and undrained analyses proceeded according to this

passes through the zone of foundation materials where

schedule. Level ground conditions were presumed to

100 percent of the available shear strength is mo-

exist just prior to the start of Stage I. The core trench

bilized. Similar results are shown in Figure 21 for the

was presumed to be in place at this time as excavation

drained case where the limit equilibrium analysis

and filling of the core trench were not modeled. As

showed the safety factor to be 2.33. The estimated

shown in Figure 18, Stage I was modeled in five load

horizontal and vertical movements in the embankment

steps by placement of the bottom five rows of elements

and foundation with consolidation taken into account

and Stage II was modeled in three load steps by the top

are shown in Figures 22 and 23 at the indicated times.

three rows of the embankment. Movements and

These results are presented in a form consistent with

stresses in the embankment and foundation were

that of data to be collected from instrumentation.

desired at the following times from the output:

(1) Start of construction, t = 0 months.

(2) End of Stage I, t = 4 months.

finite element analysis of the construction and

(3) End of the waiting period between Stages I

performance of an embankment dam was reported by

and II, t = 13.5 months.

Chang and Duncan (1977) for New Melones Dam.

New Melones Dam was constructed by the U.S. Army

(4) End of Stage II, t = 16.5 months.

Engineer District, Sacramento, on the Stanislaus River

to create a multipurpose reservoir capable of

(5) After construction had been completed for

impounding 2.4 million acre-ft of water. The dam,

13.5 months, t = 30 months.

built in a canyon, has a maximum height of 625 ft

above the streambed and a length of 1,600 ft. Plan and

(6) After reservoir filling.

cross-sectional views of New Melones Dam are shown

in Figures 24 and 25.

displacements at various times with consideration of the

effects of consolidation is shown in Figure 19. The

provide insight into three important questions related to

percentage of the available shear strength mobilized

the consolidation of the core and behavior of zoned

in the cross section for the undrained and drained

embankment dams. The questions were:

cases is shown in Figures 20 and 21, respectively. Al-

so shown in these figures is the safety factor of the

(1) What is the nature of expected movements in

critical circles from a conventional limit equilibrium

a zoned dam during the consolidation of the core?

analyses. Figure 20 shows that the results for the

undrained finite element method analysis agree with

(2) How do the stresses in the embankment

those from the slope stability analysis. In these

change during consolidation?

analyses, the critical circle (whose factor of safety

equals 1.25)

A-18

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