脉冲荷载作用下煤体裂纹扩展研究

Study on Cracks Extension of Coal Under Pulse Load

针对低渗透性煤层抽采煤层气效率低的问题,基于断裂力学裂缝应力强度因子理论,通过RFPA-Dynamic数值模拟对煤体试件在模拟地应力作用下煤样裂缝周边应力和裂缝扩展规律进行了分析,采用高压电脉冲水力压裂技术和CT扫描技术对煤体进行了压裂试验并对产生裂缝的效果及裂缝的延展演化规律进行了研究。研究表明:原煤样质地坚硬,原生节理不发育;在静水压力和高压电脉冲冲击荷载作用下煤样易产生疲劳损伤破坏,煤样有贯穿性主裂纹和分支性裂纹产生,裂纹数量多,延伸长度长,宽度较宽;在高压脉冲波作用下裂纹尖端拉应力较大,出现了应力集中现象,裂纹易产生、易发展;表明高压电脉冲水力压裂煤体效果明显,方法有效,技术可行。

For low efficiency of extracting coalbed methane from low permeability coal seams, based on the theory of fracture stress intensity factor in fracture mechanics, we use RFPA-Dynamic numerical simulation to analyze the stress of coal samples＇ cracks and the laws of their crack propagation under simulative ground stress, and take high voltage electric hydraulic fracturing technique and CT scanning technique to make fracturing experiments of the coal samples, at the same time, we study the effect of cracks and the evolution laws of crack propagation. The results show that the texture of the raw coal is hard and the primary joints are undeveloped;under the action of hydrostatic pressure and the high voltage electric shock loading, coal samples are easy to be damaged, and there are penetrating main cracks and branch cracks in the coal samples with a higher number and longer extension length; while under the action of high-voltage pulse wave, the tensile stress of the crack tip is large, the stress concentration occurs, and the cracks are easy to produce and develop. which proves that fracturing effect of coal under the action of high-voltage pulse is obvious, so this method is reliable and this technique is workable.