Study on the salt weathering and mechanism of the Banyueshan Giant Buddha in Ziyang City, Sichuan Province, China

Salt weathering recognized as an important reason for the weathering of cultural relics. To research the salt weathering of the Banyueshan Giant Buddha in Ziyang, Sichuan, China, the sandstones of the Banyueshan Giant Buddha were taken samples. Through field investigation and laboratory test, the weathering damage types and weathering mechanism of sandstones were defined and analyzed. The research showed that the main weathering damage types of sandstones include exfoliation, soiling, chapping, hollowing and encrustation. The lithotype of the sandstones is confirmed to be yellowish-gray medium-fine grained lithic feldspar sandstone by microscopy. Conventional XRD analysis showed that the clay minerals content and calcite increased in weathered sandstone samples compared with core samples. The results all showed that the soluble salts content of weathered sandstone samples is higher than that of core samples by XRF, XRD of sedimentation separation and soluble salt ion detection. The possibility of damage for soluble salts in sandstone is discussed by considering the local climate conditions, the conversion conditions of various soluble salts and the accompanying crystallization pressure. Finally, it is found that the crystallization expansion of soluble salts under temperature change and dry–wet cycles is the internal reason of promoting weathering. The research results have a good referential value for the protection of culture relics in similar geological environments.