Field Permeability Testing (Lefranc & Lugeon) in Sheffield

Sheffield’s topography spans five rivers and over 60% green space, but it’s the buried geology that trips up drainage design. The city sits on Carboniferous sandstones and shales, with pockets of glacial till and alluvium along the Don and Sheaf valleys. Permeability here isn’t guesswork. A desk study won’t tell you where perched water sits in weathered mudstone. Our team runs the field permeability test (Lefranc/Lugeon) to get that number directly from the borehole, avoiding the optimistic assumptions that lead to undersized soakaways or failed earthworks. We’ve applied the in-situ permeability protocol across hillside sites from Crookes to the Lower Don Valley, where variable fracture flow can dominate the hydraulic behaviour of the ground.

A single Lugeon test in fractured sandstone can reveal more about groundwater risk than ten lab permeability samples.

Process and scope

BS 5930:2015+A1:2020 and BS EN ISO 22282 set the framework, but execution in Sheffield’s mixed ground demands rigour. The Lugeon test packs off a section of rock core and applies five pressure stages, measuring water take to map fracture conductivity. In soil we run the Lefranc method, either constant or falling head, directly in the borehole or standpipe. The difference matters: Lugeon values above 10 often flag open joints needing grout treatment; Lefranc results in dense till below 1×10⁻⁷ m/s indicate near-impermeable behaviour. For sites where the water table is perched within made ground, we pair the test with a test pit log to confirm macrostructure before interpreting the permeability envelope. Data is delivered as a plot of pressure versus flow, with the Lugeon unit and equivalent hydraulic conductivity tabulated for direct use by the civil designer.

Local geotechnical context

We see it repeatedly across Sheffield’s valley slopes: designers assume a bulk permeability from SPT logs, then the excavation floods after the first heavy rain. Fractured Pennine sandstone doesn’t behave like porous media—flow concentrates along joint sets that only a Lugeon test can quantify. In the Don Valley, alluvial silts can trap gas and produce artesian conditions during piling; a poorly executed Lefranc test that doesn’t isolate the test section gives falsely high values. Another local risk is mine workings: shallow pillar-and-stall coal seams beneath the east of the city create preferential pathways that short-circuit dewatering systems. The cost of a missed permeable zone isn’t just a delayed programme—it’s a potential slope failure if pore pressures weren’t accounted for in the slope stability analysis.

Typical values

Parameter	Typical value
Test standard	BS EN ISO 22282-2:2012 (soil), BS EN ISO 22282-3:2012 (rock)
Soil method	Lefranc – constant head and falling head
Rock method	Lugeon – five-stage pressure test
Typical test depth	2 m to 45 m below ground level
Reporting output	Lugeon units, k (m/s), pressure-flow graph
Applicable formations	Sandstone, mudstone, alluvium, glacial till, made ground
Test duration per interval	45 to 120 minutes (rock), 30 to 90 minutes (soil)
Packer type	Single or double pneumatic packer

Associated technical services

Lugeon test in rock

Five-stage pressure test using a double packer to isolate borehole sections in sandstone, mudstone, or coal measures. Delivers Lugeon units and equivalent k for tunnel drainage design, grouting verification, and dam foundation assessment.

Lefranc test in soil

Constant or falling head test in standpipes or open boreholes within glacial till, alluvium, and made ground. Suitable for soakaway design, excavation dewatering planning, and landfill liner compliance.

Reference standards

BS 5930:2015+A1:2020 – Code of practice for ground investigations, BS EN ISO 22282-2:2012 – Geotechnical investigation and testing. Geohydraulic testing. Water permeability tests in a borehole using open systems, BS EN ISO 22282-3:2012 – Geotechnical investigation and testing. Geohydraulic testing. Water pressure tests in rock, Eurocode 7: BS EN 1997-2:2007 – Ground investigation and testing

Questions and answers

What is the cost of a field permeability test in Sheffield?

A single Lefranc or Lugeon test typically runs between £560 and £850, depending on depth and the number of pressure stages. Mobilisation, borehole preparation, and reporting are included. Sites with difficult access or multiple test intervals will shift the quote toward the upper end.

When should I specify a Lugeon test instead of a Lefranc test?

Specify the Lugeon test when the ground is rock—sandstone, mudstone, or coal measures—and you need to quantify fracture flow. The Lefranc test is for soils: glacial till, alluvium, or made ground. If the borehole log shows RQD above 30 % and you suspect open joints, a Lugeon test gives the design team the pressure-flow relationship that a standard falling-head test cannot.

How long does a field permeability test take on a Sheffield site?

A single Lefranc test in soil takes 30 to 90 minutes once the borehole is stable. A Lugeon test in rock runs 45 to 120 minutes per interval because of the five pressure stages. We can complete two to three test intervals in a standard working day, assuming the rig is already on site and the hole is conditioned.