Experimental and simulation study of fissure and hole effect on sandstone failure

Abstract

Rock masses often contain hole and fissures, which significantly weaken their mechanical properties. This study explores the influence of fissures angle on these properties. Uniaxial compression tests were conducted on laboratory sandstone samples containing hole and fissures. Particle flow code (PFC2D) simulations were utilized to analyze crack propagation and its effect on rock behavior. The research results indicate that cracks have a weakening effect on the compressive strength of rock.When the fracture direction aligns closely with the principal stress direction, the fracture's presence minimally impacts the sample's strength. When the fracture direction is oblique to the principal stress direction, the sample's bearing capacity decreases primarily due to the expansion of cracks at the hole and fissures. Under uniaxial compression, tensile-shear cracks dominate near the fissures tip, while tensile cracks form around the hole, particularly at its top and bottom. Sample failure occurs when these microcracks coalesce into a macroscopic fracture zone. Furthermore, strong force chains are the primary load-bearing mechanism, with secondary force chains playing a supportive role. Weak force chains contribute minimally to strength but maintain the stability of the strong chains. The research has important guiding significance for underground engineering in rocks with fissure and hole.

Keywords

• Holes and fissures
• Rock
• Uniaxial compression
• Particle flow code