Piled raft foundation - Revision history

Speedeckfoundations14 at 14:21, 7 August 2025

2025-08-07T14:21:24Z

← Older revision		Revision as of 14:21, 7 August 2025
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	* Shallow foundations are typically used where the loads imposed by a structure are low relative to the bearing capacity of the surface soils.		* Shallow foundations are typically used where the loads imposed by a structure are low relative to the bearing capacity of the surface soils.
	* Deep foundations are necessary where the bearing capacity of the surface soils is not adequate to support the loads imposed by a structure and so those loads need to be transferred to deeper layers with higher bearing capacity.		* Deep foundations are necessary where the bearing capacity of the surface soils is not adequate to support the loads imposed by a structure and so those loads need to be transferred to deeper layers with higher bearing capacity.
		+
		+	When ground conditions rule out the use of ground bearing rafts or shallow strip foundations (less than 1.8m deep), a piled raft foundation often presents a more cost-effective and practical alternative.

	In their normal form, raft foundations (sometimes referred to as mat foundations) are shallow foundations formed by a reinforced concrete slab of uniform thickness (typically 150-300 mm) covering a wide area, often the entire footprint of a building. This 'raft' spreads the load imposed by a number of columns or walls over the area of foundation, and can be considered to ‘float’ on the ground as a raft floats on water.		In their normal form, raft foundations (sometimes referred to as mat foundations) are shallow foundations formed by a reinforced concrete slab of uniform thickness (typically 150-300 mm) covering a wide area, often the entire footprint of a building. This 'raft' spreads the load imposed by a number of columns or walls over the area of foundation, and can be considered to ‘float’ on the ground as a raft floats on water.
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	The addition of piles to a raft increases the effective size of a foundation and can help resist horizontal loads. This can improve the performance of the foundation in reducing the amount of settlement and differential settlement, as well as improving the ultimate load capacity.		The addition of piles to a raft increases the effective size of a foundation and can help resist horizontal loads. This can improve the performance of the foundation in reducing the amount of settlement and differential settlement, as well as improving the ultimate load capacity.

−	Piled raft foundations are typically used for large structures, and in situations where soil is not suitable to prevent excessive settlement. They are an increasingly popular choice for high-rise buildings.	+	Piled raft foundations are typically used for large structures, and in situations where soil is not suitable to prevent excessive settlement. They are an increasingly popular choice for high-rise buildings.<br />
		+	<br />
		+	The reinforced concrete (RC) raft acts as an effective ground gas barrier, achieving 2.0 points in accordance with the scoring system set out in BS 8485. This provides adequate protection for CS2 and CS3 gas regimes, when used in combination with a correctly designed, detailed, and installed membrane system above the raft and/or a ventilation layer beneath (required for CS3 conditions only).

	During the design process, the optimum number and position of piles, as well as their diameter, reinforcement and length, is determined to ensure the stability of the structure while providing an economical solution, with the raft and piles acting together to ensure the required settlement is not exceeded. Typically, the piles provide most of the stiffness while the raft provides additional capacity at the ultimate loading.		During the design process, the optimum number and position of piles, as well as their diameter, reinforcement and length, is determined to ensure the stability of the structure while providing an economical solution, with the raft and piles acting together to ensure the required settlement is not exceeded. Typically, the piles provide most of the stiffness while the raft provides additional capacity at the ultimate loading.
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	* Numerical analysis of unconnected piled raft with cushion. Alaa Ata, Essam Badrawi, Marwa Nabil. [https://doi.org/10.1016/j.asej.2014.11.002 https://doi.org/10.1016/j.asej.2014.11.002]		* Numerical analysis of unconnected piled raft with cushion. Alaa Ata, Essam Badrawi, Marwa Nabil. [https://doi.org/10.1016/j.asej.2014.11.002 https://doi.org/10.1016/j.asej.2014.11.002]
		+	* Strip foundation depth and ground gas barrier reference. [https://speedeck.uk/our-solutions/construction/piled-raft-foundations/ https://speedeck.uk/our-solutions/construction/piled-raft-foundations/]

	[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]] [[Category:Construction_techniques]]		[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]] [[Category:Construction_techniques]]

