Qi Xiaohan, Zhang Yong, Hou Shuangrong, Ning Tian, Lv Qiang
College of Safety Science and Engineering, Liaoning Technical University, Huludao, 125105, Liaoning, China.
Key Laboratory of Mine Thermodynamic Disasters and Control of Ministry of Education, Huludao, 125105, Liaoning, China.
Sci Rep. 2025 Jul 12;15(1):25178. doi: 10.1038/s41598-025-10602-0.
In order to investigate the effect of cyclic freeze-thaw of liquid nitrogen on the fracturing and permeability enhancement of water-rich coal seam, the conventional triaxial loading experiments and nuclear magnetic resonance (NMR) experiments after cyclic freeze-thaw of water-saturated coal samples were designed based on the HC-SPT-100 high-pressure triaxial experimental machine and nuclear magnetic resonance (NMR) analyzer with the raw coal from the coal mine in Wang zhuang as the experimental obje fissures ct to investigate the damage and seepage characteristics of the coal samples. Dried coal samples were used in the experiment for comparison purposes. The results showed that the peak stress of the coal samples showed a decreasing trend, the modulus of elasticity showed a decreasing trend, and the Poisson's ratio showed an increasing trend with the increase of the number of liquid nitrogen cyclic freeze-thaw. The maximum elastic energy accumulated in the water-saturated coal samples was always lower than that in the dry coal samples during the loading process. The coal samples before and after liquid nitrogen freeze-thaw showed strain concentration phenomenon, and the stress concentration phenomenon of the coal samples was more obvious after water-saturated treatment. The effect of liquid nitrogen freeze-thaw on the fracturing and permeability of the water-saturated coal samples was more significant, and with the increase in the number of liquid nitrogen freeze-thaw cycles, the initial permeability of dry coal samples increases from 3.02 × 10 µm to 6.06 × 10 µmwhile the initial permeability of saturated coal samples increases from 0.11 × 10 µm to 6.93 × 10 µm. The experimental results can provide theoretical guidance for gas extraction in water-rich coal seam with more water.
为了研究液氮循环冻融对富水煤层压裂增透的影响，以王庄煤矿原煤为实验对象，基于HC-SPT-100型高压三轴实验机和核磁共振分析仪，设计了饱水煤样循环冻融后的常规三轴加载实验和核磁共振实验，以研究煤样的损伤及渗流特性。实验采用干燥煤样作对比。结果表明，随着液氮循环冻融次数的增加，煤样的峰值应力呈下降趋势，弹性模量呈下降趋势，泊松比呈上升趋势。加载过程中，饱水煤样积累的最大弹性能始终低于干燥煤样。液氮冻融前后煤样均出现应变集中现象，饱水处理后煤样的应力集中现象更明显。液氮冻融对饱水煤样的压裂增透效果更显著，随着液氮冻融循环次数的增加，干燥煤样的初始渗透率从3.02×10μm增加到6.06×10μm，而饱水煤样的初始渗透率从0.11×10μm增加到6.93×10μm。实验结果可为水含量较多的富水煤层瓦斯抽采提供理论指导。
