Question

In a field test of a geological formation of permeable soil (porosity = 20 %), the hydraulic gradient was found to be 2 %. The actual seepage velocity of the flow was found to be 0.0025 m/s. Assume that the flow is in the laminar regime. The permeability \( K \) of the aquifer is _______ m/s (rounded off to three decimal places).

Hint:

To calculate permeability, divide the seepage velocity by the product of the hydraulic gradient and porosity.

Answer 1

Correct Answer: 0.024

The seepage velocity \( v_s \) is related to the permeability \( K \), the hydraulic gradient \( i \), and the porosity \( \phi \) by the equation: \[ v_s = K \cdot i \cdot \frac{1}{\phi}. \] Given:
- Seepage velocity \( v_s = 0.0025 \, \text{m/s} \),
- Hydraulic gradient \( i = 0.02 \),
- Porosity \( \phi = 0.20 \).
Rearranging the equation to solve for \( K \): \[ K = \frac{v_s \cdot \phi}{i} = \frac{0.0025 \times 0.20}{0.02} = 0.025 \, \text{m/s}. \] Thus, the permeability \( K \) of the aquifer is \( 0.025 \, \text{m/s} \).