Study on Size Optimization of a Protective Coal Pillar under a Double-Key Stratum Structure
Abstract
:1. Introduction
2. Methods
2.1. Engineering Background
2.2. Build a Model
2.3. Theoretical Calculation of the Sectional Coal Pillar Retaining Size under Noncut Roof Conditions
2.4. Key Strata Discrimination of the Working Face
- (1)
- Rigid condition discrimination
- (2)
- Strength condition discrimination
3. Results and Discussion
3.1. Numerical Simulation Analysis of Roof Cutting and Pressure Relief
3.1.1. Analysis of the Surrounding Rock Stress Characteristics When the Roof Cutting Measure Is Not Taken
3.1.2. Analysis of the Stress Characteristics of the Surrounding Rock under Roof Cutting and Pressure Relief
3.2. Roof Cutting Scheme Design
3.3. Optimization of the Small Coal Pillar Size
4. Field Engineering Application
5. Conclusions
- Through theoretical calculations, it is concluded that the width of the section pillar should not be less than 7.15 m without taking roof cutting measures. The size of the section coal pillar can be further reduced if the measure of roof cutting and pressure relief is taken. In addition, based on the theory of key strata, it is concluded that there are main and subkey strata in the overlying strata on the working face. Moreover, limestone G4, 5.6 m above the coal seam, is the subkey stratum, and the composite rock Ge, 11.5 m above the coal seam, is the composite main key stratum.
- The numerical simulation method is used to study the stress characteristics of the surrounding rock of the goaf side after the roof cutting of the main and subkey layers. It is concluded that the main key layer plays a main control role on the rock mass activities. When the top cutting height is 12 m, a stress reduction zone of 10.5 m is formed in the surrounding rock of the goaf side.
- Through the optimization study of small coal pillar size, it is concluded that the roadway surrounding rock is more conducive to stability when a 5 m coal pillar is set. After field application, the deformation of the roadway surrounding rock is monitored in a controllable range and the roadway is good in use.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
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Density/[kg·m−3] | Bulk Modulus [GPa] | Shear Modulus [GPa] | Dilatancy Angle [°] | Frictional Angle [°] |
---|---|---|---|---|
1700 | 10 | 6 | 10.3 | 30 |
Serial Number | Rock Name | Density [kg·m−3] | Tensile Strength [MPa] | Modulus of Elasticity [MPa] | Poisson Ratio | Angle of Internal Friction [°] | Cohesive Strength [MPa] |
---|---|---|---|---|---|---|---|
G8 | K3 limestone | 2712 | 4.16 | 28,194 | 0.20 | 39°44′ | 8.15 |
G7 | Mudstone | 2684 | 2.05 | 17,048 | 0.23 | 35°18′ | 3.67 |
G6 | K2 limestone | 2712 | 4.16 | 28,194 | 0.20 | 39°44′ | 8.15 |
G5 | Mudstone | 2684 | 2.05 | 17,048 | 0.23 | 35°18′ | 3.67 |
G4 | K2 limestone | 2712 | 4.16 | 28,194 | 0.20 | 39°44′ | 8.15 |
G3 | Mud stone | 2684 | 2.05 | 17,048 | 0.23 | 35°18′ | 3.67 |
#15 coal | #15 coal | 1608 | 1.18 | 6107 | 0.29 | 30°21′ | 1.91 |
G2 | Mudstone | 2684 | 2.05 | 17,048 | 0.23 | 35°18′ | 3.67 |
G1 | Bauxitic mudstone | 2360 | 2.17 | 14,326 | 0.20 | 30°47 | 2.75 |
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Zhang, D.; Zhao, H.; Li, G. Study on Size Optimization of a Protective Coal Pillar under a Double-Key Stratum Structure. Appl. Sci. 2022, 12, 11868. https://doi.org/10.3390/app122211868
Zhang D, Zhao H, Li G. Study on Size Optimization of a Protective Coal Pillar under a Double-Key Stratum Structure. Applied Sciences. 2022; 12(22):11868. https://doi.org/10.3390/app122211868
Chicago/Turabian StyleZhang, Daming, Hui Zhao, and Gang Li. 2022. "Study on Size Optimization of a Protective Coal Pillar under a Double-Key Stratum Structure" Applied Sciences 12, no. 22: 11868. https://doi.org/10.3390/app122211868
APA StyleZhang, D., Zhao, H., & Li, G. (2022). Study on Size Optimization of a Protective Coal Pillar under a Double-Key Stratum Structure. Applied Sciences, 12(22), 11868. https://doi.org/10.3390/app122211868