| Now days, the deterioration of underground pipes by corrosion phenomenon has become a growing concern for environmental and industrial sectors in the developed countries. In fact, the annual growth of the number of breaks occurring in water systems and the huge rehabilitation's budgets have led to the research of innovative techniques in terms of assessment and prevention against corrosion damage.;The pipes used in water distribution system are mainly made of cast iron materials. The degradation by corrosion of such material pipes has received a great attention from engineers of municipalities, water companies as well as materials producers. In this context, it reveals that the lack of a coherent opinion about the service performance of these networks of water mean continues to bring into question with regard to the fracture causes, the corrosion resistance and then the reliable methods of prevention against corrosion. Therefore, this research subject was proposed in order to establish a diagnostic model based on the evaluation of soil parameters surrounding the conduct, the chronological analysis of breakage and also the evaluation of cathodic protection system once applied. The established correlations between the different parameters constituting this model have allowed us to carry out a direct inspection on the risky site in order to assess the corrosion activity developed on the external surfaces of the water means. In addition, the collected data serve to calculate the corrosion rate and then to link it to the main parameters such as the soil corrosivity, pH and chloride ion content.;The results of this study confirm that the soil resistivity is the most relevant parameter having a significant effect on the rate of external corrosion. This parameter is controlled by a combination of other factors including the concentration of chloride ions and pH. Also, the diagnostic model allows classifying the soil corrosivity surrounding the pipe according to the value of the different retained variables. On the other hand, it was found that for the same soil, the first explanatory criterion of water main's breakage is the year of the laying pipe. However, inspections have shown that in a very low soil resistivity, the soil corrosivity appears to have a crucial impact on the corrosion of the pipe regardless the year of its laying. Concerning the cathodic protection systems installed, it was founded that they are mostly functional but with varying degrees of performance. However, cathodic protection installed properly remains an effective solution to reduce the breakage of water mains.;Keywords: Water mains, Soil resistivity, Corrosion, Breakage, Cathodic Protection. |
