ORCID Profile
0000-0003-0239-3015
Current Organisation
China University of Mining and Technology
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Publisher: Elsevier BV
Date: 10-2017
Publisher: Elsevier BV
Date: 02-2020
Publisher: Oxford University Press (OUP)
Date: 11-07-2019
DOI: 10.1093/JGE/GXZ045
Abstract: The differences between mechanical properties and acoustic emission (AE) and electromagnetic radiation (EMR) characteristics of natural coal s les and saturated coal s les were analyzed by performing indirect tensile experiments. The experimental results show that coal s les go through four stages: compaction, elastic deformation, plastic deformation and failure. There is good correspondence between AE and EMR signals and the damage to coal s les. Under the action of water, tension strength of s les is reduced, while the plasticity is enhanced also, the softening coefficient of tensile strength becomes 0.65. The saturated coal s les have a longer plastic stage and a more obvious AE quiet period. The damage to natural coal s les is tension damage, while that of saturated coal s les is due to tension and shear damage, which is more sufficient and irregular. EMR is still remarkable when AE is in a quiet period, and EMR is better for the precursor of rupture. Water weakens the generation and propagation of AE and EMR signals, especially in the earlier stage. AE and EMR damage factor D, defined by AE and EMR counts, has a better description of the damage degree in the indirect tensile process. This study is of great significance for research on the damage mechanism of water-bearing coal, the stability monitoring of water-bearing coals in the actual engineering process and the effect evaluation of hydraulic flushing.
Publisher: Oxford University Press (OUP)
Date: 26-02-2018
Publisher: Elsevier BV
Date: 09-2021
Publisher: World Scientific Pub Co Pte Lt
Date: 04-09-2017
DOI: 10.1142/S0218348X17500451
Abstract: In order to explore the causes of acoustic emission (AE) signals during coal failure, the coal s les with original joints were subjected to uniaxial compression experiments, and the AE signals were monitored by AEwin Test for Express-8.0. Based on the multifractal theory, the multifractal characteristics of AE were analyzed. The results showed that the AE counts and accumulative counts change over time corresponded well with the load-time, which reflected the degree of crack evolution and loading. During the initial loading stage, the cracks expanded gradually along the trace of the original cracks, which could induce a few AE events, while with the increase of load, the cracks enlarged gradually and then joined together to form a macroscopic fracture, which would cause much more AE events within a larger value. Multifractal spectrum [[Formula: see text]] of AE was more concentrated in the right side, illustrating that the frequency of small signals was greater than that of the large signals in AE sequences, which revealed cracks expanding and microfracture events dominated during the loading process. The greater the multifractal spectrum width ([Formula: see text] was, the larger the AE signals differences were, which reflected that AE varied more intensely. The more developed the original cracks, the more obvious the multifractal characteristics. This research revealed the causes and percentage of the AE events within small or large signals, which would help us to recognize crack evolution of coal and generation mechanism of AE.
Publisher: MDPI AG
Date: 14-09-2018
DOI: 10.3390/EN11092449
Abstract: Coal dust is one of the most serious issues in coal mines. The miners at an excavation face have a high potential for exposure to high concentrations of coal dust. The main method for removing coal dust is by ventilation. To better control the coal dust at the excavation face, it is important to understand the coal dust movement patterns and distribution characteristics. This paper used the computational fluid dynamics (CFD) approach to simulate coal dust movement under two different ventilation systems. The Eulerian-Lagrange method was used to study the gas‒solid two-phase fluid behavior. The coal dust concentration distributions under the two ventilation systems are presented and further compared. From the comparison results, it is found that a vortex ventilation system has better coal dust removal performance. This ventilation system is recommended for excavation for better coal dust control and miners’ health protection.
