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| Deterioration mechanisms of conglomerate under dry-wet and freeze-thaw cycles: A case study of the Yulin Grottoes |
| ZHANG Huihui1,2, WANG Yanwu2, GUO Qinglin2, WANG Xuezhi2, TANG Chun?an1, TANG Shibin1 |
| (1. School of Civil Engineering, Dalian University of Technology, Dalian, Liaoning 116024, China; 2. Conservation Institute, Dunhuang Academy, Dunhuang, Gansu 736200, China) |
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Abstract The Dunhuang Grottoes represent a significant segment of China?s grotto temples; however, the cliff faces are highly vulnerable to weathering due to the wet-dry and freeze-thaw cycles, posing a serious threat to their long-term preservation. To investigate the deterioration mechanisms of the conglomerate rock in the Dunhuang Grottoes under these conditions, this study conducted laboratory tests simulating wet-dry and freeze-thaw cycles on conglomerate samples, utilizing regional environmental monitoring data as a reference. The findings reveal that: (1) Wet-dry and freeze-thaw cycles significantly reduce the mass, P-wave velocity, and uniaxial compressive strength of the conglomerate samples while markedly increasing their permeability; (2) Water plays a critical role in the deterioration process of the conglomerate, particularly during freeze-thaw cycles involving moisture, where the rate of deterioration accelerates and is positively correlated with water content. Compared to the fresh, dry samples, the uniaxial compressive strength decreased by 13% in the wet-dry cycle group, 12% in the dry freeze-thaw group, 36% in the saturated freeze-thaw group, and 25% in the natural freeze-thaw group; (3) Microscopic analysis indicates that the degradation of the conglomerate under wet-dry and freeze-thaw cycles results from significant changes in microstructure, including surface roughening of micro-mineral particles, structural loosening, weakening of cementation, and the formation of microcracks. These results provide crucial theoretical support for the protection of the Dunhuang Grottoes against weathering.
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2025, Vol. 44 
