开裂及接缝渗漏条件下越江盾构隧道管片混凝土氯离子运移规律研究

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

钢筋混凝土结构耐久性失效多由侵蚀性物质导致钢筋锈蚀引起,而裂缝和渗漏会加速这一劣化过程。在Matlab环境下编写有限元程序计算分析了开裂管片混凝土中氯离子运移分布规律以及裂缝深度与钢筋起锈时间的关系。研究表明:裂缝的出现改变了管片混凝土中氯离子的运移分布规律,且采用一维Fick定律计算裂缝附近处氯离子运移是不合理的;钢筋起锈时间随裂缝深度的增加而缩短,两者之间呈非线性关系,钢筋起锈时间与完整度之间较好地吻合3参数logistic函数关系。建立了管片接缝渗漏情况下,接缝渗漏液与管片混凝土中氯离子运移的耦合模型,并探讨了模型的数值计算方法。结合算例的计算表明:接缝渗漏会加快管片混凝土中氯离子运移,从而促进钢筋的锈蚀。

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.