Mechanical properties and deformation field evolution characteristics of layered cemented tailings backfill under uniaxial compression

Backfill mining has become a key approach in underground mining, offering advantages in waste management and ground control. Layered cemented tailings backfill (LCTB) structures, formed during backfill mining, are critical for stope stability. To examine the effects of middle-layer c/t ratios and curing times, LCTB specimens were prepared and tested under uniaxial compression using digital image correlation (DIC). The results indicated the following: (1) LCTB strength under compression increases with both c/t ratio and curing time. After peak stress, specimens display ductile behaviour; lower c/t ratios yield a more gradual softening process, with particle rearrangement and interlayer friction delaying failure. (2) Material uniformity strongly influences energy evolution. When the middle-layer c/t ratio approaches that of adjacent layers, dissipated energy density rises sharply during the elastic stage due to interfacial friction and microfracturing, and Uemax/Umax increases exponentially with c/t ratio before peak stress. (3) Failure mode shifts from shear along interfaces to tensile – shear composite failure across layers as c/t ratio increases, and from interlayer spalling to conjugate shear, then to tensile-dominated failure with longer curing times. (4) Displacement field evolution concentrates at layered interfaces; damage initiates earlier at low c/t ratios, while greater curing time reduces deformation dispersion and shear damage.