14
Results
Figure 23 shows the temperature contour in the dam body at the end of
placement. The placement starts at 31 Jan 2001 from level 143.1ASL and ends at 20
Jan 2002. The maximum placement temperature was 25
o
C, recorded in July 2001 and
the minimum placement temperature was 10
o
C, recorded in January 2002. The
average placement temperature for all layers was 20
o
C. The maximum temperature
developed in the dam body is about 31.0
o
C at end of placement, corresponding to a
heat of hydration of 320 j/g at 28 days compared to 33.8
o
C corresponding to 381 j/g
at 28 days as reported by Schrader in the trial test and back analysis using finite
element method.
Figure 24 shows the temperature contours measured in April 2002.The
maximum temperature is 30.6
o
C measured at the center of the dam.
Figure 25 shows the vertical temperature distribution along the right surface
wall of gallery (7.6m from upstream) at end of placement. The temperature gradient is
high at regions around the gallery and at the top of the dam body. The reason for the
lower gradient is due to the heat losses by conduction into the foundation also, the
placement was started in the winter, and the upper gradient of temperature due to
difference in temperature between the RCC and the ambient air temperature in winter
where the placement was finished. The maximum temperature is about 28.5˚C at 15m
from the base of dam (level 158mASL) at end of placement. Also it can be seen that
the temperature of RCC at the surface of gallery equal to the ambient temperature
inside the gallery (about 18˚C).
The maximum temperature developed in the dam body, as shown in Figure 25,
will be at 15m from the base of dam (level 158 mASL), so Figure 26 shows the
predicted temperature history at that level and at the center of the dam body (19.5m
from upstream) for both approaches (conventional and actual). The maximum
temperature of RCC developed in the dam body was 32.8˚C by the actual analysis
while it was about 31˚C from the conventional approach. This means that
conventional approach underestimates the maximum temperature (isn’t the
underestimation coming from different boundary conditions (ambient conditions,
placement temperatures) being applied for conventional and actual approach?
conventional approach should give higher temperatures as heat losses at the top
surface of the lift are minimised).
15
Figures 27 and 28 show a comparison between the model prediction and
measured values at the center of the dam (Level 145.5 mASL). The actual RCC
placement approach showed a very good agreement with the measured temperature,
especially at 90 days from placement, better than the conventional approach model.
The gap between simulated values and measured at the early age is mainly due to the
RCC layer exposure to sun and radiation effects. Such effect was not included in the
analysis. Also, the fiber optic cables installed at the beginning of placement were not
covered at early stage by RCC.
Figures 29 and 30 show a comparison between the measured temperature
distribution along the dam body between the data measured using DFOT,
thermocouple and the data predicted by ANSYS for the same procedure of placement
and the actual boundary conditions. A good agreement can be seen especially, at the
center of the dam. (this canceled as in paragraph above is written that radiation is not
considered, just taken into consideration by increase of ambient convection
temperatures).
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