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可控电脉冲作用煤岩冲击损伤演化特征研究

Study on impact damage evolution characteristics of coal rock under controlled electric pulse action

  • 摘要: 可控电脉冲技术能够有效改善煤岩孔裂隙结构,提高煤层透气性,在煤层增透领域具有较好的应用前景。采用自主研制的可控电脉冲致裂煤岩增透试验系统,开展电容分别为2、4、6、8 μF条件下煤岩试样的冲击测试,研究煤岩体内冲击波传播规律及结构损伤特征,并利用扫描电镜和低温N2(77 K)吸附法对煤样的微观结构进行测试分析。结果表明:可控电脉冲作用煤岩冲击压力持续了数微秒,且在煤岩试样相同位置产生的冲击波峰值压力随电容的增大而显著增大,峰值压力最大增加6.23倍;电容为2、4、6、8 μF条件下可控电脉冲作用煤岩试样产生的裂纹密度分别为1.407 72、2.064 64、9.123 04、16.700 19 m-1,煤岩试样裂纹密度与电容之间呈指数函数关系;随着电容的增大,煤样中产生了大量的新生孔裂隙,煤样的总孔容和比表面积最大分别增加了2.3、3.6倍,孔隙分形特征明显,可控电脉冲击穿煤样后对其微观孔裂隙结构具有明显的改善作用,可为煤中瓦斯运移提供良好的通道。

     

    Abstract: The controlled electrical pulse technology can effectively improve the pore and fracture structure of coal and rock, and enhance the permeability of coal seams. This technology has a promising application prospect in the field of coal seam enhancement. In this study, a self-built controlled electric pulse cracking and enhancing permeability of coal rock test system is utilized to carry out impact test of coal and rock samples under varying capacitance conditions of 2 μF, 4 μF, 6 μF and 8 μF. The shock wave propagation laws and structural damage characteristics of coal and rock are studied. Additionally, the microstructure of coal samples is examined and analyzed using scanning electron microscopy and low-temperature N2 (77 K) adsorption methods. The results show that the duration of the shock pressure exerted on the coal rock by controlled electric pulse action is several microseconds. The peak pressure of the shock wave generated at the same position of the specimen increases significantly with the increase of capacitance, and the maximum peak pressure increases by 6.23 times. The crack densities of coal rock specimens under controlled electric pulse action with capacitance of 2 μF, 4 μF, 6 μF and 8 μF are 1.407 72 m-1, 2.064 64 m-1, 9.123 04 m-1, and 16.700 19 m-1, respectively. These datasets indicated that there is an exponential function correlation between the crack density of coal rock specimens and the capacitance. With the increase of capacitance, a large number of pores and fracture appear in the coal body. The total pore volume and specific surface area of the coal body increase by 2.3 times and 3.6 times, respectively, and the pore fractal characteristics are significant. The controlled electric pulse has a significant improvement effect on the micro-pore and fissure structure of coal after penetration, thereby providing a good channel for the migration of coal seam gas.

     

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