Investigation of the Concrete in an 80 Year Old Multiple Arch Dam by Nondestructive Evaluation

The multiple-arch Gillespie Dam on the Gila River in Arizona was constructed in 1921 (Figure 1), and failed in 1993 during an overtopping flood. Twelve of the barrel arches were totally destroyed (Figure 2) in that flood. As part of a general investigation into the reasons for the dam failure, the authors evaluated the concrete in the remaining buttresses, arches and crest deck slab in early 2001. Because of the large volume of concrete to be examined, two nondestructive test (NDT) methods, Impulse Response and Impact-Echo played a major role in the investigation. This paper describes the testing approach and discusses the findings. 14 pp., 1 table, 17 figures, 4 references.