Much of Liverpool is underlain by glacial till and fluvial deposits from the Mersey Basin, where clay-rich layers alternate with sands and gravels. That variability makes laboratory permeability testing essential for predicting groundwater flow. We run falling head tests on fine-grained soils and constant head tests on sands and gravels, both to BS 5930 and Eurocode 7. Before sampling, we often coordinate with a georadar survey to map gravel lenses and avoid disturbed zones. Results include hydraulic conductivity in m/s, void ratio at test conditions, and a clear statement of saturation method. Turnaround is typically 3 to 5 working days from sample receipt.
Liverpool's glacio-fluvial soils produce hydraulic conductivity values spanning three orders of magnitude — from 10⁻⁹ to 10⁻⁶ m/s — so lab testing is not optional.
Process overview
Liverpool grew rapidly during the 19th century, with docks and warehouses built directly on soft alluvium and made ground. Many existing structures now require refurbishment, and accurate permeability data is critical for dewatering design and foundation drainage. Our laboratory program includes four dedicated services tailored to local ground conditions. We combine falling head tests on intact specimens with constant head tests on remoulded samples when the soil fabric is disturbed. For projects where field conditions are more representative, we also recommend a packer permeability test to compare lab and in-situ values. Every test is run under UKAS accreditation (ISO 17025) with full traceability.
Technical reference image — Liverpool
Local context
In the city centre, where sandstone bedrock is overlain by thin till, permeability can be moderate. But in areas like Toxteth and Speke, where thick laminated clays and silts dominate, falling head tests often yield values below 10⁻⁸ m/s. Ignoring this variability leads to overestimated drainage rates and undersized sump pumps. For deep excavations near the Mersey, the risk is even higher: tidal fluctuations can reverse gradients, and lab permeability data is the only reliable input for transient seepage analysis. We always cross-check with local borehole records from the British Geological Survey.
Falling head (fine soils) / Constant head (coarse soils)
Hydraulic conductivity range
10⁻⁹ to 10⁻³ m/s
Sample diameter
50 mm to 100 mm
Effective stress range
50 to 400 kPa
Saturation method
Back-pressure (150-300 kPa) or vacuum
Temperature correction
To 20°C per BS 1377:1990
Additional services
01
Falling head test on intact samples
For silts and clays. Uses triaxial cell with back-pressure saturation. Measures k between 10⁻⁹ and 10⁻⁶ m/s. Ideal for foundation drainage and settlement estimates.
02
Constant head test on remoulded samples
For sands and gravels. Compacted at target density. Flow measured under steady gradient. k range 10⁻⁶ to 10⁻³ m/s. Used for filter design and dewatering studies.
03
Flexible wall permeability test
Confining pressure applied via cell fluid. Suitable for low-permeability samples (<10⁻⁸ m/s). Includes pore pressure measurement at both ends. Complies with BS 1377-5.
04
Custom consolidation-permeability
Combined oedometer and falling head test. Measures k at multiple load increments. Directly links permeability to void ratio for compressible Liverpool clays.
Relevant standards
BS 1377-6:1990 (Laboratory permeability tests), BS 5930:2015 (Code of practice for ground investigations), Eurocode 7 (EN 1997-2:2007) – Geotechnical design
Common questions
How much does a laboratory permeability test cost in Liverpool?
Pricing typically ranges from £300 to £540 per test, depending on sample preparation complexity, test duration, and whether back-pressure saturation is required. Falling head tests on intact clays are at the lower end; flexible wall tests with multiple stress stages sit higher. Contact us for a quote based on your specific soil type and number of samples.
What is the difference between falling head and constant head tests?
Falling head is used for low-permeability soils (clays, silts) where water flows slowly through the sample under a decreasing head. Constant head applies a steady hydraulic gradient and is suited to sands and gravels with higher permeability. The choice depends entirely on the expected k range and soil gradation.
How long does the test take and when do I get results?
Most tests are completed within 3 to 5 working days after sample receipt. Falling head tests on stiff clays may take up to 7 days if saturation is slow. Results include a test certificate with k value, void ratio, test conditions, and temperature correction. Urgent turnaround is possible for an additional fee.
