Influence of maintenance methods on temperature and thermal stress of utility tunnel at early-age

Abstract

In order to reduce and control the generation and development of early cracks in the concrete utility tunnel, ABAQUS finite element software was used to model the temperature field and thermal stress of early-age concrete of a thin-walled box structure. For the accuracy of simulation, the hydration heat of cementitious materials was tested by TAM air method, and the actual working conditions were used. Different curing methods were modeled, such as formwork type, formwork removal time, and curing time. Simulation results showed that steel formwork shall be selected for construction in summer, and the recommended formwork removal time was 3 days, which was better to resist temperature induced cracks. Moreover, the sooner the formwork was removed, the smaller temperature difference between concrete surface and center, but it would bring difficulties to the cooling rate control. Also, higher temperature occurred at bottom plate, especially in the junction area between bottom plate and partition wall. The maximum thermal stress was found at the junction between top plate and partition. Last but not lease, attention should be paid to the occurrence of peak temperature in 26 h, temperature difference control for 26–50 h, and cooling rate control during 2–5 days.