Abstract
The combination of real-time computed tomography (CT) scanning test and loading test can visualize the evolution process of defects such as internal pores and fissures in the coal. The axial deformation of the loaded coal sample will change the layers of the same section in the real-time CT scanning test, which will affect the analysis of fracture progression. To address the concern, we presented a CT image similarity retrieval method. The dynamic development law of fracture networks under triaxial stress was investigated using image processing technologies. The results reveal that the CT images of the coal sample in the same section can be obtained using the proposed CT image similarity retrieval method, which can more accurately characterize the fracture distribution and dynamic evolution law. The coal sample under triaxial stress experienced three fracture evolution stages: the closure in the compaction and elastic stages, the initiation and development in the plastic yield stage, and the rapid expansion and penetration in the postpeak stage. The variation trend of two-dimensional fracture ratio and fracture volume was consistent. The analysis is conducive to clarifying the coal failure mechanism under triaxial stress.
Highlights
The coal contains many holes, fissures, and other defects
X-ray computed tomography (CT) has the advantages of high accuracy, nondestructive testing, and the ability to visualize the interior structure of the sample
(2) After a coal sample was first scanned to obtain the initial distribution of fractures, axial stress was continually applied to the coal sample
Summary
The coal contains many holes, fissures, and other defects. Under engineering disturbance, the instability and failure of the coal body are promoted by the initiation, expansion, interaction, and penetration of defects [1–4]. X-ray CT has the advantages of high accuracy, nondestructive testing, and the ability to visualize the interior structure of the sample As a result, it has become increasingly popular in investigating mechanical properties and seepage characteristics of coal and rock materials in recent years [14–17]. Zhong et al [27], Wang et al [28], and Tan et al [29] carried out a uniaxial compression test and real-time CT scanning tests on the coal and rock They used CT images to analyze the fracture propagation and damage evolution process. Under external loading, the axial deformation of the coal and rock can alter the layers of the same section under different deformation states in the real-time CT scanning test, and there will be errors in analyzing the evolution of the internal mesostructure. The CT images of the coal sample in the same section were obtained based on image retrieval technology and made qualitative and quantitative analyses and more accurately characterize the fracture dynamic evolution law of coal in the loading process
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