Chloride migration in segment concrete of river-crossing shield tunnels with cracks and joint leakage

The durability failure of reinforced concrete structures was always caused by rust of reinforced bars due to the corrosion of aggressive substance and the procedure was likely to be accelerated where cracks and leakage occured.A FEM program was developed in Matlab environment to study the chloride migration and rust of reinforced bars in cracked segment concrete.It was shown: cracks would alter the chloride migration in segment concrete and it was not reasonable to calculate the migration of chloride near cracks by one-dimensional Fick law;the rust time of reinforced bars would be reduced with the increase of the crack depth in terms of nonlinearity,and the logistic function with 3 parameters could well express the relationship between the rust time and the integrity.A coupling model was proposed for the chloride migration in segment joint and segment concrete,and the corresponding numerical method was developed.It was shown that the joint leakage would speed up the chloride migration in segment concrete and then accelerated the rust of reinforcing bars.