Development and mechanical performance evaluation of a novel red mud-based filler for tunnel invert backfilling

Abstract How to achieve large-scale resource utilization of red mud has become a worldwide challenge in environmental protection. This study developed a novel red mud-based filler to address the pollution issues associated with red mud stockpiling and meet the demands of tunnel engineering. Through optimized proportioning, the optimal composition was determined to be 52.4% red mud, 30% modified composite materials (12% cement, 12% steel slag, 6% hydrated lime), and 17.6% water, achieving a 28-day unconfined compressive strength of 8.17 MPa. Model tests were conducted, employing digital image correlation and acoustic emission technologies to systematically investigate the mechanical performance of the tunnel invert-filling layer-pavement layer coupled structure under static, graded, and cyclic loading conditions when using this new red mud-based filler. The results showed that the ultimate bearing capacity under static loading was 570 kN, which decreased to 500 kN under graded loading due to damage accumulation, while the material exhibited excellent plastic recovery capability under cyclic loading.