基于CT影像的砂岩文物结构特征分析

Analysis on structural features of sandstones relics using digital image technology based on CT images

对于砂岩文物,成分不同、结构不同,表面变化过程和变化结果也不同。以中国三处(石门山、云冈石窟、乐山大佛)砂岩文物为例,联合使用肉眼鉴定与灰度阈值法得到了砂岩文物CT图像中不同矿物成分的实际分布,分析了不同位置切片图像的成分特点与结构特点,研究了砂岩内部结构数字图像特征参数的变化规律,探讨了三处砂岩文物数字图像特征参数的区别及其与岩样外观表现的关系。结果表明,三处砂岩文物样品主要成分均为石英和长石,石英含量大小顺序是石门山砂岩>云冈石窟砂岩>乐山大佛砂岩;乐山大佛砂岩形状变化最小,云冈石窟砂岩次之,石门山砂岩形状最不规则;石门山砂岩纹理最复杂,乐山大佛砂岩最为简单;乐山大佛砂岩表面风化严重、但随深度增加变化不明显,云冈石窟砂岩距表面越深、风化越弱,石门山砂岩风化变化比较复杂。研究结果对石质文物保护具有重要的参考价值。

For sandstone cultural relics,the composition and structure are different,resulting in the changes in the process and result of the relics’surfaces.In this study,taking three sandstone cultural relics(or Shimenshan grotto,Yungang grotto and Leshan buddha)in China as the examples,the actual distributions of different mineral compositions in CT images of sandstone cultural relics were obtained by using the visual identification and gray threshold method.The composition types and textural features of the slice images on various locations were explored.The variations in the digital features of internal structures of the sandstones were then investigated.The relations between the digital features and the appearance of the sandstones were thereafter obtained.The results show that,the main compositions in sandstone cultural relics of the three locations are quartz and feldspar with the great-small order of the quartz contents in Shimenshan grotto>Yungang grotto>Leshan Buddha;the shapes of the sandstone in Leshan buddha change least,followed by those in Yungang grotto and then by Shimenshan grotto;the sandstone textures of the Shimenshan is the most complex,while those in Leshan buddha is the most simple;the sandstone weathering is serious on the surface and not obvious with the depth increase for the Leshan buddha,while the sandstone weathering decreases with the depth increase for Yungang grotto and exhibits a much complexity for Shimenshan grotto.The results may be referable in the protection of sandstone relics.