Analysis of Stress-Strain States in the Vicinity of Mining Excavations in a Rock Mass with Variable Mechanical Properties
Abstract
:1. Introduction
2. Analysis of the Variability of Rock and Rock Mass Properties in the Vicinity of Mining Excavations
- The values of strength and deformation properties of rocks in the rock mass can be determined on the basis of data from scattered points using statistical methods (Figure 3);
- The strength and deformation properties of the rocks surrounding the excavation may also change in time (e.g., as a result of mining works in the area of the excavation);
- For individual rock layers, no relationship was found between the change in the strength properties of the rocks and the depth of their deposition (Figure 4);
- The conducted statistical tests indicated that the strength and deformation properties of Carboniferous rocks can be treated as random variables with a normal probability distribution (Figure 1).
3. Construction of the Numerical Model
- In the first stage, the original stress state was determined in the model (modelled rock mass without excavation);
- In the second stage, the creation of the excavation was simulated by removing the elements inside its contour and introducing structural elements to the model, representing the arches of the steel supports.
4. Results of Conducted Numerical Simulations
4.1. Plasticisation Zones
4.2. Main Stress Distribution
4.3. Axial Forces in the Modelled Supports
5. Summary and Conclusions
- The actual occurrence of the variability of rock properties may have a significant impact on the conditions of the safe use of galleries;
- An increase in the variability coefficient with constant average values of material parameters increases the range of the plasticization zone in the vicinity of the excavation;
- The increase in the volume of plasticization zones with an increase in the variability coefficient from 0 to 20% is relatively small; however, at higher values, the number of plasticized elements in the model increases rapidly, and with the variability coefficient equal to 30%, the plasticization covers such a large part of the model (Figure 9f and Figure 10f) that it is impossible to balance it;
- Only the variability of strength parameters has a smaller impact on the state of the model than taking into account the variance of both strength and deformation parameters;
- Due to the variability of the strength parameters of the rock mass, elements that provide additional protection and reinforcement of the supports in the sections of increased support load in the form of beams, stands, multi-sided supports, or local anchoring of the rock mass become very significant;
- Numerical modelling of the rock mass, taking into account the variability of the material parameters of the rocks, allows for the mapping of the variability of the rock mass along the excavation and, by applying additional protection, for the improvement of the safety of excavation use.
Author Contributions
Funding
Conflicts of Interest
References
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Variant | Variability Coefficient | Volumetric Elasticity Coefficient | Shear Elasticity Coefficient | Cohesion | Internal Friction Angle | Tensile Strength |
---|---|---|---|---|---|---|
% | GPa | GPa | MPa | ° | MPa | |
average value | ||||||
2.38 | 2.17 | 5 | 30 | 1 | ||
standard deviation | ||||||
0 | 0 | 0 | 0 | 0 | 0 | 0 |
Ia | 5 | 0 | 0 | 0.25 | 1.5 | 0.05 |
Ib | 10 | 0 | 0 | 0.5 | 3 | 0.1 |
Ic | 15 | 0 | 0 | 0.75 | 4.5 | 0.15 |
Id | 20 | 0 | 0 | 1 | 6 | 0.2 |
Ie | 25 | 0 | 0 | 1.25 | 7.5 | 0.25 |
If | 30 | 0 | 0 | 1.5 | 9 | 0.3 |
IIa | 5 | 0.12 | 0.11 | 0.25 | 1.5 | 0.05 |
IIb | 10 | 0.24 | 0.22 | 0.5 | 3 | 0.1 |
IIc | 15 | 0.36 | 0.33 | 0.75 | 4.5 | 0.15 |
IId | 20 | 0.48 | 0.43 | 1 | 6 | 0.2 |
IIe | 25 | 0.6 | 0.54 | 1.25 | 7.5 | 0.25 |
IIf | 30 | 0.71 | 0.65 | 1.5 | 9 | 0.3 |
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Jendryś, M.; Duży, S.; Dyduch, G. Analysis of Stress-Strain States in the Vicinity of Mining Excavations in a Rock Mass with Variable Mechanical Properties. Energies 2020, 13, 5567. https://doi.org/10.3390/en13215567
Jendryś M, Duży S, Dyduch G. Analysis of Stress-Strain States in the Vicinity of Mining Excavations in a Rock Mass with Variable Mechanical Properties. Energies. 2020; 13(21):5567. https://doi.org/10.3390/en13215567
Chicago/Turabian StyleJendryś, Marek, Stanisław Duży, and Grzegorz Dyduch. 2020. "Analysis of Stress-Strain States in the Vicinity of Mining Excavations in a Rock Mass with Variable Mechanical Properties" Energies 13, no. 21: 5567. https://doi.org/10.3390/en13215567