1. Qualitative soil description

1.1 Soil origin

Soils and rocks take the form of aggregates of particles, generally mineral but sometimes organic, of varying size and shape. The nature and intensity of the forces binding the particles together depend on the nature of the material.

We will only be dealing here with soils, which can be defined as aggregates in which the particles are weakly bound and can be separated by agitation or trituration in water. Rocks are dealt with in the specialized articles of this treatise. This rather imprecise definition leads to a certain overlap between soils and rocks (certain marls, chalk, stiff clays, soft rocks).

Soil has two main origins:

• the disintegration of rocks by mechanical or...