The plate bearing test is one of the most reliable, cost-effective, and straightforward methods for determining a material’s ultimate load bearing capacity. By identifying a foundation’s ability to withstand different applied pressures, this test ensures the stability and safety of a wide range of semi-permanent structures.
In this guide, we'll explore the basics of the plate bearing test, including its purpose, procedure, and importance in construction. We'll also look into the technical aspects of interpreting the results and explain how this test compares to the California Bearing Ratio (CBR) test.
Introduction to Plate Bearing Tests
A plate bearing test, also known as a plate load test, is used to determine the ground’s bearing capacity and actual strength by applying an increasing load to induce settlement. It’s often used in situations where the ground particle sizes are large, or the soil has a firmer texture.
In this kind of test, a circular steel plate is positioned on the ground and an increasing load is applied until the plate begins to settle quickly. This test is carried out at the level of the foundation beneath a temporary structure – whether on the ground surface itself or in a shallow pit.
When Do You Need a Plate Load Test?
A common application of the plate load test is in the design of semi-permanent structures to ensure a designated area can handle the intended load. These can include crane bases, piling pads, stanchion bases, mezzanine floors, and working platforms.
- The plate bearing test could also be used to determine:
- The strength & durability of building materials (e.g., concrete or steel)
- The load bearing capacity of a bridge or dam
- The behaviour & performance of soil beneath an existing structure
- The integrity of a structure after a natural disaster
- The load distribution beneath a structure
Advantages of Carrying Out a Plate Bearing Test
There are several advantages to using a plate bearing test to determine the ultimate bearing capacity of a soil or material, including:
- Quick & easy to perform
- Can be conducted on-site
- Can be used to test a wide range of soil types
- Provides accurate results
- Cost & time-efficient
- Equipment is portable & easy to set up
Most importantly, measuring the performance capacity of a foundation enables you to minimise construction risk, confirm design assumptions, and establish weight load and distribution parameters for temporary structures.
Interpreting the Results of a Plate Load Test
After identifying the total value of the load required to induce settlement, you can then calculate the ultimate bearing capacity of the ground / material (the maximum vertical pressure that can be applied before shear failure occurs).
To do this, you need to divide the total load value by the area of the plate:
Ultimate load bearing capacity = Total load value required to induce settlement ÷ Area of the steel plate
With this value, you can determine the safe bearing capacity of the ground / material by dividing the ultimate bearing capacity by a factor of safety. This is typically 3.
Is a CBR Test the Same as a Plate Bearing Test?
The California Bearing Ratio (CBR) Test, like the plate bearing test, is a type of load-bearing test for examining materials at or just underneath the surface.
However, a CBR test examines a smaller surface area and relies on a plunging, penetrative motion of machinery into the ground. This test is commonly used for the designing of pavements, roads, or concrete slab foundations.
Results from a plate load test can be used to calculate an equivalent CBR value. For this, you will need to divide the load applied to the plate by the area of the plate, then multiply this result by the thickness of the material sample.
ACS for Plate Load Test Services
A plate bearing test carried out before planned construction commences is crucial for ensuring the ground or material will support the intended load of the superstructure, minimising the risk of instability or collapse.
At ACS, we offer comprehensive plate load test services in compliance with the British Standard (BS) 1377 9:1990 and IAN73/06 standards – providing you with accurate and reliable data to drive your project’s success.
See our Plate Bearing Test Services page for more details or get in touch to speak to a member of our team.