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Rock Mass Permeability Estimator

Estimate rock-mass permeability from a packer (Lugeon) test — either enter the Lugeon value directly or compute it from the water take, test-section length and pressure, then get an estimated hydraulic conductivity and a tightness rating. Used in dam, tunnel and grouting investigations.

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How to use this calculator

Enter Values

Enter your values and press Calculate to see results.

Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.

How to use this calculator

  1. Enter a Lugeon value Lu if you already have one, OR enter the water take Q (L/min), section length L (m) and test pressure P (MPa).
  2. The tool computes Lu = Q / (L·P) when you supply Q, L and P.
  3. Read the estimated hydraulic conductivity k (m/s) and the rock-mass tightness band.

How it works

One Lugeon is a water take of 1 litre per minute per metre of test section at a reference pressure of 1 MPa (about 10 bar): Lu = Q / (L·P). Hydraulic conductivity is then estimated as k ≈ Lu × 1.3×10⁻⁷ m/s, with the simpler rule k ≈ 1×10⁻⁷ m/s per Lugeon also in common use.

Tightness bands run from very tight (Lu < 1) through low (1–5), moderate (5–15) and high (15–50) to very high or open/karstic (> 50). These correlations are approximate; grouting and seepage design need site-specific correlation and interpretation of the stepped-pressure (Houlsby) test behaviour.

Worked example

Packer test in fractured rock. A 5 m test section takes 10 L/min at 1 MPa. Lu = 10 / (5 × 1) = 2 Lugeons. Estimated k ≈ 2 × 1.3×10⁻⁷ = 2.6×10⁻⁷ m/s — a low-permeability rock mass.

Common mistakes

  • Not normalising to the reference pressure — Lu is defined at 1 MPa, so P must be in MPa.
  • Treating the k ≈ Lu × 10⁻⁷ correlation as exact; it is an order-of-magnitude estimate only.
  • Reading a single Lugeon value without checking the stepped-pressure behaviour (turbulent, dilation, wash-out or void-filling).

Frequently asked questions

What is a Lugeon value?

A measure of rock-mass permeability from a packer test: 1 Lugeon = a water take of 1 litre per minute per metre of test section at a reference pressure of 1 MPa (~10 bar).

How do you calculate the Lugeon value?

Lu = Q / (L·P), where Q is the water take in litres per minute, L the test-section length in metres and P the test pressure in MPa.

How do you convert Lugeons to hydraulic conductivity?

A common approximation is k ≈ 1×10⁻⁷ m/s per Lugeon; this tool uses k ≈ Lu × 1.3×10⁻⁷ m/s and also shows the 1×10⁻⁷ estimate.

What Lugeon value is considered tight?

Less than about 1 Lugeon is very tight (low permeability); 1–5 is low, 5–15 moderate, 15–50 high and above 50 very high or open/karstic.

Is the Lugeon-to-k conversion accurate?

It is approximate — an order-of-magnitude guide. Grouting and seepage design require site-specific correlation and interpretation of the full stepped-pressure test.

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Tip: Enter any known values to calculate the remaining results.

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