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Visualization and analysis of stress waves in blasting processes by a laser-shadowgraph method

利用激光阴影图方法对爆破过程中的应力波进行可视化和分析

基本信息

批准号：
05650964
负责人：
NAKAMURA Yuichi
金额：
$ 1.34万
依托单位：
Yatsushiro National College of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

Dynamic fracture control in blasting is very important in underground excavation and demolition of concrete structures. It is necessary to examine the dynamic mechanism of stress waves, gases and cracks in blasting process for achieving high degree of fracture control. In this research, experimental results on visualization of stress waves in blasting by a laser-shadowgraph method are presented and a new method for fracture controlled blasting is suggested. The shadowgraph system using a Q switched ruby laser as a light source is set up. The system enables us to get a giant pulse beam at a desired time and to obtain the high spatial and time resolved instantaneous visualization photographs.Experiments are made on stress waves interacting with a circular hole, a circular arc-shaped free surface and a free surface with 90ﾟ corner. Model experiments are casrried out with the PMMA plate of 20 mm in thickness as a transparent material. From these experiments, the following results are obtained. The shadowgraphs show the behavior of reflected waves, deformations of the circular hole and the generation of converging shock waves in the hole by interaction of incident waves with the hole. In the case of the hole with two notches along the prpagation direction of the incident waves, it can be seen that the well-known shadow spots are produced in the vicinity of the notches. From the fact, it might be expected that utilization of the circular hole with notches is effective as the guide hole technique for achieving fracture control.

爆破动态断裂控制在混凝土结构地下开挖和拆除中具有重要意义。为了实现高度的断裂控制，有必要研究爆破过程中应力波、气体和裂缝的动力学机制。本文介绍了用激光阴影法对爆破应力波进行可视化的实验结果，为断裂控制爆破提供了一种新的方法。建立了以调Q红宝石激光器为光源的阴影成像系统。该系统能够在所需时间获得巨型脉冲光束，并获得高空间分辨率和时间分辨率的瞬时可视化照片。分别在应力波与圆孔、圆弧形自由面和90ﾟ拐角自由面的相互作用下进行了实验。用厚度为20 mm的PMMA板作为透明材料进行了模型试验。从这些实验中，获得了以下结果。阴影图显示了反射波的行为、圆孔的变形以及入射波与孔的相互作用在孔内产生会聚冲击波。在沿入射波传播方向有两个凹口的孔的情况下，可以看到在凹口附近产生了众所周知的阴影光斑。由此可见，利用带凹槽的圆孔作为导孔技术是实现压裂控制的有效途径。