| 基于团簇的岩石动态CT图像可视化与结构变形分析 |
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| 引用本文： | 黄宛莹,吴江涛,刘洁.基于团簇的岩石动态CT图像可视化与结构变形分析[J].CT理论与应用研究,2020,29(4):424-434. |
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| 作者姓名： | 黄宛莹 吴江涛 刘洁 |
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| 作者单位： | 1. 中山大学地球科学与工程学院, 广州 510275; |
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| 基金项目： | 广东省基础与应用基础研究基金（2019A1515010685） |
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| 摘 要： | 岩石的变形机制是研究岩石圈变形和局部构造活动的重要基础，岩石的微观结构是研究其变形机制的关键。微观层析成像（微观CT）技术可以无损地获取样品内部高精度三维数字化图像，为观测岩石内部结构提供了技术保证。新近发展起来的动态CT技术，使得观测岩石变形过程成为可能。本文利用一组莱塔石灰岩受差应力变形的三维动态CT图像数据，通过图像切割、图像分割等处理步骤，以团簇为基本表征单位，表征不同形状、大小孔隙的动态变化过程，分析对比全部孔隙、大团簇、小团簇和裂隙型小团簇的动态图像。结果表明:随着岩石的压缩变形，其大孔隙在不断地缩小；在变形的初始阶段，靠近施压活塞的样品上部出现了密集的新生小孔隙；当岩石所受差应力到达73 MPa时，其下半部出现了明显的剪切带，具体表现为大量的新生裂隙生成并且新生裂隙集中带与轴向成约45°交角。此前的研究观测到该样品中下部若干压缩带形成的过程；本文通过基于团簇的可视化技术，观测到了高孔隙度岩石变形过程中压缩带和剪切带共同形成的过程。同时，新生的沿剪切带分布的微小裂隙并没有显示与剪切带相同的方向，而是具有各方向均匀分布的特征。该特征可能与岩石内部复杂的局部孔隙结构有关，是值得进一步探讨的问题。
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| 关 键 词： | 动态CT 变形 可视化 灰岩 团簇 |
| 收稿时间： | 2020-04-17 |
Visualization of Pore-Structural Deformation of Dynamic CT Images of a Leitha Limestone |
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| Affiliation: | 1. School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China;2. Southern Laboratory of Ocean Science and Engineering, Zhuhai 519082, China |
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| Abstract: | The deforming mechanism of rocks is an important basis for studying the lithosphere deformation and local tectonic activity, while microstructure of rocks is the key to study its deforming mechanism. Microtomography(Micro-CT), which can obtain high-resolution three-dimensional(3D) digital images nondestructively, make it possible to observe the internal structure of rocks. The dynamic CT technique by using HADES device further enables the observation of the deformation process of rocks. In this paper, a set of 3D dynamic CT images of a Leitha limestone experienced triaxial test have been processed to characterize the evolution of pores by using the concept of cluster of percolation theory. The processing and analysis include:image cropping and masking, image segmentation, quantitative analysis and visualization. The visualization of pores has been carried out by presenting:all pores, the largest cluster, small clusters, and fracture-like small clusters. The results show that:(1) the largest percolating pore is continuously reducing while the sample is compressed;(2) new pores or cracks appear in the upper part of the sample in the early steps of the compression;(3) a shear zone emerges in the lower part of the sample after axial strain over 3.5% and it is represented by a large number of small fractures and/or pores in a zone of a dip angle around 45°. This implies that the deformation of the highly porous rock not only exhibits the formation of compaction bands as observed previously, but also shear deformation. The interesting aspect is that the orientations of small fractures distributed along the shear zone do not accompany the orientation of the shear zone, showing there is no predominant direction. This study reveals the concurrency of compaction band and shear zone by the visualization of catalogued clusters. The reason that the orientations of newly created small fractures along the shear zone do not show the same as that of the shear zone may be caused by the complexity of local microstructures of pores. This is worthwhile to be studied further in future. |
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