A CBR test is used for determining the stability of the sub soil base material for road pavement parking and loading areas or temporary foundations that need bearing pressures monitored.

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When Do you Need a CBR Test?

The process should be undertaken where you want to find out the stability of the subsoil and base material of a particular area. You can then use the information to determine the road / Highway thickness, the suitable road pavement designs, parking designs, loading designs as well as how well to establish a temporary foundation.

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The same information is used by civil engineers to come up with the suitable highway thickness and how to establish the component areas.

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Pavements

CBR testing is undertaken for the design of housing estate roads and highways to determine the strength of the subgrade soil and enable appropriate selection of suitable pavement thickness for the anticipated traffic density together with any precautions for frost heave.

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Foundations

The purpose of foundations is to transfer loads from a structure to competent soil/rock.  They come in the form of traditional shallow spread foundations (strips, pads and rafts) or deep foundations (piles and ground improvement).  The main factors influencing foundation design is the stability of the underlying ground and settlement.

Foundation depths will be influenced by the strength of the ground, seasonal moisture variations, the effects of tree roots, frost action, river erosion, groundwater elevation and buried structures / ground disturbance.

 

What is CBR Testing?

CBR Testing (California Bearing Ratio) is undertaken to provide data for road pavement design. It was first developed by the California State Highway Department.

It is a penetration test which is used to evaluate the subgrade strength primarily of roads, pavements, and foundations.

The CBR test often forms part of the overall site investigation and is useful for determining the thickness of materials needed for the proposed construction.