides of the road. In this paper we make a more detailed analysis of that pattern of damage. The event was unusual, being a substantial but controlled explosion in a residential area and consequentially our findings could be of significant value for predicting likely damage from unplanned explosions in similar residential areas. In this paper, we describe our analysis and propose an explanation of what we observe. There is believed to be much unexploded ordinance (UXO) buried near surface level at many locations around the World, from conflicts as long ago as World War I to very recent ones such as Iraq and Afghanistan, and many of that UXO will be in inhabited or cultivated areas. Additionally, uncontrolled accidental explosions, such as the one in the ammonium nitrate store in Beirut in early August 2020, illustrate what catastrophic damage can result from explosions. Our analysis of what occurred in the situation of a “controlled” explosion could provide useful guidance for predicting and mitigating against the damage from other scenarios.