Foundation of Coal Mechanics

Cheng, Yuanping; Liu, Qingquan; Ren, Ting

doi:10.1007/978-981-16-3895-4_5

Cited by 5 publications

(10 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1 mine (adjacent mines of the No. 13 mine), the elastic modulus and Poisson’s ratio of the intact coal were in the range of 0.40–2.80 GPa and 0.23–0.38, respectively. ,, Since the Poisson’s ratio of tectonic coal is generally 0.1–0.2 higher than that of intact coal, this paper selected these two mechanical parameters of the coal near the fault as 0.6 GPa and 0.4, respectively. Substituting the geostress and the mechanical parameters into eq , the coal deformation energy was calculated to be 346.848 kJ/m 3 , exactly following the in situ magnitude coal deformation energy 10 2 –10 3 kJ/t …”

Section: Discussionmentioning

confidence: 99%

Experimental Study of Multiple Physical Properties of Tectonic Coal near a Minor Fault: Implications for Coal and Gas Outburst

et al. 2023

Self Cite

View full text Add to dashboard Cite

Coal and gas outburst accidents often have occurred in minor faults and thick coal strips in recent years, which makes outbursts inseparable from geological structures or tectonic coal. In this paper, the coal samples near a minor fault were selected on the outburst belt, and the samples' basic physical properties, coal fragmentation, pore structure, and gas desorption were tested. The fractal characteristics of the samples before and after crushing were innovatively compared and analyzed. The desorbed gas expansion energy and outburst potential were accurately obtained based on the particle size distribution and the gas desorption of the samples with different grain sizes. The results show that the samples have apparent fractal characteristics, and the two fractal dimensions have an obvious linear correlation, which can somewhat characterize coal fragmentation. The fault significantly increases the pore volume and specific surface area of macropores and mesopores in coal and has less influence on micropores. From 12 m outside toward the fault center, the developed macropores increase the initial gas desorption rate by 2.11−3.11 times and the first 40 s desorption volume by 1.31−2.01 times. The desorbed gas expansion energy varies from 80.70 to 383.18 kJ/m 3 , with the DF-0 sample being the largest and the DF-12 sample being the smallest. Overall, the coal fragmentation, gas desorption, and outburst energy show a rapid decrease first and then a slight fluctuation from the fault center to the edge. The coal body is characterized by weak fragmentation, low pore abundance, and weak gas desorption near 12 m of the fault, which traps high gas-bearing coal well and increases outburst risk near the fault center. Therefore, it is significant for precise gas extraction and outburst prevention in the fault zone.

show abstract

Section: Discussionmentioning

confidence: 99%

Experimental Study of Multiple Physical Properties of Tectonic Coal near a Minor Fault: Implications for Coal and Gas Outburst

et al. 2023

Self Cite

View full text Add to dashboard Cite

show abstract

“…The amount of generated gas continuously increases with the degree of metamorphism . As the metamorphism increased, the micropores and mesopores first decreased and then increased, which made the gas adsorption capacity follow the same trend …”

Section: Introductionmentioning

confidence: 94%

“…Normally, the reservoir pressure increases linearly with the burial depth, and the linear gradient is 0.01 MPa/hm on average, similar to the vertical geostress gradient. Theoretically, neglecting the change of fracture porosity, the free gas content increases linearly with burial depth, while the adsorbed gas content approximately satisfies a Langmuir-type equation with depth . Thus, the total gas content follows the Langmuir distribution with depth, such as the case in the Xutuan mine and the Panji deep coalfield. , On the contrary, the gas contents also had an apparent linear relationship with depth near synclines, anticlines, and normal faults in the Qinan coal mine …”

