Experimental Study on Fracture Patterns and Crack Propagation of Sandstone Based on Acoustic Emission

Abstract

To investigate the fracture pattern and crack propagation of rock under different stresses, Brazilian split tests, preset angle tests, and uniaxial compression acoustic emission (AE) tests were carried out on sandstone to obtain the mechanical parameters and AE signals of the whole test process. Based on the analysis of the distribution of the characteristic AE indicators rise time/amplitude (RA) and average frequency (AF) combined with the core definition of areal density, the test results showed the following. In Brazilian split tests and preset angle tests, shear fractures and tensile fractures accompanied the whole process of rock damage and failure, and the crack type reflected by the RA-AF distribution was consistent with the theoretical analysis and actual failure results. The fracture pattern of sandstone under uniaxial compression was dominated by shear fracture, and tensile and shear cracks had the same evolutionary trend. In uniaxial compression, the development of cracks was complicated from the stage of steady development of microcracks, and the crack development was different in different specimens, which eventually leads to different failure modes. That is, the failure mode of sandstone could provide positive feedback to the RA-AF distribution. Under different stresses, the characteristics of the cumulative event rate of tensile or shear fractures varied significantly among stages, which corresponded to the various stages of rock damage and deformation.

Acoustic Emission Characteristics of Different Bamboo and Wood Materials in Bending Failure Process

“…The sudden increase of counts in the third period indicated that AE was extremely active and the development of cracks was extremely rapid. The rupture precursor recognition characteristics were that the counts keep fluctuating within a medium to high level with an obvious aggregation, but suddenly become gentle when the stress was the highest [27]. In the areas of rupture precursor characteristics in Fig.…”

“…5 reveals the relationship between AE energy, cumulative energy, and stress vs. time. The results showed that the energy and accumulated energy could be divided into three stages with the loading process: gentle period, steady period and steep period [27]. Each period could correspond to the three loading stages in Section 3.1.…”

Research on Splitting-Tensile Properties and Failure Mechanism of Steel-Fiber-Reinforced Concrete Based on DIC and AE Techniques

“…Different types of cracks correspond to different AE waveforms. Tensile cracks are generally considered to have low RA values (rise time/amplitude) and high AF values (ring count/duration), while shear cracks have high RA values and low AF values, and tension-shear cracks have low RA values and low AF values [ 43 , 44 ]. The failure mode of the AE signal in concrete can be analyzed according to Figure 10 .…”

Characterization of Fracture Source Mechanism for Rock Salt Under Quasi-Static Unconfined Compression Test Using Acoustic Emission

“…When RA, that is, the ratio of rise-time to the peak amplitude, is greater than the AF, that is, the average frequency given by the ratio of hit count by event duration, the AE event source is originated by a shear crack, and for the converse, it is a tensile crack [23,40]. Researchers have used the AF-RA crack classification concept for characterizing the AE source mechanism under different loading conditions on different types of rocks, such as sandstone, granite, diorite, and marble, as well as plain and reinforced concrete [5,23,27,30,40,41,42,49].…”