Developments of Fracture Plane Control Method and Fragmentation Control Method by High-Precise Time Control Blasting

爆破中的断裂控制在地下开挖和拆除混凝土结构中是非常重要的。它被要求在使用最少炸药的情况下产生最大的爆破效果。因此，了解爆破过程中应力波、气体和裂隙的动态行为，对于发展裂隙面控制方法具有重要意义。为此，采用高速摄像的方法进行了模型试验。建立了以Ar离子激光为光源的纹影系统，对爆破过程中的应力波和裂纹进行了可视化。利用高速摄像系统对动态断裂过程中的可视化图像进行了记录。在这项研究中，提出了一种利用装药孔附近有凹槽的圆形孔来实现对断裂面的高度控制的导孔方法。通过PMMA试件和砂浆试件的模型试验验证了该方法的有效性。…在实验中，还通过应变测量和裂纹速度测量，观察了爆破过程中应力波和裂纹的动态行为。利用纹影系统和高速摄像系统进行的模型试验为了解爆破过程中应力波和裂隙的动态行为提供了许多有用的信息。实验获得的视频图像显示了应力波的传播和沿控制断裂面扩展的裂纹的动态行为。开槽导向孔法能有效地控制裂隙面的方位，并将裂缝沿控制裂隙面驱向更远的距离。该方法可应用于时间控制爆破，实现断裂面控制和块度控制。从可视化图像可以明显看出，二次裂纹是由应力波与受控断口相互作用而产生的。较少

Fracture control in blasting is very important in underground excavation and demolition of concrete structures. It is required to produce a maximum of blasting effects with the use of a minimum of explosives. Therefore, it is valuable to obtain an understanding of the dynamic behavior of stress waves, gases and cracks in the blasting process for the development of fracture plane control methods. For the purposes, the model experiments were carried out by means of high-speed videography. A schlieren system using an Ar-ion laser as a light source was set up for visualization of stress waves and cracks in the blasting process. A high-speed video camera system was used to record visualization images in the dynamic fracture process. In this study, a guide hole method utilizing a circular hole with notches near a charge hole for achieving high degree of fracture plane control was presented. The effectiveness of the method was demonstrated by model experiments using PMMA and mortar specimens. … More In the experiment, the dynamic behavior of stress waves and cracks in blasting process was also observed by means of strain measurements and crack velocity measurements. The following conclusions are obtained.The model experiments using the schlieren system and the high-speed video camera system provide much useful information to understand the dynamic behavior of stress waves and cracks in a blasting process. Video images obtained from the experiments showed the propagation of stress waves and the dynamic behavior of cracks propagating along the control fracture plane. The guide hole method with notches is effective in controlling the orientation of the fracture plane and in driving the cracks along the control fracture plane to greater distances. This method can be applied to time controlled blasting for achieving fracture plane control and fragmentation control. It becomes evident from visualization images that the secondary crack is initiated by the interaction of stress waves with controlled fracture surface. Less