Road Construction Testing

To ensure appropriate design and compliance with local highways authority requirements, road construction testing is a crucial part of any development. In this blog, we look at how New Geosciences Limited can provide a responsive, quality focussed and value driven service from desk study stage through to construction.

Early input can save time and money

Every constraints review and Phase 1 desk study issued by New Geosciences Limited includes an assessment of potential geotechnical risks, including where poor ground conditions may result in abnormal road design and associated costs. Geological maps and memoirs, as well as available information on ground conditions sourced from British Geological Survey records and the relevant planning portal, are used to develop a ground model, and potential issues, such as as the presence of low strength or organic soils, Made Ground, or shallow groundwater, are identified. This early assessment allows for potential unforeseen costs associated with road construction to be factored in, as well as informing the likely impact on programme.

Initial testing as part of a site-wide ground investigation

To further refine the ground model, a ground investigation may be undertaken across the site, during which various tests can be used to provide a California bearing ratio (CBR) value, which indicates the strength of the soil. These tests include:

• Dynamic cone penetrometer (DCP) testing - this relatively quick and inexpensive test is undertaken in-situ and provides data to approximately 1m depth.

• Plasticity index - the results of this frequently used soil test can be compared against published data to provide an indication of CBR value.

• Laboratory CBR testing - samples can be recovered during the investigation and scheduled for laboratory CBR testing, although this test is relatively expensive and results can take several weeks to be issued.

The results of the testing are then presented in an interpretive report.

Subgrade testing

Following the initial testing, further testing of the subgrade is required to confirm the design CBR value. Local highways authority requirements vary, but generally require subgrade testing at a given interval along the line of a proposed road. The required testing may be either in-situ, for example the DCP test, or laboratory CBR testing may be required. A trial pit will also likely be required at each test location to confirm ground conditions within the zone of influence, and testing to confirm properties such as particle size distribution, plasticity index, and moisture content may also be required.

New Geosciences Limited has experience working across many authorities and can advise on the required testing in the location of your site.

Earthworks testing

On sites where levels are to be increased, it may be proposed to construct roads on areas of fill. It's important to understand the adopting authority's requirements around what material classification can be used and what testing is required to confirm the earthworks have been undertaken satisfactorily. Testing may include:

• Particle size distribution testing, to confirm the material class.

• Plasticity testing, to confirm the likely behaviour of cohesive soils.

• Compaction testing, indicating the optimum moisture content and maximum dry density of a material.

• Moisture content and density testing, to confirm the material has been compacted correctly.

• Strength testing, such as CBR or hand shear vane testing, to indicate the material meets the minimum requirements.

New Geosciences Limited will liaise with the adopting authority, confirm requirements, and arrange all testing. An interpretive verification report will then be issued, providing a summary of the testing undertaken. We can also undertake a wider earthworks monitoring service, which may be required by the NHBC, for example.

How do I find out more?

The best way to find out more is call us on 07966 469835 to discuss your site and particular requirements. You can also email us at info@newgeosciences.co.uk.