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DAM, POWERPLANT, AND APPURTENANT STRUCTURES

(e) Rock Bolting.-In its report of October 12, 1961, the Board of Consultants, in view of stress relief joints that had developed, or might develop, in the abutment rock downstream of the dam, particularly in the right abutment, and the increase of rock stresses that would result from the arch thrust, recommended that extensive rock anchorage and drainage be provided to insure stability of these arch masses. The most critical areas appeared to be those below elevation 3450 in the right abutment and somewhat below elevation 3350 in the left abutment where the intrados of the arch at the abutment lies close to the surface and where relief jointing is most noticeable. The Board was of the opinion that the anchorage in the right abutment should extend at least 25 feet back of the A-joint.

Holes ranging from 40 to 80 feet in depth were drilled between elevations 3420 and 3150 and from station 5+00 at the A-line of the powerplant, downstream to station 3+00. Most of the holes were from 60 to 70 feet in depth and all extended more than 25 feet back of the A-joint.

The holes were cleaned thoroughly with air and water. The bottom 15 feet of each hole was sandblasted to remove grease, etc., to assure bonding with grout, and the top 5 feet of each bar was wrapped with waterproof building paper to prevent bonding. When a bar was lowered into the hole, 1/2-inch plastic tubing was attached to the bottom of the bar through which a measured quantity of 0.8:1 cement grout with 5 parts of aluminum powder to 100,000 parts of cement was injected into the bottom of the hole to assure that the bottom 12 feet of hole was filled with grout. The grout stop was then set at 5 feet from the top of the hole and the top section of the bar grouted in place.

(f) Grout Adits.-Drilling and grouting from the right and left abutment grout adits was started in June 1962 in the elevation 3157.5 and elevation 3270 adits. Vent or pressure relief holes were drilled in the right abutment downstream of the dam on the powerplant A-line between elevations 3150 and 3250 to act as vents while grouting from the grout adits. Grouting in the left abutment took place in the grout adits at elevations 3315, 3367.5, 3427.5, 3480, 3547.5 and 3630 and was completed in May 1963. Grouting in the right abutment was performed from the grout adits at elevations 3157.5, 3217.5, 3270, 3322.5, 3367.5, 3427.5, 3480, 3547.5 and 3630 and this work was completed in July 1963. Holes ranged from 40 feet in depth to 100 feet. The pressure ranged from 100 to 125 pounds per square inch, with most of the holes being grouted at 125 pounds per square inch.

During the period from May 1961 through April 1964, eighty-eight 10-inch-diameter concrete cores were drilled in the dam. Ten cores were drilled in B-blocks 7, 8, 11, 14, 15 and 17. Sixty-one cores were drilled in the floor and walls of the galleries and adits of the dam at various elevations, and 17 cores were drilled in the face of the dam at various elevations. These cores were drilled in blocks 5, 6, 8, 11, 12, 14 and 26. Two cores were drilled vertically in the service bay at elevation 3188.

(g) Contraction Joints.-First contraction joint grouting was from bedrock to elevation 3060 and was completed in May 1961. The joints grouted included:

(1) Four transverse joints between blocks 9-10, 10-11, 11-12, and 12-13. Each transverse joint was separated by metal seals into two separate areas. A small area, 4 feet 6 inches wide, was located near the upstream face of the dam.

(2) Five longitudinal joints in blocks 9 through 13.

This was the total of the contraction joints below elevation 3060. Temperatures of the joints were mostly lower than the 40° F. requirement and some reached a minimum of 29° F. in the final stages of secondary cooling. Joint meters indicated joint openings of 0.105 to 0.157 inch at elevation 3037.5; and at elevation 3060 openings ranged from 0.022 to 0.089 inch in the same blocks.

Backfill between the dam and the powerplant was placed to elevation 3060 at the downstream face of the dam at the time of the grouting. This required the contraction joint piping systems extruding from the face of the dam below elevation 3060 to be grouted through 1-1/2-inch risers extending to approximate elevation 3067.

Contraction joints in the elevation 3060 to elevation 3120 lift were grouted in October 1961. Thirteen transverse joints were grouted, extending from joint T6/7 to joint T18/19 and 13 longitudinal joints in blocks 6 through 18 were grouted.

