Macro- and Micromechanics Model of Progressive Damage to Cemented Tailings Backfill Considering Initial Defect Conditions

Abstract

The large-scale collapse of the cemented tailings backfill (CTB) in mine airspace safety accidents often shows a typical progressive damage failure process, and the existence of initial defects (e.g., micropores, microcracks, etc.) can further affect the stability of mine airspace. However, there is currently a lack of research, both domestically and internationally, on the progressive damage and failure of backfill material considering initial defects. Therefore, based on a microscopic wing crack mechanics model, this paper establishes a progressive damage macro- and micromechanics model for CTB considering initial defect conditions, and modified parameters are introduced to correct the model. By incorporating varying dosages of air-entraining agent (AEA) during the CTB manufacturing process, different levels of initial defects within the CTB are quantified. The study investigates the relationship between AEA content and model parameters, fracture toughness, and initial crack size. The results indicate a high degree of conformity between the modified theoretical curve and the experimental curve. The fracture toughness of CTB decreases with increasing AEA content, whereas the compressive strength of CTB decreases with the enlargement of initial crack size. The progressive damage evolution curve of CTB can be divided into three stages. With the increase of initial damage, the pressure-tight damage stage of the filling body becomes longer, the accelerated growth stage of the damage all shows a linear growth trend, and the stage of slowing down the growth rate of the damage becomes shorter. The results of the research play a role in promoting the development of mine filling mechanics and other research and provide a theoretical basis for guaranteeing the safety and stability of the mining airspace.