Experimental Study on Fatigue Life of Gypsum-Like Rock Under Uniaxial Compression with Different Loading Frequencies

When the surrounding rock is subjected to cyclic loading, its physical and mechanical properties show fatigue damage properties under the action of periodic engineering, disturbance stress. In this research, the fatigue life test of gypsum-like rocks was carried out by using a dynamic fatigue testing machine. During the cyclic loading process, the maximum fatigue loading times increased with the increase of frequency, but the fatigue life increased first and then decreased with the increase of frequency. The stress-circumferential strain hysteresis loop of the specimen tilts to the ε axis at low frequency and to the σ axis at high frequency, which indicates that the lower the frequency, the greater the damage of the specimen in one cycle. The strain of the sample increases with time, and the action mechanism of fatigue loading can be divided into three stages: initial stage, stable development stage, and failure stage. It was observed that under the conventional uniaxial compression test conditions, the failure mode of specimens is shear failure. The end effect of specimens after fatigue loading is more obvious, and the failure modes are mainly the fatigue damage of near vertical cracks. After fatigue loading, the specimen has obvious fatigue damage. With the expansion and penetration of the internal crack, the width, length and coverage of the crack gradually increase, leading to the continuous deterioration of the physical and mechanical properties.