Ug Breakwaters
-
Upload
mahiba-shalon -
Category
Documents
-
view
231 -
download
3
Transcript of Ug Breakwaters
-
7/30/2019 Ug Breakwaters
1/34
BREAKWATERS
1
-
7/30/2019 Ug Breakwaters
2/34
-
7/30/2019 Ug Breakwaters
3/34
DESIGN INFORMATION ANDCONSIDERATIONS
Character of coastal currents
Cost and availability of material of construction.
Direction and force of prevailing winds.
Nature of bottom or the foundation
Probable maximum height, force and intensity of
waves
Design should be based on extreme phenomena of
wind and waves and not on mean or the average It should be seen that the material in the foundation is
not subjected to scour.
3
-
7/30/2019 Ug Breakwaters
4/34
CLASSIFICATION OF BREAKWATER
Heap or mound breakwater Rubble mound breakwater
Concrete blocks mound breakwater
Rubble mound breakwater
supplemented by concrete blocks Rubble mound breakwater supplemented by
patented stones
Mound with superstructure or composite breakwater
Upright wall breakwater
Special breakwater
4
-
7/30/2019 Ug Breakwaters
5/34
SELECTION OF TYPE OF BREAKWATER
Depends on the following: Availability of materials for construction
Depth of water at the site of construction
Nature of natural foundations Equipment available for construction
Funds and time available for construction
5
-
7/30/2019 Ug Breakwaters
6/34
HEAP OR MOUND BREAKWATER
Mount breakwater is a heap or assemblage of undressed
stones or blocks of various sizes, thrown at site without
any bond and binding materials between adjacent units
The foundations for mount breakwater is never prepared
nor even observed. Such construction is known as pell-
mell or rip-rap construction.
Because of large voids between adjacent units of
construction, settlement occurs for first few years which
reduce the crest level inviting frequent redumping ofstones at top
6
-
7/30/2019 Ug Breakwaters
7/34
COMPONENTS OF MOUNDBREAKWATER
1. Interior or hearth or core: function of core is to increase the bulkor size of breakwater which makes construction of mount
breakwater economical. Core is usually quarry waste or washed
dredged materials which is less pervious.
2. Filter or secondary armours: the size of units (stones) in filter
which is laid around the central core is larger than the size of
stones in core. Hence such layer is more pervious. The function
of filter zone units is to destroy the energy of waves that come
through armour layer of stones.
3. Armour blocks: these stones or blocks are like fighters in army,
hence the name. they resist major part of force (kinetic energy)
of wind and waves. They will be the largest in size and weight.
7
-
7/30/2019 Ug Breakwaters
8/34
CHARACTERISTICS OF MOUND BREAKWATER
Dissipation of kinetic energy by different layers of mound
Natural foundation is unprepared None of the layers of construction work are arranged in
special bond.
No binding materials are to be provided between adjacent
units of construction
No possibility of sliding between any layers with respect to
adjacent units
No possibility of overturning as there is no rigidity in
construction
No possibility of uplift
The mound is porous or pervious
The mound construction is flexible
Unskilled labour can be used in the construction of mound8
-
7/30/2019 Ug Breakwaters
9/34
RUBBLE MOUND BREAKWATER
Type I: In this type of construction the top core of mound
breakwater is above mean sea level. Large volume of
core is used to make construction economical. Core is
protected from all sides by filter and armour layers.
9
-
7/30/2019 Ug Breakwaters
10/34
Type II: In this type of mound the crest level of core is kept
below M.S.L by specified distance x in relation with height of
wave dividing the water coming from armour zone into jets and
making them collide among themselves.
10
-
7/30/2019 Ug Breakwaters
11/34
11
-
7/30/2019 Ug Breakwaters
12/34
ADVANTAGES & DISADVANTAGES OF MOUND
TYPE BREAKWATER
ADVANTAGES: Low in initial cost of materials of construction equipment
& labour required.
No preparation of foundation.
Construction is porous or pervious, base no possibility ofuplift.
Construction is in pell-mell fashion, bases have no
chance of slippage & overturning.
Construction is flexible. Dissipates the energy of incoming water waves most
efficiently.
12
-
7/30/2019 Ug Breakwaters
13/34
Limitations
Settlement of mound takes places for first few years by
adjustment of voids between adjacent stones & rollingdown of some stones.
Pell mell form of mound construction
Projections are chipped by water
Stones become round & role down the slopeproducing gap.
Makes the mound weak.
Requires huge quantity of materials.
Large quantity of materials is likely to be wasted. Such construction cannot be analyzed.
Occupy large area of basin.
Requires large maintenance.13
-
7/30/2019 Ug Breakwaters
14/34
CONCRETE BLOCK MOUNDBREAKWATER
Concrete blocks having rectangular section with sharp
edges are not rough enough and their faces of adjacentblocks are likely to coincide.
Hence energy of wave water cannot be killed or dissipated
even partly.
Only a small amount percentage of energy is dissipate. Also amount of concrete required in casting such blocks will
be huge.
