Our Shelby tube sampler is a thin-walled steel tube, typically 3 inches in diameter, that we push hydraulically into the base of a borehole to retrieve an undisturbed soil cylinder. In Bradford, where the underlying geology includes Carboniferous Millstone Grit overlain by glacial till and alluvial deposits along the Aire Valley, this method is essential for capturing the true in-situ structure and moisture content of cohesive soils. Before mobilising the rig, we always cross-reference with a geotechnical site investigation to confirm the target horizon, then we seal and transport the tubes vertically to maintain sample integrity.
A single Shelby tube sample can reveal the pre-consolidation stress of Bradford's glacial till – data that no SPT blow count can ever provide.
Method and coverage
Regional considerations
BS 5930:2015 and Eurocode 7 (EN 1997-2:2007) both mandate that foundation design on clays must be based on undisturbed samples, not remoulded material. In Bradford, the glacial till can vary from stiff sandy clay to laminated clay with silt partings over a vertical distance of just 2 metres. If you rely on disturbed samples or visual classification alone, you risk overestimating bearing capacity by 40% or more. We have seen designs fail on slopes above the canal corridor because the contractor used SPT correlations instead of direct shear strength from undisturbed specimens. The consequence is differential settlement and cracking within two years of completion.
Standards that apply
BS 5930:2015 – Code of practice for ground investigations, BS EN 1997-2:2007 – Eurocode 7 Part 2: Ground investigation and testing, BS 5930 – Standard Practice for Thin-Walled Tube Sampling of Fine-Grained Soils, ISO 17025 – Laboratory accreditation for mechanical testing of soils
Complementary services
Shelby Tube Sampling & Field Handling
Hydraulic push sampling from rotary boreholes, on-site extrusion in a mobile lab tent to prevent moisture loss, and immediate wax sealing. We log each tube with depth, recovery, and visual description per BS 5930.
Laboratory Testing on Undisturbed Samples
Multi-stage triaxial (UU, CU, CD), oedometer consolidation, and direct shear tests performed on your Shelby tube specimens. Results are reported with stress-strain curves and consolidation plots within 10 working days.
Sample Transport & Storage
Temperature-controlled transport from site to lab in a dedicated vehicle. Long-term storage up to 28 days under controlled humidity for projects requiring phased testing programs.
Typical parameters
Top questions
What is the difference between a Shelby tube sample and a SPT sample?
A Shelby tube sample is an undisturbed representation of the soil fabric, retaining the in-situ void ratio, structure, and water content. An SPT sample is heavily remoulded and only useful for index identification. For strength and consolidation parameters in Bradford clays, undisturbed sampling is mandatory under BS 5930.
How much does undisturbed sampling with Shelby tubes cost in Bradford?
Typical cost for Shelby tube sampling including field handling and basic lab testing (one triaxial and one oedometer) ranges from £320 to £810 per sample point. Volume discounts apply for projects with more than six sample locations.
Can you sample gravelly or sandy soils with a Shelby tube?
No. Shelby tubes are designed for cohesive soils with low plasticity index. In Bradford's alluvial gravels or sandy till, we recommend driven tube samplers or block sampling. For sands, we use the ground freezing technique to obtain undisturbed specimens.
How long does it take to get test results from undisturbed samples?
Basic index tests (moisture content, density, Atterberg limits) take 3 working days. A full suite including consolidated-drained triaxial and oedometer consolidation requires 15 working days from sample receipt in the lab.