Refrigerated brine was used during the latter part of secondary cooling, and all blocks were lowered to 40° F. except block 11 which was at 50° F. While testing the contraction joints and attempting to fill the transverse joints with water, numerous leaks appeared from cracks in the drainage and foundation galleries. The cracks were calked with lead wool by use of pneumatic chipping hammers and then grouted to seal the leaks.

Contraction joints in the 3120 to 3180 lift were grouted in January 1962 as follows: (1) Seventeen transverse joints extending from joint T4/5 through joint T20/21; (2) 15 longitudinal joints extending from block 5 through block 19; and (3) 13 special transverse joints extending from T6/7 through T18/19. Concrete temperatures were lowered to 40° or 45° F. prior to grouting. Leaks again developed and were calked with lead wool and sealed with grout.

Contraction joints in the 3180 to 3240 lift were grouted in May 1962, as follows: (1) Nineteen transverse joints extending from joint T3/4 through

CONSTRUCTION

The 3300 to 3360 grout lift was grouted in November 1962 and included the following contraction joints: (1) Twenty-one transverse joints extending from joint T3/4 through joint T23/24; (2) 21 longitudinal joints extending from block 3 through block 23; (3) 19 special transverse joints extending from T3/4 through T21/22; and (4) 1 longitudinal perimeter joint in block 3. Fewer leaks occurred in this grout lift than in previous lifts and these were calked and grouted as before. Figure 65 presents some transverse contraction joint information.

The 3360 to 3420 grout lift was grouted in December 1962 and included the following contraction joints: (1) Twenty-one transverse joints extending from joint T3/4 through joint T23/24; (2) 21 longitudinal joints extending from block 3 through block 24; (3) 20 special transverse joints extending from T3/4 through T23/24 exclusive of T21/22, which was grouted in March 1963; and (4) 2 longitudinal perimeter joints, blocks 3 and 24. Only one leak which required calking was found in this lift.

The 3420 to 3480 grout lift was grouted in March 1963 and included the following contraction joints: (1) Twenty-one transverse joints extending from joint 3/4 through joint 23/24; (2) 22 longitudinal joints extending from block 3 through block 24; (3) 21 special transverse joints extending from T3/4T through T23/24T and T21/22T of the 3360-3420 grout lift which was omitted with that lift; and (4) 2 longitudinal perimeter joints, blocks 3 and 24. Some leaks were again found and were calked and sealed with grout.

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DAM, POWERPLANT, AND APPURTENANT STRUCTURES

pounds per square inch. On March 12, the same check was made on transverse joints 24/25 and 25/26 from bedrock to elevation 3480.

The procedure consisted of installing a 1-1/2-inch water supply line to each transverse joint. A three-way header was used with valves and a gage to determine the water pressure at the header before and during the injection of water into the joints. Gages were also installed on the vent system of the joint being tested in order to keep the pressure below 25 pounds per square inch, initially. Each transverse contraction joint was tested individually.

All of the four transverse contraction joints below elevation 3480 were found to be connected to their respective transverse perimeter and transverse face perimeter.

On March 28, 1963, the T2/3 and T1/2 joints were water loaded, but it was impossible to obtain a pressure of 100 pounds per square inch due to excessive leaks where the joints crossed galleries or adits. On March 29 the joints were grouted, each grout lift from bedrock to elevation 3480 being grouted individually. All transverse joints were interconnected with their respective perimeters, and in each case the face perimeter was grouted with the perimeter. All joints were sealed off under pressure. Beginning April 15, the same procedure was used on the right end joints, but it was not possible to obtain a pressure of 100 pounds per square inch on the joints.

The 24/25 joint between elevations 3420 and 3480 developed a leak where the joint crossed the grout adit at elevation 3427.5. The joints were grouted on April 16, each joint being grouted individually.

Duplex piston-type pumps, size 10 by 3 by 10 inches, were used at each location for grouting of the contraction joints. A circulating grout supply line, 1-1/2 inches in diameter, was laid on the catwalk most convenient to the lift being grouted. Type II cement in waterproof bags was used and the starting water-cement ratio was 1:1. This was reduced to 0.8:1 when the joints became half full.

