Canadian Dam Association Bulletin - Summer 2017 - 19

Figure 4: Completed Site C Project

* a till blanket and geomembrane
is provided on the invert of the
approach channel and is sealed to
the headworks structures to limit
ingress of water into the bedrock
beneath the approach channel and
under the RCC buttress. This will
help limit swelling of the rock.
This arrangement of the headworks
structures and powerhouse required
the construction of an approach channel to convey the water from the reservoir upstream of the earthfill dam to
the intakes and spillway. The portion
of the approach channel between the
intakes and the core of the earthfill
dam is closed by a concrete gravity
dam constructed of RCC. A rendering
of the RCC buttress is presented in
Figure 3 and a rendering of the completed project is presented in Figure 4.
This arrangement resulted in
hydraulic flow patterns to the intakes
and spillway that are not fully optimized; however, initial computations
indicated that hydraulic requirements
could be satisfied with this arrangement with a wide approach channel
and optimising the approach conditions to the spillway. Extensive
physical hydraulic models tests
were carried out in a laboratory on
this arrangement of the project and
the detailed hydraulic design of
the intakes and powerhouse was
optimized to provide the required
power flow, spillway capacity and
hydraulic conditions.
Canadian Dam Association * Summer 2017

5. RCC BUTTRESS
5.1 Layout of the RCC Buttress
The RCC buttress has a number of
significantly different cross sections,
depending on the location. The buttress is divided into the following
components (listed from upstream to
downstream):
* core buttress: forming the abutment
for the core of the earthfill dam and
forming part of the main water barrier across the river;
* dam buttress: a bulkhead wall
extending from the core buttress to
the intakes of the power buttress;

* powerhouse buttress: supports the
intakes, penstocks and powerhouse;
* transition buttress: a short bulkhead wall between the powerhouse
buttress and the spillway buttress,
which also supports the auxiliary
service bay for the powerhouse; and
* spillway buttress: supports the
spillway piers and radial gates, the
low level outlets, the free overflow
auxiliary spillway, the spillway
chute slab and the stilling basin
slab and walls.
Typical cross sections of these components of the RCC buttress are presented in Figures 5, 6 and 7 for the
dam, powerhouse and spillway buttresses, respectively.
5.3 Stability Analyses
The governing load case for stability was found to be the extreme event
of a failure of the impervious blanket
and geomembrane in the approach
channel and ingress of reservoir
water into a relaxation joint that
extends from the approach channel
invert down to the lowest bedding
plane, and the associated uplift on
that bedding plane. This load case is
considered to be a proxy post-earthquake load case where the impervious
blanket and geomembrane have been
damaged by the seismic event and

Figure 5: Dam Buttress
19



Table of Contents for the Digital Edition of Canadian Dam Association Bulletin - Summer 2017

Board of Directors
President's Message
Roller Compacted Concrete Buttress at the Site C Clean Energy Project
Hurricane Igor's Impact on Newfoundland Power's Small Hydro
CDA Conference Heads to Kelowna!
CDA Directors & Officers - Call for Nominations
2017 CDA Awards - Call for Nominations
CDA Developing New Ways to Distribute Guidelines
Notice of Annual General Meeting
Time to Renew Your Membership
Buyers' Guide and Trade List
Canadian Dam Association Bulletin - Summer 2017 - intro
Canadian Dam Association Bulletin - Summer 2017 - 1
Canadian Dam Association Bulletin - Summer 2017 - 2
Canadian Dam Association Bulletin - Summer 2017 - 3
Canadian Dam Association Bulletin - Summer 2017 - 4
Canadian Dam Association Bulletin - Summer 2017 - 5
Canadian Dam Association Bulletin - Summer 2017 - 6
Canadian Dam Association Bulletin - Summer 2017 - Board of Directors
Canadian Dam Association Bulletin - Summer 2017 - 8
Canadian Dam Association Bulletin - Summer 2017 - President's Message
Canadian Dam Association Bulletin - Summer 2017 - 10
Canadian Dam Association Bulletin - Summer 2017 - 11
Canadian Dam Association Bulletin - Summer 2017 - Roller Compacted Concrete Buttress at the Site C Clean Energy Project
Canadian Dam Association Bulletin - Summer 2017 - 13
Canadian Dam Association Bulletin - Summer 2017 - 14
Canadian Dam Association Bulletin - Summer 2017 - 15
Canadian Dam Association Bulletin - Summer 2017 - 16
Canadian Dam Association Bulletin - Summer 2017 - 17
Canadian Dam Association Bulletin - Summer 2017 - 18
Canadian Dam Association Bulletin - Summer 2017 - 19
Canadian Dam Association Bulletin - Summer 2017 - 20
Canadian Dam Association Bulletin - Summer 2017 - 21
Canadian Dam Association Bulletin - Summer 2017 - 22
Canadian Dam Association Bulletin - Summer 2017 - 23
Canadian Dam Association Bulletin - Summer 2017 - Hurricane Igor's Impact on Newfoundland Power's Small Hydro
Canadian Dam Association Bulletin - Summer 2017 - 25
Canadian Dam Association Bulletin - Summer 2017 - 26
Canadian Dam Association Bulletin - Summer 2017 - 27
Canadian Dam Association Bulletin - Summer 2017 - 28
Canadian Dam Association Bulletin - Summer 2017 - 29
Canadian Dam Association Bulletin - Summer 2017 - 30
Canadian Dam Association Bulletin - Summer 2017 - 31
Canadian Dam Association Bulletin - Summer 2017 - 32
Canadian Dam Association Bulletin - Summer 2017 - 33
Canadian Dam Association Bulletin - Summer 2017 - 34
Canadian Dam Association Bulletin - Summer 2017 - 35
Canadian Dam Association Bulletin - Summer 2017 - CDA Conference Heads to Kelowna!
Canadian Dam Association Bulletin - Summer 2017 - 37
Canadian Dam Association Bulletin - Summer 2017 - 38
Canadian Dam Association Bulletin - Summer 2017 - 39
Canadian Dam Association Bulletin - Summer 2017 - 40
Canadian Dam Association Bulletin - Summer 2017 - 41
Canadian Dam Association Bulletin - Summer 2017 - 42
Canadian Dam Association Bulletin - Summer 2017 - 43
Canadian Dam Association Bulletin - Summer 2017 - 44
Canadian Dam Association Bulletin - Summer 2017 - 45
Canadian Dam Association Bulletin - Summer 2017 - CDA Directors & Officers - Call for Nominations
Canadian Dam Association Bulletin - Summer 2017 - 47
Canadian Dam Association Bulletin - Summer 2017 - 2017 CDA Awards - Call for Nominations
Canadian Dam Association Bulletin - Summer 2017 - 49
Canadian Dam Association Bulletin - Summer 2017 - CDA Developing New Ways to Distribute Guidelines
Canadian Dam Association Bulletin - Summer 2017 - 51
Canadian Dam Association Bulletin - Summer 2017 - 52
Canadian Dam Association Bulletin - Summer 2017 - Notice of Annual General Meeting
Canadian Dam Association Bulletin - Summer 2017 - Time to Renew Your Membership
Canadian Dam Association Bulletin - Summer 2017 - Buyers' Guide and Trade List
Canadian Dam Association Bulletin - Summer 2017 - 56
Canadian Dam Association Bulletin - Summer 2017 - 57
Canadian Dam Association Bulletin - Summer 2017 - 58
Canadian Dam Association Bulletin - Summer 2017 - 59
Canadian Dam Association Bulletin - Summer 2017 - 60
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