Publisher: Springer Science and Business Media LLC
Date: 22-09-2020
Publisher: Society of Exploration Geophysicists
Date: 11-2018
Abstract: Electromagnetic radiation (EMR) anomalies preceding or accompanying coal and rock dynamic disasters have been reported for many years, but the mechanism that produces these anomalies is still unclear. To investigate the role that charge separation plays in these electromagnetic (EM) anomalies, uniaxial compression experiments on three different brittle materials: coal, marble, and polymethyl methacrylate were conducted. The results of the experiments indicate that EMRs are observed in piezoelectric and nonpiezoelectric materials but EM anomalies are only observed when abrupt stress drops occur. The EMR energy rate increases with the magnitude of the stress drop, and those two variables are related by a polynomial function. The charge separation responsible for the anomalies occurs on the newly generated cracks when chemical bonds are broken. A charge distribution model has been established for this phenomenon. Based on this model, the coupling relationship between EM energy density[Formula: see text] and charge density [Formula: see text] has been determined by theoretical analysis. According to this analysis, [Formula: see text] is proportional to [Formula: see text]. In addition, the relationship between [Formula: see text] and surface energy has been established, and it indicates that [Formula: see text] increases with (1) the stress to which the surrounding material is subjected and (2) the length of newly generated cracks. Research findings reported should provide a more detailed understanding of the EM anomalies when coal and rock dynamic disasters occur and provide guidance for developing warning strategies for mine safety.
Publisher: Elsevier BV
Date: 04-2017
Publisher: Springer Science and Business Media LLC
Date: 27-11-2018
Publisher: Elsevier BV
Date: 05-2016
Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 03-2018
Publisher: Springer Science and Business Media LLC
Date: 29-04-2019
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 03-2019
Publisher: Hindawi Limited
Date: 2018
DOI: 10.1155/2018/6210594
Abstract: The acoustic emission (AE) and ultrasonic (UT) simultaneous monitoring program is designed using concrete s les under step loading. The time-varying response characteristics of AE-UT are studied and the cross-correlation analysis between AE-UT parameters is obtained. Moreover, the joint response of UT-AE spatial distribution field is analyzed, and an AE-UT joint monitoring method to detect early-warning signals of a rockburst disaster in a coal seam is proposed. The results show the following. ( 1 ) During the loading process, the AE pulses/energy and UT attenuation coefficient first slowly decrease and then increase steadily and finally rapidly increase, while the UT velocity shows a trend of first gradually increasing and then slowly decreasing and finally a sharp decline. ( 2 ) AE pulses and energy are significantly or highly correlated with the UT velocity and attenuation coefficient. The AE energy and UT attenuation coefficient can better characterize the damage evolution of concrete under step loading. ( 3 ) The UT field evolves ahead of the rupture on the surface, and the long/narrow strip distribution region of UT parameters is consistent with the future failure zone meanwhile, the AE events can visually reflect the evolution path of internal damage as well as the dynamic migration mechanism of UT field.
Publisher: Hindawi Limited
Date: 28-05-2018
DOI: 10.1155/2018/6948726
Abstract: Shale gas reservoir is a typical type of unconventional gas reservoir, primarily because of the complex flow mechanism from nanoscale to macroscale. A triple-porosity model (M3 model) comprising kerogen system, matrix system, and natural fracture system was presented to describe the multispace scale, multitime scale, and multiphysics characteristic of gas flows in shale reservoir. Apparent permeability model for real gas transport in nanopores, which covers flow regime effect and geomechanical effect, was used to address multiscale flow in shale matrix. This paper aims at quantifying the shale gas in different scales and its sequence in the process of gas production. The model results used for history matching also showed consistency against gas production data from the Barnett Shale. It also revealed the multispace scale process of gas production from a single well, which is supplied by gas transport from natural fracture, matrix, and kerogen sequentially. Sensitivity analysis on the contributions of shale reservoir permeability in different scales gives some insight as to their importance. Simulated results showed that free gas in matrix contributes to the main source of gas production, while the performance of a gas shale well is strongly determined by the natural fracture permeability.
No related grants have been discovered for Enyuan Wang.