Abstract

The liquefaction potential of cemented paste backfill (CPB) masses under cyclic loading at early ages is a critical concern in underground mine backfilling operations. Failures of CPB structures can result in severe injuries, fatalities, and substantial financial and social implications for mining operations. As underground mines face gradual depletion of shallow ore reserves in various regions worldwide, mining operations are increasingly moving to greater depths with larger volumes, leading to more severe and frequent cyclic loading events. Therefore, a thorough understanding and assessment of the liquefaction potential of CPB under dynamic loading conditions at early ages are paramount for the efficient and safer design of CPB structures. This research utilizes the shaking table technique to assess the liquefaction potential of hydrating CPB during cyclic loading at early ages. A series of shaking table tests were conducted on large fresh CPB samples cast in a specially designed flexible laminar shear box. Some of these tests were carried out at different curing ages, including 2.5 hours, 4.0 hours, and 10.0 hours, to investigate the influence of cement hydration progress on CPB's liquefaction potential. Additionally, another set of tests explored the impact of pore-water or mixing water chemistry, specifically sulphate content, on the seismic response of fresh CPB by subjecting CPB models to seismic loads with varying sulphate ion concentrations. Various parameters, such as pore water pressure, horizontal and vertical displacement, acceleration, temperature, and electrical conductivity, were continuously monitored before, during, and after shaking. The results revealed distinct cyclic behavior and performance of CPB under different conditions. Specifically, the progress of cement hydration (longer curing time) enhanced the liquefaction resistance of CPB, while the presence of sulphate ions diminished it. Furthermore, the study demonstrated that the acceleration, horizontal and vertical displacement, and excess pore water pressure of CPB under cyclic loading were significantly influenced by the curing time, depth within the CPB, and the chemistry of the mixing water. These findings contribute to a deeper understanding of the cyclic behavior and liquefaction potential of CPB at early ages, providing valuable insights for liquefaction assessment of CPB structures. Additionally, the data generated in this study will aid in the future development of constitutive models to accurately describe and predict the seismic behavior of hydrating CPB masses. Overall, this research contributes to enhancing the industry's ability to mitigate liquefaction-induced risks and optimize backfilling strategies.