Experimental Study On The Changes Of Rock Apparent Resistivity Image Under Uniaxial Compression

Resistivity is one of the most important properties of rock,we can explore the relationship between rock resistivity change and stress by the study of rock resistivity variation characteristics under the condition of loading and unloading,It is of great significance to the research of process and mechanism in earthquake,volcanic eruption and large geological tectonic movement as well as the monitor and prediction,etc.We loaded and unloaded artificial rock sample under uniaxial compression in the laboratory in this paper,and made use of the resistivity tomographic imaging technology to cellect data of four Lines which are symmetric around the center,then studied the change trend of rock resistivity image with stress,and apparent resistivity variation characteristics of different depth,different location characteristics along with the change of stress,discussed the possible mechanism of rock resistivity image changes,and the possibility of changes of making use of the apparent resistivity image trend as earthquakes,volcanic eruptions and large-scale geological tectonic movement judgment.By means of two groups of artificial samples under uniaxial loading and unloading experiments,we obtained new knowledge:(1)For the non complete electrical homogeneous isotropic samples,the apparent resistivity changes exist differences in different parts: the amplitudes of apparent resistivity changes(The biggest difference is about 25 percent)and apparent resistivity change tendency(The apparent resistivity of some positions goes up,while the apparent resistivity of some positions goes down)of different location are different under the same stress condition,so the change characteristics of the apparent resistivity of some parts cannot represent the apparent resistivity change characteristics of the whole sample.(2)In general,the amplitude of apparent resistivity changes are different in different direction.The apparent resistivity variation amplitude of the vertical direction to the compression shaft is 7.5% lower than the vertical direction to the compression shaft,but compared to the two direction,the apparent resistivity variation amplitude of 45�direction shows no obvious regularity.(3)Although the apparent resistivity change of different parts exists differences under small stress,when the stress is greater than a certain value,it has the same trendency change.(4)On the whole,the apparent resistivity images exist obvious trend changes when the stress is greater than a certain value on the four directions,with the increase of stress,the apparent resistivity reduce region expand or contract,at the same time the apparent resistivity increase region contract or expand.Where,the apparent resistivity changes fastest when the depth is about 30-50 mm and the stress is about 5-12 MPa.In this paper,the preliminary research results,we can make use of the resistivity tomographic imaging technology to obtain the dynamic changes of the apparent resistivity images,which could provide important help to monitor and predict earthquake,volcanic eruption and large-scale geological tectonic movement and so on,but also needs more experiments,especially field experiments for further research work.