Field Tests of Frost Jacking of Unexploded Ordnance

摘要

We hypothesized that frost jacking (net seasonal upward movement) of buried unexploded ordnance (UXO) occurs in cold regions where there is frost- susceptible soil and adequate moisture. We buried 18 inert ordnance shapes in highly frost-susceptible soil in Hanover, NH, to determine whether they would experience frost jacking. Sixteen of the shapes were used for two, three-way factorial experiments to study frost jacking as a function of specific ordnance type, burial depth, and orientation (vertical or at 45 degrees). Frost jacking of ordnance occurred, and the net upward movement for objects buried from 4 to 36 inches deep ranged up to 3.2 inches for one season. During winter, the ordnance moved upward at approximately the same rate at which the ground heaved; however, during thaw the ground usually subsided to a greater degree than the ordnance. Variability of net upward movement was very high. The group of ordnance that included 2.75-inch rockets and 81 -mm mortars buried 24 to 36 inches moved upward more than the smaller 20-mm and 40-mm projectiles buried 4 to 12 inches deep.