University:West Bengal University of Technology
Course: B.Tech Civil Engineering
Subject : Transportation engineering
Year of Question Paper : 2012
BREAK WATER
A breakwater is a structure constructed for the purpose of forming an artificial harbour with a basin so protected from the effect of waves as to provide safe berthing for fishing vessels. There are many different types of breakwaters; natural rock and concrete, or a combination of the two, are the materials which form 95 percent or more of all the breakwaters constructed.
Breakwaters are required for the protection of artificial and semi-natural harbours. Their location and extent will depend upon:
• The direction of the maximum waves.
• The configuration of the shore line.
• The minimum size of the harbour required for the anticipated traffic in the port.
Breakwaters may consist of two arms out from the shore, plus a single breakwater, more or less parallel to the shore line, thereby providing two openings to the harbour.
The following parameters are required before construction can commence:
• A detailed hydrographic survey of the site;
• A geotechnical investigation of the sea bed;
• A wave height investigation or hind casting;
• A material needs assessment; and
• The cross-sectional design of the structure.
CLASSIFICATION
The type of breakwaters is usually determined by:
1) The availability of materials at or near the site.
2) The depth of water.
3) The condition of the sea bottom.
4) The function of the breakwater in the harbour.
5) The equipment suitable and available for its construction.
The following four types fall under the first classification and are identified by the materials out of which they are constructed; (1) natural rock, (2) concrete block, (3) a combination of rock and concrete block, and (4) concrete shapes such as tetra pods, quadrupeds, dolosse, and others.
In the second main classification of breakwaters there are such types as:
1) concrete-block gravity walls,
2) Concrete caissons,
3) rock-filled sheet pile walls,
4) Concrete or steel-pile walls.
Rock-Mound Breakwaters:
They are mainly classified into the following two types according to the method of construction:
(1) A rock mound in which the core material extends above water level and is covered with an envelope of armour rock sometimes separated from the core material by one or more intermediate layers.
(2) Rock mound in which the core fill is stopped a considerable depth below water level and covered with a medium weight rock, which forms the base for the heavy armour capping.
In the first type of construction, called end type, the core is extended out from the shore by end or side dumping from trucks which operate on top of the core as it is brought up above water level. The second type of construction is based on the core being placed as dredged material or being dumped from scows or from trestle.
Advantages:
• Easy to be constructed, since it does not need skill labours or special equipments.
• Can be constructed on weak sea bottom.
• Can be constructed on unlevelled sea bottom.
• The maintenance is easy from the technical point of view.
• Technically, it can be constructed in any depth.
• Waves do not reflect on its surface.
Disadvantages:
• Needs a considerable amount of construction materials.
• Continuous maintenance is required.
• Sometimes there are difficulties in erection, as the rock weight increases with the increase of wave heights.
• Can’t be used for ship berthing.
Artificial Concrete Blocks:
They are used where natural rock is not available, or it cannot be produced economically or in large enough size required for armouring the breakwater.
Artificial blocks are usually made of plain concrete but rarely are reinforced. They are formed of devised irregular-shaped concrete units tested before being used in the field.
The more common ones which have been testes quite extensively are tetra pods, quadrupeds, hexapods, tribars, modified cubes, akmons, and dolosse.
Other new shapes of concrete units have been developed, tested and used in protective cover layers of rubble-mound breakwaters in the past few years.
Q.Differences between Dry-docks and Wet-docks
DRY DOCK WET DOCK
1.A dry-dock (also commonly dry dock) is a narrow basin or vessel that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform. 1. A wet dock or impounded dock is a variant in which the water is impounded either by dock gates or by a lock, thus allowing ships to remain afloat at low tide in places with high tidal ranges. The level of water in the dock is maintained despite the raising and lowering of the tide.
2. Dry-docks are used for the construction, maintenance, and repair of ships, boats, and other watercraft. 2. In wet docks, maintenance work cannot be done.
3. In high flood regions, dry docks are not capable to hold the ships at a steady flow. 3. In wet docks it is possible.
4. Routine wise cleaning of dry docks is very much easier. 4. As it is basically located at high flood region, routine wise cleaning is difficult.
5. In dry season much water will not be available for floatation. 5. Water is always available here.
6. Water level sometimes gets much lower. 6. Water level is always higher in wet docks.
7. Buoyancy of water is low in dry docks 7. Buoyancy of water is high.
Q. LIGHT HOUSE
A lighthouse is a tall tower, building, or other type of structure which is basically designed for emitting light from a system of lamps and lenses and used as an aid to navigation for maritime pilots at sea or on inland waterways.
