Sensitivity analysis of the early-age cracking risk in an immersed tunnel

Engineers know only too well that early-age cracking accounts for the decrease of long-term serviceability for a majority of infrastructure. In immersed tunnels, early-age cracks may leave paths for aggressive media, which lead to deterioration and thus compromise durability. On the other hand, the cracking risk in concrete structures depends on a number of factors, such as material properties, construction methods, curing measures, etc., which make decisions complex.
This work presents the results of a sensitivity analysis of early-age behaviour for an immersed tunnel cast in situ. Numerical modelling and local sensitivity methods are employed to evaluate the sensitivity of early-age cracking to casting temperature, formwork conductivity, formwork removal time, curing temperature and ambient temperature. The numerical results indicate that the casting and curing temperatures appear to be the most dominant factors with regard to the whole fabrication period.
This study provides a realistic method for determining the uncertainty analysis of concrete structures at an early age, and identifies the most important factors during the fabrication of immersed tunnel segments, which is beneficial for further decisions related to the control of early-age cracking.