Tension piles
Foundations provide support for structures, transferring their load to layers of soil or rock that have sufficient bearing capacity and suitable settlement characteristics.
Very broadly, foundations can be categorised as shallow foundations or deep foundations:
- 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 insufficient to support loads imposed and so they are transferred to deeper layers with higher bearing capacity.
Pile foundations are deep foundations. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete, or sometimes timber. A foundation is described as 'piled' when its depth is more than three times its breadth.
Pile foundations are principally used to transfer compressive loads from a building's superstructures, through weak, compressible strata or water onto stronger layers of soil or rock at depth.
Tension piles, also known as uplift piles or anchor piles, are a type of pile foundation that is used to resist uplift forces that might otherwise cause it to be extracted from the ground.
Uplift forces can develop as a result of hydrostatic pressure, seismic activity or overturning moments. In particular, tall structures such as chimneys, jetties and transmission towers can be subject to high wind loads and hence, overturning moments. The compressive and tensile forces generated must be transmitted to the ground along the length of the pile.
Tension piles resist uplift forces through the action of friction along their length, by under-reaming (that is enlarging the end of the pile), by the action of helical bearing plates welded to the pile shaft, or by bonding the pile into rock.
Tension piles may also be used to resist the horizontal forces from sheet piling walls. See also: Ground anchors.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
From Chaucer to Fawlty Towers.
Electrotechnical excellence, now open for entries.
Net zero electricity grids BSRIA guide NZG 5/2024
Outlining the changes needed to transition to net zero.
CIOB Global Student Challenge 2024
Universitas Indonesia wins for second year running.
New project and cultural district described in detail.
The nature of EPCs, crticism and inaccuracies.
History, issues and redesign.
From waste recycling to energy performance the hierchy.
An introduction to WERCS and WEEE responsibilities
Dealing with 2 million tonnes of waste equipment a year.
Global BACS Market: analytics and optimisation
A BSRIA glance at building automation and control systems.
What it is and how to use it.
Types of insulating plaster by binder and insulant.
Investors in People: CIOB achieves gold
Reflecting a commitment to employees and members.
Scratching beneath the surface; a guide to selection.
ECA 2024 Apprentice of the Year Award
Entries open for submission until May 31.
UK gov apprenticeship funding from April 2024
Brief summary the policy paper updated in March.