26 Jun, 2023

At Analytical Construction Services (ACS), our expert team has the experience and specialist testing capacity to carry out In-situ CBR (California Bearing Ratio) Tests utilising the latest technology.

The In-situ CBR (California Bearing Ratio) Test was developed by the California Division of Highways in the 1930’s. It was later adopted by the UK and used as a standard method as specified in BS1377-9.

This fundamental test is undertaken in the construction industry for highway, embankment subgrade, and pavement engineering projects to measure the ability of a soil sample to bear the load of a structure of a transportation route.

What Is An In-situ CBR Test Used For?

In-situ CBR Testing is a method used to assess the load-bearing capabilities of subgrade soils. It is used to provide important information to determine the following:

  • Subgrade Evaluation
  • Design Optimisation
  • Construction Quality Control
  • Material Selection
  • Comparative Analysis

The test is often used in relation to future construction of roads and pavements. Not only this, but it can also be used on existing constructions as it provides valuable information for foundation design and material selection for infrastructure projects.

What’s the Maximum Size of Material You Can Measure By CBR Testing?

Generally, the size of material that can be measured by In-situ CBR (California Bearing Ratio) Testing is around 0.8inches (or 20mm). 

The results of the field test are then analysed and used to evaluate the strength and bearing capacity of soils and other materials used in road construction and civil engineering.

What Does The Test Determine?

An In-situ CBR Test determines the soil’s resistance to penetration, and the material’s capacity to support loads and withstand deformation. This information is delivered by the CBR value that was discovered during the testing process.

It’s important for Engineers to have this information to enable them to adjust designs for pavements and foundations, determine the appropriateness of soil for a building, and assess the necessity for methods of improvement to the soil. 

In-Situ CBR Tests can aid in the decision-making process for infrastructure and construction to ensure the stability and durability of those tasks.

Our Accredited In-Situ Plate Bearing Test Procedures

In-situ California Bearing Ratio (CBR)

The key aspects of In-situ CBR Testing are detailed as follows:

  • Test Set-Up

The drilling of a cylindrical metal plunger into the ground by way of a mechanical or hydraulic jack

  • Penetration Measurement

At regular intervals, the depth of the penetration of the plunger is recorded

  • Load Application

Load is gradually applied to the plunger consistently until penetration is reached

  • CBR Calculation

CBR is calculated by the ratio force per unit area that is required for the specified penetration, by the road required for the same penetration in a standard material.

  • Reporting

Calculation of Nominal CBR Value Using the Incremental Plate Load Test

demonstration of a plate load test applied to concrete

This plate-bearing test procedure involves determining the ratio of the applied load to the corresponding penetration of a circular plate in the soil.

To do this, we apply a specified load onto a circular plate which is placed on a flat surface. We then apply this load in several equal increments and record the resulting settlements at each stage.

Our sister company, Simtec Materials Testing, discuss this further in their article ‘Plate Bearing Test vs CBR (California Bearing Ratio) Test: What’s the Difference?’.

Calculation of Nominal CBR Value Using the Dynamic Cone Penetrometer (DCP)

Our final testing procedure involves measuring the penetration resistance of the soil and relating it to the standard CBR Values.

This simplistic test consists of driving a metal cone into the ground and is generally used in circumstances where the test area is inaccessible to a 4 x 4 vehicle. However, this test is the least accurate of all.

UKAS Accredited In-Situ CBR Tests By ACS

ACS Testing offer a comprehensive range of professional on-site testing services, all carried out by our fully trained site technicians. We first obtained UKAS Accreditation in 1990, and since then, our specialist team has increased their knowledge and experience in the field. 

We are proud to offer a comprehensive range of tests all carried out to British and European Standards. Our experienced team will ensure your testing requirements are clearly understood, carried out efficiently, and accurately reported. 

Our team of experts are ready and waiting to discuss our range of testing services for any new project, simply contact us to find out more.