Designing Buildings at 09:13, 23 November 2022

2022-11-23T09:13:58Z

← Older revision		Revision as of 09:13, 23 November 2022
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	In an Unconnected Piled Raft Foundation (UCPRF), the piles are not directly connected to the raft, but are separated from it be a structural fill 'cushion' (such as a compacted a sand-gravel mixture or compacted soil) which redistributes load between the raft and piles. This can be a more efficient, and so economic solution.		In an Unconnected Piled Raft Foundation (UCPRF), the piles are not directly connected to the raft, but are separated from it be a structural fill 'cushion' (such as a compacted a sand-gravel mixture or compacted soil) which redistributes load between the raft and piles. This can be a more efficient, and so economic solution.

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

	* Driven piles.		* Driven piles.
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	* Secant pile wall.		* Secant pile wall.
	* Types of raft foundation.		* Types of raft foundation.
		+	* Types of pile foundation.

−	=== External references ===	+	= External references =

	* Numerical analysis of unconnected piled raft with cushion. Alaa Ata, Essam Badrawi, Marwa Nabil. [https://doi.org/10.1016/j.asej.2014.11.002 https://doi.org/10.1016/j.asej.2014.11.002]		* Numerical analysis of unconnected piled raft with cushion. Alaa Ata, Essam Badrawi, Marwa Nabil. [https://doi.org/10.1016/j.asej.2014.11.002 https://doi.org/10.1016/j.asej.2014.11.002]

	[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]] [[Category:Construction_techniques]]		[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]] [[Category:Construction_techniques]]

Designing Buildings at 11:53, 15 September 2020

2020-09-15T11:53:54Z

← Older revision		Revision as of 11:53, 15 September 2020
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	* Numerical analysis of unconnected piled raft with cushion. Alaa Ata, Essam Badrawi, Marwa Nabil. [https://doi.org/10.1016/j.asej.2014.11.002 https://doi.org/10.1016/j.asej.2014.11.002]		* Numerical analysis of unconnected piled raft with cushion. Alaa Ata, Essam Badrawi, Marwa Nabil. [https://doi.org/10.1016/j.asej.2014.11.002 https://doi.org/10.1016/j.asej.2014.11.002]

−	[[Category:Construction_techniques]]	+	[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Product_Knowledge]] [[Category:Construction_techniques]]

Editor at 13:18, 17 January 2018

2018-01-17T13:18:20Z

← Older revision		Revision as of 13:18, 17 January 2018
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	* Raft foundation.		* Raft foundation.
	* Screw pile foundations.		* Screw pile foundations.
		+	* Secant pile wall.
	* Types of raft foundation.		* Types of raft foundation.

Designing Buildings at 14:27, 15 January 2018

2018-01-15T14:27:12Z

← Older revision		Revision as of 14:27, 15 January 2018
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	* Foundations.		* Foundations.
	* Geothermal pile foundations.		* Geothermal pile foundations.
−	* How to lay foundations.
	* Micropiles.		* Micropiles.
	* Pad foundation.		* Pad foundation.

Editor at 15:11, 12 January 2018

2018-01-12T15:11:32Z

← Older revision		Revision as of 15:11, 12 January 2018
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	* Deep foundations are necessary where the bearing capacity of the surface soils is not adequate to support the loads imposed by a structure and so those loads need to be transferred to deeper layers with higher bearing capacity.		* Deep foundations are necessary where the bearing capacity of the surface soils is not adequate to support the loads imposed by a structure and so those loads need to be transferred to deeper layers with higher bearing capacity.

−	In their normal form, raft foundations (sometimes referred to as mat foundations) are shallow foundations formed by a reinforced concrete slab of uniform thickness (typically 150 - 300 mm) covering a wide area, often the entire footprint of a building. This 'raft' spreads the load imposed by a number of columns or walls over the area of foundation, and can be considered to ‘float’ on the ground as a raft floats on water.	+	In their normal form, raft foundations (sometimes referred to as mat foundations) are shallow foundations formed by a reinforced concrete slab of uniform thickness (typically 150-300 mm) covering a wide area, often the entire footprint of a building. This 'raft' spreads the load imposed by a number of columns or walls over the area of foundation, and can be considered to ‘float’ on the ground as a raft floats on water.

