Acoustic emission and sorptive deformation induced in coals of various rank by the sorption-desorption of gas

Majewska, Z.; Ziętek, Jerzy

doi:10.2478/s11600-007-0022-6

Cited by 15 publications

(4 citation statements)

References 17 publications

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“…The organic composition and micro–nano pore structures of the coal rock were altered to varying degrees; the stronger the degree of deformation, the more significant the change to the nano structure (Bu et al., 2015; Ju and Li, 2009; Pan et al., 2015). Different degrees of deformation can lead to different characteristics in terms of fracture development, total pore volume, and the gas adsorption capacity of coal and rock, influencing their gas content and permeability (Ju et al., 2009; Majewska and Ziętek, 2007; Pan et al., 2012). The failed coal is referred to as “tectonic” or “soft” coal and is characterized by a high gas content, high desorption rate, low strength, and low permeability (Jiang et al., 2016), all of which create the conditions for coal-gas outbursts to occur.…”

Section: Shear Deformation Of Fold Structures and Coal-gas Outburstsmentioning

confidence: 99%

Shear deformation of fold structures in coal measure strata and coal-gas outbursts: Constraint and mechanism

Jia

Feng

Wei

et al. 2017

Energy Exploration & Exploitation

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The coal measure strata formed in the late Paleozoic era underwent tectonic movements on several occasions, leading to the development of a range of fold structures in the strata as a result of highly interlayered gliding and shearing deformation. In addition, brittle ductile tectonic coals were widely distributed in the reservoir, constituting one of the primary causes of coal-gas outbursts in Chinese mines. This indicates a strong connection between shear deformation and such outbursts. In this study, structural geology, gas geology, and rock mechanics are all taken into consideration to investigate the controlling effects of the fold structure formation process on coal thickness and tectonic coal formation. Numerical simulation, based on the stress test data, was deployed to identify the stress distribution law adjacent to fold structures under the modern stress field. Additionally, the mechanical mechanism underpinning coal-gas outbursts near the fold structure was determined by making a comparison with the distribution law relating to such outbursts. The results demonstrate that the formation and evolution of the fold structure not only form the material basis of outbursts but also control their power source. During the fold formation process, interbed sliding and shearing between strong and weak rock strata were caused by differences in the mechanical properties of the coal bed and rock layer, resulting not only in a change to the local thickness of the coal seam but also in its deformation and structural alteration. Interbed shearing and local stress concentration, caused by the coal gangue, led to coal damage and the development of layered tectonic coal of consistent thickness, simultaneously improving its ability to adsorb gas and providing the material basis for coal-gas outbursts. This reduced the seam's capacity to resist such events. The conditions for these outbursts are created 1 State Key Laboratory Cultivation Base for Gas Geology and Gas Control (Henan Polytechnic University), Jiaozuo, P.R. China 2 Institute of Gas Geology, Henan Polytechnic University, Jiaozuo, P.R. by the sudden desorption of excess gas as a result of formation pressure release during coal mining and the widespread distribution of tectonic coal. Under the modern tectonic stress field, the stress distribution characteristic is controlled by the fold structure shape; and because of the aforementioned differences in the mechanical properties of the coal bed and rock layer, the interlayer deformation is asynchronous. This causes shear stress concentration within a specific range of the anticline's two wings. This concentration zone happens to be exactly aligned with that of coal-gas outbursts, meaning that shear stress concentration is considered to be both the power source for and main cause of the region's outbursts.

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Section: Shear Deformation Of Fold Structures and Coal-gas Outburstsmentioning

confidence: 99%

Shear deformation of fold structures in coal measure strata and coal-gas outbursts: Constraint and mechanism

Jia

Feng

Wei

et al. 2017

Energy Exploration & Exploitation

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“…AE recordings are utilized for forecasting rock bursts and gas and rock outbursts in coal mines [27]. The test stands for acoustic emission measurement [27], and a single-channel device for seismic-acoustic measurements was designed and engineered as a prototype. The main component is a vacuum-pressure chamber, provided with a steel waveguide and six wires for strain measurements.…”

