Underwater foundations - Revision history

Editor at 18:41, 26 April 2021

2021-04-26T18:41:14Z

← Older revision		Revision as of 18:41, 26 April 2021
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	* Dredging.		* Dredging.
	* Foundations.		* Foundations.
		+	* Pontoon bridge.
	* River engineering.		* River engineering.
	* Scour.		* Scour.

Editor at 11:35, 3 March 2021

2021-03-03T11:35:27Z

← Older revision		Revision as of 11:35, 3 March 2021
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	Divers can then place temporary steel formwork, using sandbags to anchor them in place and prevent concrete leakage from under the toe of the form. If the foundation is relatively short and in shallow water, bagged concrete or cement placed in layers may be used as formwork and left in position. Foundations in deeper water may incorporate permanent formwork in the form of precast concrete blocks which are tied in to the foundation.		Divers can then place temporary steel formwork, using sandbags to anchor them in place and prevent concrete leakage from under the toe of the form. If the foundation is relatively short and in shallow water, bagged concrete or cement placed in layers may be used as formwork and left in position. Foundations in deeper water may incorporate permanent formwork in the form of precast concrete blocks which are tied in to the foundation.

−	The concrete mix must have a high degree of workability to maintain a good flow and prevent too much cement being washed out of the mix. This ensures that the leading edge of the concrete is kept moving forward under the pressure of additional material.Extra cement should be added to offset any loss through the water, although too much cement will result in excessive laitance forming on the concrete surface.	+	The concrete mix must have a high degree of workability to maintain a good flow and prevent too much cement being washed out of the mix. This ensures that the leading edge of the concrete is kept moving forward under the pressure of additional material. Extra cement should be added to offset any loss through the water, although too much cement will result in excessive laitance forming on the concrete surface.

	= Concrete placing =		= Concrete placing =

Editor: Reverted edits by 175.136.180.82 (talk) to last revision by Designing Buildings

2021-03-03T11:34:39Z

Reverted edits by 175.136.180.82 (talk) to last revision by Designing Buildings

← Older revision		Revision as of 11:34, 3 March 2021
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	= Introduction =		= Introduction =

−	Foundations can often be required for the construction of harbour walls, sea walls, breakwaters, and so on. Underwater foundations, also known as subaqueous foundations, may be used in situations where the use of a cofferdam or caisson is prohibitively expensive or unfeasible. :)	+	Foundations can often be required for the construction of harbour walls, sea walls, breakwaters, and so on. Underwater foundations, also known as subaqueous foundations, may be used in situations where the use of a cofferdam or caisson is prohibitively expensive or unfeasible.

	Typically, dredgers or grabs working from pontoons will excavate the ground and load the spoil into barges. If rock needs to be removed, drill and blast methods can be used, or drilling and cutting by jackhammer. Softer rock formations can be dredged or broken up by air tools and then grabbed. Gravel and sands can be excavated using a suction dredger or ejector tube.		Typically, dredgers or grabs working from pontoons will excavate the ground and load the spoil into barges. If rock needs to be removed, drill and blast methods can be used, or drilling and cutting by jackhammer. Softer rock formations can be dredged or broken up by air tools and then grabbed. Gravel and sands can be excavated using a suction dredger or ejector tube.
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	Divers can then place temporary steel formwork, using sandbags to anchor them in place and prevent concrete leakage from under the toe of the form. If the foundation is relatively short and in shallow water, bagged concrete or cement placed in layers may be used as formwork and left in position. Foundations in deeper water may incorporate permanent formwork in the form of precast concrete blocks which are tied in to the foundation.		Divers can then place temporary steel formwork, using sandbags to anchor them in place and prevent concrete leakage from under the toe of the form. If the foundation is relatively short and in shallow water, bagged concrete or cement placed in layers may be used as formwork and left in position. Foundations in deeper water may incorporate permanent formwork in the form of precast concrete blocks which are tied in to the foundation.

−	The concrete mix must have a high degree of workability to maintain a good flow and prevent too much cement being washed out of the mix. This ensures that the leading edge of the concrete is kept moving forward under the pressure of additional material. Extra cement should be added to offset any loss through the water, although too much cement will result in excessive laitance forming on the concrete surface.	+	The concrete mix must have a high degree of workability to maintain a good flow and prevent too much cement being washed out of the mix. This ensures that the leading edge of the concrete is kept moving forward under the pressure of additional material.Extra cement should be added to offset any loss through the water, although too much cement will result in excessive laitance forming on the concrete surface.