	However, where a conventional raft foundation does not provide adequate support, it can be enhanced by the addition of piles, creating what is known as a piled raft foundation.		However, where a conventional raft foundation does not provide adequate support, it can be enhanced by the addition of piles, creating what is known as a piled raft foundation.

−	[[File:~~Piled raft foundation~~.jpg]]	+	[[File:Piled_raft_foundation.jpg\|link=File:Piled_raft_foundation.jpg]]

	Piles are deep foundations. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete. A foundation is described as 'piled' when its depth is more than three times its breadth (Atkinson, 2007). Pile foundations can help transfer loads through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth.		Piles are deep foundations. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete. A foundation is described as 'piled' when its depth is more than three times its breadth (Atkinson, 2007). Pile foundations can help transfer loads through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth.
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	* Micropiles.		* Micropiles.
	* Pad foundation.		* Pad foundation.
		+	* Pile cap.
	* Pile foundations.		* Pile foundations.
	* Raft foundation.		* Raft foundation.

Designing Buildings at 16:23, 8 January 2018

2018-01-08T16:23:56Z

← Older revision		Revision as of 16:23, 8 January 2018
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	However, where a conventional raft foundation does not provide adequate support, it can be enhanced by the addition of piles, creating what is known as a piled raft foundation.		However, where a conventional raft foundation does not provide adequate support, it can be enhanced by the addition of piles, creating what is known as a piled raft foundation.
		+
		+	[[File:Piled raft foundation.jpg]]

	Piles are deep foundations. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete. A foundation is described as 'piled' when its depth is more than three times its breadth (Atkinson, 2007). Pile foundations can help transfer loads through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth.		Piles are deep foundations. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete. A foundation is described as 'piled' when its depth is more than three times its breadth (Atkinson, 2007). Pile foundations can help transfer loads through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth.
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	=== External references ===		=== External references ===

−	* Numerical analysis of unconnected piled raft with cushion. Alaa Ata, Essam Badrawi, Marwa Nabil. https://doi.org/10.1016/j.asej.2014.11.002	+	* Numerical analysis of unconnected piled raft with cushion. Alaa Ata, Essam Badrawi, Marwa Nabil. [https://doi.org/10.1016/j.asej.2014.11.002 https://doi.org/10.1016/j.asej.2014.11.002]

	[[Category:Construction_techniques]]		[[Category:Construction_techniques]]

Designing Buildings at 16:12, 8 January 2018

2018-01-08T16:12:52Z

← Older revision		Revision as of 16:12, 8 January 2018
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	=== External references ===		=== External references ===

−	* Numerical analysis of unconnected piled raft with cushion. Alaa Ata, Essam Badrawi, Marwa ~~Nabilhttps~~://doi.org/10.1016/j.asej.2014.11.002	+	* Numerical analysis of unconnected piled raft with cushion. Alaa Ata, Essam Badrawi, Marwa Nabil. https://doi.org/10.1016/j.asej.2014.11.002
−		+
−		+

	[[Category:Construction_techniques]]		[[Category:Construction_techniques]]

Designing Buildings at 16:12, 8 January 2018

2018-01-08T16:12:35Z

← Older revision		Revision as of 16:12, 8 January 2018
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	Piled raft foundations are typically used for large structures, and in situations where soil is not suitable to prevent excessive settlement. They are an increasingly popular choice for high-rise buildings.		Piled raft foundations are typically used for large structures, and in situations where soil is not suitable to prevent excessive settlement. They are an increasingly popular choice for high-rise buildings.

−	During the design process, the optimum number and position of piles is determined to ensure the stability of the structure while providing an economical solution, with the raft and piles acting together to ensure the required settlement is not exceeded. Typically, the piles provide most of the stiffness while the raft provides additional capacity at the ultimate loading.	+	During the design process, the optimum number and position of piles, as well as their diameter, reinforcement and length, is determined to ensure the stability of the structure while providing an economical solution, with the raft and piles acting together to ensure the required settlement is not exceeded. Typically, the piles provide most of the stiffness while the raft provides additional capacity at the ultimate loading.

