# Permeability of Soil – Darcy’s law-Limitation, Coefficient of Permeability, Importance of Study of Seepage Analysis

# Permeability of Soil

Permeability is defined as the property of a porous material which permits the passage or seepage of water (or other fluids)through its interconnecting voids.

A material having continuous voids is called permeable. Gravels are highly permeable, while stiff clay is the least permeable.

**4 Importance Of Study Of Seepage Analysis**

The study of seepage of water through soils is important for the following engineering problems:

- Determination of rate of settlement of a saturated compressible soil layer
- Calculation of seepage through the body of earth dams, and stability of slopes.
- Calculation of uplift pressure under the hydraulic structure and their safety against piping
- Groundwater flow towards wells and drainage of soils.

**DARCY’S LAW **

**then q ∞ i.A**

**or, q= K.i.A **

Where,

K is a constant, known as the coefficient of permeability.

If a soil sample of length ‘L’ and cross-sectional area ‘A’ (measured perpendicular to the direction of flow) is subjected to a differential head of water (h1-h2), the

Darcy’s law |

**Limitation Of DARCY’S LAW**

**Coefficient Of Permeability**

The coefficient of permeability is defined as the average velocity of flow that will occur through the total cross-sectional area of the soil mass under a unit hydraulic gradient. It is denoted by ‘K’ Its unit is the same as the unit of velocities such as Cm/sec or M/sec or M/Hr. etc.

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