scholarly journals Modification of Coal Samples with Bursting Liability Subjected to Microwave Irradiation

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Yingyuan Wen ◽  
Weiming Guan ◽  
Hongchao Zhao ◽  
Honglin Liu ◽  
Huwei Li ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Microwave Irradiation ◽  
Coal Seam ◽  
Oil Recovery ◽  
Failure Process ◽  
Strain Curve ◽  
High Energy ◽  
Heating Time ◽  
Coal Bed ◽  
Stable Crack Propagation

This paper introduces the innovative technique to release the bursting liability of coal seam via microwave irradiation. To verify the feasibility of this environment-friendly technique, a series of laboratory tests incorporating acoustic emission (AE) investigation were carried out. Test results indicated that both the uniaxial compressive strength (UCS) and bursting energy index of raw and water-soaked coal samples were significantly reduced. In particular, the bursting liability was reduced by one level when the values of UCS were compared, the evidence of which is the variation of wave velocities of tested coal samples. It can also be found from the events and hits in the complete stress-strain curve and the cumulative curve of acoustic emission that the elastic modulus of the raw and water-soaked coal samples subjected to microwave irradiation decreased by 58.42% and 29.63%, respectively. This facilitates the entry into the stage of stable crack propagation more quickly, the growth rate and size of the cracks were slower and more uniform, and there were no smaller coal fragments ejecting during the failure process of the coal samples. Meanwhile, the proportion of high-energy events released in coal samples experienced a decline after the treatment of the microwave. Moreover, microwave heating principally promoted the initiation and expansion of microcracks in coal samples under the influence of microwave power of 1 kW and a heating time of 120s, which may cause the overall damage of large fractures to break into multiple small and medium cracks. Based on the experimental results, the conceptual process of using microwave in weakening the bursting liability of coal seam was then proposed, which will be the meaningful reference for microwave-assisted oil recovery and coal bed methane production.

scholarly journals Rock Stability Assessment Based on the Chronological Order of the Characteristic Acoustic Emission Phenomena

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Penghai Zhang ◽  
Tianhong Yang ◽  
Tao Xu ◽  
Qinglei Yu ◽  
Jingren Zhou ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Failure Process ◽  
High Energy ◽  
Development Stage ◽  
Crack Development ◽  
Stability Assessment ◽  
Chronological Order ◽  
Granitic Gneiss ◽  
High Energy Level ◽  
Rock Stability

Sudden inelastic deformations in rock are associated with acoustic emission (AE). Therefore, AE monitoring technique can be used to study the fracture processes of rock. In this paper, AE tests were conducted on the granitic gneiss specimens under the uniaxial compressive loading conditions. The temporal changes in AE hit parameters and spatial-temporal evolution of AE events during the failure process of the granitic gneiss specimens were studied, and several characteristic AE phenomena (i.e., dramatic increase in dominant frequency, AE energy, and hit rate, the AE event with a high energy level, and the through-going distribution of the AE events with intermediate energy levels) were statistically analyzed before the failure occurred. It was found that the chronological order of the characteristic AE phenomena was relatively certain and correspondingly had a close relationship with the crack development stage. Because of the difference of the stress level at each crack development stage, the stability at different crack development stages is different. Therefore, a rock stability assessment approach was established based on the chronological order of the characteristic AE phenomena, and then the rock stability was assessed using the proposed approach.

The Study of Identification Method for the Welding Defect Source of Low-Alloy High-Strength Steel Based on AE Technology

2011 ◽  
Vol 467-469 ◽  
pp. 1580-1585 ◽  
Author(s):  
Yan Tao Dou ◽  
Xiao Li Xu ◽  
Wei Wang ◽  
Si Qin Pang
Keyword(s):  
Acoustic Emission ◽  
High Strength Steel ◽  
Failure Process ◽  
Strain Curve ◽  
High Strength ◽  
Peak Frequency ◽  
Average Frequency ◽  
Bending Test ◽  
Characteristic Parameters ◽  
Deformation Stages

Three-bending test has been performed on the standard specimen and welding specimen with defect of low-alloy and high-strength steel in order to simulate the failure process of structural parts under loading, and the AE activities (number of hits) and stress-strain curve were measured during the whole loading process. The law of acoustic emission signals at different deformation stages has been investigated and the relation between AE characteristic parameters and the different deformation stages has been established. The typical AE waveforms such as friction noise, plastic deformation, welding microcrack initiation and propagation are obtained, which are analyzed by using spectrum characteristics analytical method. The spectrum characteristic parameters such as average frequency, peak frequency and frequency centroid, energy percentage of frequency spectrum part I and III of the typical AE defect signals are extracted, the distributing range of which are initially set. Study shows these five parameters have a closely relation with the nature of the AE signals, and based on these characteristics parameters different AE sources can be preliminary identified correctly. The study can provide some guidance to the practical application of AE acoustic emission technology in the industrial field.

