Petrophysical and mechanical characterization of sandstones from different grottoes in China

Sandstone grottoes, characterized by their magnificent carvings and massive quantity, are of significant value to humanity and constitute an integral part of China's cultural heritage. Their physical and mechanical properties depend on composition, texture, and weathering degree. This study analyzes four sandstone grottoes, i.e., Yungang Grottoes (YG), Tianlongshan Grottoes (TLS), Leshan Giant Buddha (LS), and Dazu Rock Carvings (DZ), using ICP-OES, XRD, SEM, MIP, petrography, and mechanical tests. Results show that mechanical properties are correlated with porosity, pore structure, density, and cementation. Pore structure influence strength, with unimodal pore distributions exhibiting greater strength than multimodal ones. Petrographic analysis confirmed that mechanical properties are primarily controlled by grain contact and cementation. Among quantitative petrographic indices evaluated, GVCM index demonstrated particular reliability in predicting sandstone strength. These findings highlight the importance of petrographic features in assessing sandstone stability, aiding conservation efforts for these heritage sites.