A Review of Damages and Lessons Learnt from Major Incidents in Concrete Dams

Large dams are structures considered national assets, and any incident involving them can be catastrophic in terms of loss of life, property, and social impact. Most large concrete dams have been gradually constructed over the past century. Many of these dams were built without sufficient understanding of the foundation and abutment conditions, without a proper grasp of load processes and probable environmental conditions in their design, or with incorrect assumptions about the behavior of materials and structural systems. Given that the weakness of unreinforced concrete used in the main body of dams under tensile and shear conditions leads to sudden and brittle cracks of large dimensions, a combination of various incidents can create a concerning scenario, either gradually or abruptly, posing a serious threat to the safety of the dam and reservoir system. Even modern knowledge and technology cannot entirely rule out the possibility of errors or unintended uncertainties in the behavior of these strategic structures. As a result, risk management practices, including the study of past events and minor and major incidents, have become crucial in the evaluation and assessment of large dam systems. Through systematic or case studies on the behavior and service life processes of these systems, there is hope for a deeper understanding of the dam-reservoir-foundation system's behavior, thereby enabling the prevention of similar incidents in the future. The objective of this study is to investigate the most significant historical damages sustained by large concrete dams and analyze the factors contributing to each incident and its various dimensions. In most cases of dam failure, it is impossible to attribute the damage to a single factor. Typically, major damage or failure in a concrete dam results from a combination of factors that interact with one another or form a chain of events leading to the primary failure. Overall, based on past incidents and research, it becomes clear that although factors such as overall foundation weakness, unforeseen mechanisms resulting from geological or geotechnical deficiencies within the foundation and abutment, issues arising from complex thermal loads, seepage, and unforeseen earthquake characteristics are recognized as the most common causes of severe incidents, in most cases, it is human error—stemming from a lack of sufficient knowledge about the system, ignorance of available knowledge, or non-technical managerial decisions—that enables these physical factors to take effect. Such errors during the design, construction, and operation phases provide the opportunity for the above-mentioned physical factors to exert their influence. Finally, it should be noted that most major incidents occur during the early years of the dam’s life, particularly during the initial reservoir filling, underscoring the absolute necessity of a gradual, step-by-step approach and the strict enforcement of monitoring regulations during this critical period.