Lighthouses mark dangerous coastlines, hazardous shoals, reefs, safe entries to harbours, and can also assist in aerial navigation. Once widely used, the number of operational lighthouses has declined due to the expense of maintenance and replacement by modern electronic navigational systems. In a lighthouse, the source of light is called the "lamp" (whether electric or fuelled by oil) and the concentration of the light is by the "lens" or "optic".
Components of Light House
While lighthouse buildings differ depending on the location and purpose, they tend to have common components.
A light station comprises the lighthouse tower and all outbuildings, such as the keeper's living quarters, fuel house, boathouse, and fog-signalingbuilding. The Lighthouse itself consists of a tower structure supporting the lantern room where the light operates.
The lantern room is the glassed-in housing at the top of a lighthouse tower containing the lamp and lens. Its glass storm panes are supported by metal Astragal bars running vertically or diagonally. At the top of the lantern room is a storm proof ventilator designed to remove the smoke of the lamps and the heat that builds in the glass enclosure. A lightning rod and grounding system connected to the metal cupola roof provides a safe conduit for any lightning strikes.
Immediately beneath the lantern room is usually a Watch Room or Service Room where fuel and other supplies were kept and where the keeper prepared the lanterns for the night and often stood watch. The clockworks (for rotating the lenses) were also located there. On a lighthouse tower, an open platform called the gallery is often located outside the watch room (called the Main Gallery) or Lantern Room (Lantern Gallery). This was mainly used for cleaning the outside of the windows of the Lantern Room.
Lighthouses near to each other that are similar in shape are often painted in a unique pattern so they can easily be recognized during daylight, a marking known as a daymark. The black and white barber pole spiral pattern of Cape Hatteras Lighthouse is one example.
Q. Difference between tidal basin and wet dock
1. The Tidal Basin is a partially human-made reservoir
1. A wet dock or impounded dock is a variant in which the water is impounded either by dock gates or by a lock
2. Ships cannot stay for a long time. Sometimes, Ship cannot enter to it. 2. Ships can stay for a long time.
3. Maintenance work of ships cannot be done over here. 3. Though it is difficult, maintenance work can be done.
4. Tidal basin is lower in area than wet docks. 3. These are higher in area than the tidal basins.
Course: B.Tech Civil Engineering
Subject : Transportation engineering
Year of Question Paper : 2012
BREAK WATER
A breakwater is a structure constructed for the purpose of forming an artificial harbour with a basin so protected from the effect of waves as to provide safe berthing for fishing vessels. There are many different types of breakwaters; natural rock and concrete, or a combination of the two, are the materials which form 95 percent or more of all the breakwaters constructed.
Breakwaters are required for the protection of artificial and semi-natural harbours. Their location and extent will depend upon:
• The direction of the maximum waves.
• The configuration of the shore line.
• The minimum size of the harbour required for the anticipated traffic in the port.
Breakwaters may consist of two arms out from the shore, plus a single breakwater, more or less parallel to the shore line, thereby providing two openings to the harbour.
The following parameters are required before construction can commence:
• A detailed hydrographic survey of the site;
• A geotechnical investigation of the sea bed;
• A wave height investigation or hind casting;
• A material needs assessment; and
• The cross-sectional design of the structure.
CLASSIFICATION
The type of breakwaters is usually determined by:
1) The availability of materials at or near the site.
2) The depth of water.
3) The condition of the sea bottom.
4) The function of the breakwater in the harbour.
5) The equipment suitable and available for its construction.
The following four types fall under the first classification and are identified by the materials out of which they are constructed; (1) natural rock, (2) concrete block, (3) a combination of rock and concrete block, and (4) concrete shapes such as tetra pods, quadrupeds, dolosse, and others.
In the second main classification of breakwaters there are such types as:
1) concrete-block gravity walls,
2) Concrete caissons,
3) rock-filled sheet pile walls,
4) Concrete or steel-pile walls.
Rock-Mound Breakwaters:
They are mainly classified into the following two types according to the method of construction:
(1) A rock mound in which the core material extends above water level and is covered with an envelope of armour rock sometimes separated from the core material by one or more intermediate layers.
(2) Rock mound in which the core fill is stopped a considerable depth below water level and covered with a medium weight rock, which forms the base for the heavy armour capping.
In the first type of construction, called end type, the core is extended out from the shore by end or side dumping from trucks which operate on top of the core as it is brought up above water level. The second type of construction is based on the core being placed as dredged material or being dumped from scows or from trestle.
