ORCID Profile
0000-0001-6815-3562
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Publisher: Elsevier BV
Date: 10-2017
Publisher: Elsevier BV
Date: 02-2020
Publisher: Oxford University Press (OUP)
Date: 26-02-2018
Publisher: Elsevier BV
Date: 11-2022
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: Springer Science and Business Media LLC
Date: 22-09-2020
Publisher: Elsevier BV
Date: 03-2023
Publisher: MDPI AG
Date: 11-10-2023
DOI: 10.3390/APP132011158
Publisher: MDPI AG
Date: 22-05-2019
DOI: 10.3390/EN12101959
Abstract: In order to study the mechanics and acoustic emission (AE) characteristics of fractured rock under water-rock interaction, dried and saturated sandstone s les with prefabricated double parallel cracks were prepared. Then, uniaxial compression experiments were performed to obtain their AE signals and crack propagation images. The results show that water reduces the strength and fracture toughness of fractured sandstone and enhances plasticity. After saturation, the s les start to crack earlier the cracks grow slowly the failure mode is transformed from shear failure along the prefabricated cracks to combined shear and tensile failure more secondary cracks are produced. The saturated s les release less elastic energy and weaker AE signals in the whole failure process. However, their AE precursor information is more obvious and advanced, and their AE sources are more widely distributed. Compared with dry specimens, the AE frequencies of saturated specimens in the early stage of loading are distributed in a lower frequency domain. Besides, the saturated s les release less complex AE signals which are dominated by small-scale signals with weaker multi-fractal characteristics. After discussion and analysis, it is pointed out that this may be because water makes rock prone to inter-granular fracture rather than trans-granular fracture. The water lubrication also may reduce the litude of middle-frequency band signals produced by the friction on the fracture surface. Multi-fractal parameters can provide more abundant precursory information for rock fracture. This is of great significance to the stability of water-bearing fractured rock mass and its monitoring, and is conducive to the safe exploitation of deep energy.
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: 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: Elsevier BV
Date: 09-2021
Publisher: Springer Science and Business Media LLC
Date: 07-2020
Publisher: Oxford University Press (OUP)
Date: 19-06-2018
Publisher: MDPI AG
Date: 06-10-2023
DOI: 10.3390/SU151914526
Publisher: Elsevier BV
Date: 05-2019
Publisher: MDPI AG
Date: 13-09-2022
DOI: 10.3390/FOUNDATIONS2030052
Abstract: In order to explore the evolution characteristics of multi-scale rock-like material failure, we studied the acoustic emission (AE) and electromagnetic radiation (EMR) characteristics of different scale rock-like materials by using the AE-EMR experimental system of coal and rock failure, and the AE and EMR response law of rockburst in mining sites was analyzed. The results show that under uniaxial loading, the stress–strain curve of the specimen has a compaction stage, linear elastic stage, elastic–plastic stage and failure stage. The cumulative AE count, AE energy and stress level of the specimen have an exponential relationship during loading and compression. The cumulative EMR counts of loading and unloading showed a trend of first decreasing and then increasing with the increase in stress level. Electromagnetic radiation and microseismic hypocentral distance show an abnormal change trend when rockburst occurs, and this abnormal phenomenon can be used as a precursor feature signal for rockburst monitoring and early warning.
Publisher: Informa UK Limited
Date: 12-12-2017
Publisher: MDPI AG
Date: 02-2023
DOI: 10.3390/SU15032605
Abstract: Understanding the response law and mechanism of weak currents stimulated from coal under an impact load is significant for the prediction of coal bumps in deep coal mines. In this paper, the system for the weak current measurement of coal under an impact load is established and the response characteristics of weak currents induced by the deformation of coal under an impact load are investigated. Physical models are established to describe the process of charge transfer and explain the generation mechanism of those currents. The results show that a transient current is stimulated from the coal s le when an impact load is applied, and then, the current decays slowly, tending to be a stable value that is slightly greater than the background current. The weak current flows from the loaded volume to the unloaded volume of the coal and increases with the impact velocity in a negative exponential form. Analysis of weak currents using non-extensive entropy shows that the attenuation of the weak current obeys non-extensive statistical mechanics and the non-extensive parameter q is greater than 2. The carriers are mainly electrons, of which the distribution obeys the tip effect that electrons tend to enrich towards the tip of a crack. The generation mechanism of those weak currents induced by coal deformation is the instantaneous movement of electrons under a density difference caused by the tip effect. Research results can provide a new perspective to understand the electric phenomena of coal under an impact load as well as a new method for coal bump prediction.
Publisher: Elsevier BV
Date: 04-2017
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: 05-2016
Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 11-2018
Publisher: Elsevier BV
Date: 03-2018
Publisher: Elsevier BV
Date: 04-2019
No related grants have been discovered for Dexing Li.