Experimental evaluation of sandstone under cyclic coupled compression-shear loading: fatigue mechanical response and failure behavior

A novel quantitative explanation for the fracture mechanism of sandstone containing a circular inclusion

“…59,60 The DIC method generally focuses on displacement and strain fields and still cannot directly identify the nature of cracks. 2,[35][36][37][38] In this study, the opening/sliding displacement along a crack is extracted from the DIC results to identify the nature of the crack directly. This method mainly includes four steps, that is, monitoring point selection, monitoring point displacement extraction, local coordinate conversion, and relative displacement calculation, described as follows.…”

“…Fortunately, digital image correlation (DIC) analysis offers the possibility of solving the above problems due to its advantages and effectiveness in displacement and strain measurement 59,60 . The DIC method generally focuses on displacement and strain fields and still cannot directly identify the nature of cracks 2,35–38 . In this study, the opening/sliding displacement along a crack is extracted from the DIC results to identify the nature of the crack directly.…”

“…18,33,34 DIC has some outstanding advantages, such as a simple experimental setup, low requirements for the measurement environment, high measurement sensitivity, and low cost, overcoming some problems associated with traditional experimental instruments (such as strain gauges and linear variation transformers). 20 However, the focus of current research has generally been on the displacement/strain fields 2,[35][36][37][38][39] and maximum principal strain, 40 which still cannot directly identify the nature of cracks. It is necessary to make full use of the measured deformation information, especially in the vicinity of defects, to facilitate effective quantification of deformation localization and fracture mechanisms in the preexisting defect rock.…”

Influence of dynamic disturbed frequency on rock failure characteristics under triaxial cyclic and multistage unloading confining pressure loads

“…The studies can be divided into the constant‐amplitude and variable‐amplitude cyclic loading tests. Investigations that involve constant‐amplitude loading tests show that rock deformation, strength, fatigue lifetime, stiffness, and failure modes are impacted by the stress waveform, 16,17 stress level, 18–20 stress frequency, 12,21,22 and stress amplitude 23–26 . The loading amplitude and dynamic frequency impact a lot to rock fatigue behaviors compared with other factors.…”

“…Investigations that involve constant-amplitude loading tests show that rock deformation, strength, fatigue lifetime, stiffness, and failure modes are impacted by the stress waveform, 16,17 stress level, [18][19][20] stress frequency, 12,21,22 and stress amplitude. [23][24][25][26] The loading amplitude and dynamic frequency impact a lot to rock fatigue behaviors compared with other factors. Generally, the applied sinusoidal and square waveforms generate relatively large damage on rock compared with triangular waveform.…”