Mechanical and acoustic emission characteristics of rock: Effect of loading and unloading confining pressure at the postpeak stage

Liang, Yunpei; Li, Qingmiao; Gu, Yilei; Zou, Quanle

doi:10.1016/j.jngse.2017.04.012

Cited by 73 publications

(30 citation statements)

References 30 publications

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“…By analyzing the AE characteristics of rock fractures, it is helpful to understand the rock fracturing mechanism and provide a theoretical and technical basis for field HF monitoring [14]. Numerous studies have reported laboratory-scale rock fracture analysis using AE monitoring, including the rupture process of brittle rock [15,16], the mechanical and acoustic properties of shale rocks [17,18], the characteristics of fracture propagation with bedding planes at different directions [19], and the focal mechanism of AEs during laboratory-scale HF experiments [20,21].…”

Section: Introductionmentioning

confidence: 99%

Multifractal Analysis of Acoustic Emissions during Hydraulic Fracturing Experiments under Uniaxial Loading Conditions: A Niutitang Shale Example

Tan

Xie

et al. 2020

Geofluids

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Fracture characterization is essential for estimating the stimulated reservoir volume and guiding subsequent hydraulic fracturing stimulations in shale reservoirs. Laboratory fracturing experiments can help provide theoretical and technical guidance for field operations. In this study, hydraulic fracturing experiments on the shale samples from Niutitang Formation in Hunan Province (China) under a uniaxial loading condition are conducted. The multifractal method is used to analyze the acoustic emission (AE) signals and characterize fracture initiation and propagation. The hydraulic fracturing process can be divided into three stages based on the characteristics of AE signals: the initial stage, the quite stage, and the fracturing stage. The multifractal analysis results showed that: (1) the value of the spectrum width, Δα, continues to increase as the energy accumulates until the fracturing stage starts; and (2) the difference in the multifractal spectrum values, Δf, reflects the relationship between small and large signal frequencies and can quantify the fracture scale, i.e., the lower the Δf, the larger the fracture scale and vice versa. The results were further verified using a time-frequency analysis of the AE signals and micro-CT scanning of the samples. This study demonstrates that the multifractal method is feasible for quantitatively characterizing hydraulic fractures and can aid field hydraulic fracturing operations.

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Section: Introductionmentioning

confidence: 99%

Multifractal Analysis of Acoustic Emissions during Hydraulic Fracturing Experiments under Uniaxial Loading Conditions: A Niutitang Shale Example

Tan

Xie

et al. 2020

Geofluids

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“…As a typical failure phenomenon, unloading failure of rock mass often occurs during a long-term stage due to the variation of in-situ stress field [1] or in a fast way in the rock excavation of bank slopes, dam foundation or tunnels. In this failure process, lots of ruptured rock mass appear due to the unloading effect [2][3][4][5][6], which means various scales of cracks initiate, propagate and coalesce, from nano-level or micro-level to macro-level. In Three Gorges Reservoir Area of China, many rock-based engineering structures have to face the cyclic wet-dry conditions due to yearly rise and fall of reservoir water level between 145 and 175 m [7].…”

Section: Introductionmentioning

confidence: 99%

Effect of wet-dry cycles on disintegration characteristics of clay-bearing sandstone with UF cracks

Wang¹,

Qiao²,

Li³

2020

Period. Polytech. Civil Eng.

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UF cracks in rock masses commonly occur due to the unloading effect, which constantly happens after the variation of in-situ stress field or rock excavation. When undergoing periodic water fluctuation, rock mass with UF cracks is vulnerable to deterioration or even disintegration, especially for clay-bearing sandstone. To study the effect of changes in moisture on rock samples with UF cracks, clay-bearing sandstone from the Triassic Badong group in the Three Gorges Reservoir Area were chosen and investigated. The rock samples with UF cracks are obtained by conducting triaxial unloading confining pressure experiment. The effect of wet-dry cycles on the morphology properties and microstructure of the UF surface was investigated. The characteristics of particle-size uniformity from the sieve test were obtained by the calculation of RMS of particle contents. The test results show that UF cracks widen significantly and the disintegrated mass increases rapidly in the first three wet-dry cycles, while the fractal dimension of UF surface decreases sharply, but afterwards the disintegrated mass changes gently and the UF surface tends to be flat and smooth. Then, the RMS calculation of particle contents quantitatively evaluate the clay-bearing sandstone’s disintegration properties, which indicate the particle uniformity plays a key role on its disintegration mechanism. During wet-dry cycles, the tested samples tend to disintegrate more rapidly and entirely with the decrease of particle uniformity.

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“…Compared with EMR technology, AE technology avoids the influence of charged equipment on experimental results. Besides, contact testing can better reflect the initial damage and damage evolution process of materials [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Application of Acoustic Emission Technique to the Evaluation of Coal Seam Hydraulic Flushing Effect

et al. 2019

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Hydraulic flushing has the advantages of reducing coal stress and improving coal seam permeability, so it is widely used in high gas outburst coal seams in China. However, the effect evaluation of stress relief and permeability enhancement will be necessary before coal mining. In this paper, an acoustic emission (AE) experiment system of coal seam hydraulic flushing was established, and the AE characteristics of coal during hydraulic flushing were studied. The results show that the changes in AE signals are basically consistent with those in load and water pressure. In addition, the quantitative relationship between the signals and the damage of coal around the borehole is revealed by the theory of damage mechanics. The in-situ AE test of hydraulic flushing was performed in the Liangbei Coal Mine, by measuring gas flow and coal stress simultaneously. The variation of AE activities and the effect evaluation of hydraulic flushing were analyzed. The results reveal that the changes in coal seam stress are basically consistent with those of AE signals. After the flushing has been completed for 1–3 h, the coal seam stress decreases rapidly, and the AE counts and intensity reach the peak. Therefore, this study proposes a new method for evaluating the effect of coal seam hydraulic flushing by AE, which has a very important practical significance.

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Mechanical and acoustic emission characteristics of rock: Effect of loading and unloading confining pressure at the postpeak stage

Cited by 73 publications

References 30 publications

Multifractal Analysis of Acoustic Emissions during Hydraulic Fracturing Experiments under Uniaxial Loading Conditions: A Niutitang Shale Example

Multifractal Analysis of Acoustic Emissions during Hydraulic Fracturing Experiments under Uniaxial Loading Conditions: A Niutitang Shale Example

Effect of wet-dry cycles on disintegration characteristics of clay-bearing sandstone with UF cracks

Application of Acoustic Emission Technique to the Evaluation of Coal Seam Hydraulic Flushing Effect

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