About this tool Calculate the effective test pressure for Lugeon (water pressure) tests in boreholes. Enter the gauge pressure, depth to packer midpoint, and standing water level to get the true effective pressure at the test section.
Optionally enter the flow rate and test section length to calculate the Lugeon value — the standard measure of rock mass permeability used in dam foundations, tunnel design, and grouting assessments.
Results are classified from Very Low (<1 Lu) to Very High (>50 Lu) with approximate equivalent hydraulic conductivity. Per Houlsby (1976) classification.
How to use this tool 1. Enter gauge pressure, depth to packer midpoint, and water level — the tool calculates the elevation head and effective pressure.
2. Optionally enter flow rate and test section length — to calculate the Lugeon value.
3. Read the effective pressure and Lugeon classification — use for test reporting and grouting decisions.
Technical information Elevation head (bar) = (depth to midpoint − water level) × 9.81 / 100
Effective pressure = gauge pressure + elevation head
Lugeon = (Q / L) × (P₀ / P), where Q = flow (L/min), L = test length (m), P = effective pressure (bar), P₀ = 10 bar (1 MPa)
1 Lugeon ≈ 1 × 10⁻⁷ m/s hydraulic conductivity. Classification after Houlsby (1976).
Limitations Does not account for friction losses in the standpipe or hose. For deep tests or high flow rates, friction losses can be significant and should be subtracted from the gauge pressure.
The Lugeon value assumes steady-state flow. Non-linear flow behaviour (turbulent flow, hydrofracture, washout) should be identified from the pressure-flow relationship and reported separately.
The 1 Lu ≈ 10⁻⁷ m/s equivalence is approximate and assumes a specific test geometry. It should not be used as a direct substitute for laboratory permeability testing.
Revision history 14 July 2026: Initial release
Disclaimer This tool is provided for educational and general information purposes only. It is not a substitute for professional engineering advice, design or verification.
Diggy and its contributors are not licensed engineering consultants and no results generated by this tool should be used directly for construction, design or safety-critical decisions.
All values and outputs are based on published empirical correlations and should be independently checked and confirmed by a qualified geotechnical engineer before use.
By using this tool, you accept full responsibility for how you interpret and apply the information provided.
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