A New Blasting Method for Crack Control by Using Charge Holders

断裂控制在岩石开挖和混凝土结构物局部爆破拆除中非常重要。在这项研究中，一种新的方法，实现高度的断裂控制，通过使用两个楔形空气腔的装药座，基于在钻孔中的冲击波相互作用所造成的动态效应，提出。通过实验研究了装药控制爆破裂缝的有效性。装药保持器在井眼内产生冲击波会聚效应，冲击波压力有效地作用在腔壁上。在孔洞顶点处的井壁上产生拉应力场，并引发受控裂纹。用电雷管作装药、有机玻璃板作应力波光学显示、砂浆试件和铅试件作爆破效果检测的模型试验结果如下。激光阴影照相显示，应力波从两个楔形空腔的顶点沿着裂纹控制方向向外传播。由冲击波和装药容器中气体的作用引起的爆炸效应引发裂纹，形成控制断裂面。装药容器在消除对井壁的损害和将受控裂缝驱动到更远距离方面是有效的。

Fracture control is very important in rock excavation and partial demolition of concrete structures with blasting. In this research, a new method for achieving high degree of fracture control by using charge holders with two wedge-shaped air cavities, based on the dynamic effects caused by the shock wave interactions in a borehole, are presented. The effectiveness of the charge holders for blast crack control is studied exprimentally. The charge holder produces shock converging effects in a borehole and the shock wave pressure acts effectively on the cavity walls. The tensile stress fields are produced on the borehole wall at the locations of the apexes of the cavities and controlled cracks are initiated. The following results were obtained from model experiments using a electric detonator as a charge, PMMA plate for optical visualizations of stress waves, mortar specimens and lead ones for examing blasting effcts. The photographs taken by the laser-shadowgraphy show that the stress waves propagate outward from the apexes of two wedge-shaped air cavities along the crack control directions. The blasting effects caused by the actions of the shock waves and gases in the charge holders initiate the cracks forming a control fracture plane. The charge holders are effective in eliminating the damage to the borehole wall and in driving the controlled cracks to greater distances.