Publications
Investigation into the Gaseous SO2 Attack on Sandstone in the Yungang Grottoes
Research reveals that sulfur dioxide (SO2) significantly accelerates the deterioration of sandstone at the Yungang Grottoes, a UNESCO World Heritage Site with over 1500 years of history. The study found that exposure to SO2 under varying humidity and temperature conditions leads to noticeable changes in the stone's luminosity, hue, weight, and chemical composition, including the formation of gypsum. Higher humidity and cyclic temperature fluctuations exacerbate the dissolution of carbonates and hydrolysis of feldspar, increasing ion concentrations like Ca²⁺ and SO₄²⁻ near the surface. These findings highlight the synergistic impact of environmental factors on sandstone decay, offering insights into preservation strategies for such culturally significant sites.
Determination of Water Vapor Transmission Properties of Sandstones in the Yungang Grottoes
Research reveals that water vapor transmission in the sandstone of Yungang Grottoes significantly increases with rising relative humidity due to capillary condensate flow. The study found a strong correlation between diffusion coefficients and open porosity, indicating that weathering processes alter these parameters, contributing to material deterioration. Using the wet-cup method, scientists measured water vapor transmission under varying environmental conditions, uncovering complex microstructural dynamics that affect diffusion paths. These findings highlight the vulnerability of sandstone heritage sites to moisture-induced damage, offering critical insights for conservation strategies.
Infiltration Assessments on Top of Yungang Grottoes by Time-Lapse Electrical Resistivity Tomography
Infiltrated water does not significantly contribute to the weathering process of the Yungang Grottoes, contrary to previous assumptions. Using time-lapse electrical resistivity tomography over a year, researchers tracked rainfall infiltration in shallow soil layers and found that water primarily moves horizontally into nearby gullies rather than vertically into the rock base due to geological constraints. An artificial infiltration experiment confirmed minimal vertical movement, with 10 m³ of water saturating only the top 1.36 meters of soil. This study challenges the role of infiltrated water in grotto weathering and provides critical insights for conservation efforts.
Nondestructive Testing of Hollowing Deterioration of the Yungang Grottoes Based on THz-TDS
Researchers have developed a reliable, nondestructive method to measure hollowing deterioration in the Yungang Grottoes using terahertz time-domain spectroscopy (THz-TDS). The study established a model correlating hollowing thickness with time differences in THz spectra, achieving an R-squared value of 0.99795, indicating high accuracy. This approach enables both qualitative and quantitative assessment of deterioration without damaging the stone relics, offering significant implications for their preservation and repair. The method's simplicity and effectiveness make it valuable for similar heritage sites.
Acid solution decreases the compressional wave velocity of sandstone from the Yungang Grottoes, Datong, China
Acidic solutions significantly degrade the structural integrity of sandstone from the Yungang Grottoes. Research shows that exposure to sulfuric (H₂SO₄) and nitric (HNO₃) acids at increasing concentrations leads to a marked decrease in compressional wave velocity, reduced compressive strength, and increased effective porosity—indicators of microstructural damage. Unlike water treatment, acid exposure alters the sandstone's chemical composition, complicating its structure post-weathering. The study highlights the potential deterioration risk posed by environmental pollutants like SO₂, NOₓ, and PM₂.₅, which form sulfates and nitrates, threatening the preservation of stone relics in the grottoes.
Spectral Characteristics of Chemically Weathered Sandstones in the Yungang Grottoes, China
Reflectance spectroscopy offers a non-destructive method to monitor chemical weathering in sandstones at cultural heritage sites, including the Yungang Grottoes in China. This study identifies distinct spectral absorptions linked to different weathering stages—fresh, calcite-dissolved, and argillitic-altered—using specific wavelengths (e.g., 490, 675, 900 nm for hematite; 2330 nm for calcite). Calcite dissolution reduces absorption at 2330 nm, while argillic alteration diminishes hematite-related peaks. Shifts in kaolinite-related absorptions (1410, 2205, 2350, 2380 nm) correlate with increasing kaolinite content. These findings demonstrate spectroscopy's potential for long-term weathering monitoring, aiding heritage conservation and environmental policy.
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