Question

For a saturated soil, the ratio of the rate of flux of water per unit area per unit time to the potential gradient is known as

• A. Saturated hydraulic conductivity
• B. Permeability
• C. Hydraulic head gradient
• D. Fluidity

Hint:

Hydraulic conductivity (\( K \)) depends on both the porous medium (soil) and the fluid (water) properties.
Intrinsic permeability (\( k \)) depends only on the soil pore structure and is related to \( K \) by: \( K = \frac{k \cdot \rho \cdot g}{\mu} \).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Water movement in saturated soil is governed by Darcy's Law, which states that the rate of water flow (flux) is proportional to the hydraulic gradient.
Key Formula or Approach:
Darcy's Law is written as:
\[ q = K \cdot i \] where:
- $q$ is the water flux density (volume of water per unit area per unit time, $L/T$).
- $i$ is the hydraulic potential gradient ($L/L$, dimensionless).
- $K$ is the proportionality factor, known as the hydraulic conductivity.

Step 2: Detailed Explanation:
Rearranging Darcy's equation to solve for the proportionality factor:
\[ K = \frac{q}{i} \] This shows that $K$ is the ratio of the water flux density ($q$) to the potential gradient ($i$).
In a saturated soil, this coefficient is specifically termed the Saturated hydraulic conductivity ($K_{sat}$).
- Permeability (intrinsic permeability, $k$) is a property of the soil pore geometry alone, independent of the fluid properties.
- Hydraulic head gradient is the gradient itself ($i$).
- Fluidity is related to the viscosity of the fluid.

Step 2: Final Answer:
The ratio is defined as the saturated hydraulic conductivity, corresponding to option (A).