Geological Storage of Carbon Dioxide in Coal Seam is Effective Method for Environment Protection and Energy Sustainable Development in China

2012 ◽  
Vol 616-618 ◽  
pp. 1591-1594
Author(s):  
Feng Shan Han ◽  
Li Song
Keyword(s):  
Sustainable Development ◽  
Coal Seam ◽  
Greenhouse Gases ◽  
Oil Recovery ◽  
Absorption Capacity ◽  
Coal Bed ◽  
Coal Bed Methane ◽  
Environment Protection ◽  
Geological Storage ◽  
Methane Recovery

The reduction of greenhouse gases emission is a growing concern of many countries. The geological storage of is useful and effective approaches to reduce emission. The oil and natural gas industries have long commercial practice of gas injection, enhanced oil recovery ( -EOR). Because coal seam has strong absorption capacity for ,the coal seam can be used as geological storage reservoirs, and coal seam has such characteristics that coal seam is preference for absorption and postponement for absorption, injection into coal seam can enhanced coal bed methane recovery, -ECBM, is a new energy generated by methane from injection into coal seam, and is beneficial complement of the energy , injection into coal seam can not only reduce greenhouse gases emission and but also enhance coal bed methane recovery, which is very significance to environment protection and energy sustainable development in china.

scholarly journals Mechanical properties and acoustic emission characteristics of coal samples with different fissure angle

2021 ◽  
Author(s):  
Xuebin Gu ◽  
Tongbin Zhao ◽  
Weiyao Guo ◽  
Xufei Gong ◽  
Yongqiang Zhao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Elastic Modulus ◽  
Crack Growth ◽  
Failure Mechanism ◽  
Strain Softening ◽  
Failure Process ◽  
High Energy ◽  
Emission Characteristics ◽  
Quiet Period

Abstract To study the influence of fissure angle on the failure mechanism of coal mass, uniaxial compression tests were conducted on coal specimens with different fissure angles. The failure process and acoustic emission characteristics during loading were obtained. The mechanical properties and failure mode were further analyzed. The results showed that (1) The stress-strain behavior of specimens with different fissure angles can be divided into four typical stages, compaction, elastic deformation, crack growth and propagation, and strain-softening. The existence of pre-existing fissures reduces the duration of the elastic stage with an obvious influence on the crack growth and propagation stage, and strain-softening stage. (2) The uniaxial compressive strength, elastic modulus of the specimens containing pre-existing fissure are all lower than those of the unfissured. The strength and elastic modulus do not change significantly with fissure angle, which is closely related to the primary fracture of the coal. (3) With the increase of the fissure angle, the crack initiation location moves from the center of the pre-existing fissure to the tip. While fissure angle has no obvious effect on the crack propagation direction, the cracks develop along the loading direction. (4) The AE characteristics can be divided into three typical periods, quiet period, active period, and remission period. With the increase of the fissure angle, the duration proportion of the quiet period increases, indicating that the energy storage time of coal increases. With the increase of the fissure angle, the occurrence time of low frequency and high energy signal is delayed, indicating that the large-size rupture gradually concentrates in the late loading period. (5) Compared with rock samples containing pre-existing fissure, coal specimens have more primary fractures, and the failure mechanism of coal is dominated by the non-uniform primary fractures.

scholarly journals Deformation and Acoustic Emission Characteristics of Cracked Granite during Creep

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Chunping Wang ◽  
Jingli Xie ◽  
Jian Liu
Keyword(s):  
Acoustic Emission ◽  
Axial Strain ◽  
Failure Process ◽  
Deformation Characteristic ◽  
Temporal Distribution ◽  
Confining Pressure ◽  
High Energy ◽  
Lateral Strain ◽  
Creep Tests ◽  
Confining Pressures

A series of multistage creep tests under different confining pressures with acoustic emission monitoring have been performed to investigate the deformation characteristic and failure process of cracked granite during creep. The critical axial strain of cracked sample showed an increasing tendency with the increase of confining pressure. In contrast, critical lateral strain experienced a process of descending first at low confinement and then remaining nearly constant at high confinement. Compared with loading-cracked specimen, smaller critical axial strain, greater critical lateral strain, and higher lateral creep strain rate were found for unloading-cracked specimen. Based on the spatial and temporal distribution of acoustic emission events, the cracking process during creep was analysed. The AE events with high energy are mainly concentrated at the final fracture area of the specimen. The higher the confining pressure, the more the AE events with low energy. Compared with the loading-cracked specimen, the percentage of AE events with high energy is relatively small for the unloading-cracked specimen.

Fault Growth and Acoustic Emissions in Confined Granite

1992 ◽  
Vol 45 (3S) ◽  
pp. S165-S173 ◽  
Author(s):  
David A. Lockner ◽  
James D. Byerlee
Keyword(s):  
Acoustic Emission ◽  
Fault Plane ◽  
Process Zone ◽  
Failure Process ◽  
Acoustic Emissions ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Fracture Front ◽  
Fault Growth

