Near‐surface spalling from a nuclear explosion in a salt dome

Although near‐surface spalling observed on the Salmon nuclear shot resembled that observed on other shots in different environments, the spalling process was more complex because of an artificially filled platform at surface zero. The Salmon maximum spall gap width (0.1 meter) in the vicinity of surface zero was roughly ⅙ of the width that would be expected without the platform. The radius was 460 meters, and the spalled layer thickness was 11.7 meters. Measurements established that the near‐surface layers had experienced multiple bouncing rather than successive spallation.