3400 +112

+533

3°07 +118

3325 +553 +248

85°04' 201

3250 +518 +326

73°04' 1236

3175

+541 +136

38°27' +255

Figure 42.-Dam layout for study A-20-Plan and sections. This layout was based on final abutment excavations.

axis of the dam is 900 feet. Below elevation 3300, the upstream face is vertical and 55 feet upstream from the axis. Above elevation 3300, the upstream face curves in a downstream direction to meet the axis of the dam at elevation 3710. The radius of curvature, in vertical radial planes, for this portion of the upstream face is 1,555.68 feet. All horizontal arcs in the upstream face are concentric with the axis, thus forming an upstream surface with no overhangs or abruptly changing surfaces. The upper central portion of the downstream face is formed of horizontal arcs concentric with the axis of the dam and has a constant slope of 0.31 to 1.00, horizontal to vertical. To thicken the dam at the abutments, these concentric arcs are terminated at a line on the surface where short (350-foot) radius fillets begin. These fillets continue to points near the abutments, from which tangents extend to the rock. To further increase the abutment thicknesses at elevation 3540 and above, the upstream face near the abutments was directed slightly upstream. For analytical purposes and to approximate the abutment excavation as nearly as possible, triangular abutments were assumed as shown by the long dashed lines.

Four complete trial-load analyses were made with design A-22. The first study included the effects of earthquake, while the second study was made omitting the effects of earthquake. The third study was made to bring in the effects of a revised cooling program. The fourth and last study included the effects of the cooling program and a modified reservoir storage and contraction joint grouting program. These studies were made assuming the horizontal elements as being nonsymmetrical with nonsymmetrical loading.

The loading conditions and assumptions used in each study are listed on the drawing showing the resulting arch stresses. Figures 44 through 47 show the arch stresses parallel to the faces. Cantilever stresses parallel to the faces of the dam are shown on figures 48 through 51. Principal stresses at the abutments are shown on figures 52 through 59.

In the modified cooling and grouting program in study A-22c, it was assumed that water in the reservoir would rise to elevation 3490 before grouting could be performed above elevation 3480. This specification was written in anticipation of normal runoff. However, in the years 1962 and 1963 the runoff was subnormal. In April 1963, the storage forecast for Lake Powell predicted the reservoir to be near elevation 3420 by late sun.mer 1963. Since the contractor would be ready to proceed with grouting above elevation 3480 before another runoff, the decision as to whether to stop the grouting program or to continue when the

1. Conrete placed to elevation 3540, reservoir water surface, elevat on 3240, 1oints ungrouted.

2 Concrete cooled to 40°F and contraction joints grouted
to elevation 3480, concrete placed to elevation 3715
and water surface raised to elevation 3490.

3 Contractionjoints grouted from elevation 3480 to
3660 after concrete had been cooled to temperatures
varying from 40°F at elevation 3480 to 50°F at cle-
vation 37/5, reservoir water surface raised to eleva-
tion 3700 and the effects of earthquake, earth em-
birkment and tailwater included.

Earthquake assumptions:

Dani moves upstream and downstream horizontally in
the direction of the plane of centers with an acceleration
of 0.1 gravity and a period of vibration of 10 second.
Increased water pressure acts equally on all cantilevers.
Effects of vertical acceleration not included
Effects of silt and uplift not included

Modulus of elasticity of concrete, 3,000,000 pounds per
square inch.
Modulus of elasticity of foundation rock, 600,000 pounds
per square inch.

Poisson's ratio of concrete, 0.20.

Poisson's ratio of foundation rock, 0.08.

Unit weight of concrete, 150 pounds per cubic foot.
Coefficient of thermal expansion of concrete 0.000,005,6 per
degree Fahrenheit.

All arches analyzed as unsymmetrical with unsymmetrical
loading.

Arch stresses are acting in horizontal directions parallel to the edges of the arches.

E-Stress at extrados of arch.

I Stress at intrados of arch
5. Maximum arch shear stress.
() Indicates downstream shear
Crown of arch

O Intermediate arch points.

All stresses are in pouids per square inch Compression, Tension