Figure 1.
Layout plan of the working face.
Figure 1.
Layout plan of the working face.
Figure 2.
Comprehensive histogram of the working face.
Figure 2.
Comprehensive histogram of the working face.
Figure 3.
Simultaneous excavation of double roadways.
Figure 3.
Simultaneous excavation of double roadways.
Figure 4.
Cross-section of overburden structure in the whole process of excavation and mining with small coal pillars arranged in double roadways. (a) Solid coal tunneling stage, (b) Mining stage of the upper section working face, (c) Mining stage of the working face in this section.
Figure 4.
Cross-section of overburden structure in the whole process of excavation and mining with small coal pillars arranged in double roadways. (a) Solid coal tunneling stage, (b) Mining stage of the upper section working face, (c) Mining stage of the working face in this section.
Figure 5.
Mechanical model diagram of overburden structure.
Figure 5.
Mechanical model diagram of overburden structure.
Figure 6.
Simplified model of a narrow coal pillar.
Figure 6.
Simplified model of a narrow coal pillar.
Figure 7.
Model comparison diagram.
Figure 7.
Model comparison diagram.
Figure 8.
Uniaxial compression test of the specimen.
Figure 8.
Uniaxial compression test of the specimen.
Figure 9.
Anchor rod and matching nuts and gaskets. (a) Grade 4.8 screws and nuts, (b) Grade 12.9 screws and nuts, (c) 304 stainless steel gasket.
Figure 9.
Anchor rod and matching nuts and gaskets. (a) Grade 4.8 screws and nuts, (b) Grade 12.9 screws and nuts, (c) 304 stainless steel gasket.
Figure 10.
Layout position plan.
Figure 10.
Layout position plan.
Figure 11.
Sectional view of the specimen.
Figure 11.
Sectional view of the specimen.
Figure 12.
Plane layout of the specimen. (a) Combination arrangement of two roots, (b) Combination arrangement of three roots, (c) Combined cross arrangement, (d) Combined parallel arrangement.
Figure 12.
Plane layout of the specimen. (a) Combination arrangement of two roots, (b) Combination arrangement of three roots, (c) Combined cross arrangement, (d) Combined parallel arrangement.
Figure 13.
Broken line diagram of bolt test results (a) Relation curve of elastic modulus of anchorage, (b) Axial load relationship curve of anchorage body, (c) Relation curve of residual strength of anchorage, (d) Relationship curve of strengthening coefficient of anchorage.
Figure 13.
Broken line diagram of bolt test results (a) Relation curve of elastic modulus of anchorage, (b) Axial load relationship curve of anchorage body, (c) Relation curve of residual strength of anchorage, (d) Relationship curve of strengthening coefficient of anchorage.
Figure 14.
Failure mode of the anchor body of the anchor rod. (a) Anchorless specimen, (b) three bolts, (c) two bolts, (d) four bolts.
Figure 14.
Failure mode of the anchor body of the anchor rod. (a) Anchorless specimen, (b) three bolts, (c) two bolts, (d) four bolts.
Figure 15.
Line diagram of the test results of the anchor cable specimens. (a) Relation curve of elastic modulus of anchorage, (b) Axial load relationship curve of anchorage body, (c) Relation curve of residual strength of anchorage, (d) Relationship curve of strengthening coefficient of anchorage.
Figure 15.
Line diagram of the test results of the anchor cable specimens. (a) Relation curve of elastic modulus of anchorage, (b) Axial load relationship curve of anchorage body, (c) Relation curve of residual strength of anchorage, (d) Relationship curve of strengthening coefficient of anchorage.
Figure 16.
Failure mode of the anchor body through the anchor cable. (a) Full-length cementation, (b) Pretightening at both ends.
Figure 16.
Failure mode of the anchor body through the anchor cable. (a) Full-length cementation, (b) Pretightening at both ends.
Figure 17.
Failure mode of the anchor body through the anchor cable. (a) Three opposite anchor cables, (b) Four opposite anchor cables.
Figure 17.
Failure mode of the anchor body through the anchor cable. (a) Three opposite anchor cables, (b) Four opposite anchor cables.
Figure 18.
Line diagram of the test results of the combined specimens. (a) Relation curve of elastic modulus of anchorage, (b) Axial load relationship curve of anchorage body, (c) Relation curve of residual strength of anchorage, (d) Relationship curve of strengthening coefficient of anchorage.
Figure 18.
Line diagram of the test results of the combined specimens. (a) Relation curve of elastic modulus of anchorage, (b) Axial load relationship curve of anchorage body, (c) Relation curve of residual strength of anchorage, (d) Relationship curve of strengthening coefficient of anchorage.
Figure 19.
Failure mode of the combined anchorage. (a) Cross arrangement, (b) Parallel arrangement.
Figure 19.
Failure mode of the combined anchorage. (a) Cross arrangement, (b) Parallel arrangement.
Figure 20.
Schematic diagram of the double roadway excavation layout.
