Our stabilisation quality management

Our stabilisation service

We deal with the soil stabilisation process from start to finish

Commercial evaluation
Soil sampling and mix designs
Technical design submissions
Full suite of sampling to support our stabilisation works

Soil Stabilisation design considerations

Assess the site investigation and cut/fill drawings prior to visit to help determine trial pit location
Know the formation level for the stabilisation layers
If possible, have a suitable specialist (engineering geologist/geotechnical engineer/material specialist/ground investigation specialist) present so samples from accurate levels can be taken
Where possible, assess material to at least 0.5m below the bottom of the stabilised layer
Take representative bulk samples of each material type encountered – typically 200kg
Ensure sufficient samples of each material type are taken
Run the relevant mix design on each material type encountered
Most trial pits should be undertaken in the cut areas
Samples from cut materials will be required as this material will be the fill material which might require treatment and will form the formation in the fill area
Samples from formation at underside of cut should be taken as this will be the actual material to be stabilised
Assess the cut fill and ensure that some samples are taken from the deepest areas – this is critical in areas where sulphate bearing soils are present, as these are normally covered with non sulphate bearing soils at varying depths
Any changes in material type within 500mm of the formation should be sampled in addition

Quality Management

Confirm soil properties before treatment are the same as assumed in the design. If changes are found then refer back to the designer.
Assess moisture content of material before treatment to adjust binder or water content if required
Check rate of spread of binder and adjust rate of spread if required; or re-spread if insufficient binder has been added
Check mixing depth by hand dug trial holes and adjust and re-mix to the correct depth if necessary
Assess moisture content of mix after mixing – the mix should bind together and be homogeneous when moulded into a ball by hand. For cohesive soils particularly those to be treated with lime only, targeting a moisture content wet of optimum is recommended. NDG gauge readings will provide a guide to moisture content. Take samples for laboratory moisture content testing to correlate with gauge readings. Where practical, consider rapid methods for moisture content testing, such as microwave oven for granular materials or MCV for cohesive materials and adjust water addition accordingly
Check the pulverisation after mixing. This is important for cohesive materials, especially heavy clays, to ensure that the binder is well mixed. Multiple passes or an extended mellowing period can be required for some materials to break down. This should be determined from initial trials and replicated in the main works. Remix if satisfactory pulverisation is not achieved
Check the performance or strength of the mix at agreed intervals and take samples for relevant laboratory testing
Check the compaction by in-situ testing and compare with refusal densities from laboratory specimens or a target density from compaction curves. Define compaction method from site trials and replicate for the main works. Close control and feedback to the roller operator is essential while the material is still workable, so that additional passes can be made if required
Check levels while material is still workable. If too low, more material will be placed, then the full depth of the stabilised layer re-mixed, adding more binder if deemed necessary
Complete any performance testing on the finished layer if required. Allow curing time required for the material to gain strength before testing and trafficking in accordance with specification
Protect finished works from damage by signage or physical barriers where required, until it has reached the required strength or performance for the intended use
For cold weather working, ensure that materials are frost free before treatment and treated materials are protected when low temperatures are anticipated. Additional curing time before trafficking may be required due to slower strength gain at lower temperatures
For hot weather working consider treating smaller areas so that works are completed before the material dries out
Site trials are important to establish working methods that should be used for permanent works and achieving any specific performance criteria

Testing, testing...

With our own in house lightweight deflectometer, we can test our completed work as we go. Our LWD gives an instant stiffness reading on the compacted stabilised layer, in an Mpa format recognised and required by Local Authorities and overseeing consulting engineers. This pro-active approach to testing builds confidence with the client on the performance of the stabilised platform, be it an adoptable road, piling mat, compound, or crane mat.

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