	= Concrete placing =		= Concrete placing =

175.136.180.82 at 09:57, 3 March 2021

2021-03-03T09:57:06Z

← Older revision		Revision as of 09:57, 3 March 2021
Line 1:		Line 1:
	= Introduction =		= Introduction =

−	Foundations can often be required for the construction of harbour walls, sea walls, breakwaters, and so on. Underwater foundations, also known as subaqueous foundations, may be used in situations where the use of a cofferdam or caisson is prohibitively expensive or unfeasible.	+	Foundations can often be required for the construction of harbour walls, sea walls, breakwaters, and so on. Underwater foundations, also known as subaqueous foundations, may be used in situations where the use of a cofferdam or caisson is prohibitively expensive or unfeasible. :)

	Typically, dredgers or grabs working from pontoons will excavate the ground and load the spoil into barges. If rock needs to be removed, drill and blast methods can be used, or drilling and cutting by jackhammer. Softer rock formations can be dredged or broken up by air tools and then grabbed. Gravel and sands can be excavated using a suction dredger or ejector tube.		Typically, dredgers or grabs working from pontoons will excavate the ground and load the spoil into barges. If rock needs to be removed, drill and blast methods can be used, or drilling and cutting by jackhammer. Softer rock formations can be dredged or broken up by air tools and then grabbed. Gravel and sands can be excavated using a suction dredger or ejector tube.

175.136.180.82 at 09:56, 3 March 2021

2021-03-03T09:56:08Z

← Older revision		Revision as of 09:56, 3 March 2021
Line 7:		Line 7:
	Divers can then place temporary steel formwork, using sandbags to anchor them in place and prevent concrete leakage from under the toe of the form. If the foundation is relatively short and in shallow water, bagged concrete or cement placed in layers may be used as formwork and left in position. Foundations in deeper water may incorporate permanent formwork in the form of precast concrete blocks which are tied in to the foundation.		Divers can then place temporary steel formwork, using sandbags to anchor them in place and prevent concrete leakage from under the toe of the form. If the foundation is relatively short and in shallow water, bagged concrete or cement placed in layers may be used as formwork and left in position. Foundations in deeper water may incorporate permanent formwork in the form of precast concrete blocks which are tied in to the foundation.

−	The concrete mix must have a high degree of workability to maintain a good flow and prevent too much cement being washed out of the mix. This ensures that the leading edge of the concrete is kept moving forward under the pressure of additional material.Extra cement should be added to offset any loss through the water, although too much cement will result in excessive laitance forming on the concrete surface.	+	The concrete mix must have a high degree of workability to maintain a good flow and prevent too much cement being washed out of the mix. This ensures that the leading edge of the concrete is kept moving forward under the pressure of additional material. Extra cement should be added to offset any loss through the water, although too much cement will result in excessive laitance forming on the concrete surface.

	= Concrete placing =		= Concrete placing =

Designing Buildings at 07:16, 23 November 2020

2020-11-23T07:16:07Z

← Older revision		Revision as of 07:16, 23 November 2020
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	* Water engineering.		* Water engineering.

−	[[Category:~~Construction_techniques~~]] [[Category:~~Products_/_components~~]] [[Category:DCN_Product_Knowledge]]	+	[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]] [[Category:Construction_techniques]] [[Category:Products_/_components]]

Editor at 17:57, 3 June 2020

2020-06-03T17:57:20Z

← Older revision		Revision as of 17:57, 3 June 2020
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	Pipe lines typically have a diameter of 110-150 mm and are generally capable of pumping for a distance of 300 m horizontally and 30 m vertically. Pumps may be mounted on a pontoon with an extendable steel boom. The pump works hydraulically with a diesel-driven piston that forces concrete along the pipes.		Pipe lines typically have a diameter of 110-150 mm and are generally capable of pumping for a distance of 300 m horizontally and 30 m vertically. Pumps may be mounted on a pontoon with an extendable steel boom. The pump works hydraulically with a diesel-driven piston that forces concrete along the pipes.

−	~~= Find out more =~~	+	= Related articles on Designing Buildings Wiki =
−		+
−	=== Related articles on Designing Buildings Wiki ===	+

	* Caisson.		* Caisson.
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	* Foundations.		* Foundations.
	* River engineering.		* River engineering.
		+	* Scour.
	* Tremie.		* Tremie.
	* Underpinning.		* Underpinning.
	* Water engineering.		* Water engineering.

