Abstract: To investigate the energy evolution and damage mechanisms of gangue cemented backfill (GCB) with varying water content, we prepared dry, natural, and saturated GCB samples (with water contents of 0%, 10%, and 25%, respectively). Using the stress-strain curves obtained from uniaxial compression tests, we analyzed the energy evolution laws of the GCB samples, proposed an energy strengthening/weakening coefficient, revealed the damage evolution mechanisms, and established a segmented damage constitutive model for the total stress-strain curve. The results show that the stress-strain curves of GCB samples in dry and natural states exhibit distinct “four-stage” characteristics, whereas GCB samples in a saturated state display only “three-stage” characteristics. The elastic modulus and peak strength of GCB samples decrease exponentially from the dry to the saturated state. The weakening mechanism of backfill strength due to water content can be categorized into physical, chemical, and structural effects. The drying effect strengthens the energy of the backfill, primarily through the enhancement of dissipated energy. The saturation effect weakens the energy of the backfill, predominantly through the reduction of elastic strain energy and total strain energy. During the transition from dry to saturated state, the failure modes of GCB samples mainly undergoes a transformation from tensile failure, tensile-shear mixed failure and V-shaped shear failure, accompanied by block detachment. The deformation and failure of GCB samples with different water contents follow the same type of damage evolution process. However, increased water content promotes the development of backfill damage. The established segmented damage constitutive model of GCB samples with different water contents accurately describes the load damage and failure processes of GCB samples. The research results can provide theoretical reference for further studies on the mechanical behavior and stability of gangue cemented backfill.

Key words: water content state, gangue cemented backfill, energy evolution, segmented damage constitutive model, uniaxial compression