Study On The Prediction Of Corrosion Remaining Life Of Underground Pipeline And Safety Evaluation In Waterfront City

In recent years, it is common to see many explosions caused by pipeline rupture and leakage. This brings a great threat to people’s life and property. While the corrosion of pipelines is one of the main causes of pipe rupture. At the same time, China is a country subjected to seawater intrusion badly. Seawater intrusion can change the characteristics of soil and groundwater, and accelerate the corrosion of buried pipeline, which will bring serious consequences. Therefore it is of great importance for us to study on the safety evaluation and residual life of underground pipeline corrosion in the coastal areas.In this paper, a case study of Dalian, laboratory simulation test, numerical simulation and theoretical analysis are combined to predict the residual life of underground pipeline corrosion in coastal area and conduct safety evaluation. The main research contents and conclusions are as follows:(1)Through the laboratory simulation test of pipeline corrosion, it is needed to observe the effects of different concentrations of NaCl solution on the corrosion of pipeline, calculate the corrosion rate of the corresponding in weight loss method, build predicting model of corrosion rate in three exponential smoothing method. Eventually predicting mode will be verified. Research shows that in the environment of high concentration Cl- a high corrosion rate appears in the pipeline, and Cl- concentration has a great influence on pitting corrosion. The three exponential smoothing method can be applied in predicting corrosion rate of pipeline in the coastal area.(2)Finite element method was carried out on the residual strength of corroded pipes. The equivalent stress of the corroded pipes under different loads are obtained. Uniform corrosion, spot corrosion and superimposed corrosion are considered separately. The residual life of underground pipeline can be forecasted by FEM method. The results from this method will be compared with the theoretical results. Test study Indicates that relationship between the equivalent stress and corrosion depth can approximate to quadratic curve. When the corrosion defect depth is less than 30% of the pipe wall, with the increase of the pipeline length, the equivalent stress suffered by corroded pipeline will tend to be stable. Pipeline will be easier to be damaged in the case of superimposed corrosion. It is feasible to predict the residual life of underground pipeline by FEM method.(3)Basing on the factors of pipeline corrosion, a safety evaluation system of pipeline corrosion in the coastal cities by using fault tree analysis method. Through that system the weak links in pipeline failure will be found.