Study on Acoustic Emission Characteristics and Damage Evolution Law of Red Sandstones under Different Loading Rates

Abstract

Uniaxial compression experiments with different loading rates and acoustic emission tests were conducted to study the loading rate effects on the mechanical and acoustic emission characteristics of red sandstones. The mechanical and acoustic emission parameters of red sandstones were analyzed with varying loading rates. Furthermore, the red sandstone damage evolution model was established based on the acoustic emission cumulative ringing count. The results show that: (1) The elastic modulus decreases linearly with the increase of the logarithm of loading rate, while the peak strength generally shows a gradually increasing trend with the logarithm of the loading rate. (2) With the increase of loading rate, the AE event rate’s peak value increases gradually, and the cumulative number of AE events decreases. (3) The evolution law of the characteristic stresses determined by the AE event rate and cumulative AE event number is the same as that of the loading rate. That is, with the increase of the loading rate, it shows a gradually decreasing evolution trend. (4) The damage evolution model of red sandstone can better describe the damage evolution process of red sandstone. According to the evolution characteristics of damage variables, the damage evolution process of red sandstone can be divided into three stages: the initial damage stage, the damage stable development stage, and the damage accelerated stage. (5) The damage variable at the damage stress point can reflect the actual damage degree of rock, and the size of the damage variable is closely related to the initiation, propagation, and transfixion of microcracks inside the rock. When the loading rate is low, the damage degree of red sandstone at the damage stress is usually more prominent because the rock’s microcrack develops more fully.