对称表面动载下有限块体的破裂过程

FRACTURE PROCESS OF A FINITE BLOCK UNDER SYMMETRIC DYNAMIC LOADINGS

实验表明,受对称布置的表面爆炸载荷的脆性块体,会在通过载荷作用点连线的某一平面上破裂。为解释这一现象并进一步探讨利用类似方法破碎岩块的可能性,本文介绍了应用弹性动力学理论建立的计算模型以及所进行的动光弹和混凝土块模型试验。研究结果表明:在所述载荷条件下,应力波特别是自由界面反射的拉伸波对块体的破碎起重要作用;由于多向拉应力集中,在块体加载端面梭边中部最易产生径向裂隙,此后在侧面反射波的作用下裂隙延伸,与中部可能存在的裂纹贯通,从而将块体破开;对称加载使应力波在块体内多次叠加有利于块体充分破碎。

Tests showed that a brittle block subjected to two point explosion loadings at two symmetric surfaces could fracture along a plane passing through the line connecting the two loading points. This paper discusses the computational model based on the elastic dynamical theory as well as the dynamic photoelastic experiment and concrete model tests, which could be used to explain this phenomenon and the possibility of breaking rock boulders by this method. The results from this study indicat that in the described loading conditions, the stress waves, especially the tensile stress wave reflected from the free face, play an important role in breaking the block. Because of existence of multi - dimensional tensile stress concentration, radial cracks tend to appear at the edges of the loading surface. Then, under the influence of reflected wave from the lateral free face, these cracks would extend and join in the center of the block, then finally split the block. The symmetric loading could cause superposition of stress waves and make the block easily fully fractured.