Research on the Characteristics of Acoustic Emission Activities of Granite and Marble under Different Loading Methods

Abstract

At present, there is no corresponding standard for the engineering application of rock acoustic emission technology. To better apply acoustic emission technology to engineering practice, in this paper, the acoustic emission characteristics of different rock samples of marble and granite under uniaxial compression were analyzed by indoor acoustic emission test, the factors affecting the acoustic emission characteristics of rocks are studied, and the failure mechanism and damage characteristics of rock are discussed. The research contents include analyzing the curve fitting relationship between the acoustic emission event rate, the number of events, the stress time, and study of the similarities and differences of acoustic emission characteristics of marble and granite; analysis of damage characteristics of marble and granite based on acoustic emission parameters; by analyzing the relationship between the Felicity ratio of different rocks and the stress level during cyclic loading, the applicability of studying the Kaiser and Felicity effects of rocks; variation of acoustic emission event rate and rock peak intensity under different loading methods and loading rates. The results show that the acoustic emission of marble and granite has experienced the initial compaction zone, the rising zone, the peak zone, and the falling zone, and the two kinds of rocks have different acoustic emission phenomena in different stages, and the duration of each stage is also different; before the instability of the two kinds of rocks, there is a quiet period of acoustic emission, and the higher the rock strength, the longer the duration of this quiet period, which means that the calm period can be used as a precursor feature of rock mass instability for disaster prediction; during the cyclic loading process of rock, the damage development law is divided into three stages: initial stage, stable stage, and instability stage. When the Kaiser effect did not appear for the two rock stresses before 20%, between 20% and 70% of the peak strength, the Kaiser effect is obvious. When the stress exceeds 80% of the peak value, the Kaiser effect fails, and the Felicity effect appears; the variation of the loading rate affects the variation of the acoustic emission event rate, and the increase of the loading rate leads to aggravated rock damage. The theoretical stress-strain curve can reasonably reflect the actual stress-strain characteristics of rock by combining the number of acoustic emission events with the rock damage model. The results are consistent with the acoustic emission test, which verifies the inevitable relationship between acoustic emission and damage to the rock.