Study on causes and prevention technologies of hidden cracks in secondary lining concrete of high ground temperature tunnels
Junjun Duan
Sichuan-Tibet Railway Company Limited
Chuang Jiang
China Railway Design Corporation
DOI: https://doi.org/10.59429/pest.v8i1.13408
Keywords: high ground temperature tunnel; secondary lining concrete; hidden cracks; curing technology; fly ash content; drying shrinkage; thermal stress; plateau environment
Abstract
In the construction of plateau railway tunnels, high ground temperature environments significantly increase the risk of hidden surface cracks in secondary lining concrete, compromising structural durability and long-term safety. Based on extensive field tests conducted in a plateau railway project, this paper systematically investigates the distribution characteristics, formation mechanisms, and key influencing factors of hidden cracks. A comprehensive prevention technology system centered on "temperature reduction and shrinkage control, enhanced moisture retention, and process solidification" is proposed. Through two-phase comparative field tests, it was demonstrated that an integrated approach— Incorporating 40% fly ash content, optimized water-binder ratio, concrete placing temperature ≤15°C, and the application of 2–3 layers of curing agent combined with mist-spray curing—Remarkably reduces the occurrence of hidden cracks. Test results indicate that this strategy lowered the hidden crack panel ratio from 22.9% to 3.6%, effectively enhancing the crack resistance of secondary lining concrete under high-temperature and low-pressure conditions. This study provides both theoretical insights and practical technical references for tunnel concrete construction in similar geological and climatic environments.
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