Soil expansivity evaluation
Introduction
Soil is called the superficial part of the Earth's crust, biologically active, which comes from the disintegration or physical or chemical alteration of the rocks and the residues of the activities of living beings that settle on it.[1].
There are many processes that can contribute to creating a particular soil, some of these are: wind deposition, sedimentation in water courses, weathering, and deposition of organic material.
In a simplified way it can be said that the stages involved in soil formation are the following:
"Installation of living beings (microorganisms, lichens, mosses, etc.) on that inorganic substrate." This is the most significant phase, since with its vital and metabolic processes, the weathering of minerals continues, initiated by inorganic mechanisms. In addition, plant and animal remains through fermentation and putrefaction enrich this substrate.
"Mixture of all these elements together, and with interstitial water and air." Initially, the alteration of physical and chemical factors of the rocks occurs, carried out, fundamentally, by the geological action of water and other external geological agents, and subsequently by the influence of living beings, which is fundamental in this formation process. A structure in superimposed levels, known as a soil profile, and a defined chemical and biological composition are thus developed. The local characteristics of the systems involved—lithology and relief, climate and biota—and their interactions give rise to the different types of soil.
The processes of mechanical alteration and chemical weathering of rocks determine, in a certain way, the creation of a mantle of alteration or eluvium that, when, due to the action of slope transport mechanisms, is displaced from its position of origin, is called colluvium.
What is commonly known as soil can develop on the colluvium materials; The soil is the result of the physical, chemical and biological dynamics of the altered materials of the colluvium, originating within it a vertical differentiation into horizontal levels or horizons. In these processes, those of a biological and biochemical nature come to acquire great importance, whether due to the decomposition of plant products and their metabolism, by microorganisms and sapper animals.
The set of disciplines that focus on the study of soil are included in the group called Soil Sciences, although pedology predominates among them and the adjective edaphic is even used for everything related to soil. The study of soil involves the analysis of its mineralogy, its physics, its chemistry and its biology.