	If there are one or more ineffective piles, the raft can allow some degree of load redistribution to other piles, reducing the influence of the pile’s weakness on the overall performance of the foundation.		If there are one or more ineffective piles, the raft can allow some degree of load redistribution to other piles, reducing the influence of the pile’s weakness on the overall performance of the foundation.
		+
		+	In an Unconnected Piled Raft Foundation (UCPRF), the piles are not directly connected to the raft, but are separated from it be a structural fill 'cushion' (such as a compacted a sand-gravel mixture or compacted soil) which redistributes load between the raft and piles. This can be a more efficient, and so economic solution.

	= Find out more =		= Find out more =
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	* Screw pile foundations.		* Screw pile foundations.
	* Types of raft foundation.		* Types of raft foundation.
		+
		+	=== External references ===
		+
		+	* Numerical analysis of unconnected piled raft with cushion. Alaa Ata, Essam Badrawi, Marwa Nabilhttps://doi.org/10.1016/j.asej.2014.11.002
		+
		+

	[[Category:Construction_techniques]]		[[Category:Construction_techniques]]

Designing Buildings at 16:03, 8 January 2018

2018-01-08T16:03:28Z

← Older revision		Revision as of 16:03, 8 January 2018
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	In their normal form, raft foundations (sometimes referred to as mat foundations) are shallow foundations formed by a reinforced concrete slab of uniform thickness (typically 150 - 300 mm) covering a wide area, often the entire footprint of a building. This 'raft' spreads the load imposed by a number of columns or walls over the area of foundation, and can be considered to ‘float’ on the ground as a raft floats on water.		In their normal form, raft foundations (sometimes referred to as mat foundations) are shallow foundations formed by a reinforced concrete slab of uniform thickness (typically 150 - 300 mm) covering a wide area, often the entire footprint of a building. This 'raft' spreads the load imposed by a number of columns or walls over the area of foundation, and can be considered to ‘float’ on the ground as a raft floats on water.

−	However, where a conventional raft foundation provide adequate support, it can be enhanced by the addition of piles, creating what is known as a piled raft foundation.	+	However, where a conventional raft foundation does not provide adequate support, it can be enhanced by the addition of piles, creating what is known as a piled raft foundation.

−	~~Pile foundations~~ are deep foundations. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete. A foundation is described as 'piled' when its depth is more than three times its breadth (Atkinson, 2007). Pile foundations can help transfer loads through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth	+	Piles are deep foundations. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete. A foundation is described as 'piled' when its depth is more than three times its breadth (Atkinson, 2007). Pile foundations can help transfer loads through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth.

	The addition of piles to a raft increases the effective size of a foundation and can help resist horizontal loads. This can improve the performance of the foundation in reducing the amount of settlement and differential settlement, as well as improving the ultimate load capacity.		The addition of piles to a raft increases the effective size of a foundation and can help resist horizontal loads. This can improve the performance of the foundation in reducing the amount of settlement and differential settlement, as well as improving the ultimate load capacity.
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	Piled raft foundations are typically used for large structures, and in situations where soil is not suitable to prevent excessive settlement. They are an increasingly popular choice for high-rise buildings.		Piled raft foundations are typically used for large structures, and in situations where soil is not suitable to prevent excessive settlement. They are an increasingly popular choice for high-rise buildings.

−	During the design process, the optimum number and position of piles is determined to ensure the stability of the structure while providing an economical solution, with the raft and piles acting together to ensure the required settlement is not exceeded. ~~Typiucally~~, the piles provide most of the stiffness while the raft provides additional capacity at the ultimate loading.	+	During the design process, the optimum number and position of piles is determined to ensure the stability of the structure while providing an economical solution, with the raft and piles acting together to ensure the required settlement is not exceeded. Typically, the piles provide most of the stiffness while the raft provides additional capacity at the ultimate loading.

−	If there are one or more ~~innefective~~ piles, the raft can allow some degree of load redistribution to ~~the~~ other ~~non-defective~~ piles, reducing the influence of the pile’s weakness on the overall performance of the foundation.	+	If there are one or more ineffective piles, the raft can allow some degree of load redistribution to other piles, reducing the influence of the pile’s weakness on the overall performance of the foundation.

	= Find out more =		= Find out more =