Behaviour of Backfill Undergoing Cementation Under Cyclic Loading

Cemented paste backfill (CPB), a man-made soil undergoing cementation, is extensively applied to support underground mine openings or spaces and provide regional ground stability. The large underground cavities created by the ore extraction are backfilled with the tailings (fine-grained soils) mixed with cement and water in the form of CPB. Cyclic loading-induced liquefaction potential of CPB structures is a crucial concern in underground mine workplaces and backfilling operations. Failures of CPB structures can cause loss of life and/or serious injuries and have significant financial ramifications for a mine. However, no studies have used the shaking table testing method to address the cyclic and liquefaction response of CPB undergoing hydration. This research highlights new findings of using a shaking table to understand the effect of the progress of cement hydration (curing time) on the geotechnical response of hydrating CPB during dynamic loading events. CPB blends were produced, casted into a flexible laminar shear box and kept for curing to different maturity ages. Various factors (e.g., horizontal and vertical deformation, development of excess pore water pressure, temperature, electrical conductivity, acceleration, effective stress) were monitored before, during, and after shaking. Microstructural evolution of CPB was also studied. Cyclic loading was applied using a 1-D shaking table. The findings indicate that the maturity age or the cement hydration development and the depth in the CPB have a significant influence on the acceleration and excess pore water pressure (PWP), as well as on the horizontal and vertical deformation of the CPB when subjected to cyclic loading. It is also found that the cyclic loading has an insignificant effect on the progress of the cementation hydration. Furthermore, young (2.5 h old) CPB material can be susceptible to liquefaction, whereas older CPBs (curing time ≥ 4 h) are resistant to liquefaction under the studied cyclic conditions. These results provide a better comprehension of cyclic behavior of natural or man-made soil undergoing cementation and the efficient and safer design of CPB structures. This will contribute to increase the safety of the underground mine openings and workplaces.