Data from: The benefit of a tough skin: bullet holes, weathering and the preservation of heritage

Projectile damage to building stone is a widespread phenomenon. Sites damaged 100 years ago during the First World War still see daily use, while in a more contemporary setting numerous reports show the damage to buildings in Babylon, Mosul and Palmyra. While research has been carried out on the long-term effects of conflict such as fire damage, little is known about the protracted damage sustained through the impact of bullets, shrapnel and other metal projectiles outside of the field of engineering focused on ceramics and metals. To investigate alterations to mineral structure caused by projectile damage, impacts were created in medium-grained, well-compacted, mesoporous sandstone samples using 0.22 calibre lead bullets shot at a distance of 20 m. Half these samples were treated with a surface consolidant (Wacker OH 100), to mimic natural cementation of the rock surface. These samples were then tested for changes to surface hardness and moisture movement during temperature cycles of 15–65°C. Petrographic thin section analysis was carried out to investigate the micro-scale deformation associated with high-speed impact. The results surprisingly show that stress build-up behind pre-existing cementation of the surface, as found in heritage sites that have been exposed to moisture and temperature fluctuations for longer periods of time, can be alleviated with a bullet impact. However, fracture networks and alteration of the mineral matrices still form a weak point within the structure, even at a relatively low impact calibre. This initial study illustrates the need for geomorphologists, geologists, engineers and heritage specialists to work collectively to gain further insights into the long-term impact of higher calibre armed warfare on heritage deterioration.弹体对建筑石材的损伤是一种普遍存在的现象。百年前在第一次世界大战期间受损的遗址至今仍在日常使用；而在当代，诸多报道均提及巴比伦、摩苏尔与帕尔米拉的建筑遭受弹体破坏。尽管已有针对火灾损伤等冲突长期影响的相关研究，但在聚焦陶瓷与金属的工程领域之外，学界对子弹、弹片及其他金属弹体冲击所造成的长期损伤仍知之甚少。为探究弹体损伤引发的矿物结构变化，研究团队使用0.22口径铅弹，在20米距离外对中粒、压实良好的介孔砂岩样品实施冲击以制造损伤样本。其中一半样品采用表面固结剂（Wacker OH 100）进行处理，以模拟岩石表面的自然胶结过程。随后，对这批样品在15℃至65℃的温度循环条件下的表面硬度变化与水分运移特征展开测试。此外，通过岩石薄片分析研究了高速冲击相关的微观尺度变形机制。研究结果出乎意料地发现：长期暴露于温湿度波动中的遗产遗址，其表面原有胶结层后方积聚的应力，可通过弹体冲击得到缓解。不过，即便在较低口径的冲击下，断裂网络的形成与矿物基质的改性仍会成为石材结构的薄弱环节。这项初步研究表明，地貌学家、地质学家、工程师与遗产保护专家亟需开展协同研究，以进一步揭示大口径武装冲突对文化遗产劣化的长期影响。