Section: Introductionmentioning

confidence: 97%

Implications of Geological Conditions on Gas Contents: A Case Study in the Pingdingshan Coalfield

et al. 2023

Self Cite

View full text Add to dashboard Cite

Coalbed methane occurrence and its geological control factors are important for coal and gas co-mining. In recent years, more than 50% of the outburst accidents occurred near the faults and the thickening strips in Chinese mines. Therefore, studying the gas occurrence and its controlling factors is vital to prevent gas disasters in outburst mines with complex geology. In this paper, the distributions of faults, coal thickness, and gas content were characterized and analyzed based on fractal theory and geostatistics. Then, finer coal thickness inverted by the cross-layer boreholes for gas extraction was analyzed at a single working face. The geological control characteristics of gas contents were finally studied. The results show that coal thickness, burial depth, and fault complexity are the geological factors controlling gas contents from a regional to local scale. The sedimentary environment determines the regional coal thickness distribution and even stratification, which leads to higher gas content in the eastern thick-coal region than in the west. And the gas content varies linearly with burial depth in the same geological zonation. The fault fractal dimension is a quantitative representation of fault complexity. The dense distribution of minor faults is why the sizable fractal dimension in the local region is crucial in controlling the uneven enrichment of gas content. Therefore, more refined geological detection and characterization is the way to gas precision control in the future.

show abstract

“…Coal deformation is mainly affected by pore compression strain, adsorption expansion strain, and thermal expansion strain. 27 Assuming that the deformation of the coal seams caused by adsorption expansion, thermal expansion, and pore compression is elastic, the nonisothermal mechanical equation of coal can be expressed as 28 i k j j j y…”

Section: Coal Deformationmentioning

confidence: 99%

“…where ε v = ε 11 + ε 22 + ε 33 and σ ̅ is the mean stress (σ ̅ = −σ kk /3). The equation of stress equilibrium for gas-bearing coal can be defined as 28…”

Section: Coal Deformationmentioning

confidence: 99%

Ultrasonic-Assisted Coalbed Methane Recovery: A Coupled Acoustic–Thermal–Mechanical–Hydrological Model

Yang

Wang

et al. 2023

Energy Fuels

View full text Add to dashboard Cite

Ultrasonic propagation in coal seams is accompanied by heat transfer, which has the potential to increase coal seam permeability, enhance coalbed methane (CBM) recovery, and prevent coal and gas outbursts. Therefore, it is important to analyze the effects of heat transfer by ultrasonic vibration on CBM recovery and evaluate the prospects of engineering applications of ultrasonic heating technology. In this study, the factors affecting heat transfer by ultrasonic vibration were analyzed theoretically; then, CBM recovery under the condition of ultrasonic heating was simulated by establishing a coupled acoustic–thermal–mechanical–hydrological model. The correctness of acoustic–thermal model was validated by matching simulated data with experimental data. And the accuracy of the gas flow model was verified by comparing the production data from CBM extraction boreholes with the simulated data. The research results were as follows: heat transfer by ultrasonic vibration was affected by frequency and sound pressure. When the ultrasonic frequency varied from 30 to 40 kHz and the sound pressure varied from 0.1 to 0.12 MPa, the lower the frequency, the higher the sound pressure, and the better the ultrasonic vibration heat transfer effect. In addition, the thermal expansion volumetric strain of the coal matrix caused by the ultrasonic heating of coal seams was weaker than the shrinkage volumetric strain of the coal matrix caused by gas desorption, improving the porosity and permeability of the coal seams. Furthermore, the gas drainage standard area increased by 20.8 m2 after 720 days of CBM recovery when replacing conventional CBM recovery with ultrasonic-assisted CBM recovery. With a production time of 720 days, the maximum production of CBM after ultrasonic excitation at a frequency of 40 kHz and a sound pressure of 0.10 MPa increases from 3744 to 9740 m3/day compared to conventional excitation. Our fully coupled acoustic–thermal–mechanical–hydrological model can improve current understandings of heat and mass transfer in thermal simulation of ultrasonic-enhanced CBM recovery.

show abstract

Foundation of Coal Mechanics

Cited by 5 publications

References 13 publications

Experimental Study of Multiple Physical Properties of Tectonic Coal near a Minor Fault: Implications for Coal and Gas Outburst

Experimental Study of Multiple Physical Properties of Tectonic Coal near a Minor Fault: Implications for Coal and Gas Outburst

Implications of Geological Conditions on Gas Contents: A Case Study in the Pingdingshan Coalfield

Ultrasonic-Assisted Coalbed Methane Recovery: A Coupled Acoustic–Thermal–Mechanical–Hydrological Model

Contact Info

Product

Resources

About