In this study, the uniaxial compression test and PFC ^2D numerical simulation were carried out on the artificial rock specimen with T-shaped prefabricated fractures. The effects of the lengths l₁, l₂ of the main fractures, the length l₃ of the secondary fracture, and the angle β between the secondary fracture and the loading direction on the uniaxial compressive strength and crack evolution law of specimen were studied. The research results show that the change of l₁, l₂ and β has obvious effect on the compressive strength and crack growth of the specimen, but the change of l₃ has little effect on the compressive strength of the specimen. When l₃ = 40 mm and l₁ ≠ l₂, the angle β influences on the crack propagation and failure mode of the specimen.

Dynamic biaxial compression tests and Particle Flow Code numerical simulations of the cement mortar specimens with a single joint were carried out to study the mechanical properties and crack evolution of artificial rock samples with a single joint. The effects of lateral stress 𝜎2, loading rate V , the dip angle β (between the vertical loading direction and the joint) on the biaxial compressive strength 𝜎 _b, and the evolution lawof crackwere investigated. Test results showed that; (1) when both the dip angle β and the loading rate V remained unchanged, the biaxial compressive strength 𝜎 _b increased with the increase in the lateral stress 𝜎2, while 𝜎2 had no obvious effect on the crack evolution law; (2) when both the dip angle β and the lateral stress 𝜎2 were kept unchanged, the loading rate V had an insignificant effect on the biaxial compressive strength 𝜎 _b and the crack evolution law; (3) when both the lateral stress 𝜎2 and the loading rate V were constant, the biaxial compressive strength 𝜎 _b decreased first and then increased with the increase in the dip angle β ; however, the dip angle β did not significantly affect the crack evolution law. The conclusions obtained in this paper are presented for the first time.

In this study, the uniaxial compression test and the numerical simulation of the twodimensional particle flow code (PFC2D) were used to study the mechanical properties and failure laws of rock masses with parallel cracks. The experiment considers the influences of crack length (��º, crack angle (��1, ��2), and numerical changes in the rock bridge length (ℎ) and bridge angle (��) on failures of rock-like specimens. The results indicate that the uniaxial compressive strength (UCS) of the rock-like specimens with parallel cracks decreases with increasing �� under different �� values. The smaller angle between the preset crack and the loadinging direction (��) resulting in higher UCS. In addition, a larger ℎ results in higher UCS in the specimen. When ��1 or ��2 is fixed, the UCS and elastic modulus of the specimen show an ‘M’ shape with an increase in ��. Moreover, the crack growth or failure mode of samples with different �� values is similar. When ��1 or ��2 is small, the failure of the specimen is affected by the development and expansion of wing cracks. If one of ��1 and ��2 is large, the failure of the specimen is dominated by the expansion and development of the secondary cracks which is generated at the tip of the prefabricated crack. Furthermore, when the angle between the prefabricated crack and the loading direction is ��1 = 0°, the rock bridge is less likely to reach penetration failure as ℎ increases. Secondary crack connections between the prefabricated cracks occur only when �� is small.
When �� ¡ 30°, the failure mode of the specimen is crack tip cracking which leads to penetration failure of the specimen, or the overall splitting failure.