Numerical simulation of mechanical and fracture behavior of composite rock containing weak interlayers

Uniaxial compression simulation tests were conducted on composite rock containing weak interlayers, investigating the influence of the number of weak interlayers and dip angle (theta = 0 degrees 90 degrees) on the physical and mechanical parameters, anisotropy, and failure modes of the rock. The results demonstrate a correlation between the uniaxial compressive strength and elastic modulus with the number of weak interlayers and dip angle. The axial strain of the peak strength generally increases with an augmented number of weak interlayers, exhibiting a pattern of increase, decrease, and subsequent increase with varying dip angles. Microcracks predominantly originate in the interface and loading plate area, extending to the weak interlayer and adjacent regions, forming continuous fractures until the rock undergoes complete failure. The number and dip angle of the interlayer not only impact the physical properties but also govern the failure mode of the rock. The increase in weak interlayers shifts the postpeak curve from brittle to ductile damage, resulting in diverse final failure modes at different dip angles. A total of five distinct final failure modes were identified by examining the macroscopic fracture surface of the rock.