Measuring Structural Behavior of Glen Canyon Dam

This paper describes layouts of two systems and the methods used for measuring the deformation of Glen Canyon Dam, a large, concrete, arch structure. The deformation is caused by water loading and changing temperature. Measurements are made by triangulation and plumblimes. Precise triangulation is made from piers downstream from the dam to targets at several elevations on the downstream face of the dam and abutments. Also, monuments in three wells extending into the foundation near the dam's toe are triangulated. The positions of the monuments are projected vertically by an optical plummet and coordinated with the triangulation of the targets on the dam's face. Plumblines are installed in five formed vertical wells that extend in the dam between the top elevation and the foundation. Reading stations are located at several elevations on each plumbline. Development of items of apparatus used in each system is described. The methods of measurements, plan of periodic observations, derivation of results, and purpose of the measurements are briefly examined.