Section: Measurements Of Acoustic Emission and Volumetric Strain Durimentioning

confidence: 99%

“…The test facility has been modified since time of measurements made for coal [27]. At first, the integrating system in the seismic-acoustic instrumentation, which calculated the surface area of impulses over a given level of discrimination, would split the entire measurement range of 3 V into 10 identical channels, 300 mV each.…”

Section: Measurements Of Acoustic Emission and Volumetric Strain Durimentioning

confidence: 99%

Shale Gas in Poland

Jarzyna¹,

Bała²,

Krakowska³

et al. 2017

Advances in Natural Gas Emerging Technologies

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An example of interpretation of the Silurian and Ordovician shale formations in the Baltic Basin in Poland regarding determination of potential sweet spots is presented. Short geological information shows the position of shale gas play. Description of the data-laboratory measurement outcomes (petrophysical and geochemical) and well logging-presents results available for analyses. Detailed elemental analyses and various statistical classifications show the differentiation between sweet spots and adjacent formations. Elastic property modelling based on the known theoretical models and results of comprehensive interpretation of well logs is a good tool to complete information, especially in old wells. Acoustic emission investigations show additional characteristic features of shale gas rock and reveal that acoustic emission and volumetric strain of a shale sample induced by the sorption processes are lower for shale than for coals.

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“…The deformational behavior and failure mechanism of the rock can be inferred through dynamic observations of the AE reflections. AE technology has played an important role in safety monitoring in underground coal mines [3,4].…”

Section: Introductionmentioning

confidence: 99%

Laboratory Study of Deformational Characteristics and Acoustic Emission Properties of Coal with Different Strengths under Uniaxial Compression

Hang

Cao

2021

Minerals

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Acoustic emission (AE) can reflect the dynamic changes in a material’s structure, and it has been widely used in studies regarding coal mechanics, such as those focusing on the influence of loading rate or water content change on the mechanical properties of coal. However, the deformational behavior of coals with various strengths differs due to the variation in microstructure. Hard coal presents brittleness, which is closely related to certain kinds of geological disasters such as coal bursts; soft coal exhibits soft rock properties and large deformation mechanical characteristics. Therefore, conclusions drawn from AE characteristics of a single coal sample have application limitations. This paper studies the deformation patterns and AE characteristics of coals with different strengths. A uniaxial compression experiment was carried out using coal samples with average uniaxial compressive strengths of 30 MPa and 10 MPa; the SAEU2S digital AE system was used to measure the AE counts, dissipation energy, and fracturing point distributions at each deformation stage of the different coals. The results show that the bearing capacity of hard coal is similar to that of the elastic stage and plastic deformation stage, but it may lose its bearing capacity immediately after failure. Soft coal has a relatively distinct stress-softening deformation stage and retains a certain bearing capacity after the peak. The AE counts and dissipation energy of hard coal are significantly higher than those of soft media, with average increases of 49% and 26%, respectively. Via comparative analysis of the distribution and development of internal rupture points within soft coal and hard coal at 15%, 70%, and 80% peak loads, it was observed that hard coal has fewer rupture points in the elastic deformation stage, allowing it to maintain good integrity; however, its rupture points increase rapidly under high stress. Soft coal produces more plastic deformation under low loading conditions, but the development of the fracture is relatively slow in the stress-softening stage. We extracted and summarized the AE characteristics discussed in the literature using one single coal sample, and the results support the conclusions presented in this paper. This study subdivided the deformation process and AE characteristics of soft and hard coals, providing a theoretical guidance and technical support for the application of AE technology in coal with different strengths.

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Acoustic emission and sorptive deformation induced in coals of various rank by the sorption-desorption of gas

Cited by 15 publications

References 17 publications

Shear deformation of fold structures in coal measure strata and coal-gas outbursts: Constraint and mechanism

Shear deformation of fold structures in coal measure strata and coal-gas outbursts: Constraint and mechanism

Shale Gas in Poland

Laboratory Study of Deformational Characteristics and Acoustic Emission Properties of Coal with Different Strengths under Uniaxial Compression

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