Complete Guide to Soil Permeability Testing
The Soil Permeability Calculator computes the coefficient of permeability (k) using standard lab tests or empirical methods. Vital for drainage, seepage control, and groundwater flow. Integrates with Drainage Pipe and Earth Pressure calculators.
What is Permeability?
Measure of how easily water flows through soil:
\( k = \frac{Q L}{A h} \) (Constant Head)
Why Calculate It?
- Drainage: Subgrade, trenches
- Seepage: Dams, retaining walls
- Dewatering: Excavation planning
- Contamination: Leachate flow
Key Equations
Constant Head
\( k = \frac{Q L}{A h} \)
Falling Head
\( k = \frac{a L}{A t} \ln \left( \frac{h_1}{h_2} \right) \)
Hazen Empirical
\( k = C (D_{10})^2 \) (C ≈ 100–150)
Step-by-Step Process
- Select method
- Input test data
- Compute k
- Classify soil
Example: Constant Head
Q=10 cm³/s, L=10 cm, A=20 cm², h=50 cm:
- k = 0.01 cm/s
- Classification: Clean sand
Typical Values
| Soil Type | k (cm/s) | Drainage |
|---|---|---|
| Clean Gravel | 1–100 | Excellent |
| Clean Sand | 10⁻³–1 | Good |
| Silty Sand | 10⁻⁵–10⁻³ | Fair |
| Clay | < 10⁻⁷ | Poor |
Applications
- Foundations: Underdrain design
- Dams: Core permeability
- Landfills: Liner efficiency
- Tunnels: Groundwater inflow
Best Practices
- Use remolded samples
- Saturate fully
- Run multiple tests
- Check for air bubbles
Common Mistakes
- Using wrong units
- Air entrapment
- Wall leakage in permeameter
- Ignoring temperature
Advanced Topics
- Anisotropic permeability
- Flow nets
- Pumping tests
- Geosynthetics
Conclusion
Accurate permeability ensures safe drainage and seepage control. Our Soil Permeability Calculator delivers instant k values from lab or field data. Pair with Drainage Pipe for complete subsurface design. Build on solid ground!