Dynamic directional fracture of dual-borehole blasting is very vital to the rock fragmentation and final contour of some projects, such as the tunnel and slope. In this paper, a rock-like material, polymethyl methacrylate (PMMA), is utilized to explore the effects of borehole distance d, delayed time t_d, and guide hole type on crack propagation behavior under dual-borehole blasting through numerical simulations. To improve the deficiency of constitutive model and the post-failure response of brittle material and reduce the mesh dependency, a coupling scheme of Johnson-Holmquist (JH-2) model, failure criterion, and crack softening failure model is adopted here. First, the crack propagation results of single-borehole blasting well reproduced inner and outer actions of blasting, which proved the reliability of this scheme. For the dual-borehole blasting, it was found that the increase of borehole distance indeed penalized the crack coalescence and the length of crack produced at the common guide hole. Compared with the common guide hole, the grooved guide hole at d = 30 cm contributes more crack coalescences, which is independent of the delayed time; at d = 40 cm, the longer cracks are produced at grooved guide hole than common one and the crack coalescence is related to the delayed time. The grooved guide hole was more conducive to the coalescence and lengthening of crack. More importantly, the crack coalescence manner showed mutual, direct, and indirect ones, and two manners could coexist in one model. In addition, guide hole also could enrich the crack coalescence manner. Lastly, the crack stagger depends on the change of tensile stress at one crack tip into the compressive one at another one; the crack coalescence indicates tensile stress fields of two crack tips have no mutual influence.

双孔爆破动态定向断裂对隧道、边坡等工程的岩石破碎和最终轮廓至关重要。在本文中，利用类岩石材料聚甲基丙烯酸甲酯 (PMMA) 来探索钻孔距离d、延迟时间t _{d 的影响}, 并通过数值模拟引导孔类型对双孔爆破裂纹扩展行为的影响。为了改善本构模型和脆性材料失效后响应的不足，降低网格依赖性，本文采用Johnson-Holmquist（JH-2）模型、失效准则和裂纹软化失效模型的耦合方案。首先，单孔爆破裂纹扩展结果很好地再现了爆破的内外作用，证明了该方案的可靠性。对于双孔爆破，发现孔距的增加确实有损于共同导向孔处产生的裂纹合并和裂纹长度。与普通导向孔相比，d处的带槽导向孔 = 30 cm 有助于更多的裂缝聚结，这与延迟时间无关；在d  = 40 cm 处，沟槽导向孔处产生的裂纹比普通导向孔长，裂纹合并与延迟时间有关。带槽的导向孔更有利于裂纹的聚结和拉长。更重要的是，裂缝聚结方式表现为相互的、直接的和间接的，两种方式可以在一个模型中并存。此外，导孔还可以丰富裂纹的聚结方式。最后，裂纹交错取决于裂纹尖端的拉应力变为另一裂纹尖端的压应力；裂纹合并表明两个裂纹尖端的拉应力场没有相互影响。