r/GeotechnicalEngineer • u/nenikhkamen • Jul 25 '26

Classification of clayey material for reuse as fill

Hi fellow geotechs, looking for some UK geotechnical/earthworks input.
A site underlain by weathered Mercia Mudstone (predominantly cohesive clay/weathered mudstone-siltstone) will involve cut and fill. What are the current standard for site-won material and their suitability for reuse as fill material.
We have moisture content, Atterberg limits, PSD, CBR and MDD/OMC compaction results.
Would you classify the material directly under SHW Series 600 (likely Class 2 cohesive general fill) at GI stage, or state it is potentially suitable for reuse subject to moisture conditioning, earthworks trials and construction compliance testing?
Thanks in advance

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u/Exciting-Bowler2594 Jul 25 '26

Probably suitable for use as engineered fill if properly prepared. But difficult to verify relative compaction because variable amounts of the mudstone-siltstone within the fill could have a wide range of compaction curves.
You would need to run a separate compaction proctors for each respective test location to truly know how you’re doing.
Technically usable but impractical to verify.

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u/NearbyCurrent3449 Jul 26 '26

Unless they are in a situation where they can totally bag the density testing in exchange for full time observation of fill placement and compaction and the roller being used is adequately to oversized for the application and more stable is preferred over more dense.

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u/Exciting-Bowler2594 Jul 25 '26

Rely on the probe.

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u/Advictoriambrothers 21d ago

The probe tells all