Early age cracking potential of inner lining of coal mine frozen shaft

Recently, the application of high performance concrete (HPC) is popular in inner lining of frozen shaft in water-rich stratum. The circular crack of inner lining concrete easily appears in the early age (0 similar to 240 h) leading to water burst accidents in the service period. The early-age cracking potential of HPC in inner lining is investigated by Temperature Stress Test Machine (TSTM) in the laboratory. The complex boundary, temperature history and variable restraint degree, was performed simultaneously by TSTM in this study. The experimental analysis indicated that (1) The range of restraint degree is almost 40% to 89.3% under steel frame restrained condition which can almost realize actual constraint degree of inner lining; (2) The cracking potential increased slightly for Mixture C60, C70, and increased severely once the Mixture strength exceeded C70; (3) The integrated crack indicators of C60, C70 and C90 repeat such as cracking stress, crack age, cracking temperature and cracking thermal drop were fluctuant slightly with the concrete strength increased; (4) The increasing of concrete strength decreased the cracking potential of inner lining concrete under steel frame restrained condition, though the tensile strength is improved. (C) 2022 Published by Elsevier Ltd.

Automated summary

The study found that the cracking potential of inner lining concrete slightly increases with the increase of concrete strength, but it increases significantly once the strength exceeds C70. The crack indicators at different concrete strengths fluctuate slightly as the concrete strength increases, but overall, an increase in concrete strength decreases the cracking potential of inner lining concrete under steel frame restrained condition.