Physical Modeling of the Geotechnical Behaviour of Cemented Backfill Plug with and Without Nanoparticles Under Simulated Field Overburden Pressure

The proper geotechnical design of mine backfill plugs is crucial for ensuring both the safety and efficiency of mining operations. However, the geotechnical behavior of cemented paste backfill (CPB) plugs incorporating nanoparticle additives remains poorly understood. This research article investigates the geotechnical responses of CPB plugs both with and without nanoparticles (NPs), specifically nano-calcium carbonate (nano-CaCO 3 ). The study considers the effects of realistic field overburden pressures on the CPB plugs, analyzing parameters such as strength development, pore water pressure evolution, total stress evolution, and pore structure changes. To accurately simulate field conditions, a novel physical model equipped with various sensors and a mechanical loading system was developed, considering factors like backfill height and backfilling rate. Monitoring experiments, along with mechanical and microstructural tests, were conducted using the physical model to assess the geotechnical characteristics of the CPB plugs under realistic vertical mechanical loading conditions. The study's key findings revealed that the addition of NPs significantly enhances the strength and strength-gaining rate of CPB plugs compared to control samples. This improvement is attributed to several mechanisms, including the filler effect of NPs, acceleration of the hydration process, and the generation of more hydration products. Furthermore, curing CPB plugs under field overburden pressures was observed to lead to enhanced mechanical properties, primarily due to pore structure refinement (lower void ratio/porosity), faster pore water dissipation, and accelerated hydration progress. However, as the CPB hardens and gains strength, the impact of applied vertical stress (overburden pressure) weakens, particularly in comparison to the initial stages. Notably, CPB plugs with NPs experienced a lower and faster decrease in the pore water pressure and total stresses compared to those without NPs. These findings have significant implications for designing higher-performance CPB plugs while enhancing the sustainability of backfilling and mining operations. The study contributes valuable insights into optimizing the utilization of nanotechnology in geotechnical engineering applications.