Experimental study on temperature characteristics and multi‐field analysis for concrete spalling of tunnel linings exposed to high temperatures

Abstract The paper is aimed at investigating the temperature characteristics of the spalling of lining concrete. In this study, the combustion furnace and Hydrocarbon (HC) heating curve were employed to study the spalling for normal strength concrete (NSC) and high strength concrete (HSC). Further discussions were conducted on thermal stress and vapor pressure. The results showed that in the event of concrete spalling, the spalling duration of HSC is 20 min, with a maximum spalling depth ranging from 11 to 14 cm, while the spalling duration of NSC is 10 min, with a maximum depth ranging from 2.9 to 6.8 cm. The spalling of concrete was closely related to three factors: temperature, temperature rise rate, and temperature gradient. The thermal stress near the spalling region increased significantly and exceeded the tensile strength of concrete. The vapor pressure exhibited a hump profile near the spalling region. As a result, the thermal stress was believed to cause numerous micro‐cracks in the concrete initially, resulting in a drastic decrease in tensile strength. It is the vapor pressure due to the phase change in concrete that finally causes spalling.