188. Installation of Structural Behavior Apparatus. The layout of the embedded instruments is shown on figures 35 and 36. Installation details and instrument terminations are shown on figure 37.

For major installations, the individual meters and their coiled cables were packed in boxes capable of holding approximately 30 meters. These boxes of meters were placed in a work skip along with all other items required for the installation, such as strain meter spiders, ground wire, no-stress strain meter cover plate, shovels, several sheets of scrap plywood, and other small items. The skip was placed on the block with the contractor's cableway, after the concrete in the block had been brought to grade a few feet from the downstream face. Work then began on installing groups of meters located near the downstream face of the dam, while concrete placement was continued toward the upstream face.

1. Embedded Instruments

189. Strain Meters. Strain meters were installed in configurations, as shown by details W, X, R, and S on figure 37. Sixty-nine groups of 12 strain meters each were installed in a fixed configuration determined by a holding device or "spider" as shown in detail X. Fifteen no-stress installations were made, each of which consisted of one horizontal and one vertical strain meter embedded beneath a 40-inch-diameter steel cover plate 7/16 inch thick as shown in detail W. Three "trios" of strain meters at both the upstream and downstream face, as shown in details R and S, were installed at each of three different locations in the dam.

The no-stress and the trio installations were made by shoveling out freshly placed mass concrete in the desired locations, placing the instruments in their proper positions, and hand placing the excavated material (minus large cobbles) around the instruments. The cables were then embedded 6 inches below the top of the lift and routed to a central location and into terminal boxes. No mechanical vibration was allowed in the vicinity of the embedded instruments.

The groups of strain meters were assembled to their spiders at the site and installed in formed blockouts or voids in the fresh concrete. Initially the box, or form, that was used to form the void was made of wood. Its dimensions were approximately 42 inches square at the top, 40 inches square at the bottom, and 24 inches deep. Later in the construction program, the contractor fabricated five re-usable sheet metal forms of similar dimensions and used them in place of the wooden forms which required replacement for each new installation. The concrete used for backfill over the strain meters was of the same mix proportions as the mass concrete, except that the maximum-size aggregate was 1-1/2 inches. Generally, two groups of instruments were prepared for installation, and 1-1/2 cubic yards of backfill concrete were ordered. The concrete was placed on sheets of plywood, and then shoveled into the instrument voids and hand placed around the meters. No mechanical vibration was used to consolidate the backfill concrete. the installation was completed, short lengths of cooling pipe were embedded a few inches into the concrete to define the instrument location and prevent traffic across the area. These pieces of pipe were easily broken off level with the concrete surface before the next concrete lift was placed. In addition to the pieces of pipe, the surface of the concrete above each instrument installation, including cable runs, was painted with orange

After

spray paint. The contractor's personnel working in these locations were warned to stay away from areas that were painted orange. No instruments were broken or damaged after embedment or during the time required for the concrete to set. However, on three occasions, cables were cut when holes were drilled into the top of a lift in which instruments were embedded. On these occasions, the cables were dug up, satisfactorily repaired, and the instruments were returned to service.

190. Stress Meters. Stress meters were installed in two configurations. Six stress meters were installed with the group 12 strain meters in block 13 at elevation 5670 as shown on figure 39. Fifty-five stress meters were installed as shown in detail Y on figure 37.

All stress meters were installed in the fresh mass concrete by first placing a covering of sand and cement grout on the vertical or horizontal surface which was to bear against the meter. The diaphragm of each meter was then brought into close contact with the bearing surface by firmly rotating the diaphragm plate into the grout. Concrete backfill, consisting of the excavated mass concrete minus large cobbles, was hand placed around the chamber of the meter and against the back of the diaphragm to hold it in place. No mechanical vibration was used to consolidate the backfill concrete.

191. Joint Meters. All joint meters were installed as shown in detail Z on figure 37. When a joint meter terminated in a low block, the cable was attached to the meter in the shop, and installation was completed at the time the block was placed. When a termination was made in a high block, the cable was embedded in the high block with about 30 inches of cable stored in a formed recess for attaching to the meter in the low block. Prior to placing the low block, the meters were connected directly to the cables, and allowed to cool before test record checks were made. The joint meter was placed inside a 16-inch length of standard 2-inch-diameter pipe for temporary protection and hung above the top of the lift that was to be placed. After concrete had been placed to grade, a recess was dug to the previously installed joint meter socket, the socket's protective plug removed, and the joint meter screwed into place in the socket. The displaced concrete was then hand placed around the joint meter to complete the installation.

