Dynamic regimes of cemented backfill at early-age

In view of the mechanics characteristic of cemented tailings backfill (CTB) at early age, the separation Hopkinson pressure bar test device was used to explore the effects of curing age and impact energy. A total of 48 CTB samples with diameter of 50 mm and length of 25 mm were prepared with curing ages of 3, 5, 7 and 9 d. Impact tests under different impact energy (10, 20, 30 and 40 J) were carried out. The microstructure of CTB at different ages was analyzed by scanning electron microscopy (SEM). The results show that, the curing age mainly affects the mechanical properties and internal structure of early-age CTB. With increasing curing age, the mechanical properties of early-age CTB change from viscoelasticity to brittleness. The impact energy mainly affects the response of dynamic peak compressive strength to strain rate. Under low strain rate, the structure of CTB is broken, but still has bearing capacity, affecting the formation of later strength. It is concluded that the structural loses completely under the action of high strain rate. Therefore, the control of impact energy and the protection of curing age should be fully considered in actual production process.