# 5 Empirical Formula for Determination of the Coefficient of Permeability of Soil(K)

## 5 Empirical Formula for Determination of the Coefficient of Permeability

The coefficient of permeability of soil(K) can also be computed from several empirical formulae, which are given below:

### 1. Jaky’s Formula

Jakey in 1944 found an empirical formula of ‘K’ for all soils; $K = 100 D_{m}^{2}$ , Where $D_{m}$ is grain size (in cm) that occurs with the greatest frequency.

### 2. Allen Hazen’s Formula

$K = C D_{10}^{2}$ , where C is a constant. The value of C is taken approximately equal to 100, when $D_{10}$ is expressed in cm.

### 3. Terzaghi’s Formula

Terzaghi (1955) developed the following formula for fairly uniform sands, which reflects the effects of grain size and void ratio.

$K = 200 D_{e}^{2} . e^2$ , Where $D_{e}$ = Effective grain size.

### 4. Kozney’s Formula

$K = \frac{1}{K_{k} \eta S_{s}^{2}} \times \frac{n^3}{1-n^3}$ , where $S_{s}$ = Specific surface of particles, $\eta$ = Viscosity, and $K_{k}$ = Constant( that is equal to 5 for spherical particles).

### 5. Louden’s Formula

$\Rightarrow log_{10} (KS_{s}^{2}) = a + bn$

Where a and b are constants, the value of which are 1.365 and 5.15 respectively for permeability at 10°C.