<p>Deep hard rock exists in a true triaxial stress environment and undergoes various unloading stress paths due to engineering excavation. Currently, the stress–strain relationship of rocks is often described based on loading stress paths, neglecting the influence of unloading stress paths on rock deformation and failure. This limitation hinders the accurate understanding of the hard rock failure mechanisms induced by deep engineering excavation. To investigate the deformation and failure behavior of surrounding rock under excavation unloading stress paths, this study considers the hard rock deformation and failure anisotropic characteristics, induced by excavation unloading stress paths and initial stress differences. Brittleness indices reflecting these factors are established. The effects of unloading stress paths and initial stress differences are incorporated as internal variables, and quantitative strength and deformation parameters are linked to the evolution equations of these variables. A mechanical failure model considering the excavation unloading stress path effect in hard rock is established and integrated into the Cellular Automata Software for engineering rockmass fracturing process for calculation and validation. Finally, based on rockburst and spalling observations in Shuangjiangkou hydropower station underground powerhouse pilot tunnel, the engineering advantages and significance of the proposed model are discussed in comparison with other models.</p>