He Haixia, Wang Kai, Pan Jienan, Wang Xianglong, Wang Zhenzhi
School of Resources & Environment, Henan Polytechnic University, Jiaozuo 454000, China.
Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region, Jiaozuo 454000, Henan, China.
ACS Omega. 2022 May 5;7(19):16728-16739. doi: 10.1021/acsomega.2c01269. eCollection 2022 May 17.
It is important to explore the changes in coal pores in response to triaxial compression and shear deformation for coal mine gas drainage and efficient coalbed methane mining. To study the variation in coal pores depending on stress, first, a mechanical analysis was carried out, and then the characteristics of coal samples before and after triaxial compression were quantitatively analyzed combined with low-temperature nitrogen adsorption experiments. The compressive strength of the coal samples with a high elastic modulus is significantly greater than that of coal samples with a low elastic modulus. Sihe coal samples with a larger elastic modulus experienced higher peak stress and strain during compression than those from the Chengzhuang Mine with a smaller elastic modulus. With the exception of the coal sample from the Chengzhuang Mine with a confining pressure of 15 MPa, the peak strength and axial strain of the coal samples gradually increased with an increase in confining pressure. The larger the elastic modulus, the greater the axial strain. After triaxial compression, pores with diameters ranging from 2 to 5 nm exhibited a significant change. After the compression of coal with a high elastic modulus, the pore volume and pore specific surface area decreased with the increase in confining pressure, by 60.7 and 59.7%, respectively (compared with raw coal). The complex pore structure consisting of mesopores and macropores (>11 nm) became simpler. The volume and specific surface area of the pores of the coal samples with a low elastic modulus first increased, then decreased, and then increased again with the increase in confining pressure, and after compression, the roughness and complexity of macropores of coal samples are greater than those of micropores. The changes induced in the coal samples of the two mining areas in response to compression differ, which are related to the mechanical properties of the coal bodies.
研究煤矿瓦斯抽采及高效煤层气开采中煤孔隙在三轴压缩和剪切变形作用下的变化规律具有重要意义。为研究煤孔隙随应力的变化情况，首先进行了力学分析，然后结合低温氮吸附实验对三轴压缩前后煤样的特性进行了定量分析。高弹性模量煤样的抗压强度明显高于低弹性模量煤样。弹性模量较大的寺河煤样在压缩过程中的峰值应力和应变高于弹性模量较小的成庄矿煤样。除成庄矿围压为15 MPa的煤样外，煤样的峰值强度和轴向应变随围压增加而逐渐增大。弹性模量越大，轴向应变越大。三轴压缩后，直径为2～5 nm的孔隙出现显著变化。高弹性模量煤压缩后，孔隙体积和孔隙比表面积随围压增加而减小，分别减小了60.7%和59.7%（与原煤相比）。由中孔和大孔（>11 nm）组成的复杂孔隙结构变得更简单。低弹性模量煤样孔隙的体积和比表面积随围压增加先增大，后减小，再增大，压缩后煤样大孔的粗糙度和复杂性大于微孔。两个矿区煤样压缩后的变化不同，这与煤体的力学性质有关。