−	[[Category:Construction_techniques]] [[Category:Products_/_components]]	+	[[Category:Construction_techniques]] [[Category:Products_/_components]] [[Category:DCN_Product_Knowledge]]

Editor at 12:16, 2 May 2018

2018-05-02T12:16:17Z

← Older revision		Revision as of 12:16, 2 May 2018
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	The flow rate of concrete is controlled by raising and lowering the tremie, but care must be taken not to lift the tremie out of the concrete mass, otherwise the seal will be broken and the concrete will be weakened by water as it rushes out of the pipe. This may result in a damaged surface to the mass of concrete which will need to be removed before work can recommence. One tremie will serve an area of approximately 30 sq. m, and where all the concrete cannot be placed from one position, more than one tremie can be used for simultaneous placing.		The flow rate of concrete is controlled by raising and lowering the tremie, but care must be taken not to lift the tremie out of the concrete mass, otherwise the seal will be broken and the concrete will be weakened by water as it rushes out of the pipe. This may result in a damaged surface to the mass of concrete which will need to be removed before work can recommence. One tremie will serve an area of approximately 30 sq. m, and where all the concrete cannot be placed from one position, more than one tremie can be used for simultaneous placing.
		+
		+	For more information, see Tremie.

	== Placing by skip ==		== Placing by skip ==
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	* Foundations.		* Foundations.
	* River engineering.		* River engineering.
		+	* Tremie.
	* Underpinning.		* Underpinning.
	* Water engineering.		* Water engineering.

	[[Category:Construction_techniques]] [[Category:Products_/_components]]		[[Category:Construction_techniques]] [[Category:Products_/_components]]

Editor at 11:01, 2 May 2018

2018-05-02T11:01:03Z

← Older revision		Revision as of 11:01, 2 May 2018
Line 1:		Line 1:
	= Introduction =		= Introduction =

−	Foundations can often be required for the construction of harbour walls, sea walls, breakwaters, and so on. Underwater foundations may be used in situations where the use of a cofferdam or caisson is prohibitively expensive or unfeasible.	+	Foundations can often be required for the construction of harbour walls, sea walls, breakwaters, and so on. Underwater foundations, also known as subaqueous foundations, may be used in situations where the use of a cofferdam or caisson is prohibitively expensive or unfeasible.

	Typically, dredgers or grabs working from pontoons will excavate the ground and load the spoil into barges. If rock needs to be removed, drill and blast methods can be used, or drilling and cutting by jackhammer. Softer rock formations can be dredged or broken up by air tools and then grabbed. Gravel and sands can be excavated using a suction dredger or ejector tube.		Typically, dredgers or grabs working from pontoons will excavate the ground and load the spoil into barges. If rock needs to be removed, drill and blast methods can be used, or drilling and cutting by jackhammer. Softer rock formations can be dredged or broken up by air tools and then grabbed. Gravel and sands can be excavated using a suction dredger or ejector tube.

Designing Buildings at 07:13, 2 May 2018

2018-05-02T07:13:46Z

← Older revision		Revision as of 07:13, 2 May 2018
Line 1:		Line 1:
	= Introduction =		= Introduction =

−	Underwater foundations may be used in situations where the use of a cofferdam or caisson is prohibitively expensive or unfeasible~~. Foundations can often be used for the construction of concrete harbour walls, sea walls, breakwaters, and so on~~.	+	Foundations can often be required for the construction of harbour walls, sea walls, breakwaters, and so on. Underwater foundations may be used in situations where the use of a cofferdam or caisson is prohibitively expensive or unfeasible.

−	Typically, dredgers or grabs working ~~off~~ pontoons excavate the ground and load the spoil into barges. If rock needs to be removed, drill and blast methods can be used, or drilling and cutting by jackhammer. Softer rock formations can be dredged or broken up by air tools and then grabbed. Gravel and sands can be excavated using a suction dredger or ejector tube.	+	Typically, dredgers or grabs working from pontoons will excavate the ground and load the spoil into barges. If rock needs to be removed, drill and blast methods can be used, or drilling and cutting by jackhammer. Softer rock formations can be dredged or broken up by air tools and then grabbed. Gravel and sands can be excavated using a suction dredger or ejector tube.

