Many are accustomed to perceive the soil exactly in the form in which it is presented now. However, nature has been shaping it for millions of years. Initially, the surface was a rock. Over time, it was subject to erosion, the influence of rain and minerals. The remains of the first and subsequent plants enriched the soil with humus. Thanks to these metamorphoses, the upper layer increased, becoming better in composition and structure. For geological reasons, the mechanical and chemical characteristics vary over the entire surface. Soil - soil, the whole variety of rocks, man-made formations. All this has been the object of human engineering and economic activity for a long time.
Classification
There are several basic varieties of soil. These include, in particular:
- Monolithic rocky and semi-rocky with rigid structural connections.
- Dispersed, separate-granular without strong structural binders. Cohesive - clayey, non-cohesive - coarse clastic.
Soil is used in the construction of the foundation of buildings, inengineering structures, as well as in road surfaces, embankments and dams. Well suited for creating underground channels: tunnels, storage facilities and more. Soil science is a science whose field of study is soil.
Types of soils and their properties
To build a reliable foundation, it is necessary to take into account the physical qualities of the soil that is in the base. The soil table contains basic information. Before starting work, a calculation of the earth resistance must be carried out. When evaluating its technical suitability, aspects such as:
- Uniform composition.
- The coefficient of friction of the parts of the soil mass against each other should also be taken into account.
- The maximum amount of water absorption, as well as its initial presence.
- The ability of soil to retain liquid it absorbs despite efforts to remove it.
- Water erodibility and solubility, compressibility, looseness, plasticity and similar characteristics.
- Cohesion, as well as particle shape and size. In this case, the strength of the bonds that the soil has is implied.
Soil types are divided into two broad categories, which differ in structure, physical properties and development methods. Intermediate groups of rocky broken rocks are also implied. They consist of stones that are unrelated to each other or connected by foreign impurities. The latter are called conglomerates.
Loose structures
This group consists ofsandy soil types that do not lose their volume when dried. In their pure form, they have almost negligible interparticle bonding. Clay is also included. It is able to increase its volume when wet and, depending on the humidity, can have good cohesion. Sands do not have plasticity. After the application of force, they are instantly compressed, but do not retain the shape given to them. But clay is very easy to modify. Under the influence of an external force, it contracts rather slowly, but strongly.
Rock structures
These rocks are cemented and soldered together. Externally, these structures are a continuous array or a fractured layer. Saturated with water, they show a high percentage of compressive strength. These structures are readily soluble and softenable in water. They are well suited as a base for foundations due to their strength, resistance to compression and frost. The undoubted advantage of these structures is also the fact that they do not require additional opening and deepening.
Conglomerates and non-rock structures
Most of them are loose crystalline and sedimentary coarse-grained rocks. These structures are able to withstand buildings of several floors. On these soils, a strip foundation is laid, the depth of which is not less than half a meter. On the territory of the Russian Federation there are quite a lot of varieties of rock structures that have a wide variety of physical properties.
Loose structure
It should be saidthat soil-sand is considered a fairly common structure. What is this category? The composition of the soil includes a free-flowing mixture of grain quartz, as well as other materials that appeared due to the weathering of very small rock particles. These structures are divided into several subgroups. These are, in particular, gravelly, medium and large, silty rocks. All of these structures are easily developed, have high water permeability, and are well compacted under pressure. When laying sand in a uniform layer in terms of density and volume, you can lay a good foundation for subsequent construction. The use of its maximum characteristics will occur if the freezing level is located above groundwater. It all depends on the characteristics of the region in which the construction takes place. Sand compression occurs in a short time, which means that the sedimentation of such a structure will not require much time. Its size is directly proportional to its ability to withstand loads. The particle size of dusty sand varies from 0.005 to 0.05 mm. It will not be a good base for construction, as it does not cope well with high loads. Sandy soil can sag under pressure. Also, it almost does not freeze through and easily passes water. If the foundation is based on such soil, then it must be laid at a depth not exceeding 70 cm, but not less than forty centimeters.
