Study on mechanical degradation mechanism of rock under seismic disturbance stress

Abstract

During the action of periodic seismic disturbance stress, the rock mass surrounding buried structures will show fatigue damage under the action of cyclic load. In order to explore the fatigue characteristics and mechanical degradation mechanism of this kind of rock mass under seismic stress wave, fatigue loading and uniaxial compression tests were carried out on gypsum rock samples. The conclusions are as follows: With the increase of seismic wave amplitude, the stress loading and unloading velocity gradually increases, and the opening of the stress-strain hysteresis loop gradually increases; With the increase of seismic wave frequency, the dip Angle of hysteresis loops gradually incline to σ axis, and the variation amplitude of hysteresis loops on ε axis decreases gradually. It shows that the greater the amplitude of seismic wave, the lower the frequency, the greater the damage of rock. Under the seismic wave disturbance, with the increase of the number of disturbances, the original cracks in the sample gradually spread and infiltrated, and the secondary cracks gradually developed, indicating that the physical and mechanical properties of the rock gradually deteriorated under the seismic wave disturbance. There is a strong correlation between the acoustic emission phenomenon of samples and the stages of the stress-time curve in the whole process of uniaxial compression. According to the acoustic emission characteristics, the stress-time curve in the whole process of uniaxial compression can be divided into four stages: initial loading stage, stable crack growth stage, unstable crack growth to failure stage, and post-peak stage. Compared with the sample before fatigue, the peak strain decreases significantly and the impact energy index increases significantly after fatigue loading. It indicates that some original cracks in the sample are compressed under seismic disturbance, the brittleness of the sample is enhanced, and the rockburst tendency is greatly enhanced.