Characteristic Point of the Relatively Quiet Period for Limestone Failure Under Uniaxial Compression

Abstract

Abstract In view of the precursory characteristic point of limestone failure under uniaxial compression, the underlying mechanisms are not sufficiently clear. Experimental studies examining the acoustic emission (AE) characteristics of the complete limestone failure process have been carried out under uniaxial compression. The experimental results, including accumulative AE counts, the curve of stress and strain, AE rate and stress-time, AE energy rate and stress-time, AE amplitude-time, and AE frequency- time were obtained in detail. The experimental results clearly indicate that AE activities of the samples were generated during the entire process of uniaxial compression. However, the abnormal AE activities appeared in the late stage of the unstable crack propagation phase. These parameters, such as the AE rate, AE energy rate, AE amplitudes, and AE frequencies, were observed to decrease sharply after a relatively quiet period. However, the accumulative AE counts remained at nearly constant values. Stress passed through the quiet period quickly before the peak stress, where the AE activities were enhanced. The AE rate increased suddenly and AE energy rate rose rapidly when the stress reached the peak stress of the samples. As a consequence, the relatively quiet period could be used as the precursory information of rock failure, and the starting point of a relatively quiet period could be predicted as a precursory characteristic point of rock failure. The start point of the relatively quiet period was approximately located in the range of 88 to 98 % of the peak stress.