Field Permeability Testing (Lefranc/Lugeon) in Newbridge

A single Lefranc constant head test in soil typically runs for 30 to 60 minutes once the borehole is prepared. A Lugeon test in rock takes longer — a complete five-pressure-stage cycle usually requires 90 to 120 minutes. If multiple packer intervals are tested in a deep borehole, the full programme can extend over one or two days. The testing includes stabilisation time at each pressure step and a pressure-recovery phase to check for fracture dilation or clogging effects.

The Lefranc method measures hydraulic conductivity in soil or very soft rock using an open section of borehole casing; water flows out into the formation under a constant or falling head. The Lugeon method is designed specifically for rock masses — it isolates a section of borehole with inflatable packers and injects water at stepped pressures up to 10 bar. Lugeon values indicate fracture aperture, connectivity and the presence of turbulent flow in rock joints, which the Lefranc test cannot capture.

Yes, with careful planning. A borehole advanced for SPT sampling can be reamed to NX diameter and cased to accommodate Lefranc testing in the soil zone. For the Lugeon test, the borehole must extend into competent bedrock and be free of casing across the test interval. It is common practice on Newbridge sites to combine SPT profiling, Lefranc tests in the till, and Lugeon tests in the underlying limestone within a single borehole to minimise mobilisation costs.

For a Lefranc or Lugeon test on a Newbridge site, budget between €610 and €1060 per test interval, depending on borehole depth, access conditions and the number of pressure stages required. Mobilisation, drilling, packer setup and reporting are included. A programme with multiple packer intervals in a single borehole reduces the per-test cost. We provide a fixed-price quotation after reviewing the site location and ground conditions.

There is no single threshold, but in Irish dam and basement practice a Lugeon value above 5 to 10 typically triggers consideration of grouting. Values above 30 suggest open, interconnected fractures. However, the decision also depends on the project — a small residential basement in Newbridge tolerates more seepage than a dry dock or a water-retaining structure. The five-stage pressure curve also matters: a flat curve suggests laminar flow in tight rock, while a steep curve or pressure-dependent behaviour indicates fracture dilation that may require targeted grouting.