- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 23 Sep 2020
Pile foundations are a type of deep foundation, principally used to transfer loads from superstructures, through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete, or sometimes timber.
The design of piling mats will depend on the ground conditions and the piling equipment being used, as well as the rig loadings (which typically range from 5 to over 150 tonnes). If a piling mat is too deep it will be incurring unnecessary costs, whilst if it is too shallow it may need time- and cost-inefficient repairs. A soft spot in the surface of just 1 sq. m, can be enough to unbalance a rig.
Typically, the top of a piling mat will be around 600 mm above the pile cut-off level, and it will extend beyond the outermost pile positions by at least 2 m. The edges of the mat and the ramps onto and off it should be clearly marked.
The most suitable materials for piling mats are generally well-graded natural gravels, clean-crushed concrete, crushed hard rock, and so on. As long as it has rebar and timber removed, graded recycled demolition material can also be used. Mats are rolled and compacted in layers. The mat should be free-draining to prevent any build-up of water or slurry on its surface. On sites with a high water table, a separating membrane may be positioned between the mat and the sub-grade to prevent the upward migration of fine-grained soils into the mat.
Piling mats should be inspected daily to ensure they are in proper working condition. If any excavations, trenches or holes have formed in the surface, they must be properly backfilled to ensure they are as stable as the rest of the mat.
It is mandatory that every site with an operational piling rig has a Working Platform Certificate (WPC) that states the piling mat has been correctly designed and installed. The WPC must be signed by the principal contractor and provided for the piling contractor before any piling commences on the site.
 Find out more
 Related articles on Designing Buildings Wiki
Featured articles and news
Not forgetting part F and the new part overheating part O.
As energy prices jump up in cost.
With people in the UK from Ukraine.
Industry leader Steve Murray takes on role.
An abundant and versatile building material.
600,000 heat pump installations targeted per year by 2028.
Helping prevent those unwanted outcomes.
How has transport changed due to Covid-19 ?
Will you need it ? after June 15 and the new Part O ?
Create an account and write the first of many articles.
CIAT commentary after the first meeting.
Who is to blame?
Research recommends focussing on portfolio success rather than project success.
The revised standard for mapping underground utilities.
Cross-industry steering group seeks support in delivery.