−	Divers place temporary steel formwork, using sandbags to anchor them in place and prevent concrete leakage from under the toe of the form. If the foundation is relatively short and in shallow water, bagged concrete or cement placed in layers may be used as formwork and left in position. Foundations in deeper water may incorporate permanent formwork in the form of precast concrete blocks which are tied in to the foundation.	+	Divers can then place temporary steel formwork, using sandbags to anchor them in place and prevent concrete leakage from under the toe of the form. If the foundation is relatively short and in shallow water, bagged concrete or cement placed in layers may be used as formwork and left in position. Foundations in deeper water may incorporate permanent formwork in the form of precast concrete blocks which are tied in to the foundation.

−	The concrete mix must have a high degree of workability to maintain a good flow and prevent too much cement being washed out of the mix. This ensures that the leading edge of the concrete is kept moving forward under the pressure of additional material. ~~In any case, extra~~ cement should be added to offset ~~the~~ loss through the water, although ~~it should be considered that~~ too much cement will result in excessive laitance forming on the concrete surface.	+	The concrete mix must have a high degree of workability to maintain a good flow and prevent too much cement being washed out of the mix. This ensures that the leading edge of the concrete is kept moving forward under the pressure of additional material.Extra cement should be added to offset any loss through the water, although too much cement will result in excessive laitance forming on the concrete surface.

	= Concrete placing =		= Concrete placing =

−	Concrete is placed by one of three methods:	+	Concrete is generally placed by one of three methods:

	== Placing by tremie ==		== Placing by tremie ==
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	A tremie is a steel tube suspended in the water from a crane. A hopper is fixed to the top end to receive the concrete. The tremie is positioned vertically over the area to be concreted with the lower end resting on the bottom. After the pipe has been filled with concrete it is raised off the bottom to allow it to flow. This should allow the flow to continue to feed the interior of the initial mass.		A tremie is a steel tube suspended in the water from a crane. A hopper is fixed to the top end to receive the concrete. The tremie is positioned vertically over the area to be concreted with the lower end resting on the bottom. After the pipe has been filled with concrete it is raised off the bottom to allow it to flow. This should allow the flow to continue to feed the interior of the initial mass.

−	The flow rate of concrete is controlled by raising and lowering the tremie, but care must be taken not to lift the tremie out of the concrete mass, otherwise the seal will be broken and the concrete will be weakened by water as it rushes out of the pipe. ~~If the seal is broken it~~ may result in a damaged surface to the mass of concrete ~~and~~ need to be removed before work can recommence. One tremie will serve an area of approximately 30 sq. m, ~~but~~ where concrete cannot be placed from one position, more than one tremie can be used for simultaneous placing.	+	The flow rate of concrete is controlled by raising and lowering the tremie, but care must be taken not to lift the tremie out of the concrete mass, otherwise the seal will be broken and the concrete will be weakened by water as it rushes out of the pipe. This may result in a damaged surface to the mass of concrete which will need to be removed before work can recommence. One tremie will serve an area of approximately 30 sq. m, and where all the concrete cannot be placed from one position, more than one tremie can be used for simultaneous placing.

	== Placing by skip ==		== Placing by skip ==

−	Bottom-opening skips can be used, which are fitted with a top cover held in position by water pressure. The skip is filled with concrete before being gently lowered into the water~~. If it is lowered too rapidly, the covers may be disturbed and the concrete inside damaged~~. On reaching the bottom, the skip is emptied.	+	Bottom-opening skips can be used, which are fitted with a top cover held in position by water pressure. The skip is filled with concrete before being gently lowered into the water. On reaching the bottom, the skip is emptied.

−	This is a slower method than a tremie pipe but can be more practical for thin beds, whereas tremies are more appropriate for large pours.	+	If it is lowered too rapidly, the covers may be disturbed and the concrete inside damaged. This is a slower method than a tremie pipe but can be more practical for thin beds, whereas tremies are more appropriate for large pours.

	== Pumping ==		== Pumping ==
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	Concrete pumping is a method used when very large concrete pours are required.		Concrete pumping is a method used when very large concrete pours are required.

−	Pipe lines typically have a diameter of 110-150 mm and are capable of pumping for a distance of 300 m horizontally and 30 m vertically. Pumps ~~are~~ mounted on a pontoon with an extendable steel boom. The pump works hydraulically with a diesel-driven piston that forces concrete along the pipes.	+	Pipe lines typically have a diameter of 110-150 mm and are generally capable of pumping for a distance of 300 m horizontally and 30 m vertically. Pumps may be mounted on a pontoon with an extendable steel boom. The pump works hydraulically with a diesel-driven piston that forces concrete along the pipes.

	= Find out more =		= Find out more =