Numerical simulation of the layered filling process of cemented paste backfill based on thermo-hydro-mechanical-chemical coupling analysis

Layered backfilling is a critical construction method for ensuring the overall stability of backfill in deep mines. Its cyclic "fill-cure-refill" operation mode induces complex thermo-hydro-mechanical-chemical (THMC) coupling effects and significant spatiotemporal heterogeneity within the backfill body. Addressing the limitation that existing research predominantly focuses on single continuous filling and lacks in-depth investigation into the physical field transfer mechanisms at layered interfaces, this paper establishes a fully coupled THMC numerical simulation model for Cemented Paste Backfill (CPB) considering a time-varying computational domain. On this basis, the influence laws of the cement-sand ratio (c/s ratio), inter-layer interval time, and layering strategy (continuous, two-layer, and three-layer) on the spatiotemporal evolution of temperature, seepage, and stress fields were systematically analyzed. Results indicate that the c/s ratio is the primary driver of multi-field evolution; higher ratios increase peak temperatures and matrix suction rates, enhancing early strength. Interval time governs pore water pressure (PWP) dissipation; longer interval utilizes a "peak-shifting effect" to reduce heat accumulation and improve vertical stress. Furthermore, a three-layer strategy creates "sawtooth-like" PWP dissipation, effectively preventing the high-pressure accumulation and stress lag associated with continuous filling. This work clarifies THMC mechanisms at layered interfaces, providing a theoretical basis for optimizing backfill consolidation.