It is significant to study electromagnetic emission of tensile cracking in rock for seismic science and rock mechanics. The electromagnetic emission during single crack propagation of 2-D rock test specimen is studied. A model to describe the electromagnetic emission during propagation process of single crack is proposed. Hertz array is introduced along the crack surface in this model. The distribution law of electromagnetic field is detected during the rock fracturing process. When ignoring the effect of phase difference, the electromagnetic field during the crack propagation is the spatial overlay of radiation by Hertz oscillators along the fracturing surface. The electromagnetic field created by Hertzian array may be one small part of the actual field. The issue discussed above is complex, systematically and microcosmically study should be done to describe the electromagnetic emission properties of rock material.
Since fracture coalescence study play an important role on understanding the basic failure mechanics of rock. Many extensive research have been done to understand and elucidate crack initiation, propagation, interaction and coalescence by using different materials and methods under different compressive direction since twenties century (Horii, 1985b, Tang, Lin & Wong, 2001, 2003, 2006, 2007). When a solid is fractured, work is performed to create new material surfaces in a thermodynamically irreversible manner. In Griffith's theory (Griffith, 1924) of ideally brittle materials, the work of fracture is spent in the rupture of cohesive bonds. The fracture surface energy, which represents the energy required to form a unit of new material surface, corresponds to a normal separation of atomic planes. The energy required for the rupture of atomic bonds is only a small portion of the dissipated energy in the fracture process. The plastic zone accompanying the crack tip is very small and the physical process of the crack tip has been the focus of much attention.
Electromagnetic wave will emerged with rock fracturing, this phenomenon is firstly observed in singular electromagnetic status during earthquake procedure (Warwick, 1982, Parrot, 1985, Fraser Simth, 1990, Adams, 1990). Singular electromagnetic phenomenon occurred during the recent big earthquake. The frequency of the electromagnetic VLF and ULF, and explanation is that electromagnetic field appeared due to redistribution, generation and movement of free charges.