Quantitative Assessment of Sandstone Weathering Based on Multi-Data Combination of Nondestructive Testing in the Yungang Grottoes, China

The Yungang Grottoes, a representative sandstone UNESCO World Heritage Site in China, hold significant cultural and historical value. However, its long-term preservation is increasingly threatened by ongoing weathering. To scientifically assess the current condition of the sandstone, in-situ nondestructive testing was conducted by combining ultrasonic pulse velocity, Leeb hardness, X-ray fluorescence, and microscopic imaging techniques on two walls of Cave 10. This testing provided spatial distributions of physical and chemical properties of weathered sandstone. A CRITIC-linear weighted approach was applied to determine the weights of each nondestructive indicator and accomplish a comprehensive evaluation of sandstone weathering. The results show that the sandstone’s properties on the west wall of the Front Chamber changed with height, whereas those on the north wall of the Chanting Corridor were distributed quite uniformly. The differences in sulfur and calcium element content between the two tested walls can be attributed to their distinct microenvironmental conditions. The quantitative assessment further indicates more severe weathering on the north wall of the Chanting Corridor. Overall, these findings provide theoretical and practical basis for scientific conservation of sandstone cultural heritage sites.