Flexural toughness characteristics of basalt fiber reinforced shotcrete composites in high geothermal environment

Abstract

The shotcrete in high geothermal tunnel environments should have enough toughness to help the surrounding rock stabilize and resist the deformation of the surrounding rock. In this paper, the failure crack length, flexural strength, load–deflection curve and energy absorption of shotcrete composites with 0.1%–0.4% basalt fiber (BF) content in simulated high geothermal environment (20 ℃~60 ℃) were investigated, and the calculation model of flexural toughness was established. The results showed that the flexural failure cracks of shotcrete increased by 245.0% ~ 445.0% and 88.9% ~ 133.0% by curing at high temperature and adding BF. The 60 ℃ is beneficial to the flexural strength of BF reinforced shotcrete composites (BFRSC), with an increase range of 25.4% to 51.5%. The obvious characteristic of load–deflection curve of BFRSC is that no post-peak curve can be observed. The high temperature is conducive to the improve the deformability of shotcrete, especially 40 ℃ curing. The content of 0.3% BF is the best to enhance the flexural toughness of shotcrete, in which the 90-day energy absorption increases by 26.1%. The flexural toughness of shotcrete in high geothermal environment can be calculated according to the composite material theory considering orientation effective coefficient, length effective coefficient, and interfacial adhesion coefficient.