Abstract：There are many different mechanical phenomena in deep rock engineering comparing with shallow- buried rock engineering. To research the microcrack of deep rock，the relative size and stable conditions of microcracks are analyzed；and the microcracks can be classified into latent crack and overt crack with the reference of the static and variable states. The mechanical phenomena of nucleation and expansion of deep rock microcracks are studied. Based on the basic theory of electrochemistry，the interface properties of rock microcrack and its solution are analyzed；and the electric double layer structure composed of rock microcrack and solution is studied. The change law of the electric double layer capacitance and its macroscopic impedance due to expansion of rock crack are researched. The relations between the specific parameter of rock AC impedance spectroscopy and the nucleation and expansion of rock microcrack are investigated. The result shows that the electrochemical method is effective to test expansion of rock crack. It is a new method to study rock fracture behavior.
