X射线岩石CT的历史与现状

采用X射线CT技术无损探测岩石内部结构和裂纹演化过程 ,起源于 2 0世纪 80年代后期 ,由最初对CT图像的认识逐步深化为对岩石裂纹演化规律的分析和应用研究。基于室内岩石试件扫描断面的CT图像 ,目前在岩石变形破坏过程的实时监测、加荷条件多样化、裂纹演化规律性、裂纹宽度的定量测量、岩石裂纹三维图像重建、损伤演化与损伤变量分析、CT成果应用研究等方面取得了一系列进展。岩石CT面临的主要问题是如何获得各种试验条件下精确的CT图像及其成果的应用研究。岩石CT的生命力在于自身理论、技术发展和在相关领域的应用程度

HISTORY AND PRESENT SITUATION OF X-RAY COMPUTERIZED TOMOGRAPHY (CT) OF ROCKS

Since the late 1980's, X ray Computerized Tomography (CT) technique has become the main approach to detect the internal structure of rocks and the evolution of cracks within the rocks, owing to its high resolution, high scanning velocity and nondestructive measurement ability. The apparatus of X ray CT of rocks is composed of two parts: CT equipment and loading system. The implication of X ray CT of rocks is to get the information of the evolution of internal structures of rocks through the CT images of the rocks under various experimental conditions. The basic method of CT of rocks is to compare the CT images of the same scanned section of the rock under different stress level. Although it has only a ten years history, the CT of rock has made significant progress. In its initial stage, the CT technique was used for detecting the internal structures of rocks, and now it has been used to observe the evolution law of cracks and its application. The capacity of CT lies on the function of CT apparatus and loading system, as well as the processing capacity of the CT images. The CT of rocks is based on the analysis of the CT images of the cross section of rock sample under different conditions. At present, it can be used for real time scanning under uniaxial loading, triaxial loading, unloading and cyclic loading conditions. It discovers that the crack nucleates near the surface of rock sample, and then propagates toward the inner part of the sample. The evolution of the crack is step by step, i.e. the widening and propagation of the crack occur alternatively. The deformation and failure of rocks are intrinsically the evolution of crack. The width of the crack can be determined quantitatively in two ways: actual measurement and theoretical calculation. There are two methods for reconstruction of the 3 dimensional image of crack in rock: the stereo display of 3 dimensional sampling and the spatial connection of crack at CT image scale. By regarding the deformation process of rock as the damage process of material, the analysis of damage evolution and damage variables can be carried out on the basis of CT number. The applicability of CT results depends on the similarity of the prototype of the rockmass and the experimental condition. The main problem faced by CT technique is how to get precise CT images under various experimental conditions as well as the application of its results. The progress of CT technique for rock testing depends on its theory and technology, and on its applicability to the relevant fields.