The Impacts of Aging Infrastructure and Evolving Load Conditions: Case Study of an Earth Retaining Wall Failure

During the height of the rainy season in São Paulo, Brazil, a 97-meter-long section of an earth retaining wall of the Tamanduateí River channel failed. The failure affected an important avenue in a dense urban area, causing major traffic disturbances and decreasing the flow section of the river channel. This work details the post-failure investigation, challenged by extremely limited access to collect the necessary forensic evidence as the reconstruction of the ruptured section progressed rapidly. Based on analyses of design documentation, forensic evidence collected, and fluviometric historic data, it was concluded that the 30-year-old structure failed as a result of systematic overloading over the previous decade. Structural overload was a result of the intensification of rainfall and increased water levels in the channel during rainy seasons, and faulty storm-water drainage infrastructure adjacent to the wall, which ultimately led to complete saturation of the retained soil and wall failure. Furthermore, we contend that the evolving nature of traffic on the adjacent avenue, not considered during the design of the retaining wall, led to a gradual deterioration of the safety levels of the structure, further contributing to its failure. This case study showcases the consequences of insufficient maintenance and the need for continuous reassessment of operating conditions of infrastructure throughout its service life. It also serves as a reminder that extreme weather conditions due to climate change and lack of investment in retrofitting will contribute to higher failure rates of vital aging infrastructure.