Laboratory California Bearing Ratio CBR

UKAS Accredited

Standard(s): BS 1377-2:2022
Lab Test
The Laboratory California Bearing Ratio (CBR) test measures the strength of soil by assessing its resistance to penetration under controlled laboratory conditions. Conducted in accordance with BS 1377-2:2022, the test determines how much pressure is required to push a standard plunger into a prepared soil sample. The higher the resistance to penetration, the higher the CBR value, indicating stronger material suitable for supporting construction loads.

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The Process

A representative soil sample is compacted into a mould at a specified moisture content and density. In many cases the sample is soaked for a set period to simulate worst-case site conditions. A standard plunger is then pressed into the soil at a controlled rate while the applied force is recorded. The measured resistance is compared to a standard reference value to calculate the CBR percentage.

The Reason

The strength of subgrade soils plays a critical role in the design of pavements and earthworks. Laboratory CBR testing provides a reliable way to assess soil performance under controlled conditions. This allows engineers to determine whether a soil is suitable for use in construction or if ground improvement or alternative materials are required.

The Application

Laboratory CBR testing is widely used in road construction, car parks, access roads, and other pavement structures. The results are used in pavement design calculations and to assess the suitability of soils used in subgrades, embankments, and engineered fill.

Frequently Asked Questions

Where can I get laboratory CBR soil testing in the UK?

Amtest provides Laboratory California Bearing Ratio (CBR) testing in accordance with BS 1377-2:2022, helping contractors and engineers confirm the strength of soils used in construction.

What types of soil can be tested for CBR at Amtest?

Amtest can test a wide range of soils used in earthworks and pavement construction, including subgrade materials and engineered fill.

How do I arrange laboratory CBR testing with Amtest?

You can contact Amtest to organise soil sample delivery or discuss sampling requirements. Our laboratory team will confirm sample quantities, testing procedures, and reporting times to support your project schedule.

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Laboratory California Bearing Ratio CBR

The Laboratory California Bearing Ratio (CBR) Test measures the strength of soil for use in road construction and sub-base design. It assesses the pressure required to penetrate a soil sample with a standard plunger and compares it to the pressure needed for equal penetration in a standard crushed rock material.

The Process

  1. Sample Preparation: A representative soil sample is collected and compacted into a cylindrical mold to simulate in-situ conditions.
  2. Penetration Test: A plunger with a standard area is used to apply pressure to the compacted soil. The penetration depth and corresponding pressure are recorded.
  3. Comparison and Calculation: The measured pressure is then divided by the pressure required to achieve the same penetration in a standard crushed rock. The result is expressed as the California Bearing Ratio (CBR).

Why Is This Test Important?

  • Soil Strength Evaluation: The CBR value provides an indication of the strength and load-bearing capacity of soil, which is essential for designing pavements, road foundations, and sub-bases.
  • Quality Assurance: Ensures that the soil meets the necessary specifications for use in road construction and foundation work.
  • Material Suitability: Helps determine the suitability of the soil for different applications, with higher CBR values indicating stronger, more durable materials.

The Laboratory CBR Test is a vital method for assessing soil suitability for construction projects, particularly in road and foundation engineering. Contact us for reliable and accurate testing.

BS 1377-2:2022