The failure process in a brittle granite was studied by using acoustic emission techniques to obtain three dimensional locations of the microfracturing events. During a creep experiment the nucleation of faulting coincided with the onset of tertiary creep, but the development of the fault could not be followed because the failure occurred catastrophically. A technique has been developed that enables the failure process to be stabilized by controlling the axial stress to maintain a constant acoustic emission rate. As a result the post-failure stress-strain curve has been followed quasi-statically, extending to hours the fault growth process that normally would occur violently in a fraction of a second. The results from the rate-controlled experiments show that the fault plane nucleated at a point on the sample surface after the stress-strain curve reached its peak. Before nucleation, the microcrack growth was distributed throughout the sample. The fault plane then grew outward from the nucleation site and was accompanied by a gradual drop in stress. Acoustic emission locations showed that the fault propagated as a fracture front (process zone) with dimensions of 1 to 3 cm. As the fracture front passed by a given fixed point on the fault plane, the subsequent acoustic emission would drop. When growth was allowed to progress until the fault bisected the sample, the stress dropped to the frictional strength. These observations are in accord with the behavior predicted by Rudnicki and Rice’s bifurcation analysis but conflict with experiments used to infer that shear localization would occur in brittle rock while the material is still hardening.

scholarly journals Experimental Research on Brittleness and Rockburst Proneness of Three Kinds of Hard Rocks under Uniaxial Compression

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Rongchao Xu ◽  
Yiding Jin ◽  
Yumin Zhang
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Fracture Mechanism ◽  
Large Scale ◽  
Rock Fracture ◽  
Failure Process ◽  
High Energy ◽  
Brittle Rock ◽  
Evaluation Index ◽  
Unstable Crack

Rockburst is a highly destructive geological disaster caused by excavation and unloading of hard and brittle rock mass under high geostress environment. Quantitative evaluation of rock brittleness and rockburst proneness is one of the important tasks in potential rockburst assessment. In this study, uniaxial compression and acoustic emission tests were carried out for basalt, granite, and marble, and their brittleness and rockburst proneness were quantitatively evaluated. The acoustic emission evolution characteristics of the three rocks during uniaxial compression were analyzed, and the differences of fracture mechanism of the three rocks were compared. The results show that (1) based on the brittleness evaluation index, basalt is the most brittle rock, followed by granite, and marble is the weakest; (2) based on the rockburst proneness evaluation index, combined with the macroscopic failure phenomenon and morphology of the samples, the rockburst proneness of basalt is the strongest, followed by granite, and marble is the weakest; (3) there exists a positive correlation between rockburst proneness and brittleness, and the fitting results show that they are approximately exponential; and (4) brittleness has an important influence on the rock fracture mechanism. Unlike marble, basalt and granite with strong brittleness continuously present high-energy acoustic emission signals in the stage of unstable crack propagation, and large-scale fracture events continue to occur; from the calculation results of the acoustic emission b value, the stronger the brittleness of rock, the larger the proportion of large-scale fracture events in the failure process.

Determining the appropriate method of a coal seam hydrotreating using acoustic emission

2018 ◽  
Vol 11 (49) ◽  
pp. 290-299
Author(s):  
Shadrin A.V. ◽  
Keyword(s):  
Acoustic Emission ◽  
Coal Seam

Growth Process of SiC Grains Prepared by High-energy Microwave Irradiation

2014 ◽  
Vol 29 (2) ◽  
pp. 149-154 ◽  
Author(s):  
Shan HUANG ◽  
Ji-Gang WANG ◽  
Song LIU ◽  
Fan LI
Keyword(s):  
Microwave Irradiation ◽  
Growth Process ◽  
High Energy

scholarly journals Acoustic Emission Characteristics and Joint Nonlinear Mechanical Response of Rock Masses under Uniaxial Compression

Energies ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 200
Author(s):  
Zhongliang Feng ◽  
Xin Chen ◽  
Yu Fu ◽  
Shaoshuai Qing ◽  
Tongguan Xie
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Inclination Angle ◽  
Failure Modes ◽  
Strain Curve ◽  
Particle Flow Code ◽  
Rock Masses ◽  
Physical Experiments ◽  
Inclination Angles ◽  
Joint Inclination

The joint arrangement in rock masses is the critical factor controlling the stability of rock structures in underground geotechnical engineering. In this study, the influence of the joint inclination angle on the mechanical behavior of jointed rock masses under uniaxial compression was investigated. Physical model laboratory experiments were conducted on jointed specimens with a single pre-existing flaw inclined at 0°, 30°, 45°, 60°, and 90° and on intact specimens. The acoustic emission (AE) signals were monitored during the loading process, which revealed that there is a correlation between the AE characteristics and the failure modes of the jointed specimens with different inclination angles. In addition, particle flow code (PFC) modeling was carried out to reproduce the phenomena observed in the physical experiments. According to the numerical results, the AE phenomenon was basically the same as that observed in the physical experiments. The response of the pre-existing joint mainly involved three stages: (I) the closing of the joint; (II) the strength mobilization of the joint; and (III) the reopening of the joint. Moreover, the response of the pre-existing joint was closely related to the joint’s inclination. As the joint inclination angle increased, the strength mobilization stage of the joint gradually shifted from the pre-peak stage of the stress–strain curve to the post-peak stage. In addition, the instantaneous drop in the average joint system aperture (aave) in the specimens with medium and high inclination angles corresponded to a rapid increase in the form of the pulse of the AE activity during the strength mobilization stage.

Sign in / Sign up

Export Citation Format

Share Document