A Real-Time Visual Investigation on Microscopic Progressive Fatigue Deterioration of Granite Under Cyclic Loading

• Published in: Rock mechanics and rock engineering Vol. 56; no. 7; pp. 5133 - 5147
• Main Authors: Fan, L. F., Qiu, B., Gao, J. W., Du, X. L.
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.07.2023; Springer Nature B.V
• Subjects: Civil Engineering; Compressive strength; Computed tomography; Crack initiation; Cyclic loading; Cyclic loads; Deterioration; Earth and Environmental Science; Earth Sciences; Fatigue tests; Geophysics/Geodesy; Granite; Investigations; Materials fatigue; Microstructure; Original Paper; Porosity; Real time; Three dimensional analysis; Tomography; Two dimensional analysis; Cyclic loading; Microstructure deterioration; Real-time CT technology; Multi-level stress; Crack initiation stress
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-023-03326-y

This paper mainly studied the microscopic progressive fatigue deterioration of granite under cyclic loading. Firstly, a series of real-time computer tomography (CT) tests were conducted to investigate the microstructure morphology of granite under the multi-level cyclic loading. Two-dimensional (2D) analysis and three-dimensional (3D) analysis were carried out by the areal porosity and volumetric porosity to quantitatively study the progressive fatigue behavior of granite planarly and spatially, respectively. Then, the crack initiation stress of granite was determined according to the experimental results, which was used as the maximum cyclic stress of single-level cyclic loading performed subsequently. Finally, the effects of cyclic number of single-level cyclic loading on the microscopic fatigue properties of granite, such as areal porosity and volumetric porosity, were further discussed. The results show that for the granite under the multi-level cyclic loading, both of the areal porosity and volumetric porosity of granite keep constant approximately when the maximum cyclic stress is smaller than 46.04% of the uniaxial compressive strength (UCS), then they increase rapidly as the maximum cyclic stress reaches 46.04% of UCS and above. Moreover, for the granite under the single-level cyclic loading, both of the areal porosity and volumetric porosity increase monotonously as the cyclic number. However, attentions should be paid that the increases of areal porosity and volumetric porosity mainly concentrate during the first twenty cycles. Besides, it is interesting that the present real-time CT technology can be used to investigate the microscopic fatigue deterioration of granite intuitively and continuously. Highlights Multi-level cyclic loading and single-level cyclic loading were conducted. Real-time CT tests were performed on granite during cyclic loading. Real-time microscopic fatigue deterioration of granite was studied. The effects of single-level cyclic loading number on granite were discussed.