The 3480 to 3540 grout lift was grouted in November 1963 after the reservoir had reached elevation 3395. The joints grouted were as follows: (1) Twenty-three transverse joints extending from joint 2/3 through joint 24/25; (2) 8 longitudinal joints, L-2, L-3, L-4, L-30, and L-22 through L-25; (3) 23 special transverse joints extending from T2-3T to T24 25T; and (4) 2 longitudinal perimeter joints, blocks 2 and

Grouting of the final grout lift between elevations 3660 and 3715 was completed December 20, 1963. This included 23 transverse joints and 23 special transverse joints from the 2/3 joint through the 24/25 joint. Joint meters and dial indicator gages were read at time intervals during the grouting to detect movement of blocks. Prior to grouting, the joints were filled with water and those which leaked were calked with lead wool. All joints except four T and four TT joints were grouted under pressure and these joints would not hold pressure. Joint meters and dial indicator gages were read at time intervals before and during grouting to detect movement of the dam blocks.

Water loading and grouting of end contraction joints 1/2 and 25/26 from elevation 3480 to elevation 3660 and the top two lines of the reinjectable grout system below elevation 3480 was completed January 21, 1964. The 1/2 transverse joint was water loaded but due to extensive leaks only pressures between 21 and 40 pounds per square inch could be held. In the 25/26 joint, pressures between 40 and 60 pounds per square inch were held for 6 hours but it was impossible to obtain 100 pounds per square inch. An attempt was made to inject grout into the 3420 to 3480 grout lift through the reinjectable grout system but grout was refused.

As individual unit pay items were provided for these installations, no unusual difficulties were experienced in minor changes in the quantity of items. Some difficulties occasionally occurred when inexperienced workmen were assigned to the meter installation work. The most efficient and best installations were made when a single experienced crew was responsible for the meter installation.

179. DEFLECTION MEASUREMENTS. in addition to the embedded instrument installations, two systems of measurements employing refined methods of surveying were provided for determining the manner in which the dam deflects during periods of reservoir filling and operation.

One system comprises five plumblines, each in a formed well (fig. 267) extending from the top of the dam to a point near the foundation. The wells are located in the maximum section and at points approximately one-third and two-thirds the distances between the maximum section and the abutments. The plumblines are located in blocks 4, 7, 12, 18 and 21 of the dam, and have a total of 19 reading stations. At each reading station, movement between the dam and plumbline is measured using a micrometer slide and microscope apparatus. The micrometer can be read in ten-thousandths of an inch. The reading stations are oriented in plan so that measurements of deformation are in planes which are radial and tangential to the dam's axis. By this expedient, the measurements require no trigonometric resolution to obtain deformation in the desired directions. Readings are

made periodically and are tabulated on forms in a manner that computer card punching can be made directly from the data sheet without further transposition. or trigonometric resolution. The second system for determining deflection of the dam consists of a grid system of 68 targets placed on the downstream face of the dam and 17 targets on the foundation along the abutments. Locations of the targets are charted periodically from primary theodolite stations on each abutment downstream of the dam and from secondary stations on the canyon rim, using precise triangulation surveying methods. This system is discussed in further detail under section 186 on surveys.

180. UPLIFT PRESSURE PIPES. Hydrostatic uplift at the base of the dam is measured at 41 locations by pipes connecting to wells at the concrete-rock contact plane and terminating in the dam galleries. Located in blocks 2, 4, 5, 7, 11, 16, 19 and 25, the pipes are arranged in seven lines, each line being made up of from five to seven pipes. Permanent data showing the elevation at which the pipes are installed are recorded on data sheets and readings are made at appropriate intervals. Pressure is measured by means of a Bourdon-type pressure gage calibrated in feet of water, attached through a gage cock to the uplift pipe. When zero pressure is indicated in a pipe, the water level is determined by sounding. Continued zero pressure with water standing at the level of the pipe is investigated further by adding a transparent standpipe section to the pipe to observe the level to which the water rises.

181. DRAINAGE MEASURING DEVICES. Weirs have been installed to elevation 3480 in the gallery gutters to measure total drainage flows from the following areas.

(1) Each foundation tunnel, including the access tunnel to the left diversion tunnel.

(2) Each area between the above tunnels.

(3) Each area in the foundation gallery from the lowest of the above tunnels to the pump sump.

(4) Each area in the drainage gallery from right and left of the transverse adit in block 11 to the top of the drainage curtain.