Joint meters, probably because of the flexible bellows in the body of the meter, appeared to be much more susceptible to damage through handling than any other type of meter. Several joint meters were damaged during installation and replaced. A few joint meters ceased to function properly after their installation.

192. Resistance Thermometers. Resistance thermometers were installed in the mass concrete as shown in details U and P of figure 37. Thermometers installed at the surface of the dam were hand placed from 1 to 2 inches from the forms rather than in direct contact with the forms as shown in detail P.

One thermometer was installed 10 feet into the rock foundation of block 22 at approximately elevation 5865. The installation was made by drilling a hole into the rock, inserting the thermometer, and injecting backfill grout into the hole.

193. Terminal Boxes and Boards. Terminal boxes were installed as shown on figure 38. The six boxes of reading station 1 were installed at a height of 3 feet 6 inches above the gallery floor. All subsequent boxes were installed at the more convenient height of 3 feet 10 inches above the floor. The terminal boxes were embedded during concrete placement, but the terminal boards were not installed until the gallery forms were stripped, and all cables to the reading station were brought through conduit to the boxes. Each cable was connected to its respective cluster of contacts as shown on figure 204. All terminal boxes at a reading station were interconnected with No. 0 A. W.G. bare stranded-copper ground wire which was then attached to the gallery reinforcement steel. In April 1962, instructions were received from the Denver office to provide ground-wire circuits from each instrument to the terminal boards. All instruments installed after that time were connected by No. 14 A. W. G. bare stranded-copper ground wire to a common ground wire which was then attached to the grounding lug inside the terminal box.

194. Rock Anchor Bar Load Cells. Load cells were installed on rock anchor bars at three locations in the spillway intake area in conjunction with the program of installing

40-D 4868

anchor bars for stabilizing the rock in an area near the dam. The area involved was immediately downstream of the dam axis on the left side of the spillway intake channel, where a large rock slide had occurred during the excavating.

Three of the anchor bars were supplied by the contractor with scarfed ends for field welding to the end stubs of the load cells which were Government supplied. Instructions for the anchor bar and load cell installations were received by the project from the Denver office.

The load cell anchor bar installations in the holes drilled into the rock were made in the same manner as the installation of the anchor bars without load cells. A load cell anchor bar installation is shown on figure 45.

Bearing plate pads of sand- cement grout were formed for each load cell anchor bar as well as for anchor bars without load cells as shown on figure 45. The bearing plates were placed on the pads at the time the pads were being finished in order to maintain the bearing plates within 1° of normal to the axis of the anchor bars.

The three load cells, designated as LC-1, LC-2, and LC-3, which were sent to the project from Denver, were field welded to anchor bars 109, 125, and 139, respectively, as shown on figure 45. To protect the strain meter units of the load cells from excessive heat during welding, burlap was wrapped about the welding stub of the load cell and soaked with water. The portion of the welding stub near the strain meter unit was thus maintained cool to the touch throughout the welding process. A strain meter test set was attached to the meter leads and no appreciable change in resistance ratio was noted during welding. Care was taken to prevent damage to the load cells during all handling and welding operations and during the time the installation of the anchor bars was made in the holes drilled into the rock. The electrical cable from the load cell was terminated in an outlet box which was clamped to the face of the threaded bar that extended above the bearing plate and nut.

The schedule of readings of ratio, reverse ratio, and total resistance for each load cell required that readings be obtained after each step in the installation procedure, from the time the load cells were unpacked and inspected until immediately prior to nut torquing.

The schedule then required readings during nut torquing at several succeedingly higher torques including the final torque. After nut torquing, readings were made at 15-minute intervals for 2 hours, then at hourly intervals for 4 hours, then twice daily for 4-1/2 days. Finally readings were taken twice weekly, and after a 4-week period were reduced to weekly intervals.

All original data sheets with meter readings from the schedule were transmitted to the Denver office where they are on file.

