Investigation of Damage and Deformation Characteristics of Soft Red Mudstone Using Acoustic Emission Parameter Analysis under High-Cycle Cyclic Loading Conditions
Investigation of Damage and Deformation Characteristics of Soft Red Mudstone Using Acoustic Emission Parameter Analysis under High-Cycle Cyclic Loading Conditions
A high-cycle cyclic loading test was conducted using acoustic emission(AE)monitoring techniques to investigate the damage and deformation characteristics of soft red mudstone under different upper stress limits and loading frequencies.Based on the analysis of AE parameters,the influence of dynamic stress limits and loading frequency on the damage and crack propagation patterns of the red mudstone were systematically studied.The results showed that when the dynamic stress limit was lower than the critical dynamic yield stress value,the mudstone underwent a process of initial shear contraction followed by slow shear dilation.The development of microcracks in rock samples and the expansion of clay minerals gradually became dominant.Low-frequency AE signals were generated during the static loading phase,while high-frequency AE signals primarily occurred during the cyclic loading phase.Moreover,with an increase in loading frequency,the proportion of ultra-high-frequency AE signals exceeding 300 kHz gradually increased.The cracks produced in the red mudstone under cyclic loading were primarily tensile cracks.Among them,shear cracks in the first stage(Stage Ⅰ)accounted for a relatively larger proportion compared to other stages.However,the proportion of shear cracks decreased as the dynamic stress amplitude decreased or the loading frequency increased.Due to the self-healing effect of cracks,the damage-induced cracks caused by dynamic loading were gradually repaired within the mudstone.Additionally,as the elapsed time increased,the Kaiser effect associated with AE gradually diminished and even disappeared.
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