The Great Wall, as a UNESCO World Heritage site, embodies profound historical value and cultural meaning. Safeguarding the Great Wall is of paramount importance for promoting Chinese cultural heritage and preserving historical continuity (https://whc.unesco.org/en/list/438/, accessed 15 Nov 2025). In Beijing, the Ming Great Wall is widely distributed across six districts—Pinggu, Miyun, Huairou, Yanqing, Changping, and Mentougou—with a total preserved length of approximately 573 km (Fig. 1a) (https://www.chinadiscovery.com/great-wall/facts/how-long-is-the-great-wall-of-china, accessed 15 Nov 2025). The walls are primarily constructed with tamped earth cores faced with bricks, filled with local rubble and compacted soil, and bound with lime mortar as the principal adhesive1,2. Nevertheless, after centuries of natural weathering and anthropogenic influences, concealed structural pathologies—including voids, detachments, and water infiltration—have developed within the masonry, posing a threat to its stability. For instance, during the initial construction phase, shrinkage cracks often formed in the mortar joints as the material dried. Under cyclic freeze-thaw and hydraulic erosion processes, these microcracks propagated, eventually producing internal voids or detachments between bricks and rammed earth.

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