Plastic structures. Subcategories
The plastic characteristics of soils make it possible to divide them into several subgroups. Considerthe main ones. Loose structures, in the content of which 5–10% clay, are called sandy loams. Some of them, when diluted with water, become fluid, similar to a liquid. Because of this, such soil is also called floating. Such structures are unsuitable for laying foundations. Loams in their composition have from 10 to 30% clay. They are light, medium and heavy. These indicators provide an intermediate position of such soils between clay and sand.
Natural foundation material
The physical characteristics of soils are of great importance in the construction of structures. Far from every rock you can build a building. Unlike a free-flowing structure, clay has a high compressibility. At the same time, under load, the compaction process is rather slow. Accordingly, the settlement of buildings on such soil will take more time. Combined soil layers - from rock and loose structure - do not have resistance to liquefaction. Because of this, they have a low bearing capacity. The composition of the soil includes the smallest particles, the size of which does not exceed 0.005 mm. This structure also contains a small amount of loose particles. Clay is easy to compress and wash out. After years of maturation, this structure will serve as an excellent base for laying the foundation of a house. However, there are a number of caveats here, because in its natural state, clay is almost impossible to find dry.
The fine structure of the rock contributes to the formation of the capillary effect. It leads to a constant wet state of the clay. But the disadvantage of this kind of structure is not in its moisture, but in its heterogeneity. She does not pass water well. Because of this, the liquid spreads through various soil impurities. At low temperatures, the clay begins to freeze to the building, which leads to its swelling. This helps to raise the foundation. Clay moisture content is uneven. In turn, this means that it will rise differently in each place. All this leads to the destruction of the building. In some places it is stronger, in others slightly, but the soil acts on the foundation over the entire surface. Soil types, depending on their properties, affect foundations in different ways.
Macroporous structures
This is a separate category, which is formed by clay soils. They got their name macroporous due to the presence of large gaps between the particles. The pores are visible even to the naked eye. When viewed, it can be seen that they significantly exceed the skeleton of the soil. This structure includes loess rocks. They contain more than 50% of dust particles. These structures are widespread in the south of Russia and the Far East. Under the influence of moisture, such a rock soaks and loses its stability. If the initial stage of clay soils was formed due to structural sediments in the water, in which microbiological processes were present, then it is called silt. They are most often found in marshy and wetlands and in the zone of peat extraction. If the foundation is being erected in an area where there is a high probability of the presence of loess and silt soils, then the necessary measures should be taken tostrengthening the building.
Determining the consistency on the site
The structure of clay soils is determined visually during development with a shovel. For example, a plastic mixture will stick to the tool. Hard ground will behave in a completely different way. The types of soils are determined by rolling them into a cord or rubbing them with the palms. So you can evaluate their plasticity. Clay soils are well compressed, eroded and swell when freezing. These structures are among the most finicky and unfavorable for foundation construction. On such terrain, the foundation should be laid to the full depth of freezing. The assessment of the soil composition on the site is carried out by means of a watering can. Record the time of absorption of water from the surface. If soaking occurs within a second, then the structure is rocky or sandy. Quite quickly takes water and wet peaty rock. But on the surface of clay soil, the liquid lingers.
After that, take a little soaked layer and squeeze it in the palm of your hand. If the structure has broken up into grains or seeped through the fingers, then this is rocky or sandy rock. Clay is easy to compress and will lock into a lump. It feels rather slippery. If the soil feels soapy, silky, and doesn't compress as much, then it's most likely silty or loamy. The peaty structure is similar to a sponge.
How to determine the structure at home?
A full tablespoon of soil is placed in a glass of clean water. It needs to be mixed andleave. After a few hours, you can see the result. If there is a layered sediment at the bottom, and the water itself is relatively clean, then you have added loamy soil. Sand, stones on the bottom and clear liquid - this is another structure. It is most likely a rock. In particular, it can be sandy or rocky soil. Grayish water and whitish grains characterize the limestone structure. Peaty soil will make the water cloudy. At the same time, thin and light fragments will float on the surface, and a small sediment will appear at the bottom. If there is clay and silt in the water, then it will become cloudy. This will form a thin sediment at the bottom.
