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Abstract The test equipment of litho-electric experiment under loading was designed. Through experiments a convenient and effective coupling electrode material，the over-saturated clay，was found. The changing rule of the electrical conductivity of main rock specimens in the coal-bearing strata in Huaibei and Huainan Coalfield(HHC) in relation to changes of current，voltage and stress was also studied experimentally. And resistivity-stress regression equations of different rock masses were fitted with much high correlation coefficient. Research results show that：(1) within the range of elastic deformation，the electrical conductivity of the coal-bearing rocks in HHC increases with the enhancive stress，i.e. the rock resistivity decreases with increasing stress；(2) the electrical conductivity of the weak sandy mudstone is more susceptible to the variation of stress than the hard sandstone and diorite；(3) there exists a good correlation between the resistivity of the rock and stress；(4) under certain conditions of stress，the electrical conductivity of the weak sandy mudstone will be enhanced with the increase of the voltage and the current，thereby the resistivity is reduced，while the electrical conductivities of the hard sandstone and diorite are to some extent unaffected by voltage and current. In measuring and testing released zone of surrounding rock of roadway by high density resistivity method in mines in HHC，measured apparent resistivity section or resistivity inversion section is combined with the resistivity-stress regression equations obtained from litho-electric experiment to analyze the development of released zone of surrounding rock of roadway. The technology has been successfully applied to engineering practice.
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Received: 28 January 2010
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