Cross-scale analysis on the mechanical behavior of the conglomerate of Yulin Grottoes in China

Investigating the mechanical properties of the surrounding rock of the caves is crucial for the preservation of grotto heritage sites. To comprehend the mechanical characteristics of conglomerates in the Dunhuang region of China, various experiments were utilized, including Scanning Electron Microscope, X-ray Diffraction, CT scanning, nanoindentation, and mechanical tests. These methods enabled the exploration of morphological features and mechanical properties of the grotto conglomerate at both micro and mesoscales. Additionally, numerical simulations were employed to conduct a cross-scale study of the micro-meso-macro mechanical properties of conglomerate samples, establishing connections between the uniaxial compression strengths at different scales. The results indicate that conglomerates are highly heterogeneous rock formations with complex compositions, exhibiting noticeable mechanical variability. As the size increases, this variability gradually diminishes. Furthermore, nanoindentation tests revealed that the hardness of conglomerate particles is tens of times higher than that of the cementing material. In the preservation of cave structures, particular attention should be given to maintaining or enhancing the bonding capacity of the cementing material within conglomerates. This study provides a feasible approach for conducting cross-scale analysis on rock samples with complex compositions and poor homogeneity, especially in scenarios involving limited test samples. The findings offer theoretical insights into the preservation of cave cliff structures.