El especialista en suelos, al concebir un proyecto, debe proyectar las estructuras no solamente para las propiedades del suelo al comienzo de la obra sino que también para toda la vida útil de la misma. El tamaño y la forma de un depósito determinado, como las propiedades mecánicas del suelo que lo componen, pueden presentar grandes variaciones de manera muy significativa. Muchas de estas variaciones se producen independientemente de la actividad humana, mientras que otras se deben a la presencia de la obra. El suelo no es inerte, sino que es bastante activo y muy sensible a las condiciones de su entorno.

Pressures

In general, an increase in pressure on a soil element produces an increase in shear resistance, a decrease in compressibility and a reduction in permeability; The opposite effects occur if pressures decrease. The changes produced by a reduction in pressure are usually smaller than those produced by an increase in pressures of the same magnitude. The soil therefore behaves like a non-perfectly elastic body.

During the formation of a sedimentary soil, the total pressure at a given level continues to increase as the height of the soil layer above the point considered increases. Thus, the properties of a sedimentary soil at a given depth are continually changing as the deposit forms. The removal of topsoil, for example by erosion, results in pressure reduction. A soil element that is in equilibrium under the maximum pressure it has ever experienced is called normally consolidated, while a soil in equilibrium under a pressure lower than that which consolidated it is called overconsolidated.

Time

Time is a variable that intervenes in the other factors that contribute to variations in soil behavior (especially pressures, humidity and environmental conditions). To appreciate the complex effects of a variation in pressure, water must be expelled or absorbed by the soil element. Due to the relatively low permeability of fine-grained soils, a certain time is required for this water to escape or penetrate such soils. On the other hand, time is an obvious factor in chemical reactions, such as those that occur in weathering processes. Meteorological, or atmospheric, weather is defined as the state of the atmosphere at a certain moment. Humidity (absolute and relative), temperature and pressure are taken into account at a certain place and time. Since each of the moments is more or less prolonged in time, and in extension, it is called a type of time.

Water

Water can have two detrimental effects on soil. Firstly, the mere presence of water decreases the attractive forces between clay particles. Secondly, interstitial water can, in certain particular situations, withstand the applied stresses, thus modifying the behavior of the soil.

A sample of clay, which may have a strength similar to that of poor cement when dry, may turn to sludge when immersed in water. Thus, increasing humidity in a soil generally reduces its resistance.

The conditions of "interstitial water" can vary due to natural causes and androgenic interventions. Among the natural causes is the annual variation in precipitation, and therefore in the humidity in the soil. In the dry season, due to the low precipitation, the water table decreases, in contrast to this, in the rainy period, the abundance of water causes a rise in the water table. This variation in humidity in the soil produces a significant variation in the properties of the soil throughout the year.

On the other hand, many construction processes modify groundwater conditions, and consequently cause important variations in soil characteristics.

Moisture content influences the physical properties of a substance: weight, density, viscosity, refractive index, electrical conductivity, and many others.

Environment or atmosphere

There are several characteristics of a soil environment that can have an important influence on its mechanical behavior. Among these characteristics are the nature of the interstitial fluid and temperature.

For example, a sedimentary or compacted clay may have been formed with an interstitial fluid of a certain chemical composition and at a certain temperature, but both factors may vary throughout the life of the deposit. A classic example is marine clay, deposited in water with a high salt content: 35 g of salt per liter of water, under typical marine conditions. Marine clays have frequently suffered tectonic uplifts, which is why they are above sea level, and the water that filters through them has a salt content much lower than sea water. Thus, over time, there is a slow and gradual decrease in the salt contained in the pores of the clayey sediment, so that after many thousands of years of washing or leaching, the interstitial fluid can be very different from the original that existed at the time of the formation of the sediment. Reducing the electrolyte content of water around soil particles can reduce the net attractive force between them. In other words, the dragging of salt from between the pores can reduce the shear resistance of the soil.

Soils that can be used for cultivation are said to be fertile. This means that the soil is rich enough in the necessary nutrients to allow the sustained growth of plants and trees useful to humans. The actual capacity of a soil to maintain such growth is called productivity and depends on the soil being fertile and having an adequate structure and consistency that allows it to be worked easily. Plowing aerates the soil, allows water circulation and facilitates the growth of plant roots. Although rainfall is adequate, some soils are unproductive because they drain too quickly, that is, they are too permeable. Other soils may be sterile because they are impermeable.

Contenido

Según el proceso de formación, el suelo puede ser:.

Sedimentary soils

To explain the formation of sedimentary soils, the three phases of the process must be considered: (I) The formation of sediment; (II) Transport of sediments III) The deposition of sediments.

The main mode of sediment formation is the physical and chemical weathering of rocks on the Earth's surface. In general, silt, sand and gravel particles are formed by the physical weathering of the rock, while clay particles are formed by chemical alteration processes. The formation of clay particles from rocks can occur by a combination of elements in solution or by the chemical decomposition of other minerals.

Sediment can be transported by one of five agents: water, air, ice, gravity, and living organisms. The mode of transport affects sediments mainly in two ways: a) it modifies the shape, size and texture of the particles through abrasion, wear, impact and dissolution; b) produces a classification or grading of the particles.

After the particles have been formed and transported they are deposited to form sedimentary soil. The three causes of this deposit in water are: reduction in velocity, decrease in solubility and increase in electrolytes. When a stream empties into a lake, ocean, or large volume of water, it loses most of its speed. The strength of the current thus decreases and sedimentation occurs. Any change in the temperature of the water or in its chemical nature can cause a reduction in the solubility of the stream, producing the precipitation of some of the dissolved elements.

The table summarizes some of the effects of the five agents mentioned on the sediments.

