煤样CT扫描重构研究进展:原理、方法及应用

CT scanning and reconstruction of coal samples: principle, method and application

  • 摘要: 煤体内部微观构造直接影响煤的力学性质和渗流性质,是诱发煤与瓦斯突出、水害、自燃等灾害的内在因素,分析煤体微观构造及其与力渗性质的相互影响至关重要。在众多微观分析手段中,CT扫描因其无损性、可视化等特有的优势被广泛运用于煤体内部微观构造的分析与研究。基于此,分析了CT的研究原理、方法和重构过程,论述了CT扫描对煤岩体内部构造与其力学、渗透性能相关成果,在此基础上进一步论述了CT扫描在煤体性能分析的主要应用以及发展方向。CT扫描成像与材料密度相关,密度越大的材料吸收X射线的能力越强,成像越亮。CT扫描根据空间分辨率可以分为高分辨率(dm)、超高分辨率(cm)、显微断层扫描(mm)和纳米断层扫描(nm),但扫描成像分辨率与样品尺寸成反比。在CT扫描重构之前,需要对灰度图片进行降噪、去除伪影和分割等处理来减小重构结果的误差,常见的处理方法有中值滤波法、均值滤波法、截取分析单元体、阈值分割等。在数值重构过程中阈值分割是最常用的方法,结合核磁共振、压汞、XRD等多手段进行阈值确定有助于提高重构精度。CT扫描应用与煤体力学与渗流的研究分析主要分为2类:一种是煤体力学渗流特征的实验室试验分析,包括常规力学试验、动载试验、压裂试验、渗流试验、水岩作用试验、液氮冻融、微波致裂等,主要分析试验过程中的孔隙演化;另一种则是将CT扫描煤体重构的模型导入至数值分析软件中,之后进行相应的加载、致裂、渗流等模拟。最后,讨论和展望了CT扫描在煤体孔隙和矿物表征中仍需要注意的问题,包括煤体CT扫描孔隙和矿物成分阈值的精确确定、煤体CT扫描重构表征单元体的确定和样品尺寸与扫描分辨率的协调与确定。

     

    Abstract: The internal microstructure of coal directly affects the mechanical properties and seepage properties of coal. It is the internal factor that induces coal and gas outburst, water damage, spontaneous combustion and other disasters. It is very important to analyze the microstructure of coal and its interaction with the permeability property. Among many microscopic analysis methods, CT scanning is widely used in the analysis and study of the internal microstructure of coal because of its unique advantages such as nondestructive and visualization. Based on this, this paper analyzes the research principle, method and reconstruction process of CT. The results of CT scanning on the internal structure of coal rock mass and its mechanical and permeability properties are discussed. On this basis, the main application and development direction of CT scanning in coal body property analysis are further discussed. CT scan imaging is related to the density of the material, and the denser the material is, the stronger the X-ray absorption ability, the brighter the image. CT scanning can be divided into high resolution (dm), ultra-high resolution (cm), micro tomography (mm) and nano tomography (nm) according to spatial resolution. However, the resolution of the scanning image is inversely proportional to the sample size. Before CT scan reconstruction, it is necessary to carry out noise reduction, artifact removal and segmentation to reduce the error of reconstruction results. Common processing methods include median filtering, mean filtering, intercepting analysis units, threshold segmentation, etc. Threshold segmentation is the most commonly used method in the process of numerical reconstruction. The threshold determination by means of NMR, mercury injection and XRD is helpful to improve the reconstruction accuracy. The application of CT scanning and the research and analysis of coal mechanics and seepage are mainly divided into two categories: one is the laboratory test analysis of mechanical seepage characteristics of coal, including conventional mechanical experiment, dynamic load experiment, fracturing experiment, seepage experiment, water-rock interaction experiment, liquid nitrogen freeze-thaw, microwave cracking, etc., which mainly analyzes the pore evolution during the experiment; the other is to import the model of coal body reconstruction by CT scan into the numerical analysis software. Then the corresponding simulation of loading, cracking and seepage was carried out. Finally, this paper discusses and looks forward to the problems that still need attention in the characterization of coal pores and minerals by CT scanning. It includes the accurate determination of pore and mineral composition threshold of coal body CT scanning, the determination of the reconstruction characterization unit of coal body CT scanning, and the coordination and determination of sample size and scanning resolution.

     

/

返回文章
返回