Energy and Damage Evolution of Cemented Backfill Under Triaxial Compression: Considering the Influence of Different Magnesium Slag Contents

This paper investigates the deformation, failure and energy evolution laws of MFG-CTB under different magnesium slag dosages and confining pressures through conventional triaxial compression tests. On this basis, a damage constitutive model was established based on energy dissipation. The results show that the optimal dosage of magnesium slag as an alkali activator is 30%. At this dosage, the total porosity and macropore proportion of MFG-CTB are the lowest, and its triaxial compressive strength is increased by 112.7% and 130.5% respectively compared with the backfill without magnesium slag. However, the triaxial compressive strength of MFG-CTB first increases and then decreases with the increase of magnesium slag dosage. In addition, the addition of magnesium slag reduces the ductility, increases the stiffness and enhances the energy storage capacity of MFG-CTB. With the increase of magnesium slag dosage, the failure mode of MFG-CTB under low confining pressure changes from tensile-shear composite failure to single shear failure, while that under high confining pressure transforms from local compression-shear failure to overall compression-shear failure, with the main crack gradually approaching the middle of the specimen. Finally, the damage constitutive model of MFG-CTB established based on dissipated strain energy and considering residual strength.