Dynamic Mechanical and Microstructural Properties of Outburst-Prone Coal Based on Compressive SHPB Tests
Abstract
:1. Introduction
2. Laboratory Specimen and Test Setup
2.1. Specimen Procurement and Preparation
2.2. Apparatus and Basic Principles for SHPB Tests
2.3. Methodology and Apparatus of SEM and NMR Tests
3. Results and Discussion
3.1. Effect of Strain Rate on Dynamic Mechanical Properties
3.2. Effect of Strain Rate on Fragment Size Distribution
3.3. Effect of Strain Rate on Microstructural Characteristics
4. Conclusions
- (1)
- The dynamic stress-strain response of specimens primarily comprised stages of compression, linear elastic deformation then, micro-crack evolution, followed by unstable crack propagation, culminating in rapid unloading. The compressive strength inclined linearly with the applied strain rate.
- (2)
- When the impact loading rate was relatively low, only the micro-cracks consuming reduced energy adsorption participated in rupturing the coal specimen, and fragments failed in tension as apparent in the development of a typical tensile failure surface. With the impact’s stress increasing, the fragments failed predominantly in shear. The equivalent particle size of the coal fragments decreased with the applied strain rate. The equivalent particle size of outburst-prone coal was smaller than that of outburst-resistant coal.
- (3)
- Observed by the SEM and NMR, the microstructure changed dramatically with the strain rates. When the impact load was low, the pores and fractures were mainly isolated, and the connectivity between them was poor. As the impact load increased, the primary fractures expanded and propagated through the isolated pores, causing numerous pores to break to form secondary fractures.
- (4)
- With the increase of strain rate, the proportion of fractures in coal tended to increase, the ratio of pore throat with diameter <0.1 μm decreased, and the ratio of pore throat with diameter >10 μm firstly decreased slightly and then increased rapidly.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Specimen | Dry Density, ρd (g/cm3) | Uniaxial Compressive Strength, σc (MPa) | Tensile Strength, σt (MPa) | Elastic Modulus, Et (GPa) | Poisson Ratio, ν |
---|---|---|---|---|---|
Xintian coal (prone) | 1.36 | 4.76 | 0.68 | 2.34 | 0.28 |
Xinzhouyao coal (resistant) | 1.29 | 11.45 | 1.45 | 3.98 | 0.24 |
Specimen Number | Average Strain Rate (1/s) | <0.1 μm Throat Ratio (%) | >10 μm Throat Ratio (%) |
---|---|---|---|
Y1 | 17.80 | 58.14 | 16.35 |
Y2 | 27.78 | 55.45 | 13.44 |
Y3 | 39.99 | 54.54 | 12.94 |
Y4 | 47.43 | 54.53 | 20.58 |
Y5 | 71.56 | 46.84 | 25.18 |
Y6 | 89.69 | 40.75 | 33.11 |
Y7 | 107.91 | 38.85 | 36.01 |
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Yang, Z.; Fan, C.; Lan, T.; Li, S.; Wang, G.; Luo, M.; Zhang, H. Dynamic Mechanical and Microstructural Properties of Outburst-Prone Coal Based on Compressive SHPB Tests. Energies 2019, 12, 4236. https://doi.org/10.3390/en12224236
Yang Z, Fan C, Lan T, Li S, Wang G, Luo M, Zhang H. Dynamic Mechanical and Microstructural Properties of Outburst-Prone Coal Based on Compressive SHPB Tests. Energies. 2019; 12(22):4236. https://doi.org/10.3390/en12224236
Chicago/Turabian StyleYang, Zhenhua, Chaojun Fan, Tianwei Lan, Sheng Li, Guifeng Wang, Mingkun Luo, and Hongwei Zhang. 2019. "Dynamic Mechanical and Microstructural Properties of Outburst-Prone Coal Based on Compressive SHPB Tests" Energies 12, no. 22: 4236. https://doi.org/10.3390/en12224236