3D Numerical Modelling of the Application of Cemented Paste Backfill on Displacements around Strip Excavations
Abstract
:1. Introduction
2. Laboratory Tests of the Cemented Paste Backfill
- Ts—tensile strength, (MPa);
- k—ratio of length to diameter;
- P—maximum load, (N);
- d—diameter, (mm);
- t—length (mm).
Cement Content (%) | Curing Period (Week) | |||||||
---|---|---|---|---|---|---|---|---|
I | II | III | IV | |||||
UCS (MPa) | Ts (MPa) | UCS (MPa) | Ts (MPa) | UCS (MPa) | Ts (MPa) | UCS (MPa) | Ts (MPa) | |
5 | 0.193 | 0.068 | 0.364 | 0.098 | 0.476 | 0.122 | 0.535 | 0.155 |
10 | 0.296 | 0.141 | 1.250 | 0.270 | 1.439 | 0.377 | 1.583 | 0.485 |
15 | 1.234 | 0.471 | 2.312 | 0.653 | 2.947 | 0.938 | 3.473 | 1.211 |
3. Numerical Modeling of Strip Mining with Cemented Paste Backfill
4. Discussion
- a—backfill compressibility index, (%);
- S—the surface of the exploited strip, (m2);
- g1—the average thickness of the backfill after compression, (m);
- g2—the average height of backfilling the strip, (m).
- g—average thickness of the exploited strip, (m);
- d1—subsidence of the direct roof, (m);
- d2—floor lift, (m);
- k—height not backfilled, (m);
- Δd—subsidence of the roof before backfilling, (m).
5. Conclusions
- For the cemented paste backfill (15% of cement), the compressive strength in the fourth week was 3.473 MPa and was greater by 54% and 84% for the 10% and 5% cement addition, respectively;
- In the case of tensile strength, the maximum value was 1.211 MPa for cemented paste backfill (15% cement) and was 60% and 87% higher for 10% and 5% cement addition, respectively.
- Filling the excavations with 5%, 10%, or 15% cemented paste reduced the total displacement values by 13% and 18%, respectively;
- The exploitation of the inter-strip rock pillars in the third stage of the deposit exploitation caused an increase in displacement by 52%, 44%, and 38%, respectively, compared to the second stage;
- Filling the post-exploitation spaces between artificial pillars with 5%, 10%, and 15% cemented paste reduced the total displacements by 10%, 31%, and 28%, respectively, compared to the third stage of operation;
- The value of the backfill compressibility in the second and fourth stage of filling the strip did not exceed the value of 2.5%, which indicates that the filling effectively contributed to the reduction in displacements around the workings.
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
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Layer | Parameters | ||||||
---|---|---|---|---|---|---|---|
Tensile Strength (MPa) | Unit Weight (MN/m3) | Young’s Modulus, E, (MPa) | Poisson’s Ratio, ν | Cohesion, c, (MPa) | Friction Angle, ϕ, (°) | ||
Grey dolomite | 3.5 | 0.0269 | 30,000 | 0.24 | 0.721 | 43.13 | |
Dolomite with useful minerals of galena and sphalerite | 3.0 | 0.0264 | 14,700 | 0.22 | 0.52 | 40.641 | |
Limestone | 2.5 | 0.0255 | 33,000 | 0.3 | 0.618 | 41.788 | |
Backfill with cement content (%) | 5 | 0.155 | 0.0170 | 3613 | 0.2 | 0.039 | 10.898 |
10 | 0.485 | 0.0178 | 6960 | 0.18 | 0.073 | 17.224 | |
15 | 1.211 | 0.0185 | 12,027 | 0.16 | 0.116 | 23.606 |
Stage Number | Mining Strips without Backfill | Cement Content (%) | ||
---|---|---|---|---|
5 | 10 | 15 | ||
TD (mm) | TD (mm) | TD (mm) | TD (mm) | |
I | 2.2 | - | - | - |
II | - | 1.9 | 1.8 | 1.8 |
III | - | 2.9 | 2.6 | 2.5 |
IV | - | 2.6 | 1.8 | 1.8 |
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Skrzypkowski, K. 3D Numerical Modelling of the Application of Cemented Paste Backfill on Displacements around Strip Excavations. Energies 2021, 14, 7750. https://doi.org/10.3390/en14227750
Skrzypkowski K. 3D Numerical Modelling of the Application of Cemented Paste Backfill on Displacements around Strip Excavations. Energies. 2021; 14(22):7750. https://doi.org/10.3390/en14227750
Chicago/Turabian StyleSkrzypkowski, Krzysztof. 2021. "3D Numerical Modelling of the Application of Cemented Paste Backfill on Displacements around Strip Excavations" Energies 14, no. 22: 7750. https://doi.org/10.3390/en14227750