Figure 61.-Dam study A-22d (final), complete trial-load analysis-Arch stresses at abutment intrados.

Figure 62.-Dam study A-22d (final), complete trial-load analysis-Arch stresses normal to abutments.

100

100

200

SCALE OF FEET

STUDY A-22d ALWAYS THINK SAFETY

UNITED STATES

DEPARTMENT OF THE INTERIOR

BUREAU OF RECLAMATION

COLORADO RIVER STORAGE PROJECT

GLEN CANYON

DAM

COMPLETE TRIAL LOAD ANALYSIS

ARCH STRESSES NORMAL TO ABUTMENTS

F.D.

DRAWN
TRAGED.
CHECKED.
DENVER, COLORADO,

SUBMITTED

RECOMMENDED.

APPROVED.

Precooling to obtain a maximum 50° F. placing temperature was required because of the size of blocks to be placed in the dam and because of the relatively high placing temperatures which would normally occur at the site without such measures. Blocks as large as 70 by 190 feet were to be in contact with the foundation. Larger blocks than this, up to 191.28 feet on one side and 210.88 feet on the other side, occurred at the termination of several longitudinal joints in the dam but were located where the foundation restraint was materially reduced. Large blocks such as these would crack severely unless the temperature drop from the maximum concrete temperature to the grouting temperature was controlled to a maximum of about 35° F. This would be possible only if the maximum placing temperature was held to 50° F. or less. Without this restriction, placing temperatures could be as high as 80° F. in the summer with a resulting temperature drop of about 70° F.

Postcooling was performed by circulating cold water through embedded cooling coils placed on the top of each 7-1/2-foot construction lift in the dam. Artificial cooling of the concrete was primarily required because Glen Canyon Dam was designed as an arch dam with both the transverse and longitudinal contraction joints grouted ahead of the rising reservoir. Only by postcooling could the concrete be cooled and grouted in the relatively short construction period. The cooling systems further controlled the temperature rise so that the peak temperatures obtained would be appreciably lower than those which would occur without pipe cooling. Details of the concrete cooling systems are shown on figure 63. Temperature studies using the adiabatic temperature rise obtained from laboratory studies indicated that the temperature rise could be limited to 25° F. for blocks adjacent to rock. This meant that the maximum temperature drop would be limited to 35° F. for those areas where restraint was high.

The specifications requirement for the operation of the cooling systems provided for a 12-day initial cooling period for each 7-1/2-foot placement lift to be followed by final cooling of each 60-foot grouting lift to its final temperature. The final cooling period was estimated to take about 52 days. Refrigerated water was required for all final cooling because river water temperatures were not sufficiently low to accomplish the desired cooling. Temperatures at the time of grouting were originally to be 40° F. in the lower part

of the dam, ranging from 40° F. at elevation 3450 to 50° F. at the top of the dam. Later analyses, however, showed that higher closure temperatures could be permitted without significantly changing the stresses in the dam. Final cooling was then directed to be 40° F. up to elevation 3300, 45° F. between elevations 3300 and 3360, 50° F. between elevations 3360 and 3600, and 55° F. above elevation 3600.

Longitudinal joints were placed in all blocks except the end blocks of the dam, and were terminated before they reached the downstream face of the dam. So that these joints would not continue to the face, the specifications required that all concrete in the upstream and downstream blocks separated by such longitudinal joints be cooled to 50° F. prior to placing concrete above the termination of the joint. Reinforcement was also placed over the top of the joints to minimize any cracking tendency to the face.

The specifications provided for artificial cooling of backfill and tunnel plug concrete in the two diversion tunnels and in the mass concrete beneath the machine shop. In the diversion tunnels, such cooling was necessary so that periphery grouting of the backfill and plug concrete could be accomplished as soon as possible after placement of the concrete. Cooling of the mass concrete beneath the machine shop was deemed necessary because of the dimensions of the mass and the required location of control joints. The 60° F. temperature in both places was the estimated final stable-state temperature of the adjacent rock.

32. CONTRACTION JOINTS. Glen Canyon Dam was constructed in blocks which were separated from other blocks by transverse and longitudinal contraction joints. The purpose of the block construction was to confine the volumetric shrinkage cracks to predetermined planes throughout the mass concrete, which cracks could be grouted to form a monolithic structure after full volumetric shrinkage was obtained.

