Coupling Effect of Intruding Water and Inherent Gas on Coal Strength Based on the Improved (Mohr-Coulomb) Failure Criterion
<p>Three-phase structure of coal containing water and gas.</p> "> Figure 2
<p>Coal samples from Songzao, Pingdingshan, and Tashan mine.</p> "> Figure 3
<p>(<b>a</b>) Sketch of suction calibration test; (<b>b</b>) Illustration of filter paper test.</p> "> Figure 4
<p>Calibration curve for Whatman No. 42 filter paper (<span class="html-italic">w<sub>f</sub></span> < 20%).</p> "> Figure 5
<p>(<b>a</b>) Moisture contents of filter papers; (<b>b</b>) Fitted relationship curves of matrix suction and moisture content.</p> "> Figure 6
<p>RLW-2000M rock mechanical testing system (Chaoyang Instrument Factory, Changchun, China) and deformeter (Teratech, Burlington, MA, USA).</p> "> Figure 7
<p>Strength criterion shown in ((σ − <span class="html-italic">P</span><sub>g</sub>), τ) coordinates.</p> "> Figure 8
<p>Relationship between (σ<sub>1</sub> − <span class="html-italic">P</span><sub>g</sub>) and (σ<sub>3</sub> − <span class="html-italic">P</span><sub>g</sub>): (<b>a</b>) Songzao; (<b>b</b>) Pingdingshan; and (<b>c</b>) Tashan.</p> "> Figure 9
<p>Relationship between internal friction angle and moisture content.</p> "> Figure 10
<p>Relationship between effective cohesion and matrix suction.</p> "> Figure 11
<p>Relationship between peak strength and gas pressure: (<b>a</b>) Songzao; (<b>b</b>) Pingdingshan; and (<b>c</b>) Tashan.</p> "> Figure 12
<p>Relationship between peak strength and moisture content: (<b>a</b>) Songzao; (<b>b</b>) Pingdingshan; and (<b>c</b>) Tashan.</p> "> Figure 13
<p>(<b>a</b>) Mercury intrusion experiment curves; (<b>b</b>) Distribution curves of pore volume of coal samples.</p> ">
Abstract
:1. Introduction
2. Development of the Theory
2.1. Effective Stress of Coal Containing Water and Gas
2.2. Failure Criterion for Coal Containing Water and Gas
3. Matrix Suction of Coal
3.1. Methods of Measuring Matrix Suction
3.2. Coal Samples
3.3. Test Procedure
3.4. Test Results
4. Triaxial Compression Strength
4.1. Experimental Methods
4.2. Experimental Results and Analysis
5. Discussion
6. Conclusions
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Location | Coal Type | Fixed Carbon | Volatile Matter Content | Porosity | Average Pore Size |
---|---|---|---|---|---|
Songzao | Meagre coal | 66.4% | 13.2% | 5.88% | 4.08 nm |
Pingdingshan | Fat coal | 57.1% | 17.7% | 5.16% | 8.60 nm |
Tashan | 1/3 Coking coal | 57.8% | 28.1% | 4.23% | 14.65 nm |
No. | Soaking Time (Day) | Moisture Content | ||
---|---|---|---|---|
Songzao | Pingdingshan | Tashan | ||
1 | 1 | 1.73% | 1.25% | 0.91% |
2 | 2 | 2.85% | 2.31% | 1.95% |
3 | 4 | 4.02% | 3.43% | 3.01% |
4 | 8 | 5.21% | 4.42% | 4.05% |
No. | 25 °C, NaCl Solution, Related Parameters | Moisture Content of Filter Paper | |
---|---|---|---|
Molarity (mol/L) | Suction (MPa) | ||
1 | 0.4 | 9.75 | 17.05% |
2 | 0.5 | 12.56 | 15.36% |
3 | 1 | 25.43 | 11.66% |
4 | 2 | 51.47 | 7.75% |
5 | 3 | 77.50 | 5.46% |
6 | 4 | 103.53 | 3.87% |
Location | Moisture Content | Strength (MPa) | ||||||||
---|---|---|---|---|---|---|---|---|---|---|
Gas Pressure = 0.5 MPa | Gas Pressure = 1.5 MPa | Gas Pressure = 2.5 MPa | ||||||||
Songzao | 1.73% | 12.57 | 13.61 | 12.71 | 11.24 | 11.22 | 10.66 | 9.37 | 8.23 | 8.91 |
2.85% | 11.77 | 11.99 | 12.25 | 9.65 | 9.20 | 9.80 | 7.97 | 7.60 | 7.61 | |
4.02% | 11.28 | 10.85 | 10.48 | 9.00 | 8.90 | 9.17 | 6.56 | 6.24 | 6.75 | |
5.21% | 9.90 | 9.78 | 10.49 | 7.79 | 8.53 | 7.75 | 6.32 | 6.50 | 6.16 | |
Pingdingshan | 1.25% | 21.46 | 21.36 | 20.57 | 17.45 | 17.89 | 18.62 | 14.16 | 13.98 | 14.70 |
2.31% | 19.39 | 18.47 | 18.56 | 15.85 | 14.97 | 16.80 | 12.88 | 12.68 | 13.23 | |
3.43% | 18.15 | 17.73 | 18.59 | 15.69 | 15.61 | 14.28 | 11.63 | 12.42 | 11.64 | |
4.42% | 17.43 | 17.31 | 17.25 | 13.39 | 13.72 | 14.37 | 11.19 | 11.47 | 11.21 | |
Tashan | 0.91% | 34.97 | 31.52 | 32.51 | 27.35 | 28.06 | 28.09 | 23.91 | 25.74 | 25.92 |
1.95% | 31.29 | 33.08 | 29.17 | 27.22 | 28.83 | 25.76 | 24.50 | 21.72 | 21.97 | |
3.01% | 31.00 | 31.05 | 28.55 | 24.48 | 26.71 | 27.62 | 21.73 | 21.24 | 22.88 | |
4.05% | 30.36 | 27.70 | 29.38 | 23.82 | 23.96 | 25.72 | 21.10 | 21.64 | 21.28 |
Location | Sample Condition | Moisture Content | Gas Pressure (MPa) | Experimental Strength (MPa) | Theoretical Value (MPa) | Deviation |
---|---|---|---|---|---|---|
Songzao | dry | 0% | 0 | 17.91 | 18.42 | 2.85% |
dry + methane | 0% | 2.5 | 12.19 | 12.87 | 5.58% | |
water saturated | 5.21% | 0 | 11.36 | 11.95 | 5.19% |
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Lu, Y.; Zhou, Z.; Ge, Z.; Zhang, X.; Li, Q. Coupling Effect of Intruding Water and Inherent Gas on Coal Strength Based on the Improved (Mohr-Coulomb) Failure Criterion. Minerals 2016, 6, 118. https://doi.org/10.3390/min6040118
Lu Y, Zhou Z, Ge Z, Zhang X, Li Q. Coupling Effect of Intruding Water and Inherent Gas on Coal Strength Based on the Improved (Mohr-Coulomb) Failure Criterion. Minerals. 2016; 6(4):118. https://doi.org/10.3390/min6040118
Chicago/Turabian StyleLu, Yiyu, Zhe Zhou, Zhaolong Ge, Xinwei Zhang, and Qian Li. 2016. "Coupling Effect of Intruding Water and Inherent Gas on Coal Strength Based on the Improved (Mohr-Coulomb) Failure Criterion" Minerals 6, no. 4: 118. https://doi.org/10.3390/min6040118