低频振动激励含瓦斯煤孔裂隙变化特征研究

Study on change characteristics of gas-containing coal pores and fissures under low frequency vibration excitation

为了探明低频振动激励对煤体孔裂隙特征的改造机制,采用工业显微CT扫描和低场核磁共振设备开展低频振动前后煤体孔裂隙扫描实验,测试不同振动激励频率下煤体的孔裂隙特征参数。研究结果表明:低频振动激励前后煤体的裂隙度和孔隙度均呈现上升趋势,煤岩内部裂隙发育特征呈现一致性,振动激励的改造效果集中在对大尺寸裂隙的改造,即对原生孔缝发育的改造效果更好;低频振动激励能增加煤体内部结构的复杂性与非均质性,能有效促进孔裂隙的发育;低频振动激励对煤体孔隙改造作用集中在煤体的中孔与大孔,且当激振频率处在共振频带时,上述规律均显著增强。研究结果可为含瓦斯煤的孔裂隙改造提供参考。

In order to explore the transformation mechanism of low-frequency vibration excitation on the characteristics of coal pores and fissures,the industrial micro-CT scanning and low field nuclear magnetic resonance(NMR)equipment were used to conduct the scanning experiments of coal pores and fissures before and after low-frequency vibration,and the characteristic parameters of pores and fissures in coal under different vibration excitation frequencies were tested.The results show that both the fissure degree and porosity of coal present the upward trend before and after low-frequency vibration excitation,and the development characteristics of internal fissures in coal rock present the consistency,the transformation effect of vibration excitation focuses on the transformation of large-sized fissures,which means that the transformation effect on the development of primary pores and fissures is better,the low frequency vibration excitation can increase the complexity and heterogeneity of the internal structure of coal,and effectively promote the development of pores and fissures,the transformation effect of low-frequency vibration excitation on coal pores is concentrated in the middle and large pores of coal body,And when the excitation frequency is in the resonance frequency band,the above rules are significantly enhanced.The research results can provide reference for the transformation of pores and fissures in gas-containing coal.