The spacing of the transverse contraction joints was governed primarily by the location of penstock and river outlet pipes through the dam. This resulted in 40and 70-foot spacings of the transverse joints in the central portion of the dam. Sixty-foot spacings were selected for the joints near the abutments to obtain block proportions which would facilitate concrete placement. One longitudinal joint was placed in each block except the end blocks. These longitudinal joints

were deemed necessary because of the thickness of the dam, this thickness being 295 feet at the base at the reference plane. The longitudinal joints were staggered across adjacent rows so as not to form a continuous joint throughout the length of the dam. In the central portion of the dam, longitudinal joints were located 75 feet and 106.5 feet downstream of the axis of the dam, resulting in maximum 130- and 161.5-foot lengths of upstream blocks, since the axis of the dam was 55 feet downstream of the vertical part of the upstream face. Near the abutments, the upstream blocks were made 151 and 179.5 feet long in order to better balance the length of the upstream and downstream blocks. The layout of the joints is shown on figure 64.

Tests of the foundation rock at the damsite indicated that the sandstone in the abutments would undergo deformation which was not entirely elastic. In order to compress the sandstone and obtain elastic properties in the rock, provisions were made to apply water at a pressure of about 200 pounds per square inch in the end contraction joints to obtain the expected inelastic "set." Double metal seals were installed completely around each grouting lift in the end joints to permit the application of water under this higher than normal pressure. This pressure would be held for only a short time, and then would be released and the joints drained of water. Grouting of the joints would then be accomplished through the Bureau's normal grouting system with normal grouting pressures. Owing to the inelastic behavior of the abutment rock, subsequent filling and lowering of the reservoir could conceivably result in opening up of the end contraction joint at each end of the dam. Since the standard grouting systems are filled with grout, they are not available for any further grouting operations. Systems of reinjectable grout valves were therefore installed in these end joints in addition to the normal systems. The Capitaine reinjectable valve from France was selected as being the best available valve at the time for this purpose. For details of the reinjectable grouting system see figure 67.

33. GALLERIES, ADITS, AND CHAMBERS. (a) General. -The galleries and adits serve as access to the interior of the dam for inspection

of the dam behavior and to service the dam after construction. The isometric drawings, figures 68 and 69, show the location of all galleries and adits in the dam. All the galleries in the dam are 5 by 7.5 feet except the grouting adits which are 6 by 7.5 feet, the adits to the powerplant which are 7 feet 8 inches by 8 feet 7 inches, and electrical service adits which are 4 feet by 7 feet 6 inches. The vertical stairwells are 6 feet in diameter. All longitudinal galleries were laid out on chords between contraction joints. Inclined galleries with a slope of 7-1/2 to 10 and vertical stairwells are provided with metal stairs. Vertical stairwells were limited to about 45 feet where possible, with frequent landings provided on the spiral stairs. Gutters, 12 inches wide and of varying depth, are located in all galleries and adits where the possibility of drainage is expected. Ventilation of the gallery system is accomplished by means of fans located in various areas of the dam. All galleries are located a minimum distance from the upstream face of the dam equal to 10 percent of the hydraulic head at the gallery floor.

(b) Foundation Gallery. -The centerline of the foundation gallery is located 14.5 feet downstream of the axis of the dam. It approximates the profile of the foundation as closely as possible. A 5-foot minimum clearance between the gallery and the excavated surface was established. The primary function of the gallery was to provide an area from which the main grout curtain ("A" holes) figure 14, were drilled and grouted and from which the upstream drainage curtain holes were drilled. This gallery also provides access to the foundation tunnels and to the plumbline weil reading stations.

(c) Drainage Gallery. -The centerline of the drainage gallery is located 147.5 feet downstream of the axis of the dam. It also approximates the profile of the abutments and foundation as closely as possible. The 5-foot minimum clearance between the gallery and the excavated surface also was used. The gallery originally terminated at elevation 3187.50 but was extended to elevation 3427.50 on each side to connect the grouting adits for ease in movement of materials and equipment for grouting the abutments. The gallery collects drainage water and by means of gutters and piping carries the water to the sump in the foundation gallery.

(d) Pump Chamber and Pump Chamber Gallery.-The pump chamber gallery is located at elevation 3187.50, 24.5 feet downstream of the axis of the dam. It connects the powerplant with the adits in blocks 7 and 18. It provides access to the sump pump