Experimental Study on Uniaxial Compressive Fatigue Property of Cracked Rock-like Materials

To study the fatigue failure behavior of rocks with penetration cracks and reveal the fatigue damage and failure mechanism of rocks with defects, the cracked white cement specimens were prepared by pre-embedded strip method. The effects of various crack inclination angles and stress distribution on crack propagation was revealed by uniaxial compression fatigue test. The result showed that the fracture trajectory of the low cycle fatigue test was basically the same as that of the static test. The crack initiated from the crack tip and the crack angle was about 45°~75°, which could be considered as typical tensile Mode I fracture. The relationship between crack propagation length and the number of cycles revealed that the crack growth rate increased rapidly with the number of cycles and then underwent a stable phase and finally increased rapidly, which has been verified that the fatigue failure process went through three stages: initial plastic deformation stage, slow growth stage and rapid infiltration stage. According to the analysis of fatigue strain energy, energy required by the crack in the initiation stage was relatively large, and after the crack started to expand, the strain energy density remained basically unchanged, indicating that the energy required in the process of crack expansion tended to be stable. Comparing the strain energy density curves of different stress levels and stress ratios, the strain energy density gradually increased at larger stress levels and stress ratios, indicating that the sample could absorb more energy under larger stress levels and stress ratios, and the energy of crack initiation and propagation was faster.