爆炸荷载作用下预裂缝宽度对裂纹扩展的影响

Influence of pre-splitting crack width on crack propagation under blast loading

为探究预裂缝宽度对爆生、原生裂纹扩展的影响,基于焦散线系统和有限元数值模拟方法开展了一系列研究.结果表明:预裂缝可加强炮孔与预裂缝之间岩体破碎,阻碍爆生裂纹向保护岩体扩展,引导爆生裂纹向预裂缝两端扩展;在爆生气体膨胀作用下,预裂缝有闭合趋势,随着预裂缝宽度的增加,裂缝闭合用时增长,预裂缝面闭合后产生挤压应力峰值减小;爆炸荷载下,保留岩体内原生裂纹靠近炮孔一侧翼裂纹起裂时的应力强度因子小于背离炮孔一侧;随着预裂缝宽度的增加,原生裂纹的扩展长度与其两端应力强度因子均呈现先降低再上升的变化规律,原生裂纹迎爆侧起裂时的应力强度因子逐渐降低.

In order to investigate effects of pre-splitting crack width on crack propagation under blast loading,a series of studies have been carried out by digital laser dynamic caustics system and numerical simulation.The results show that the existence of pre-splitting crack benefits the damage of rock between blast center and the pre-splitting crack,prevents the propagation of blasting cracks to retained rock mass,and guides blasting cracks to propagate towards two ends of the pre-splitting crack.Under blasting gas loading,crack surfaces of the pre-splitting crack have a closure trend.With the increase of pre-splitting crack width,the closure time of crack surfaces becomes longer,and the peak of pressure stress between crack surfaces becomes smaller.Under blast loading,the stress intensity factor(SIF)of the wing crack in the retaining rock mass near the blast-hole is smaller than that on the side opposite the blast-hole.With the increase of pre-splitting crack width,the extension length and dynamic stress intensity factors of the primary crack show a trend of decrease first and then increase,and stress intensity factors of the wing crack in the retaining rock mass near the blast-hole decrease gradually.