Study on Acoustic Emission Characteristics of Muddy Limestone under Brazilian Splitting Tests at Various Loading Rates

To explore the correlation between Acoustic Emission(AE) and fracture response characteristics and loading rates in the failure and instability of muddy limestone, Brazilian splitting tests combined with acoustic emission measurements were conducted on muddy limestone specimens at various loading rates, mechanical parameters, AE phenomena, and fracture response features of muddy limestone were analyzed. The results demonstrate that the peak strength, elastic modulus, peak strain, and residual strength of the rock specimen exhibit stage-dependent loading effects. The peak strength and elastic modulus initially increase and then decrease with increasing loading rate, whereas the residual strength increases as the loading rate increases. The evolution patterns of AE parameters at various loading rates are consistent, exhibiting phased growth characteristics. As the loading rate increases, distinct AE signals occur earlier, cumulative ring count and cumulative energy first increase and then decrease, with the energy release characteristics transitioning from isolated event type to cluster event type. The loading rate has a significant effect on failure mode and fracture form. With increasing loading rate, rock specimens gradually evolve from shear-tensile failure dominated by shear-tensile mechanisms to tensile failure. At low loading rates, ample deformation and damage occur within the rock, resulting in more severe fragmentation. The AE b transitions from a pattern of first rising then fluctuation and finally falling(0,05~0.50mm/min) to a pattern of initial decreasing, followed by fluctuation and finally falling(1.00mm/min).