What Is the Soil Hydraulic Conductivity & Darcy Permeability Calculator?
Soil permeability (hydraulic conductivity k) is the constant of proportionality in Darcy's Law relating seepage velocity to hydraulic gradient.
How Does the Soil Hydraulic Conductivity & Darcy Permeability Calculator Work?
In constant head tests, k = (Q·L) / (A·h·t). In falling head tests, k = (a·L / (A·t))·ln(h1 / h2) where a is the standpipe area.
Soil Hydraulic Conductivity & Darcy Permeability Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
k_{\text{constant}} = \frac{Q \cdot L}{A \cdot h \cdot t}, \quad k_{\text{falling}} = \frac{a \cdot L}{A \cdot t} \ln\left( \frac{h_1}{h_2} \right)
Darcy hydraulic conductivity equation relates steady volumetric permeameter seepage outflow to hydraulic gradient and specimen cross-sectional area.
How to Use the Soil Hydraulic Conductivity & Darcy Permeability Calculator
- Choose constant head or falling head method.
- Enter specimen cylinder dimensions and test duration.
- Input water head and collected outflow volume.
Step-by-Step Example Calculation
Constant Head Test on Medium Sand (Q = 250 mL in 60s, h = 45 cm)
Input Values:
testType:constant-head
sampleLengthCm:15.0
sampleDiameterCm:10.0
testDurationSeconds:60
collectedVolumeMl:250
constantHeadDifferenceCm:45.0
Worked Steps: Permeability k is 1.77 × 10⁻² cm/s (1.77 × 10⁻⁴ m/s), indicating clean sand with excellent free drainage.
Understanding Your Result
Hydraulic Conductivity (k): Permeability in cm/s and m/s.
Drainage Class: Gravel/sand (high), silt (moderate), clay (impermeable barrier).
Factors That Affect the Result
- Soil void ratio, particle grain size distribution (D10), organic content, and fluid viscosity/temperature.
When Should You Use This Calculator?
- Dam seepage analysis, groundwater well drawdown, retention pond infiltration, and landfill liner design.
Assumptions & Limitations
- Assumes 100% water-saturated laminar Darcy flow without piping or preferential flow channels.
Frequently Asked Questions
Calculation Accuracy & Reference Note
ASTM D2434 and ASTM D5084 laboratory test compliant.