Mechanical Response and Cracking Behavior of Defected and Tailings-Filled Layered Specimens

This study investigated the impact of tailings-filled material on the mechanical properties and fracture behavior of defected layered specimens under uniaxial compression. PFC2D was used to analyze the internal stress distribution, microcrack development, and energy evolution within the specimens. The results show a negative correlation between defect length and both peak strength and elastic modulus. Although tailings filling improved the peak strength and elastic modulus of defected specimens, these values remained lower than those of intact specimens. As defect length increased, the failure mode of defected specimens shifted from lithology-controlled to defect-controlled. The tailings-filled zone facilitated crack propagation toward the filled area, and in specimens with longer defects, cracks were more likely to extend along the cemented interface. At lower stress levels, stress concentration at the defect tips was especially significant. The tensile stress concentration in the tailings-filled zone reduced the stress concentration at the defect tips. As defect length increased, the peak values of boundary energy, elastic strain energy, and dissipated energy gradually decreased. For specimens with the same defect length, tailings-filled specimens exhibited higher energy peaks than unfilled defected specimens. The microcrack curve followed the dissipation energy trend, indicating that the initiation and propagation of internal microcracks were the primary mechanisms of energy dissipation.