Author Contributions
Resources, and funding acquisition Y.Y. and L.W.; investigation, conceptualization, project administration and supervision, Y.Y., L.W. and L.P.; formal analysis and data curation, L.P., F.W. and H.M.; validation, writing-original draft, and writing-review & editing L.P. We are grateful to the staff at the Gaocheng coal mine for their assistance during the on-site sampling.
Figure 1.
(a) The location of the Gaocheng coal mine; (b) the specific coal collection location in the Gaocheng coal mine; (c) the typical appearance of pulverized coal with an outburst property.
Figure 1.
(a) The location of the Gaocheng coal mine; (b) the specific coal collection location in the Gaocheng coal mine; (c) the typical appearance of pulverized coal with an outburst property.
Figure 2.
(a,b) Surface micromorphology of the pulverized coal; (c) X-ray diffraction pattern of pulverized coal; (d) part of the briquette specimens.
Figure 2.
(a,b) Surface micromorphology of the pulverized coal; (c) X-ray diffraction pattern of pulverized coal; (d) part of the briquette specimens.
Figure 3.
The density standard deviation of briquettes with different particle sizes.
Figure 3.
The density standard deviation of briquettes with different particle sizes.
Figure 4.
Variation of the uniaxial compression test result error bars with the coal particle size. (a) The relationship between uniaxial compressive strength and coal particle size; (b) the relationship between elastic modulus and coal particle size; and (c) the relationship between deformation modulus and coal particle size.
Figure 4.
Variation of the uniaxial compression test result error bars with the coal particle size. (a) The relationship between uniaxial compressive strength and coal particle size; (b) the relationship between elastic modulus and coal particle size; and (c) the relationship between deformation modulus and coal particle size.
Figure 5.
Stress–strain curves of the uniaxial compression of briquettes with different particle sizes: (a) group A, (b) group B, (c) group C and (d) group D.
Figure 5.
Stress–strain curves of the uniaxial compression of briquettes with different particle sizes: (a) group A, (b) group B, (c) group C and (d) group D.
Figure 6.
Uniaxial compression failure morphology of briquettes with different particle sizes: (a) group A, (b) group B, (c) group C and (d) group D.
Figure 6.
Uniaxial compression failure morphology of briquettes with different particle sizes: (a) group A, (b) group B, (c) group C and (d) group D.
Figure 7.
Test results concerning variations of triaxial compression with particle size: (a) peak strength and (b) elastic modulus.
Figure 7.
Test results concerning variations of triaxial compression with particle size: (a) peak strength and (b) elastic modulus.
Figure 8.
The triaxial compression stress–strain curves of briquettes with different particle sizes: (a) group A, (b) group B, (c) group C and (d) group D.
Figure 8.
The triaxial compression stress–strain curves of briquettes with different particle sizes: (a) group A, (b) group B, (c) group C and (d) group D.
Figure 9.
Variations of the triaxial compression strength with the confining pressure of briquettes of different particle sizes.
Figure 9.
Variations of the triaxial compression strength with the confining pressure of briquettes of different particle sizes.
Figure 10.
The cohesion and internal friction angle of each group.
Figure 10.
The cohesion and internal friction angle of each group.
Figure 11.
(a) The relationship between material strengths and different particle sizes; (b) the relationship of ε1 and different particle sizes.
Figure 11.
(a) The relationship between material strengths and different particle sizes; (b) the relationship of ε1 and different particle sizes.
Figure 12.
Sectional view of briquettes with different particle sizes: (a) group A, (b) group B, (c) group C and (d) group D.
Figure 12.
Sectional view of briquettes with different particle sizes: (a) group A, (b) group B, (c) group C and (d) group D.
Figure 13.
Schematic diagram of the molding process during briquetting. (a) Loosely packed particles, (b) particles formed under loading and (c) the interpenetration of particles.
Figure 13.
Schematic diagram of the molding process during briquetting. (a) Loosely packed particles, (b) particles formed under loading and (c) the interpenetration of particles.
Figure 14.
Schematic diagram of briquettes’ failure mode under loading. (a) The structural surface friction between particles, (b) structural wedge friction, (c) fragmentation along the fracture surface and (d) compaction of loose particles.
Figure 14.
Schematic diagram of briquettes’ failure mode under loading. (a) The structural surface friction between particles, (b) structural wedge friction, (c) fragmentation along the fracture surface and (d) compaction of loose particles.
Figure 15.
Abstract diagram of the structure of briquettes with different particle sizes: (a) group A, (b) group B, (c) group C and (d) group D.
Figure 15.
Abstract diagram of the structure of briquettes with different particle sizes: (a) group A, (b) group B, (c) group C and (d) group D.
Table 1.
The natural coal particle size distribution of the No. II-1 coal seam in the Gaocheng coal mine after screening.
Table 1.
The natural coal particle size distribution of the No. II-1 coal seam in the Gaocheng coal mine after screening.
Particle Size (mm) | >50 | 25–50 | 13–25 | 6–13 | 3–6 | 0.5–3 | <0.5 |
---|
Weight (kg) | 194.41 | 343.62 | 746.93 | 847.12 | 1706.52 | 2983.01 | 3178.92 |
Proportion (%) | 1.94 | 3.42 | 7.44 | 8.44 | 17.01 | 29.3 | 31.68 |
Table 2.
The density of briquettes with different particle sizes (kg/m3).
Table 2.
The density of briquettes with different particle sizes (kg/m3).
