地质科技通报 (Jul 2022)
Influencing factors of capillary water migration characteristics of the sandstones in Baoding Mountain, Dazu Stone Carvings
Abstract
The Dafo Bay stone carvings in Baoding Mountain, Dazu District, Chongqing City, are suffering from serious capillary water damage, salt damage, biological and other derivative diseases caused by capillary water, which have brought a long-term negative effect on the protection of the world cultural heritage. Based on the field investigation of the Dafo Bay, the strata of the statuary cliff are divided into three sets: the upper sandstone of the reclining Buddha, the sandstone of the reclining Buddha and the lower sandstone of the reclining Buddha. Through a series of tests and experimental studies, the characteristics of sandstone in the Baoding Mountain area and the influence of temperature and humidity on capillary water are analyzed.The testing items include thin section identification, X-ray diffraction, chemical composition test, scanning electron microscopy, mercury injection test, Karsten tube penetration test, etc.The research results indicated that: compared with the upper and lower layers of the reclining Buddha sandstone, the Reclining Buddha body sandstone has the lowest maturity and the largest porosity and pore distribution range, which provides relatively good conditions for the migration of capillary water. The capillary water absorbability and capillary water elevation of the reclining Buddha body sandstone are the best, and the rise of capillary wateris closely related to the ambient temperature, relative humidity, and air circulation. In the tight sandstone of the Dazu Stone Carvings, a large number of interconnected micropores cannot play a role in the migration of capillary water. The effective pore diameter for capillary water migration in the reclining Buddha sandstone should be above 1 133.0 nm, and may reach 760.2 nm in extreme cases.The research results provide reliable data for an accurate understanding of the formation and evolution of capillary water in Dazu Stone Carvings, explain the formation mechanism of salt damage in Dazu Stone Carvings in winter, and provide a theoretical basis for managing capillary water in Dazu Stone Carvings.
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