Acoustic emission-based damage characterisation of alkali-resistant glass fibre-reinforced shotcrete under high-and-variable temperature curing conditions

To reveal the damage and failure characteristics of hybrid alkali-resistant glass fibre-reinforced shotcrete (HAR‑GFRS) under high and variable temperature conditions and ensure the construction safety of high-geotemperature tunnels, this study conducts mechanical tests, acoustic emission (AE) experiments and other analyses. The results indicate that: elevated temperatures during the initial curing phase accelerate cement hydration rates. However, higher initial temperatures (above 60°C) result in uneven distribution of cement hydration products within the specimens, thereby reducing the mechanical strength of HAR-GFRS. AE characteristic parameters indicate that implementing cooling measures to control the temperature of the surrounding rock during the initial excavation phase can enhance the effectiveness of support systems. Due to the high temperatures during the initial curing period, a positive correlation was observed between the proportion of tensile failure during the compaction stage and the curing temperature. The elastic stage and failure stage exhibit similar failure modes due to the combined effects of high stress and the compaction of internal pores within the specimen. The development of macrocracks and microcracks is positively regulated by shotcrete’s uniformly dispersed fibre bundles and individual fibres. This research endeavours to offer theoretical underpinnings for the construction of concrete columns in high-temperature tunnel projects.