Analysis of Energy Evolution and Acoustic Emission Characteristics of Rocks under Cyclic Loading and Unloading

This paper presents two experimental schemes, graded cyclic loading and unloading, and variable lower limit cyclic loading and unloading, to investigate the energy evolution and acoustic emission characteristics of rocks under different cyclic loading and unloading paths. The experiments were conducted using a WAW-300B microcomputer-controlled hydraulic servo universal testing machine and an AMSY-6 acoustic emission testing instrument. The evolution characteristics of both the acoustic emission ring count and energy count during the loading process were monitored in real-time, and the energy evolution and damage status of the rocks in each cycle were inferred from the stress–strain curve. The results show that: (1) under both types of cyclic loading and unloading paths, the elastic energy, dissipative energy, and total energy of the rocks are positively correlated with the number of cycles; (2) through comparative analysis of the energy dissipation rate and storage rate, it is concluded that the gradual accumulation of dissipative energy ultimately leads to rock failure; (3) based on the energy dissipation method, the study reveals that rock damage is more severe under the variable lower limit cyclic loading and unloading path; (4) under both types of cyclic loading and unloading, the acoustic emission ring count exhibits the Kaiser effect, and Felicity is negatively correlated with the number of cycles. This holds significance in comprehending the behavior of rock deterioration and forecasting its state of destruction.