Effect of height to diameter ratio on dynamic characteristics of cemented tailings backfills with fiber reinforcement through impact loading

• The size effect on dynamic characteristics of cemented tailings backfill was investigated. • The internal distribution of cracks and fibers were conducted using computed tomography (CT). • The mechanism between fibers and hydration products was explored. The safety and durability of underground backfilled stopes of metalliferous mines are so crucial owing to several dynamic events such as rock bursting, loads triggered by blasting, and loading conditions under stress. Besides, the effect of height to diameter ratio on dynamic properties of fiber reinforced paste backfill has not yet been explored suitably, but this factor is vital to determine the design properties of mining with backfill. This study deals the findings of the dynamic tests done on fiber reinforced cemented tailings backfills (FRCTB) considering different height to diameter ratios under impact loading. A cement mortar mixed with polypropylene fiber with 12 mm length was made, cast in six diverse molds (H × D: 25 × 50; 30 × 50; 35 × 50; 40 × 50; 45 × 50; and 50 × 50 mm), and experimented through Split-Hopkinson pressure bar (SHPB) setup. Later, internal crack formation within FRCTB was observed by employing a computerized X-ray imaging (CT) and scanning-electron microscope (SEM) system. The results indicated that fracture number/path and failure damage of FRCTB decreases with increasing H/D ratio while their dynamic strengths drop with growing mean strain rate. Fractures arise because of the greatest micro-cracks as a function of stress application. These cracks rise with an increase in specimen size, resulting in lower strengths. Through SEM and CT observations, it is found that polypropylene fiber boosts the cementation of FRCTB and frequent hydration products are attached to fiber surface. Assessing research findings in mine backfill applications will help the better consideration of FRCTB dynamic characteristics, and the actual strength resistance and dynamic durability design of deep mining with backfilling.