Bearing capacity
The term 'bearing capacity' refers to the capacity of soil to support applied loads that are acting on it. In the construction industry, this typically relates to the capacity of soil to support building foundations, in which case, the bearing capacity can be calculated from the maximum average contact pressure between the foundation and the soil that would not produce shear failure.
Three modes of failure limit bearing capacity:
The ultimate bearing capacity of soil (qu) is the maximum pressure which can be supported without failure occurring.
The net ultimate bearing capacity (qnu) does not take into consideration the over-burden pressure and can be calculated as:
qnu = qu - Ydf
Where:
- Y = unit weight of soil
- Df = foundation depth
The net safe bearing capacity (qns) considers only shear failure, and can be calculated as:
qns = qnu / F
Where
The allowable bearing capacity (qs) is the ultimate bearing capacity divided by a factor of safety, and can be written as:
On particularly soft soil, significant settlement can occur without shear failure. In such instances, the maximum allowable settlement is used as the allowable capacity.
Karl von Terzaghi developed a theory for evaluating the ultimate bearing capacity of shallow foundations. His theory states that a shallow foundation is one where the depth is less than or equal to its width.
[edit] Related articles on Designing Buildings
- Bedrock.
- Building foundations.
- Dead loads.
- Floor loading.
- Force.
- Ground conditions.
- Ground improvement techniques.
- Ground investigation.
- Insitu testing of soils.
- Live loads.
- Lateral loads.
- Load bearing.
- Loadbearing capacity.
- Load-bearing wall.
- Moment.
- Moorfields building sets UK pile-loading record.
- Pile foundations.
- Pile integrity test.
- Point load.
- Settlement of buildings.
- Shear force.
- Stiffness.
- Structural engineer.
- Structural principles.
- Subsoil.
- Testing pile foundations.
- Topsoil.
- Types of soil.
- Types of structural load.
- Uniformly Distributed Load.
- Uplift forces.
Featured articles and news
International Electrician Day, 10 June 2025
Celebrating the role of electrical engineers from André-Marie Amperè, today and for the future.
New guide for clients launched at Houses of Parliament
'There has never been a more important time for clients to step up and ...ask the right questions'
The impact of recycled slate tiles
Innovation across the decades.
EPC changes for existing buildings
Changes and their context as the new RdSAP methodology comes into use from 15 June.
Skills England publishes Sector skills needs assessments
Priority areas relating to the built environment highlighted and described in brief.
BSRIA HVAC Market Watch - May 2025 Edition
Heat Pump Market Outlook: Policy, Performance & Refrigerant Trends for 2025–2028.
Committing to EDI in construction with CIOB
Built Environment professional bodies deepen commitment to EDI with two new signatories: CIAT and CICES.
Government Grenfell progress report at a glance
Line by line recomendation overview, with links to more details.
An engaging and lively review of his professional life.
Sustainable heating for listed buildings
A problem that needs to be approached intelligently.
50th Golden anniversary ECA Edmundson apprentice award
Deadline for entries has been extended to Friday 27 June, so don't miss out!
CIAT at the London Festival of Architecture
Designing for Everyone: Breaking Barriers in Inclusive Architecture.
Mixed reactions to apprenticeship and skills reform 2025
A 'welcome shift' for some and a 'backwards step' for others.
Licensing construction in the UK
As the latest report and proposal to licence builders reaches Parliament.
Building Safety Alliance golden thread guidance
Extensive excel checklist of information with guidance document freely accessible.
Fair Payment Code and other payment initiatives
For fair and late payments, need to work together to add value.
Pre-planning delivery programmes and delay penalties
Proposed for housebuilders in government reform: Speeding Up Build Out.
High street health: converting a building for healthcare uses
The benefits of health centres acting as new anchor sites in the high street.