Investigating Pore Water Pressure Development in Paste Backfill Under Conditions Mimicking Field Loading

This paper presents and discusses the outcomes of an experimental study aimed at investigating changes in pore water pressure (PWP) in cemented paste backfill (CPB) materials incorporating polycarboxylate ether-based superplasticizer (PES). The research mimics real-world backfill field curing conditions, encompassing factors such as thermal (T; field curing temperatures), hydraulic (H; drainage conditions), mechanical (M; field vertical stress), and chemical (C; presence or absence of PES) factors. Utilizing a developed THMC backfill curing system, controlled THMC experiments were conducted to assess the impact of these factors and their interactions on pore water pressure (PWP) in CPB with or without PES. Results reveal that both individual THMC factors and their interactions significantly affect PWP development within CPB. The study also highlights the impact of PES on PWP in CPB, showing that adding 0.125% of PES can lead to a reduction in pore water pressure values by approximately 50% after 28 days of curing. Moreover, the results obtained demonstrated the effectiveness of the experimental THMC test techniques developed in this study in successfully mimicking field-like loading conditions, substantiating their usefulness for subjecting laboratory CPB samples to realistic loading scenarios in the field. These findings are of great importance for the mining industry and backfill designers, providing technical insights into complex THMC interactions affecting PWP in CPB-PES. Understanding these relationships is vital for optimizing CPB and barricade design, ensuring structural integrity, enhancing mine productivity, and guiding future research on numerical models for PWP prediction across all CPB structures.