酸对云冈石窟砂岩的劣化作用试验研究

云冈石窟所处的山西省大同市是我国重要的产煤区和煤化工基地,空气污染导致窟区内SO₂浓度超标。云冈石窟砂岩主要成分中的长石及钙质胶结物,对酸的作用极其敏感。为模拟硫酸对云冈石窟洞窟岩石的劣化作用,设计了硫酸浸泡劣化试验。通过测量不同pH值硫酸溶液浸泡的砂岩岩样的质量、波速以及溶液的pH值,并对比腐蚀前后岩样的抗压强度、物质结构,来研究硫酸对石窟岩石的破坏机理及其规律。结果表明:酸对此类钙质胶结砂岩的破坏非常迅速,且主要破坏岩石的钙质胶结物;随着反应次数的增加,波速明显降低;酸对岩样表层的作用特别严重;随着胶结物的丧失,岩石强度降低明显。

Acid-Induced Degradation of Sand Rock in Yungang Grottoes

Datong city, where the Yungang Grottoes is located in, is an important coal producing and coal chemical industry base in China. The SO2 concentration in the Grottoes area exceeds the standard because of air pollution. The feldspar and calcareous cement, which are the main mineral compositions of the sandstone in Yungang Grottoes, are very sensitive to acid. A sulfuric acid solution and sand rock reaction test was carried out to simulate the rock degradation. To study the mechanism of Grottoes rock deterioration caused by sulfuric acid, three steps are included in the test: immersing the sandstone samples into static sulfuric acid solution of different pH values; measuring the solution’s pH value, the mass and wave velocity of sandstone samples during the tests; and comparing the changes of samples’ compressive strength and physical structure before and after the test. Test results show that the sulfuric acid poses very quick degradation on calcium cementation sandstones, and it mainly focuses on damaging the calcium cement. As the reaction cycle increases, the wave velocity declined markedly. Degradation by sulfuric acid is extremely serious on the surface layer of sandstone samples. With the loss of calcareous cement, the rock strength reduces significantly.