高海拔山区隧道喷射混凝土配合比优化设计及性能研究OA

To prepare shotcrete suitable for high-altitude mountainous regions,this study employed orthogonal experimental design to investigate the effects of early-strength admixture dosage,water-binder ratio,accelerator dosage,and sand ratio on the slump,8 h compressive strength,and 28 d compressive strength of shotcrete.The results show that the early-strength admixture dosage and water-binder ratio significantly affect the shotcrete's flowability and compressive strength.The sand ratio influences flowability as well as early and late compressive strength,though to a lesser extent.The accelerator dosage has a minor effect on both early and late compressive strength.Secondly,through range analysis and grey target decision theory,an optimal mix proportion design for shotcrete is obtained:early-strength admixture dosage of 26%(mass fraction),water-binder ratio of 0.30,accelerator dosage of 7%(mass fraction),and sand ratio of 50%.Finally,XRD,TG,and SEM microstructural analyses elucidate the mechanisms by which the accelerator and early-strength admixture influence shotcrete performance,the two exhibit a synergistic effect,significantly enhancing the early strength of the cement paste.These findings provide technical support for the optimized design and preparation of shotcrete for tunnels in high-altitude and rugged mountainous regions.