Measured Deformation Behavior of Glen Canyon Dam

Representative results obtained during 3 years of measurements from each of two systems installed to determine the deformation behavior of the Bureau of Reclamation's Glen Canyon Dam, a large concrete arch structure, are presented. The deformation is caused by water loading and by changing temperature of the mass concrete. Measurements are by precise triangulation from piers downstream from the dam to targets on its face, using a theodolite, and by observations on five plumb lines installed in formed vertical wells in the dam. Also, monuments in three wells which extend into the foundation near the toe of the dam are triangulated. The results show the deformation of the dam is comparable from the measurements by both systems which are independent of each other. The annual range of deformation from the plumb lines during a 60○ temperature range is approximately 1/2 in. at the top of the dam in its maximum section and the deformation of the dam is upstream approximately 1-1/2 in. for the period of record. The measurement system layout and photographs of apparatus are shown. The programs of periodic observations, field procedures, techniques, timesaving and error minimizing equipment devised by field personnel, computing methods, and results are described.