Mechanical Behavior of Gas-Transmission Pipeline in a Goaf
2. Finite-Element Model of Pipe–Soil Interactions in Mined-Out Conditions
2.1. Finite-Element Model Parameters
2.2. Soil Model of Each Rock Stratum
2.3. Pipeline Model
2.4. Finite-Element Model of Pipe–Soil Interaction
2.5. Validation of the Finite-Element Model
- Grid verification
- Comparison of the finite-element analysis results with theoretical values
3. Influencing Factors on the Mechanical Behavior of a Buried Pipeline in the Goaf
3.1. Effect of the Horizontal Angle
3.2. Effect of Friction Coefficient
3.3. Effect of Coal-Seam Dip Angle
- The equivalent stress of the pipeline increases when the horizontal angle of inclination is reduced, whereas the maximum equivalent stress occurs at the center of the pipeline. With a reduction in the horizontal angle, the high-stress zone of the pipeline barely changes after the coal-seam mining is complete; however, the maximum equivalent stress increases. In the process of coal-seam mining, a lesser angle between the pipeline and the coal-seam mining strike corresponds to a faster increase in the maximum equivalent stress of the pipeline; the change in the equivalent stress of the pipeline increases with the mining length.
- A local high-stress zone gradually appears with an increase in the excavation length when the coal seam is mined longitudinally. The high-stress zone of the pipeline remains stable when the mining length is >200 m. When the mining length is 40 m, a small amount of stratum displacement occurs in a small range, which is mainly concentrated above the mining area and has no surface impact. Surface displacement gradually occurs, and the range of the stratum displacement gradually increases with an increasing mining length.
- The equivalent stress of the pipeline increases with an increase in the pipe–soil friction coefficient when the width of the goaf is constant. The effect of the pipe–soil friction coefficient on the equivalent stress of the pipeline is significantly apparent with a wider goaf.
- With an increase in the coal-seam dip angle, the von Mises stress decreases, and the position of the maximum stress towards the side of the coal-seam uphill. The maximum equivalent stress of the pipeline is 432 MPa when the inclination angle of the coal seam is 15° and the goaf width is 300 m. The pipeline reached failure under these working conditions. Therefore, to reduce the influence of coal mining on the gas pipeline above the goaf, the mining angle of the coal seam should be maximized.
- We suggest that the angle between the coal seam mining direction and the pipeline axial direction be 90° to reduce the influence of coal seam mining on the buried pipeline when it is horizontal. For the coal seam with a dip angle to the horizontal direction, we suggest that the mining direction and the horizontal direction be inclined to mining in order to reduce the influence of coal seam mining on the buried pipe.
- The pipeline is affected not only by internal pressure but also by internal fluid. We suggest to introduce the fluid-structure coupling model to study the mechanical behavior of the goaf pipeline in practical engineering.
Data Availability Statement
Conflicts of Interest
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|Rock Classification||Density/kg·m−3||Elastic Modulus/MPa||Poisson’s Ratio||Cohesion/MPa||Friction Angle/°||Expansion Angle/°|
|Grid Size/m||Grid Number||Maximum Subsidence/m||Maximum von Mises Stress/MPa|
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Zhao, B.; Zhang, H.; Wang, Y.; Zhou, Y.; Zhang, J. Mechanical Behavior of Gas-Transmission Pipeline in a Goaf. Processes 2023, 11, 1022. https://doi.org/10.3390/pr11041022
Zhao B, Zhang H, Wang Y, Zhou Y, Zhang J. Mechanical Behavior of Gas-Transmission Pipeline in a Goaf. Processes. 2023; 11(4):1022. https://doi.org/10.3390/pr11041022Chicago/Turabian Style
Zhao, Bin, Hailun Zhang, Yu Wang, Yutong Zhou, and Jiaxin Zhang. 2023. "Mechanical Behavior of Gas-Transmission Pipeline in a Goaf" Processes 11, no. 4: 1022. https://doi.org/10.3390/pr11041022