Permeability: flexible-wall (triaxial) calculator

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Worked example — results

• ✓ Inflow/outflow within 0.75–1.25
• ✓ Gradient ≤ 30 (ASTM guidance)

Method, formulas and assumptions

• Area = PI()*(50/1000)^2/4 = 0.0019635 m²
• Hydraulic gradient Δu/(γw L) = 20/9.81/(100/1000) = 20.387
• k at test temperature = (12.4*1E-6)/(60*60)/(0.0019635*20.387) = 8.605e-8 m/s
• Viscosity ratio ηT/η20 = 10^(247.8/(23+133.15))/10^(247.8/153.15) = 0.93092
• k at 20 °C = 8.605e-8*0.93092 = 8.010e-8 m/s
• Inflow/outflow ratio = 12.9/12.4 = 1.0403

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