Casting of concrete blocks of odd shapes and sizes and
weight with required irregularity is difficult and costly. Also the transportation from the factory to the site will be
costly.
Hence concrete block mound breakwater is rare.
14
-
7/30/2019 Ug Breakwaters
15/34
RUBBLE MOUND BREAKWATERSUPPLEMENTED BY CONCRETE BLOCKS
In this type concrete blocks are laid towards seaside of
mound to act as extra armour block over the usual
armour blocks of rubble stones which are heavy and
irregular in shape. Remaining construction is similar to rubble mound
breakwater.
The concrete blocks can be laid in
Pell-mell fashion Well compacted fashion
15
-
7/30/2019 Ug Breakwaters
16/34
16
-
7/30/2019 Ug Breakwaters
17/34
17
-
7/30/2019 Ug Breakwaters
18/34
RUBBLE MOUND BREAKWATERSUPPLEMENTED BY PATENTED STONES
After making no. of experiments various countries have
developed different types and shapes of concrete blocks
which are hydraulically rough as well as stable in any of
their positions and do provide permeable construction.
Such units are patented by each of the companies forworldwide use.
1. Tetrapods: they are assembly of symmetrically
prepared four-legged truncated cones with proper
amount of reinforcements.2. Tribars: they are three legged connected with a plate at
mid-height. If properly placed this tribar group will get
interlocked and remain stable.
18
-
7/30/2019 Ug Breakwaters
19/34
3. Modified cubes: these are made from ordinary cubes. On
each faces of the cubes a long and wide groove is
made, which can be used to interlock adjacent units.These are much heavier than tetrapods and tribars,
hence, shall resist the forces of incoming waves by
impact.
4. Dollosse: an artificial stone is experimented to act asarmour block in South Africa.
5.Akman armour: developed in Netherland
6. Stabit armour: experimented and tried in England and
New Zealand.
19
-
7/30/2019 Ug Breakwaters
20/34
20
-
7/30/2019 Ug Breakwaters
21/34
21
-
7/30/2019 Ug Breakwaters
22/34
22
-
7/30/2019 Ug Breakwaters
23/34
23
-
7/30/2019 Ug Breakwaters
24/34
WALL TYPE BREAKWATER
It is a big regular wall raised to construct a harbour basin on
solid natural or artificial foundation to resist the forces and
their components generated by incoming water and waves.
Types of wall breakwater
Wall breakwater of smaller size units
Wall breakwaters of large size units
Mass concrete units Caissons units
24
-
7/30/2019 Ug Breakwaters
25/34
ESSENTIALS FOR WALL TYPE BREAKWATERS
This type is suitable for sheltered sites & not reliable for
very heavy seas. When depth is not great & the bottom is firm, upright wall
breakwater could be built.
These breakwaters should not be constructed in a depth
of water less than twice the greatest storm likely to visitthe site of the proposed structure.
The sea bed at the site should be resistant to erosion
and the foundations should be free from uneven
settlements. For sea bed locations having low bearing capacity, a
rubble base may be provided to distribute the load on a
wider base.
25
-
7/30/2019 Ug Breakwaters
26/34
For locations having to bed material like silt, soft clay,
etc., it is desirable to remove such strata with the
dredgers.
The sheet piles may also be driven to improve the
bearing capacity in locations having low bearing
capacity, upto moderate depths.
The design should be such that no portion of the
breakwater may overturn due to the wave pressureexerted on its surface.
It should be seen that no horizontal course of the wall is
uplifted and gets dislocated.
Wall breakwaters of small units must have proper bondand binding.
Wall breakwaters of large units like mass construction
must have discontinuity in construction joints.
26
-
7/30/2019 Ug Breakwaters
27/34
27
-
7/30/2019 Ug Breakwaters
28/34
28
-
7/30/2019 Ug Breakwaters
29/34
29
-
7/30/2019 Ug Breakwaters
30/34
ADVANTAGES OF WALL BREAKWATER
Reduces the amount of material
Avoids dangers of unequal settlement Increases the size of harbour basin
Maintenance cost is least as compared to that of mound
breakwater
DISADVANTAGES
30
Involves building a good height of wall under water
Calls for special case and costly methods of
construction
-
7/30/2019 Ug Breakwaters
31/34
MOUND WITH SUPERSTRUCTURE ORCOMPOSITE BREAKWATER
Such construction is adopted to get advantage of mound
at bottom as well as to get advantage of solid or rigid
construction at top.
Solid construction is adopted usually between low water
level and high water level.
Mound with superstructure are classified into the
following two types:
Mound with superstructure founded at low water level.
Mound with superstructure founded below low water
level.
31
-
7/30/2019 Ug Breakwaters
32/34
SPECIAL BREAKWATERS
Floating type breakwater
Hydraulic breakwater
Pneumatic breakwater
32
-
7/30/2019 Ug Breakwaters
33/34
33
-
7/30/2019 Ug Breakwaters
34/34
34