Residual soils

Residual soils originate when the products of weathering are not transported as sediments, but rather accumulate at the site where they are formed. If the rate of decomposition of the rock exceeds the rate of removal of the decomposition products, an accumulation of residual soil occurs. Among the factors that influence the rate of alteration of the nature of weathering products are climate (temperature and rainfall), the nature of the original rock, drainage and bacterial activity.

The profile of a residual soil can be divided into three zones: a) the upper zone, in which there is a high degree of weathering, but also a certain carryover of materials; b) the intermediate zone in the upper part of which there is a certain weathering, but also a certain degree of deposition towards the lower part of it; and, c) the partially weathered zone that serves as a transition from the residual soil to the original unaltered rock.

Temperature and other factors have favored the development of significant thicknesses of residual soils in many parts of the world.

The thickness of the residual soils can reach considerable thicknesses:[1]​.

Artificial deposits

In the two previous sections, the formation of soil deposits by nature has been discussed. A man-made deposit is called an embankment or fill. The embankment actually constitutes a sedimentary deposit in which man carries out all the formation processes, in a controlled way to achieve previously defined results. The soil is extracted by excavation or blasting from a certain deposit whose material meets pre-established specifications; It is transported by a vehicle that can be a truck, a van, a bulldozer, or by barges or pipelines and is deposited in the predetermined location. The material can be left as it falls, or it can be arranged and compacted, to achieve the desired mechanical characteristics.

El especialista en suelos, al concebir un proyecto, debe proyectar las estructuras no solamente para las propiedades del suelo al comienzo de la obra sino que también para toda la vida útil de la misma. El tamaño y la forma de un depósito determinado, como las propiedades mecánicas del suelo que lo componen, pueden presentar grandes variaciones de manera muy significativa. Muchas de estas variaciones se producen independientemente de la actividad humana, mientras que otras se deben a la presencia de la obra. El suelo no es inerte, sino que es bastante activo y muy sensible a las condiciones de su entorno.

Pressures

In general, an increase in pressure on a soil element produces an increase in shear resistance, a decrease in compressibility and a reduction in permeability; The opposite effects occur if pressures decrease. The changes produced by a reduction in pressure are usually smaller than those produced by an increase in pressures of the same magnitude. The soil therefore behaves like a non-perfectly elastic body.

During the formation of a sedimentary soil, the total pressure at a given level continues to increase as the height of the soil layer above the point considered increases. Thus, the properties of a sedimentary soil at a given depth are continually changing as the deposit forms. The removal of topsoil, for example by erosion, results in pressure reduction. A soil element that is in equilibrium under the maximum pressure it has ever experienced is called normally consolidated, while a soil in equilibrium under a pressure lower than that which consolidated it is called overconsolidated.

Time

Time is a variable that intervenes in the other factors that contribute to variations in soil behavior (especially pressures, humidity and environmental conditions). To appreciate the complex effects of a variation in pressure, water must be expelled or absorbed by the soil element. Due to the relatively low permeability of fine-grained soils, a certain time is required for this water to escape or penetrate such soils. On the other hand, time is an obvious factor in chemical reactions, such as those that occur in weathering processes. Meteorological, or atmospheric, weather is defined as the state of the atmosphere at a certain moment. Humidity (absolute and relative), temperature and pressure are taken into account at a certain place and time. Since each of the moments is more or less prolonged in time, and in extension, it is called a type of time.

Water

Water can have two detrimental effects on soil. Firstly, the mere presence of water decreases the attractive forces between clay particles. Secondly, interstitial water can, in certain particular situations, withstand the applied stresses, thus modifying the behavior of the soil.

A sample of clay, which may have a strength similar to that of poor cement when dry, may turn to sludge when immersed in water. Thus, increasing humidity in a soil generally reduces its resistance.

The conditions of "interstitial water" can vary due to natural causes and androgenic interventions. Among the natural causes is the annual variation in precipitation, and therefore in the humidity in the soil. In the dry season, due to the low precipitation, the water table decreases, in contrast to this, in the rainy period, the abundance of water causes a rise in the water table. This variation in humidity in the soil produces a significant variation in the properties of the soil throughout the year.

On the other hand, many construction processes modify groundwater conditions, and consequently cause important variations in soil characteristics.

Moisture content influences the physical properties of a substance: weight, density, viscosity, refractive index, electrical conductivity, and many others.

Environment or atmosphere

There are several characteristics of a soil environment that can have an important influence on its mechanical behavior. Among these characteristics are the nature of the interstitial fluid and temperature.

For example, a sedimentary or compacted clay may have been formed with an interstitial fluid of a certain chemical composition and at a certain temperature, but both factors may vary throughout the life of the deposit. A classic example is marine clay, deposited in water with a high salt content: 35 g of salt per liter of water, under typical marine conditions. Marine clays have frequently suffered tectonic uplifts, which is why they are above sea level, and the water that filters through them has a salt content much lower than sea water. Thus, over time, there is a slow and gradual decrease in the salt contained in the pores of the clayey sediment, so that after many thousands of years of washing or leaching, the interstitial fluid can be very different from the original that existed at the time of the formation of the sediment. Reducing the electrolyte content of water around soil particles can reduce the net attractive force between them. In other words, the dragging of salt from between the pores can reduce the shear resistance of the soil.

Soils that can be used for cultivation are said to be fertile. This means that the soil is rich enough in the necessary nutrients to allow the sustained growth of plants and trees useful to humans. The actual capacity of a soil to maintain such growth is called productivity and depends on the soil being fertile and having an adequate structure and consistency that allows it to be worked easily. Plowing aerates the soil, allows water circulation and facilitates the growth of plant roots. Although rainfall is adequate, some soils are unproductive because they drain too quickly, that is, they are too permeable. Other soils may be sterile because they are impermeable.