Experimental study on the influence of biaxial confining pressure on dynamic cracks and its interaction with blasting stress wave

Abstract

The influence of the biaxial confining pressure on the stress field at the dynamic crack tip is studied, and the changes of each stress component with the change of the confining pressure are analyzed. And the mechanism of irregular caustic spot on the crack path is also illustrated. A dynamic caustics system with PMMA material is used to better observe the whole process of interaction because PMMA is a transparent rock-like material. There are two groups, with and without a confining pressure. The experimental results are in good agreement with the theoretical results. The experimental results show that the biaxial confining pressure greatly shortens the overall time from the initiation to arrest of the blasting crack, and limits the scope of the blasting effect. The peak stress intensity factor (SIF) of the crack tip during wave propagation is generally higher when a biaxial confining pressure is applied. The biaxial confining pressure also reduces the effect of blasting stress wave and blasting gas on cracks. The P-wave and S-wave in the blasting stress wave cause different deformation of the crack surface, thus changing the propagation path of the light and converging the light in both symmetrical and unsymmetrical ways. When the crack path is affected by stress waves reflected from different directions, caustic spots of different shapes will appear on the entire fracture path.