Energy Dissipation-Based Fatigue Damage Evolution of Rocks Subjected to Uniaxial Cyclic Compression Based on Electromechanical Impedance Method

The fatigue damage evolution of rocks subjected to cyclic loading and unloading has always been a hot spot that receives worldwide attention in the field of rock mechanics. Recent studies that rely on advanced nondestructive testing (NDT) techniques enable accurate monitoring and assessment of the dynamic damage in cyclically loaded rocks, and well contribute to revealing the complicated failure mechanism. These works are critical to ensure safe underground tunnelling and mining activities. As a promising NDT technique, the electromechanical impedance method (EMI) has been successfully applied to many aspects in structure health monitoring. In this paper, the EMI method was extended to measuring the rock fatigue damage. Firstly, uniaxial cyclic compression tests with increasing amplitude were performed on three types of cylindrical rock specimens, including sandstone, granite and carbonaceous shale. The varying mechanical properties and energy conversion characteristics were analyzed. In particular, the damage evolution characterized by elastic energy dissipation was determined. Concurrently with cyclic tests, conductance signatures in response to two excitation modes of the surface-bonded piezoelectric transducers were collected, and the spectral localized and overall variations were analyzed. It is discovered that the resonant frequency shift and the statistic metric MAPD within the transverse mode-dominated frequency range could accurately indicate the rock fatigue damage. This research sufficiently confirms the effectiveness and reliability of the EMI method in quantifying the accumulative damage of different rocks under uniaxial cyclic loading and unloading.