Risk Prediction Model for Formation of Underground Cavities and Sinkholes due to Defective Sewer Pipes

Sinkhole formation due to internal erosion around defective sewer pipes is identified as a serious threat in urban infrastructure system. Post-repair and rehabilitation after pipe failure are not effective as emergency pipe repairs are very costly and pipe failure leads to various public and environmental consequences. Only a few studies have been conducted on the prediction of the risk of ground erosion around pipe defects. Therefore, the main objective of this article is to propose a model which can predict the risk of formation of sinkholes around sewer pipelines based on the weighted factors method when a pipe defect is certain. The proposed methodology relies on different factors which contribute to void development and severity of the consequences. The Risk of Erosion (ROE) combines the effect of Likelihood of Erosion void formation (LOE) and Consequence of Erosion cavity formation and ground failure (COE). The LOE rating is related to many parameters, including soil properties, hydraulic conditions, and pipe defect characteristics, while the COE rating is related to the environmental, economic, and social consequences of pipe failure. Therefore, this model, which can predict the risk of developing a sinkhole close to an existing pipe defect, will enable sewer assets maintenance teams to evaluate each pipe and prioritize the maintenance and rehabilitation work based on the risk to each pipe.