Figure 20.
Schematic diagram of the double roadway excavation layout.
Figure 21.
Support drawing of roadway section.
Figure 21.
Support drawing of roadway section.
Figure 22.
Schematic diagram of the station layout.
Figure 22.
Schematic diagram of the station layout.
Figure 23.
Surface displacement of roadway.
Figure 23.
Surface displacement of roadway.
Figure 24.
Comparison of roadway surface displacement.
Figure 24.
Comparison of roadway surface displacement.
Table 1.
Physical and mechanical parameters of the specimens.
Table 1.
Physical and mechanical parameters of the specimens.
Numbering | Proportioning | Compressive Strength/MPa | Density/g·cm−3 |
---|
Individual Value | Average | Individual Value | Average |
---|
1-1 | 0.65:1 | 10.9 | | 1.31 | |
1-2 | 0.65:1 | 11.4 | 11.1 | 1.28 | 1.3 |
1-3 | 0.65:1 | 10.98 | | 1.3 | |
2-1 | 0.60:1 | 17.81 | | 1.38 | |
2-2 | 0.60:1 | 17.96 | 17.81 | 1.41 | 1.41 |
2-3 | 0.60:1 | 17.65 | | 1.42 | |
Table 2.
Statistical table of the average strengthening coefficient of the specimens.
Table 2.
Statistical table of the average strengthening coefficient of the specimens.
Layout | Reinforcement Method | Elastic Modulus Strengthening Coefficient Ke | Axial Load Strengthening Coefficient KF | Residual Strength Strengthening Coefficient Kp |
---|
Anchor | End anchorage | 1.535 | 1.512 | 1.817 |
Full-length anchorage | 0.976 | 1.012 | 1.09 |
Opposite anchor | Full-length cementation | 1.543 | 1.759 | 2.334 |
Pretightening at both ends | 0.854 | 0.981 | 1.188 |
Combined arrangement | Combined reinforcement | 0.919 | 1.046 | 1.033 |
Table 3.
Load of coal pillars with different widths.
Table 3.
Load of coal pillars with different widths.
Width of Coal Pillar/m | 4 | 5 | 6 | 7 | 8 |
---|
Acting force on coal Pillar/kN | 4183.7 | 4595.6 | 5007.5 | 5419.4 | 5831.3 |
Coal pillar load/MPa | 1.05 | 0.92 | 0.83 | 0.77 | 0.73 |
Table 4.
Support scheme of small coal pillar crossing anchor cable.
Table 4.
Support scheme of small coal pillar crossing anchor cable.
Number of Anchor Cables | Anchor Cable Spacing/m | Row Spacing of Anchor Cable/m | Support Resistance of Single Anchor Cable/kN | Support Strength of Anchor Cable/MPa |
---|
3 | 1.2 | 1.0 | 220 | 0.169 |
4 | 1.0 | 1.0 | 220 | 0.225 |
5 | 0.8 | 1.0 | 220 | 0.282 |
Table 5.
Bearing capacity of coal pillars with different widths.
Table 5.
Bearing capacity of coal pillars with different widths.
| Coal Pillar Width | 4 m | 5 m | 6 m | 7 m | 8 m |
---|
Bearing Strength | |
---|
0.5 MPa | 2000 | 2500 | 3000 | 3500 | 4000 |
0.56 MPa | 2240 | 2800 | 3360 | 3920 | 4480 |
0.625 MPa | 2500 | 3125 | 3750 | 4375 | 5000 |
Table 6.
Support resistance provided by the concrete-filled steel tubular pier column.
Table 6.
Support resistance provided by the concrete-filled steel tubular pier column.
| Coal Pillar Width | 4 m | 5 m | 6 m | 7 m | 8 m |
---|
Number of Anchor Cables | |
---|
3 | 4275.5 | 4393.4 | 4511.2 | 4629 | 4746.9 |
4 | 4035.5 | 4093.4 | 4151.2 | 4209 | 4266.9 |
5 | 3775.5 | 3768.4 | 3761.2 | 3754 | 3746.9 |
Table 7.
Reduction factor and bearing capacity of piers with different diameters.
Table 7.
Reduction factor and bearing capacity of piers with different diameters.
Type of Steel Pipe (mm) | Elastic Ultimate Strength/kN | Reduction Factor | Actual Bearing Capacity/kN |
---|
Φ159 × 8 × 3700 | 1900 | 0.479 | 910.1 |
Φ168 × 8 × 3700 | 2200 | 0.496 | 1091.2 |
Φ180 × 8 × 3700 | 2300 | 0.516 | 1186.8 |
Φ194 × 8 × 3700 | 2600 | 0.538 | 1398.8 |
Φ194 × 6 × 3700 | 2100 | 0.538 | 1129.8 |
Φ194 × 10 × 3700 | 3000 | 0.538 | 1614 |
Φ194 × 12 × 3700 | 3500 | 0.538 | 1883 |