Experimental study on resistivity and acoustic emission characteristics of red sandstone under cyclic loading
To investigate the evolutionary patterns of resistivity and acoustic emission in sandstone with varying saturation levels under different loading paths,particularly focusing on the resistivity characteristics during the quiescent phase of acoustic emission,we conducted uniaxial,constant amplitude cyclic loading,and increased amplitude cyclic loading tests on dry,semi-saturated,and saturated red sandstone specimens,respectively.The test results reveal a close correlation between resistivity changes and stress levels,offering insights into internal pore alterations and the compaction,initiation,and development of micro-cracks within the rock under loading conditions.As saturation increases,the quiescent period of acoustic emission before failure exhibits a significant extension.The variation in resistivity effectively mirrors the propagation of sub-critical cracks and the accumulation of internal damage within the rock during the quiescent phase of acoustic emission.Under distinct loading paths,the conduction mechanism in dry specimens is primarily skeleton conduction,demonstrating an overall upward trend.In contrast,saturated specimens predominantly exhibit water conductivity,leading to a downward trend in resistivity.During cyclic loading,when stress levels exceed 50％of the peak strength,the Kaiser effect in red sandstone with different saturations diminishes,giving way to the Felicity effect,accompanied by a declining Felicity ratio.
rock mechanicssaturationcyclic loading-unloadingresistivityacoustic emissionFelicity ratiofailure precursor
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