At Flaming Gorge Dam, two general methods of measurement are used to gain this essential information, each method having a separate function in the overall scheme. One method of measurement involves four types of instruments that are embedded in the mass concrete of the structure. The other method involves two types of precise surveying measurements of an external nature. Data obtained from both the internal and the external methods of measurements are correlated to determine the behavior of the structure. In addition to the above measurements hydrostatic pressure at the base of the structure is measured from a system of pipes that are installed at selected locations on radial lines across the base. The pipes extend between the rock-concrete contact plane and the galleries where pressure head or depth to water surface measurements are made. 41. Locations of Embedded Meters and Thermometers. The following subsections describe the layouts of the measurement systems and the locations and use of the various devices. Sections 186 through 199 describes their installation and operation, while section 42 briefly describes the instruments and presents a drawing of each. (a) Embedded Instruments. --The installation of embedded instruments consists of 912 strain meters, 61 stress meters, 116 joint meters, and 32 resistance thermometers placed in the mass concrete of the dam and terminated by means of electrical cable connecting the instruments to 51 terminal boards located at 22 appropriate reading stations in the system of galleries throughout the dam. The locations of the instruments and details of their installation are shown on figures 35 through 39. Readings from the instruments are made periodically by means of special portable-type Wheatstone bridge test sets. Data supplied by the strain meters, stress meters, and joint meters are in terms of total resistance of the meter and in terms of resistance ratio of the two coils contained in the meter. Data supplied by the resistance thermometers are in terms of resistance of the coil of the thermometer. All data are recorded on appropriate data sheets. The strain meters, stress meters, and resistance thermometers embedded in the mass concrete of Flaming Gorge Dam will furnish data over a long period of time for determining the stress behavior of the structure. The joint meters detect the condition of joint opening until the joints are grouted, and after that time serve as the means of determining the effectiveness of the grouted joint. The strain meter installation ranks first in numbers and importance. On 15 radial lines through the dam, groups of strain meters in three-dimensional configuration are embedded in the mass concrete to measure volume changes from which the stresses can be computed. The strain meters also measure temperature at their locations. The groups of strain meters on the radial lines are installed near the base of the maximum section of the dams and in arch elements at four elevations in the dam. Each group of strain meters comprises 12 instruments installed as a cluster. Each radial line of strain meter groups contains one pair of "no-stress" strain meters. The patterns of radial lines are generally on the centerlines of blocks and were selected to define a system of horizontal and vertical planes that represent approximate arch and cantilever elements on which stress information is obtained by the trial load design analysis of the dam. Stress information at a number of arch-cantilever intersections common to both methods of investigation is thus available. Cantilever and arch stresses are determined at the base of the maximum section where maximum cantilever stresses are to be expected. Similarly, the stresses are determined at sections in four arches which are about uniformly spaced through the elevation of the dam and at elevations where the distributions of arch and cantilever stresses are desired. To obtain stress distribution in each of the sections, the groups of strain meters are placed at five locations between the upstream and downstream faces of the dam except at the locations in the arch nearest the top of the dam where three groups are placed between the faces of the dam. At the base location, the groups of instruments are located at elevation 5595 near the plane of centers of the dam. At the higher elevations the instruments are located at three to five sections in arches at elevations 5670, 5760, 5880, and 6000. At these elevations, the locations of investigation are on the plane of E BLOCK 17 [] @l FEI 60470 BLOCK 19-EL.6000 600005 Strainmeter trios at El 6000.0 EI 58800- Pis E15865.0- Gallery El 5865 El 5760 0. £ BLOCK 19 See Dwg 591-0-859 for Details R and S See Dwg 591 -0-860 for list of reference drawings Unless otherwise indicated, dimensions shown for locations of instruments in Pairs of No stress Straimeters, Detail W, are located in same concrete Figure 36. --Layout of structural behavior instruments in dam blocks 3, 5, 7, 9, 16, 17, 19, and 22. |