Prediction on service life of concrete pipeline buried in chlorinated environment under nonuniformly distributed earth pressure

This paper proposes an analytical model to estimate the service life of concrete pipelines buried in chloride contaminated soils, which properly considers the effects of nonuniformly distributed earth pressures on both the internal tensile stress of concrete protective cover and the chloride diffusion coefficient through the nonhomogeneous coefficient of earth pressure. It is assumed that the underground concrete pipeline arrives at the service life end when cracking induced by expansion pressure due to the corrosion products occurs in the concrete protective cover. Hence, the whole service life of underground concrete pipeline is composed of chloride diffusion period and protective cover corrosion period. The diffusion of chloride ions is simulated through a diffusion model for dual compound media and the service life of this period is evaluated by solving the diffusion equation. The service life of corrosion period is estimated based on the corrosion expansion pressure with the aid of the concrete tensile strength. The validity of chloride diffusion model is examined through the comparison between the present analytical analysis and the numerical analysis from finite element simulations, guaranteeing that there are reliable results available for the subsequent analysis of corrosion period. Comprehensive parametric studies are conducted to explore the effects of nonuniformly distributed earth pressures and concrete cover thickness on the pipeline service life. The results demonstrate that the nonuniformly distributed earth pressures lead to the occurrence of tensile stress in the protective cover and give rise to the increase in the chloride diffusion coefficient, which in fact accelerates the diffusion of chloride ions in the concrete pipeline and induces the cracking of concrete protective cover and thus significantly shortens the service life of concrete pipelines buried in chlorinated environment.