Study on the expansion characteristics and semi-empirical damage model of cemented sulfur-containing tailings backfill

In cemented sulfur-containing tailings backfill (CSTB), secondary products from sulfide oxidation alter the internal pore structure, induce expansion cracking, and consequently degrade the mechanical strength. Laboratory experiments elucidated the evolution of the expansion rate ( ε ) with curing times (14–102 days) and sulfur content, and the influence of backfill microstructure on ε . The expansion rate exhibited a positive correlation with both curing times and sulfur content, showing a distinct inflection point at 28 days beyond which it accelerated. This accelerated expansion was concomitant with a sharp increase in the content of harmful pores, attributed to the formation of isolated pores within the backfill matrix. A time-dependent semi-empirical damage model for strength was established based on the Lemaitre strain equivalence hypothesis and the Weibull distribution. This model incorporates the expansion rate ( ε ) as its key state variable, which is itself a function of curing time ( T ) and sulfur content ( C ). The proposed semi-empirical damage model demonstrates strong agreement with the experimental data. The evolution laws of the key state variables are empirically derived from experimental data within the tested parameter ranges (sulfur content 8%–16%, curing time 14–102 days), and the model is therefore presented as a semi-empirical formulation for engineering applications. This model successfully delineates the evolution of total damage in the backfill under varying mix parameters and curing times. This study aims to forecast the long-term strength and damage evolution of cemented sulfur-containing tailings backfill under various curing times, thereby providing a theoretical foundation for backfill design in mining operations.