Abstract: The defies of tailings storage and high-stress conditions in deep mining have emerged as critical factors limiting mining’s security, efficiency, and sustainability. The current investigation explores potential of utilizing tungsten tailings to create cementitious backfill (CTB) and inspects their macroscopic strength features and microscopic damage evolution mechanisms under varying sizes and amounts of hydroxypropyl methyl cellulose (HPMC). The research employed grinding tools with bottom diameters of 50 mm, 75 mm, and 100 mm, combined with HPMC dosages of 0%, 0.15%, 0.25%, and 0.35%, keeping a H/D (height/diameter) ratio of 2:1 for CTBs. Experimental outcomes revealed that when HPMC rate rose from 0% to 0.35%, compressive strength (UCS) of CTBs declined significantly in a linear fashion. Besides, UCS unveiled a primary growth tracked by a drop by changes in fill size, demonstrating a pronounced size effect. CTBs incorporating HPMC showed reduced segregation and bleeding in the course of pouring, decreased tailings settling, lower elastic modulus, and improved stored elastic potential energy during the elastic deformation phase. Within the initial 1% strain range, fills with HPMC exposed reduced energy dissipation. Failure arrays were mostly characterized by macroscopic tensile cracks, with occasional mixed tensile-shear cracks and smaller fractures. At the microscopic level, the morphology revealed interwoven distributions of ettringite and calcium silicate hydrate gels that tightly enveloped the tungsten tailings. HPMC-doped specimens displayed more pronounced pore structures. The findings offer valuable data and notional insights for optimizing fill’s fluidity, as well as strength/damage evolution of solidified materials in the course of filling and extraction. This study contributes to advancing green, economical, safe, and sustainable mining practices.