In the plan for the loading of the anchor bars, which was by torquing the nuts using a torque wrench, the first anchor bar to be loaded was 139, which had LC-3 attached. The bearing plate, threaded end of the anchor bar, and the nut were carefully cleaned with a wire brush. The plate and nut were then placed on the bar, and while one man held the bar from twisting with a wrench on the notched shoulder of the bar, a second man tightened the nut with the torque wrench. The torque application was increased by stages until a maximum of 550 foot-pounds was reached. The resulting stress in the anchor bar, as determined from a nomograph included with the load cell installation instructions, was only 4, 000 pounds per square inch. Anchor bar 125 with LC-2 attached was then tightened similarly, and the stress obtained was 8,800 pounds per square inch.

When the stress obtained from the recommended torque was so low, it was decided to increase the applied torque, and to lubricate the anchor bar threads. The anchor bars were unloaded, and a new zero reading was obtained for the load cells. The anchor bar threads on LC-3 were then lightly lubricated, and the nut was again tightened by stages to the recommended torque. Very little increase in stress was obtained over the first method.

The bar was unloaded and a new zero stress reading obtained for the second time. Both the anchor bar threads and the bearing surfaces of the plate and the nut were heavily

oiled with SAE 30W motor oil. The bar was then torqued by stages to a maximum of 704 foot-pounds which was the maximum for which the torque wrench could be set. The remainder of the anchor bars were then torqued in a similar manner. Because of the cold weather at the time the anchor bars were loaded, the exposed ends and plates could not be painted. All exposed metal was coated with grease and covered with burlap.

2. Deflection Measurements

195. Plumblines and Reading Station Apparatus. Plumbline wells were formed in blocks 8, 14, and 18. The three 12-inch-diameter vertical wells were formed in the mass concrete with expandable metal forms. Some difficulty was experienced by the contractor in maintaining alinement of the wells within specification tolerances for plumb. During the 1962 construction season, forms 14 inches in diameter were fabricated and used in the mass concrete. The wells were reduced to a diameter of 12 inches at gallery reading stations, and at the suspension chambers in the roadway on top of the dam.

Installation of the plumblines, their suspension assemblies, and weights was performed by project personnel. The suspension spider was fabricated from 1/4-inch aluminum plate and was triangular in shape. Permanent deflection measuring devices for the plumblines were not available at the time of installation. A temporary reading station system consisting of a trapezoidal-shaped recess plate was installed. The reading apparatus consists of a slide bar and an engineer's 50 scale as a T-head. To obtain a set of deflection readings, the reading instrument was first used on the left-hand edge, and then on the right-hand edge of the plate.

Installation of the permanent deflection measuring equipment was made in February 1964. The reading station assemblies were installed essentially as shown on figure 48. Minor field modifications were required for this installation.

Deflection measurements were obtained at all reading stations before and after installation of each of the three plumblines. Initial reading dates for the permanent installations are as follows: block 14, February 6, 1964; block 8, February 10, 1964; block 18, February 12, 1964.

196. Deflection Targets and Theodolite Piers. Deflection targets were installed as shown on figure 46.

Theodolite piers were installed as shown on figure 47. Installation of the targets and theodolite piers was performed under the supervision of the Bureau survey organization, and all measurements and observations were made by survey personnel.

Two basic types of targets, each selected as being easiest to read and most readily recognizable under the lighting conditions, were used at this project. The target used on the dam consisted of a white cross on a black background. These targets were 2-1/2 inches in diameter, and the bar widths of the cross ranged from one-eighth to three-eighths of an inch depending on the distance of the target from the theodolite piers. The target which was installed primarily on the abutment rock was a black and white bullseye target. These targets were 1-7/8 inches in diameter, and had a 1/8- to 3/8-inch black bullseye with concentric white and black rings.

The instrument used in making deflection measurements was purchased specifically for that purpose. It is an European-made 1-second precision theodolite with a horizontal circle reading accuracy of 0.2 second of arc. In use, five direct and five reverse readings are made on each target. Eight direct and eight reverse readings are made on the control targets mounted on the baseline piers.

Hydrostatic Measurements

197. Uplift Pressure Pipes.

A system of uplift pressure pipes was installed in blocks 7, 13, and 19 as shown on figure 49. The pipes were installed by the contractor prior to concrete placement. Drilling into the foundation through vertical pipes was performed by the contractor after all foundation grouting had been completed in the surrounding area.