In a recent article published in Scientific Reports, researchers highlighted the complexities and challenges associated with the initial mining phase of thick coal seams, particularly focusing on the issues arising from hard roof strata and thick parting layers.
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These geological features significantly impact the safety and efficiency of mining operations. The authors emphasized the need for innovative approaches to enhance top coal caving performance (TCCP) and reduce the risks associated with rock pressure. The study proposed a hydraulic fracturing technique to improve the stability of the mining environment and optimize recovery rates during the initial mining phase.
Background
Mining thick coal seams presents significant challenges due to the complex geological conditions, particularly hard roof strata and thick parting layers. These factors increase rock pressure, leading to larger first weighting intervals that heighten the risk of rock falls and operational hazards.
Traditional mining methods frequently fail to address these issues, resulting in suboptimal top coal caving performance (TCCP) and reduced recovery rates. As the demand for coal continues, there is an urgent need for innovative solutions that enhance safety and efficiency in mining operations.
The hydraulic fracturing technique can effectively mitigate the risks associated with hard roofs and improve the stability of the mining environment.
The research seeks to address these critical challenges and contribute to safer and more productive coal extraction practices in complex geological settings.
The Current Study
The authors propose a graded hydraulic fracturing technique to tackle the identified challenges. This method involves strategically placing boreholes and using high-pressure water injection systems to induce fractures in both the top coal and the roof strata. The design includes two types of boreholes: fracturing boreholes and additional boreholes placed in the haulage roadway.
The fracturing boreholes are designed to penetrate the coal-rock strata effectively, while the haulage roadway boreholes facilitate the injection of pressurized water.
Hydraulic fracturing involves several key steps: hole sealing, high-pressure water injection, and pressure maintenance expansion. Initially, the boreholes are sealed to prevent fluid loss.
Pressurized water, sourced from goaf water for top coal fracturing and an activated fluid for roof fracturing, is injected into the boreholes to induce fractures.
The fracturing process is divided into three stages: initiation, development, and interconnection of fractures. The optimal fracturing height is 20.85 meters above the working face, effectively reducing the cantilever beam length formed by thick partings.
Results and Discussion
Implementing the hydraulic fracturing technique demonstrated significant improvements in safety and recovery rates during the initial mining phase. The study presents data indicating that the method effectively reduces the length of the cantilever beam formed by thick parting layers, minimizing the risks associated with rock pressure.
The authors report a marked decrease in the first weighting interval, which correlates with enhanced stability in the working face. The hydraulic fracturing process facilitates the collapse of the fractured zone, further contributing to the safety of the mining operation.
The results also highlight the graded fracturing approach's effectiveness in optimizing water resource use. Utilizing goaf water for top coal fracturing and an activated fluid for the roof conserves water and enhances the efficiency of the fracturing process.
The authors discuss the implications of these findings for future mining operations, suggesting that the hydraulic fracturing technique could serve as a model for addressing similar challenges in other mining contexts. The study emphasizes the need for ongoing research to refine the method and explore its applicability in various geological settings.
Conclusion
In conclusion, the article comprehensively analyzes the challenges faced during the initial mining of thick coal seams. It proposes a novel hydraulic fracturing technique as a viable solution.
The study underscores the importance of addressing geological complexities to enhance safety and recovery rates in mining operations. It indicates that the proposed method mitigates the risks associated with hard roof strata and thick parting layers and optimizes resource utilization.
The authors advocate for further research to expand the application of this technique and improve its effectiveness in diverse mining environments. Overall, the study contributes valuable insights into mining engineering, offering practical solutions to enhance operational safety and efficiency in challenging geological conditions.
Source:
Chang Z., Wang X., et al. (2024). Safety and high-recovery mechanisms and application research for initial mining of thick-coal-seam with complex structure and thick-hard roof. Scientific Reports 14, 19638. DOI: 10.1038/s41598-024-70085-3, https://www.nature.com/articles/s41598-024-70085-3