煤岩的纳微力学特性研究:以Pocahontas煤岩为例

Nanomechanics of coal: a case study of Pocahontas coal

煤岩的力学特性是煤炭开采设计及安全开发过程中要考虑的重要因素。尽管目前对煤岩的宏观力学性质已经有深入的研究,但是对煤岩纳微尺度力学性能测试及相应的力学参数测试却少有涉及。笔者采用原子力显微镜峰值力轻敲模式(AFM PeakForce Tapping mode)对美国阿帕拉契亚山脉地区Pocahontas煤岩进行试验,定量分析其纳微尺度形貌,纳微尺度的力学参数及相应的纳微尺度力学特性。研究表明:原子力显微镜峰值力轻敲模式可以定量测定纳微尺度煤岩的形貌、折减杨氏弹性模量(DMT)、黏附力、变形量和耗散能,并将测试结果以二维和三维的形式进行展示。该测试煤岩的DMT模量为10~14 GPa,黏附力约20 nN,最大变形量约12 nm,耗散能约3 keV。该结果表明:原子力显微镜峰值力轻敲模式可以用来测定煤岩纳微尺度力学参数,为研究煤岩的纳微力学特性及相应的煤岩力学数值模拟试验奠定基础。该试验方法不仅对研究纳微尺度煤岩破裂机理和解释煤岩瓦斯耦合作用(吸附等)而产生的力学现象有一定的指导作用,同时也为探索煤岩纳微力学特性提供一种新的研究方法和视角。

Mechanical properties of coal are fundamental for coal mining design and safe production. Even though mechanical properties of coal coring samples were studied extensively,nanoscale mechanical properties of coal were rarely reported previously. This work reported a quantitative measurements of mechanical properties of Pocahontas coal and its topography using atomic force microscopy (AFM) in PeakForce Tapping mode. Measurement results show that AFM PeakForce Tapping mode has the capacity to quantify the topography,DerjaguinMuller-Toporov (DMT) modulus,adhesion,deformations and dissipation energy of coal,which can also be represented via 2D and 3D figures.The DMT modulus,adhesion,maximum deformation and dissipation energy are approximately 10~ 14 GPa,20 nN,12 nm and 30 keV,respectively. This study demonstrates that AFM PeakForce Tapping mode can be used to investigate nanoscale mechanical properties of coal. The applied method thus provides a new way to understand the coal failure mechanism and the mechanical coupling mechanism of coal and methane interaction at nanoscale and to investigate the nanomechanics of coal.