If you are planning foundations, pavements, or working platforms, you need to know whether the ground can support the loads you intend to apply. A plate bearing test, also known as a plate loading test or plate testing, is an in-situ method used to assess the bearing capacity of the ground and the settlement under a given load using direct measurements on site.
This guide explains what the test is, how plate loading works, how plate load testing is carried out, what information it gives you, and how you should use the results in design, so you can make informed, safe, and efficient decisions in construction and civil engineering.
What Is a Plate Bearing Test?
A plate bearing test is an in-situ test in which a steel plate (often a circular steel plate, also called a bearing plate) is placed on the ground and loaded in stages. The purpose is to observe how the soil and other soils and construction materials behave under loading.
The test is used to determine:
- The bearing capacity and ultimate bearing capacity
- The bearing capacity and settlement characteristics
- The settlement of the ground and settlement under a given load
- Whether the ground can support the intended design load
In other words, the test shows you the real load bearing behaviour of the ground at foundation level.
What Is Plate Loading and How Does It Work?
Plate loading consists of loading a steel plate in controlled stages and measuring deformation.
During a plate loading test:
- A plate size and plate diameter (or diameter) are selected, commonly 300mm or 450mm or 600mm, depending on the purpose of the test.
- The plate is set at the test location, usually carried out at foundation level or normally carried out at foundation depth.
- A load is applied in stages. Each stage is a load increment (or increment), corresponding to each load increment of pressure.
- At each stage, you measure deformation at each stage and record the settlement under a given load.
The process consists of loading a steel plate step by step until the given load or a defined limit is reached.
What the Test Is Used to Determine
A plate bearing test is used to determine:
- The ultimate bearing capacity
- The bearing capacity of the ground at the test level
- Whether the capacity to withstand the design load and reaction load is adequate
- The load and reaction load required for safe design
- The relationship between bearing capacity and settlement
You can also determine the ultimate bearing capacity from the load–settlement behaviour and then use it in the design with appropriate safety margins.
Understanding Bearing Capacity and Settlement
Bearing capacity describes how much pressure the ground can carry before failure or excessive deformation. Settlement describes how much the ground moves under load.
The test helps you understand:
- The bearing capacity and settlement relationship
- The settlement of the ground at working load
- The settlement under a given load that your structure will experience
- The strength and deformation characteristics of the soil
Together, these tell you whether the ground offers enough stability and safety for your project.
Plate Size, Plate Diameter, and Why They Matter
The plate size, plate diameter, and area of the bearing plate affect how stresses spread into the soil.
- Smaller plates reflect more local behaviour.
- Larger plates average behaviour over a wider zone.
Typical sizes include 300mm and 450mm or 600mm. The test can advise on the plate diameter to suit the type of information required and the ground conditions.
The Loading Process in More Detail
During the test:
- The load applied is increased step by step.
- Each step is a load increment.
- You record the deformation at each stage.
- You observe how settlement develops with loading.
This staged process shows not just a single value, but the full bearing capacity and settlement characteristics of the ground.
Interpreting the Results
From the measurements, you produce a load–settlement curve. This curve shows:
- How the soil responds to loading
- The settlement under a given load
- The point at which stiffness reduces or failure begins
From this, the data can be used to determine the ultimate bearing capacity and assess whether the ground is suitable for the intended design load.
Because this is an in-situ test, it gives accurate and reliable data and data for informed engineering decisions.
Standards and Engineering Context
In the UK, plate bearing tests are commonly carried out in accordance with BS 1377 Part 9 (often written as BS 1377, BS 1377 Part, BS, or 1377).
The method is widely used for civil engineering, civil engineering purposes, and construction and civil engineering projects, especially where shallow foundations or working platforms are involved.
Applications in Construction
A plate bearing test is commonly used in the design of:
- Foundations and slabs
- Pavements and formation layers
- Working platforms
- Ground for working platforms
- Pads for crane outriggers
- Temporary structure support areas
It is especially useful where the behaviour of soils and construction materials near the surface controls performance.
Relationship to the CBR Test
The CBR test (California Bearing Ratio) is another way to assess ground strength, especially for roads and pavements.
- The plate bearing test measures actual bearing capacity and settlement.
- The California bearing ratio gives a relative strength index, often reported as a CBR value or equivalent CBR.
Both methods can be used together to build a more complete picture of ground conditions.
Site and Ground Investigation
A plate bearing test should be part of a wider ground investigation and site investigation.
These investigations help you understand:
- The ground conditions
- The soil profile and variability
- The most appropriate test location
- Any limitations subject to site conditions
The plate bearing test is then targeted at the level that matters most for performance.
Why the Plate Bearing Test Is So Useful
The method is popular because:
- It provides accurate and reliable data
- It directly measures real behaviour
- It shows both bearing capacity and settlement
- It supports decisions about stability and safety
- It gives clear evidence of whether the ground can support the intended loads
Final Thoughts
A plate bearing test or plate loading test is one of the most direct ways to understand how the ground will perform under load. It is an in-situ method that shows real bearing capacity, real settlement under a given load, and real strength and deformation characteristics.
When combined with proper ground investigation and site investigation, it gives you the confidence to design foundations, platforms, and pavements based on measured behaviour rather than assumptions.