Display omitted •3D printing is an encouraging method to manufacture the lower tensile strength of CTB material.•Three shapes (cross, quarter, and 8 equal parts) of 3D printing polymers (3D-PPL) were employed.•Dynamic splitting characteristics of 3D-PPL reinforced CTB unveiled a robust strain rate dependence.•The best mechanical strength results were obtained for cross-shaped reinforced CTB (31.6% increase)•Addition of 3D-PPL effectively inhibits the overall damage process of ordinary CTB materials. Originally developed for polymer materials, 3D printing is an encouraging technique to create versatile geometric shapes and high-precision construction elements from various materials. 3D-printed polymer structures are now employed effectively in various industries, including construction and mining since they significantly improve the ductility properties of cementitious materials like cemented tailings backfill (CTB). Considering the lower tensile strength of CTB (compared to its compressive strength), the study of fill's tensile properties is significant for improving the safety and ensuring the stability of the underground CTB structures. Indeed, this aspect is fairly crucial for the development of green mining which allows sustainable and affordable mining operations. To supremely enhance the tensile strength of CTB, three kinds (OR: ordinary resin) and forms (cross, quarter, and 8 equal parts) of 3D printing polymers (3D-PPL) were employed for this study. A number of experiments including Brazilian splitting tests, digital image correlation (DIC) measurements, and SEM failure/micro-structure analyses were fulfilled for exploring both dynamic splitting and crack propagation behavior of 3D-PPL reinforced CTBs. Results designated that dynamic splitting characteristics of 3D-PPL reinforced CTB samples unveiled a robust strain rate dependence. Besides, the tensile strengths of 3D-PPL reinforced CTB samples are increased under the same conditions and the best results are obtained for cross-shaped reinforced CTB increased by 31.6%. 3D-PPL reinforced CTB samples are characterized with higher strains, and the addition of 3D-PPL effectively inhibits the overall damage process of ordinary CTB and improves the backfill’s strength property. As a result, the results of this study are vital and prominent for realizing the tensile/crack behavior of the backfills placed in underground mined-out openings.