PH level
Soil can be subdivided according to the degree of acidity. So, in terms of pH, the structures are weakly acidic, neutral or slightly alkaline. In the latter, the acidity level of the soil varies from 6.5 to 7.0. It is excellent for garden plants, including vegetables, and contributes to their faster growth and development. Acidic soil has indicators from 4.0 to 6.5, but from 7.0 to 9.0 - this is already an alkaline structure. In addition to those indicated, there are also extreme points of the scale - from 1 to 14, however, in the practice of European gardening, they practically do not occur. Knowledge of these data is necessary for the correct selection of plants for planting. Soil acidity can be reduced by mixing the structure with lime. Organic conditioners will help raise the pH level. However, the latter process is quite expensive. In this regard, in areas with alkaline soil, acidophilus can be grown in containers and tubs that are filled withacidic structure.
Growing plants
When choosing soil for plantings, it is necessary to focus on such points as:
- Scope of its application. There is a soil for flowers, seedlings, as well as garden and universal. It is possible to purchase peat. It all depends on what the soil is needed for, what kind of cultural or decorative plantings will be grown on it.
- Types of plants. If you are going to grow representatives of one category, then the best choice would be a special soil for him. But if there are several, a universal one will do.
- Consumed volume.
To make the soil mixture looser, use vermiculite. So that the roots do not rot from stagnant water, a drainage layer is laid on the bottom when planting plants. For cacti and a number of other plants, the soil is mixed with a loose structure. If planting takes place in infertile places, then its quality will help improve peat. Hydrogel improves moisture and air exchange processes. Charcoal is used to lower the pH level. It is added to the soil for flowers (for example, for orchids) and other plants.
Useful impurities
Vegetable soil structures are mainly used in landscaping. But the scope of structures with various "useful" impurities is much wider due to the inclusion of stones, clay and other components in the composition. What is the percentage of essential beneficial ingredients? As a rule, fertile soil is a combination of 50% peat, 30%black soil and 20% sand. Thus, its composition includes an increased content of organic compounds and minerals. The fertile soil is highly water resistant. This structure ensures complete nutrition of cultivated plants, regardless of their stage of growth.
At agrotechnical enterprises, farms, as well as in private areas, fertile soil is used quite actively. He copes well with the tasks that are posed in the process of growing cultural plantations. Of particular importance is the fact that it helps to improve the structure of the soil, increases productivity. In addition to everything, such a mixture does not need additional use of fertilizers.
How to improve soil structure?
For poor stony and sandy soils, rotted manure mixed with straw is used. It is better to give preference to horse than cow. It contributes to the retention of moisture and useful components in the root system of plants. But fresh manure cannot be added. Garden compost can be used for the same purpose. A mixture of rotted horse manure, lime and peat is called mushroom compost. If it is necessary to create a slightly alkaline reaction in neutral soils, then this mixture is perfect. Leaf humus is suitable for plants that need acidic soil, that is, for moisture-loving acidophiles. Conditions, mulches and acidifies the soil. For the same purposes, you can use wood chips and sawdust. Peat is used to oxidize the soil. It decomposes quickly, butcontains virtually no nutrients. In winter, you can use bird feathers, which are rich in phosphorus. They are also added to areas where potatoes are supposed to be planted. To improve the permeability and structure of clay soils, chopped wood is used. The bark is also used for mulch, due to its appearance and qualities. It is desirable to use the conditioner at the same time or instead of applying organic fertilizers. Plots of soil that are only planned to be sown are dug up and mixed with them a few months before the start of planting. To fertilize already planted plants, the soil is enriched with a layer of mulch from conditioning organic materials with fertilizers at the very beginning and end of the season.
