Abstract
The shift of armed conflicts to more urbanised environments has increased the risk to cultural heritage sites. Small arms impacts are ubiquitous in these circumstances, yet the effects and mechanisms of damage caused are not well known. A sandstone target was shot under controlled conditions to investigate surface and subsurface damage. A 3D model of the damaged block, created by structure from motion photogrammetry, shows that internal fracturing was at least as extensive as the visible surface fractures. Backscatter electron imaging of the damaged surface shows a shift from intragranular fracturing and grain size reduction at <5 mm from the impact point to primarily circumgranular fracturing and grain ‘plucking’ at 20 mm from the impact point. Internal fracture intensity decreased with distance from the centre of the crater. Volumes around the impact point are therefore at greater risk of subsequent weathering deterioration, but significant damage extends to the periphery of the target, rendering whole blocks vulnerable. The surface crater, despite being one of the most conspicuous aspects of conflict damage, has many times less area than internal and surface fractures.
Highlights
This study extends the work of Gilbert et al [7] by characterising the surface morphology of impact damage and quantifying macro-scale fracture networks using 3D models generated by photogrammetry
Surface damage from the impact consists of a shallow, bowl-shaped impact crater which is truncated by material loss along a stepped surface from one corner of the block
Surface fracture traces with macroscopic apertures are present on the remaining stone, with radially oriented traces centred on the crater, and traces sub-parallel to the target face (XY plane) up to 80 mm from the crater centre (Figure 2)
Summary
Ideological extremism is a driver of intentional demolition of cultural property, a tactic infamously employed by Islamic State (IS)/Da’esh. Historic sites such as Palmyra, Mosul, and Nimrud made media headlines after IS propaganda videos were released showing the use of sledgehammers, bulldozers, and explosives to cause damage [2]. Collateral damage may be caused by airstrikes and artillery, such as the severe damage to Sana’a in Yemen by Saudi airstrikes [3] This wide spectrum of damage sources has culminated in the harm to, or loss of, many heritage sites across the Middle East and North Africa region
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