Fracture propagation and pore pressure evolution characteristics induced by hydraulic and pneumatic fracturing of coal
Abstract A two-dimensional unsteady seepage model for coal using a finite element program is developed, and the temporal variations of key factors such as water pressure and hydraulic gradient are analyzed in this paper. Additionally, the triaxial rock mechanical experiment and utilized pneumatic fr...
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Nature Portfolio
2024-05-01
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| Online Access: | https://doi.org/10.1038/s41598-024-60873-2 |
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| author | Cao Zhengzheng Yang Xiangqian Li Zhenhua Huang Cunhan Du Feng Wang Wenqiang Ni Xianjie Liu Shuai Li Zhen |
| author_facet | Cao Zhengzheng Yang Xiangqian Li Zhenhua Huang Cunhan Du Feng Wang Wenqiang Ni Xianjie Liu Shuai Li Zhen |
| author_sort | Cao Zhengzheng |
| collection | DOAJ |
| description | Abstract A two-dimensional unsteady seepage model for coal using a finite element program is developed, and the temporal variations of key factors such as water pressure and hydraulic gradient are analyzed in this paper. Additionally, the triaxial rock mechanical experiment and utilized pneumatic fracturing equipment on raw coal samples to investigate both hydraulic and pneumatic fracturing processes are conducted. Through these experiments, the relationship between pressure and crack formation and expansion are examined. The analysis reveals that the pore pressure gradient at the coal inlet reaches its peak during rapid surges in water pressure but diminishes over time. Conversely, the pore pressure gradient at the outlet side exhibits a gradual increase. Hydraulic fracturing is most likely to occur at the water inlet during sudden increases in water pressure. Besides, as the permeability of coal decreases, the duration for seepage stabilization prolongs due to the intensified pore pressure gradient resulting from sudden increases in water pressure. Moreover, an extended period of high hydraulic gradient further increases the risk of hydraulic fracturing. The experimental findings indicate that coal samples initially experience tensile failure influenced by water and air pressure. Subsequently, mode I cracks form under pressure, propagating along the fracture surface and becoming visible. The main types of failure observed in hydraulic and pneumatic fracturing are diametrical tensile failure, and the development of fractures can be categorized into three distinct stages, which contains the initial stage characterized by slight volume changes while water pressure increases, the expansion stage when pressure reaches the failure strength, and the crack closure stage marked by little or even decreasing volume changes during pressure unloading. The acoustic emission signal accurately corresponds to these three stages. |
| format | Article |
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| issn | 2045-2322 |
| language | English |
| publishDate | 2024-05-01 |
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| spelling | doaj-art-ca86a528918c4ef589cb179072b5fba82025-08-20T02:32:26ZengNature PortfolioScientific Reports2045-23222024-05-0114111610.1038/s41598-024-60873-2Fracture propagation and pore pressure evolution characteristics induced by hydraulic and pneumatic fracturing of coalCao Zhengzheng0Yang Xiangqian1Li Zhenhua2Huang Cunhan3Du Feng4Wang Wenqiang5Ni Xianjie6Liu Shuai7Li Zhen8International Joint Research Laboratory of Henan Province for Underground Space Development and Disaster Prevention, School of Civil Engineering, Henan Polytechnic UniversityInternational Joint Research Laboratory of Henan Province for Underground Space Development and Disaster Prevention, School of Civil Engineering, Henan Polytechnic UniversityHenan Mine Water Disaster Prevention and Control and Water Resources Utilization Engineering Technology Research Center, Henan Polytechnic UniversityHenan Mine Water Disaster Prevention and Control and Water Resources Utilization Engineering Technology Research Center, Henan Polytechnic UniversityHenan Mine Water Disaster Prevention and Control and Water Resources Utilization Engineering Technology Research Center, Henan Polytechnic UniversityHenan Mine Water Disaster Prevention and Control and Water Resources Utilization Engineering Technology Research Center, Henan Polytechnic UniversityState Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines, Anhui University of Science and TechnologyHenan Mine Water Disaster Prevention and Control and Water Resources Utilization Engineering Technology Research Center, Henan Polytechnic UniversityCollege of Safety and Emergency Management Engineering, Taiyuan University of TechnologyAbstract A two-dimensional unsteady seepage model for coal using a finite element program is developed, and the temporal variations of key factors such as water pressure and hydraulic gradient are analyzed in this paper. Additionally, the triaxial rock mechanical experiment and utilized pneumatic fracturing equipment on raw coal samples to investigate both hydraulic and pneumatic fracturing processes are conducted. Through these experiments, the relationship between pressure and crack formation and expansion are examined. The analysis reveals that the pore pressure gradient at the coal inlet reaches its peak during rapid surges in water pressure but diminishes over time. Conversely, the pore pressure gradient at the outlet side exhibits a gradual increase. Hydraulic fracturing is most likely to occur at the water inlet during sudden increases in water pressure. Besides, as the permeability of coal decreases, the duration for seepage stabilization prolongs due to the intensified pore pressure gradient resulting from sudden increases in water pressure. Moreover, an extended period of high hydraulic gradient further increases the risk of hydraulic fracturing. The experimental findings indicate that coal samples initially experience tensile failure influenced by water and air pressure. Subsequently, mode I cracks form under pressure, propagating along the fracture surface and becoming visible. The main types of failure observed in hydraulic and pneumatic fracturing are diametrical tensile failure, and the development of fractures can be categorized into three distinct stages, which contains the initial stage characterized by slight volume changes while water pressure increases, the expansion stage when pressure reaches the failure strength, and the crack closure stage marked by little or even decreasing volume changes during pressure unloading. The acoustic emission signal accurately corresponds to these three stages.https://doi.org/10.1038/s41598-024-60873-2Rock mechanicsHydraulic fracturingPneumatic fracturingPore pressureAcoustic emission |
| spellingShingle | Cao Zhengzheng Yang Xiangqian Li Zhenhua Huang Cunhan Du Feng Wang Wenqiang Ni Xianjie Liu Shuai Li Zhen Fracture propagation and pore pressure evolution characteristics induced by hydraulic and pneumatic fracturing of coal Scientific Reports Rock mechanics Hydraulic fracturing Pneumatic fracturing Pore pressure Acoustic emission |
| title | Fracture propagation and pore pressure evolution characteristics induced by hydraulic and pneumatic fracturing of coal |
| title_full | Fracture propagation and pore pressure evolution characteristics induced by hydraulic and pneumatic fracturing of coal |
| title_fullStr | Fracture propagation and pore pressure evolution characteristics induced by hydraulic and pneumatic fracturing of coal |
| title_full_unstemmed | Fracture propagation and pore pressure evolution characteristics induced by hydraulic and pneumatic fracturing of coal |
| title_short | Fracture propagation and pore pressure evolution characteristics induced by hydraulic and pneumatic fracturing of coal |
| title_sort | fracture propagation and pore pressure evolution characteristics induced by hydraulic and pneumatic fracturing of coal |
| topic | Rock mechanics Hydraulic fracturing Pneumatic fracturing Pore pressure Acoustic emission |
| url | https://doi.org/10.1038/s41598-024-60873-2 |
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