No. | Group A | Group B | Group C | Group D |
---|
1 | 1322.20 | 1251.60 | 1177.35 | 1108.88 |
2 | 1326.04 | 1224.75 | 1172.90 | 1159.19 |
3 | 1261.27 | 1263.44 | 1175.54 | 1157.19 |
4 | 1261.36 | 1226.50 | 1181.57 | 1167.38 |
5 | 1210.10 | 1240.75 | 1180.20 | 1184.26 |
6 | 1274.34 | 1234.53 | 1174.73 | 1155.40 |
7 | 1218.36 | 1241.75 | 1174.04 | 1156.76 |
8 | 1239.78 | 1261.75 | 1175.43 | 1157.85 |
9 | 1217.14 | 1235.10 | 1221.93 | 1160.11 |
10 | 1355.11 | 1194.79 | 1173.48 | 1162.26 |
11 | 1304.74 | 1226.84 | 1182.29 | 1169.74 |
12 | 1246.63 | 1237.41 | 1186.04 | 1165.89 |
13 | 1337.97 | 1233.35 | 1185.76 | 1172.64 |
| 1275.00 | 1236.35 | 1181.64 | 1159.81 |
Table 3.
The uniaxial compression test results of briquettes with different particle sizes.
Table 3.
The uniaxial compression test results of briquettes with different particle sizes.
Group | No. | RC/MPa | ET/MPa | E50/MPa |
---|
A | A-1 | 0.86 | 63 | 52 |
A-2 | 0.78 | 70 | 57 |
A-3 | 0.69 | 66 | 62 |
Mean | 0.77 | 66.33 | 57.00 |
Coefficient of variation | 0.11 | 0.05 | 0.09 |
B | B-1 | 0.31 | 32 | 32 |
B-2 | 0.35 | 30 | 30 |
B-3 | 0.26 | 26 | 26 |
Mean | 0.31 | 29.33 | 29.33 |
Coefficient of variation | 0.15 | 0.10 | 0.10 |
C | C-1 | 1.05 | 56 | 47 |
C-2 | 1.01 | 54 | 43 |
C-3 | 1.00 | 54 | 45 |
Mean | 1.02 | 54.67 | 45.00 |
Coefficient of variation | 0.03 | 0.02 | 0.04 |
D | D-1 | 1.57 | 79 | 62 |
D-2 | 1.57 | 79 | 64 |
D-3 | 1.90 | 127 | 96 |
Mean | 1.68 | 95.00 | 74.00 |
Coefficient of variation | 0.11 | 0.29 | 0.26 |
Table 4.
Triaxial test results of briquettes with different particle sizes.
Table 4.
Triaxial test results of briquettes with different particle sizes.
Group | No. | σ3/MPa | σ3-1/Mpa | σ1/MPa | ET/GPa | ε0/10−3 | ε1/10−3 |
---|
A | A-4 | 0.20 | 0.23 | 2.85 | 0.13 | 44.25 | 26.72 |
A-5 | 0.40 | 0.37 | 3.67 | 0.17 | 31.11 | 9.31 |
A-6 | 0.60 | 0.58 | 5.28 | 0.23 | 29.17 | 11.67 |
A-7 | 0.80 | 0.78 | 6.01 | 0.24 | 51.20 | 29.85 |
A-8 | 1.00 | 1.01 | 7.92 | 0.35 | 32.80 | 12.01 |
B | B-4 | 0.20 | 0.17 | 2.04 | 0.10 | 39.39 | 22.54 |
B-5 | 0.40 | 0.42 | 3.49 | 0.13 | 40.95 | 18.86 |
B-6 | 0.60 | 0.61 | 4.95 | 0.19 | 38.83 | 15.98 |
B-7 | 1.00 | 0.98 | 6.61 | 0.29 | 51.01 | 35.79 |
C | C-4 | 0.20 | 0.22 | 3.36 | 0.10 | 37.99 | 12.09 |
C-5 | 0.40 | 0.38 | 4.61 | 0.14 | 40.32 | 11.13 |
C-6 | 0.60 | 0.58 | 6.23 | 0.18 | 46.97 | 15.65 |
C-7 | 0.80 | 0.78 | 7.61 | 0.21 | 47.81 | 14.74 |
C-8 | 1.00 | 0.98 | 8.76 | 0.24 | 47.85 | 15.22 |
D | D-4 | 0.20 | 0.17 | 4.06 | 0.15 | 31.41 | 9.34 |
D-5 | 0.40 | 0.38 | 5.68 | 0.16 | 47.60 | 15.46 |
D-6 | 0.60 | 0.58 | 6.81 | 0.20 | 41.80 | 12.56 |
D-7 | 0.80 | 0.78 | 8.55 | 0.31 | 31.62 | 9.53 |
D-8 | 1.00 | 1.01 | 10.14 | 0.25 | 52.62 | 17.11 |
Table 5.
Linear fitting results for group A, B, C and D.
Table 5.
Linear fitting results for group A, B, C and D.
Group | K | Q | R2 (Correlation Coefficient) |
---|
A | 6.35 | 1.38 | 0.972 |
B | 5.71 | 1.16 | 0.965 |
C | 7.18 | 1.90 | 0.994 |
D | 7.23 | 2.83 | 0.996 |
Table 6.
Cohesion and internal friction angle of briquettes with different particle sizes.
Table 6.
Cohesion and internal friction angle of briquettes with different particle sizes.
Group | c/MPa | Variation of c Based on Group A/% | φ/(°) | Variation of φ Based on Group A/% |
---|
A | 0.13 | N/A | 46.71 | N/A |
B | 0.12 | −7.79 | 44.58 | −4.56 |
C | 0.15 | 15.38 | 49.07 | 5.05 |
D | 0.22 | 69.23 | 49.20 | 5.33 |