Advantages:
• Easy to be constructed, since it does not need skill labours or special equipments.
• Can be constructed on weak sea bottom.
• Can be constructed on unlevelled sea bottom.
• The maintenance is easy from the technical point of view.
• Technically, it can be constructed in any depth.
• Waves do not reflect on its surface.
Disadvantages:
• Needs a considerable amount of construction materials.
• Continuous maintenance is required.
• Sometimes there are difficulties in erection, as the rock weight increases with the increase of wave heights.
• Can’t be used for ship berthing.
Artificial Concrete Blocks:
They are used where natural rock is not available, or it cannot be produced economically or in large enough size required for armouring the breakwater.
Artificial blocks are usually made of plain concrete but rarely are reinforced. They are formed of devised irregular-shaped concrete units tested before being used in the field.
The more common ones which have been testes quite extensively are tetra pods, quadrupeds, hexapods, tribars, modified cubes, akmons, and dolosse.
Other new shapes of concrete units have been developed, tested and used in protective cover layers of rubble-mound breakwaters in the past few years.
Q.Differences between Dry-docks and Wet-docks
DRY DOCK WET DOCK
1.A dry-dock (also commonly dry dock) is a narrow basin or vessel that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform. 1. A wet dock or impounded dock is a variant in which the water is impounded either by dock gates or by a lock, thus allowing ships to remain afloat at low tide in places with high tidal ranges. The level of water in the dock is maintained despite the raising and lowering of the tide.
2. Dry-docks are used for the construction, maintenance, and repair of ships, boats, and other watercraft. 2. In wet docks, maintenance work cannot be done.
3. In high flood regions, dry docks are not capable to hold the ships at a steady flow. 3. In wet docks it is possible.
4. Routine wise cleaning of dry docks is very much easier. 4. As it is basically located at high flood region, routine wise cleaning is difficult.
5. In dry season much water will not be available for floatation. 5. Water is always available here.
6. Water level sometimes gets much lower. 6. Water level is always higher in wet docks.
7. Buoyancy of water is low in dry docks 7. Buoyancy of water is high.
Q. LIGHT HOUSE
A lighthouse is a tall tower, building, or other type of structure which is basically designed for emitting light from a system of lamps and lenses and used as an aid to navigation for maritime pilots at sea or on inland waterways.
Lighthouses mark dangerous coastlines, hazardous shoals, reefs, safe entries to harbours, and can also assist in aerial navigation. Once widely used, the number of operational lighthouses has declined due to the expense of maintenance and replacement by modern electronic navigational systems. In a lighthouse, the source of light is called the "lamp" (whether electric or fuelled by oil) and the concentration of the light is by the "lens" or "optic".
Components of Light House
While lighthouse buildings differ depending on the location and purpose, they tend to have common components.
A light station comprises the lighthouse tower and all outbuildings, such as the keeper's living quarters, fuel house, boathouse, and fog-signalingbuilding. The Lighthouse itself consists of a tower structure supporting the lantern room where the light operates.
The lantern room is the glassed-in housing at the top of a lighthouse tower containing the lamp and lens. Its glass storm panes are supported by metal Astragal bars running vertically or diagonally. At the top of the lantern room is a storm proof ventilator designed to remove the smoke of the lamps and the heat that builds in the glass enclosure. A lightning rod and grounding system connected to the metal cupola roof provides a safe conduit for any lightning strikes.
Immediately beneath the lantern room is usually a Watch Room or Service Room where fuel and other supplies were kept and where the keeper prepared the lanterns for the night and often stood watch. The clockworks (for rotating the lenses) were also located there. On a lighthouse tower, an open platform called the gallery is often located outside the watch room (called the Main Gallery) or Lantern Room (Lantern Gallery). This was mainly used for cleaning the outside of the windows of the Lantern Room.
Lighthouses near to each other that are similar in shape are often painted in a unique pattern so they can easily be recognized during daylight, a marking known as a daymark. The black and white barber pole spiral pattern of Cape Hatteras Lighthouse is one example.
Q. Difference between tidal basin and wet dock
1. The Tidal Basin is a partially human-made reservoir
1. A wet dock or impounded dock is a variant in which the water is impounded either by dock gates or by a lock
2. Ships cannot stay for a long time. Sometimes, Ship cannot enter to it. 2. Ships can stay for a long time.
3. Maintenance work of ships cannot be done over here. 3. Though it is difficult, maintenance work can be done.
4. Tidal basin is lower in area than wet docks. 3. These are higher in area than the tidal basins.
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