Soil Texture : Inter particle forces

 Soil Texture : Inter particle forces

The interaction of soil particles with other particles is influenced by the following forces :

Weight of the particle Fg

Particle surface forces Fs

Weight is the result of gravitational forces and is function of the volume of the particle.

For equidimensional particles such as spherers of diameyter D , the weight Fg is directly proportional to D3.

Particle surface forces are of an electric nature.

They are caused by un satisfied electrical charges in the particles crystalline structure.

Surface forces F3 are directly proportional to the surface areaand hence for equideimensional particles to D 2

The ratio of weight of a particle to the particle surface forces Fg/Fs is directly proportional to D

Thus for large particle sizes which include soil particles in the coarse fraction > 0.075 mm ,the weight of the particle is predominant over the surface forces.

As the particle diameter decreases , the ratio Fg/Fs decreases thus for very small values of D , the surface forces predominate.

This accounts for cohesive nature of most fine grained soils.