Buttress Dam • Roman engineers, often erroneously, judged the stability of a dam wall to be inefficient, they backed it up by irregularly spaced buttresses. • A third of the Roman dams in the Iberian peninsula were buttress dams. • The most remarkable of the Roman buttress dams is the one near the village of Esparragalejo. This is the first multiple arch dam Evolution of the Modern Buttress Dam Today buttress dams as derivations from the massive gravity type with the introduction of intermediate spaces. These spaces allow the discharge of water seeping through the dam and its foundation, thus greatly reducing uplift pressures. Given the absence of uplift, more substantial savings were possible by inclining the upstream face, thereby mobilizing the vertical water load on the upstream face for sliding stability. Classifications OF BUTTRESS DAMS 1. Massive head buttress dams 2. Deck slab buttress dam 3. Multiple arch buttress dam
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Buttress Dam• Roman engineers, often erroneously, judged the stability of a dam wall to be
inefficient, they backed it up by irregularly spaced buttresses.
• A third of the Roman dams in the Iberian peninsula were buttress dams.
• The most remarkable of the Roman buttress dams is the one near the village of Esparragalejo. This is the first multiple arch dam
Evolution of the Modern Buttress Dam
Today buttress dams as derivations from the massive gravity type with the introduction of intermediate spaces.
These spaces allow the discharge of water seeping through the dam and its foundation, thus greatly reducing uplift pressures.
Given the absence of uplift, more substantial savings were possible by inclining the upstream face, thereby mobilizing the vertical water load on the upstream face for sliding stability.
Classifications OF BUTTRESS DAMS
1. Massive head buttress dams
2. Deck slab buttress dam
3. Multiple arch buttress dam
Massive head buttress dams
1 . Massive round head 2. Massive flat head
Deck slab buttress dam
1. Simple slab deck 2. Continuous slab deck
Forces on the buttress dams
WATER
F1
R
1
R2P
F2
R0 R1
w
Prestessing is used to minimize the quantity of concrete and counteract tensions.
Prestressing can be applied in at least three manners to a buttress dam.
» To 'pull down' the upstream face
» To 'jack up' the downstream face
» To compact the buttress on to the foundation
CONSTRUCTION PROCESS
1. Stream must be diverted or blocked from flowing through the site.
2. A coffer-dam (a temporary structure to impound the water) must be built.
3. Another small coffer dam is built to block the leakages.
4. Pumps are used to remove the water from site.5. Compact the site.
6. Foundation area - must be cleaned before the first concrete is placed.7. Form work-Modern steel formwork is of cantilever design.8. Forms made of wood or steel are constructed.9. May be necessary to install extensive systems of rock bolts or anchor
bolts.
10. Instruments has to be installed:a. monitor groundwater levels
b. joint movement
c. potential seepage
d. slope movements
e. seismic activity
FOUNDATION PREPERATION
Excavation in bedrock.
Construction on unconsolidated deposits.
Grouting.
Pour the concrete.
Functional Importance of Elements of the Buttress Dam
Structure of a Buttress Dam
Crest
Heel
Gallery
Toe
Spillway(inside dam)
NWLNormalwater level
MWLMax. level
Free board Sluice way
Upstream Down stream
Buttress
Buttress
NWLNormalwater level
MWLMax. level
Upstream Down stream
Buttress
Buttress
A thin, erect, tabular concrete supporting member used in construction of slab and buttress dams. Also a projecting structure providing lateral support to a rock face or a portion of a dam.
Heel
NWLNormalwater level
MWLMax. level
Upstream Down stream
Heel
Heel
The upstream contact of a dam with its foundation.
Toe
NWLNormalwater level
MWLMax. level
Upstream Down stream
Toe
Toe
The downstream contact of a dam with its foundation.
Crest
NWLNormalwater level
MWLMax. level
Upstream Down streamCrest
Crest
The top of a dam.
Dam Pavements
The top part of the dam can be designed as a road.Same time it can act as a bridge.
Spillway
NWLNormalwater level
MWLMax. level
Upstream Down stream
Spillway(inside dam)
Spillway Types
Spillway
The structure on or at the side of a dam that contains and guides the flow of the excess water supplied to a reservoir. Spillways inside the reservoir are called glory holes and consist of a vertical shaft a tunnel which exits below the dam.
Spillway
Controlled SpillwayWater flow control by using gates
Uncontrolled SpillwayThe elevation of spillway crest use to
control the water flow.
Auxiliary Spillways/Emergency Spillways
Primary Spillways
Side Channel Spillways
Siphon Spillways
Shaft Spillways/Morning Glory Spillways
Sluiceway - An opening in the dam near the ground level, which is used to clear the silt
accumulation in the reservoir side.
Sluiceway
NWLNormalwater level
MWLMax. level
Upstream Down stream
Sluice way
Gallery
NWLNormalwater level
MWLMax. level
Upstream Down stream
Gallery
Gallery
A long, narrow passage inside of a dam used for inspection, grouting, or spillway.
Free Board - a portion of a dam maximum water level in a reservoir.
Free board
NWLNormalwater level
MWLMax. level
Upstream Down stream
Free board
Penstock
A conduit, commonly steel pipe, leading from the reservoir to a power generating plant downstream from the reservoir.
Usage of Penstock
Turbine
Fish Ladders
A structure built at the side or up the face of a dam to enable migration of fish upstream and downstream. Examples
Bartlett DamVerde River, AZ
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