182 SE SMOGRAPH STATION. A seismograph stapon, located approximately 11 miles northwest of the domate, records earthquake shocks. Records from the stabon show the magnitude of any earthquake

tremors in the vicinity and also serve to determine any possible change in local seismic activity that may occur in the area due to the increased weight of the reservoir. The equipment from the Bureau's Hungry Horse project was initially installed, but was replaced by new equipment in September 1964 when replacement parts for the obsolete equipment could no longer be obtained. Installation was made by members of the U.S. Coast and Geodetic Survey who also trained Bureau personnel in operation of the station.

The seismograph vault was constructed under specifications No. DC-5163 by W. W. Clyde and Co. of Springville, Utah, in the summer of 1959. The vault is 10 by 22 feet with reinforced concrete floor, walls, roof, retaining walls, and instrument piers. The walls and roof were 9 inches thick, the floor was 4 inches thick and the retaining wing walls ranged from 9 to 6 inches in thickness. The roof sloped 2 feet in 22 feet toward the open end of the vault. Backfill was placed around three sides and over the roof. A complete electrical system was installed by the contractor and electric power was supplied by Arizona Public Service Co. over a line which they constructed.

Approximately 2 miles of 12-foot-wide unsurfaced

road was constructed under specifications No. DC-5163 to provide access from U.S. Highway No. 89 to the vault.

3. Concrete Cooling and Grouting

183. CONCRETE COOLING. Initial cooling of the mass concrete in the dam was provided to remove the

of hydration. This was accomplished by circulating chilled water for a period of 12 days through 1-inch aluminum tubing, placed on top of each 7.5-foot lift (fig. 63). Secondary cooling to shrink the blocks prior to grouting continued for about 40 days or until a temperature of 40° F. was reached in concrete below elevation 3450 and 50° F. in concrete for elevation 3450 to the top of the dam.

Cooling water first came from a package refrigeration unit located just downstream of block 11, with a similar unit being used to cool the mass concrete in the machine shop and service bays. This package unit was used to cool concrete in the dam until August 3, 1960, and then a chiller, supplied with liquid ammonia from the main refrigeration plant, was used.

Between January and April 1961, six chillers were installed to supply additional cooling water. Three chillers were installed upstream of unit bay 1 of the powerplant and were connected to 8-inch headers

installed on brackets above the elevation 3120 catwalk across the downstream face of the dam. The fourth chiller supplied cooling water for concrete in the machine shop, the service bay, and the dam above elevation 3060. Two chillers were placed on the elevation 3180 catwalk for initial cooling above elevation 3180 while the other cooling system was used for secondary cooling of the elevation 3120 grout lift.

In January 1962, three chillers were moved to the downstream end of the refrigeration plant on the elevation 3715 bench. Gravity flow of cooling water through the cooling coils was used for both initial and secondary cooling. Pressure was reduced by valves located on the elevation 3240 catwalk on the downstream face of block 21. Two pumps, rated at 1,800 gallons per minute at 392 feet of head, were installed on the elevation 3240 catwalk to pump the water back to the chillers.

Pressure-reducing valves and return pumps were also installed on the elevation 3300 catwalk on the face of block 22 for initial cooling. These pumping stations were raised to higher stations as necessary. The cooling water was delivered through 8-inch horizontal headers installed across the face of the dam. Vertical 4-inch headers led from the 8-inch header to blocks being cooled, and 1-1/2-inch headers led from there to the 1-inch aluminum cooling pipe. As the blocks became small, near the top of the dam, the flow of cooling water had to be reduced below 4 gallons per minute to keep the lifts from cooling faster than 1-1/2° F. per day. Cooling water normally flowed at the rate of 4 gallons per minute, except during some cold periods when the rate of flow was increased to prevent freezing.

184. UNUSUAL STRESSES DURING CONSTRUCTION. Numerous horizontal and vertical cracks appeared in the dam blocks beginning in 1960. These cracks appeared especially during final cooling and grouting. They were plugged with lead wool before grouting of a grout lift and sealed by the contraction joint grouting. A number of cracks showed up in block 8-B. Two mats of reinforcing steel were placed in the elevation 3112.5 lift to stop a crack which extended from the 8-B-9-B block line at elevation 3067.5 and from the 7-B-8-B block line at elevation 3075 extending to the top and across the surface of the elevation 3097.5 lift and to the top of the elevation 3105 lift. The crack was not noted higher than elevation 3105.

It was thought that changing the intensity or pattern of the temperature stresses within each block by reducing the temperature gradient might be a solution to avoid this cracking. The cooling procedure