Man-made soils are natural soils and soils that have undergone change and displacement as a result of human production and economic activity. Such material is also called artificial soil. They make it for industrial needs, as well as for the improvement of urban areas.
Purpose of artificial soil
Man-made soils are often used as the foundation of residential, engineering and industrial buildings. Also, railway embankments and earthen dams are constructed from this material.
As a rule, the volume of construction on industrial soils is measured in hundreds of billions of cubic meters.
Engineering and geological properties of soil
The characteristics of the soil are determined by the composition of its parent rock or waste received during its processing. Also, the engineering and geological properties of technogenic soil can be determined by the nature of the impact of a person on it. So that specialists could accurately determine the characteristics of the extracted building material, GOST was created under the number 25100-95. It is called "Soils and their classification." In this document, the material for the construction of engineering structures (embankments and foundations of buildings) is allocated in a separate class.
The classification of industrial soils consists of several groups:
- Group 1: rocky, frozen and dispersed. They can be distinguished by the nature of structural bonds.
- Group 2: cohesive, rocky, incoherent, not rocky and icy. From each other they differ in durability.
- Group 3: natural formations that changed during a natural occurrence in the ground, as well as natural displaced formations that were changed as a result of physical and physico-chemical effects. Also in the third group, experts include bulk and alluvial soils, which were changed as a result of heat exposure.
Also, the class of technogenic soils is determined by dividing it into types and types. Subdivided by the material composition, name, effect, origin, condition of formation and other conditions. Many experts believe that the existing classification of anthropogenic bulk soils has a number of drawbacks and requires some refinement.
Cultural layers
Cultural layers are called formations of a peculiar composition, due to the geological conditions of the area where the material lies. It is determined by the nature of economic activity. Such anthropogenic soil has a heterogeneous composition in vertical and square. In the modern world, it is actively used in construction.
In order to obtain a cultural layer that lies several hundred meters deep in the earth, it is necessary to develop a method of engineering and geological survey. During such work, engineers will be required to arrange places for the collection of construction waste, as well as household and industrial waste. It is worth considering that carrying out such work on the territory of old cemeteries and cattle cemeteries is strictly prohibited by Russian law.
Displaced natural formations
Natural displaced formations are those soils that were removed from the places of its natural occurrence, and then underwent partial production processing. This building material is formed from dispersed cohesive and incoherent soil.
Rocky and semi-rocky rocks are first crushed on machines, and then they are moved already as dispersed coarse soil. Also come with frozen rocks. According to the method of laying, the displaced formations are divided into alluvial and bulk. In turn, bulk soils, depending on the nature of the formation, are divided into systematic and unplanned loose ones. They are also divided depending on the application into construction and industrial.
Due to the strength characteristics of technogenic soils, they are used for the construction of road and railway embankments. Also, this material is used for the construction of dams, dams, foundations for buildings.
Soil Features
The engineering-geological features of technogenic soils used in the construction of embankments and dumps include:
- Violation of the structure of the rock in the body of the embankment as a result of a decrease in the strength of the building material.
- Fractionation of soil and self-balancing of slopes.
- Strength Change. Shear resistance increases due to compaction or decreases as a result of strong moisture.
- Formation of an embankment of pore pressure in water-saturated soils, resulting in an increased risk of landslides.
Depending on the lithological composition, experts divide the embankments into two types: homogeneous and heterogeneous. This factor is variable and depends on the natural fractionation of this building material in the process of filling. In this case, small fractions are usually concentrated in the upper part of the embankment, and large fractions in the lower part. This happens as a result of the use of building materials that are heterogeneous in composition.
Soil strength
The strength characteristics of bulk technogenic soils are determined, taking into account the conditions for the formation of slopes. When calculating the stability of the embankment, engineers need to consider the incompleteness of compaction of the soil mass, which is evaluated after shear tests.
The maximum density of industrial soil, which is used for the construction of embankments, is achieved after several years and depends on the type of material used. For example, sandy-sandy soils with impurities from peat are compacted within 2-4 years from the date of completion of construction. Loams and clays reach their maximum density within 8-12 years. Mounds of sandy loam and sand of medium and fine fractions are compacted within 2-6 years.
Washed up soil
Washed industrial soil is created by hydromechanization using a piping system. During the construction process, specialists carry out organized and unorganized reclamations. The first are necessary for civil engineering purposes. They are being built already with predetermined properties. With the help of such structures, dense strata of sand, dams and dams are calculated, designed for the average pressure of water.
Unorganized alluviums are used to move soil in order to free up land for further work, such as the extraction of natural building materials and other minerals.
The erection of soil structures and the liberation of territories by hydromechanization includes several stages:
- Hydraulic development of soil using hydraulic monitors and dredger shells.
- Hydrotransport of extracted material through distribution and trunk pipelines.
- Organization of alluvial man-made soil in earthworks or in free territories, which should serve to accommodate mined rock.
Properties of alluvial building material
Engineering and geological properties of alluvial soils are determined by their composition and physico-chemical interaction of its individual particles with water. The composition of the technogenic soil used in construction depends on the place of its extraction in natural conditions, as well as the methods of work associated with the construction and reclamation of this building material.
The properties of alluvial soil depend primarily on physical and geographical factors, such as the topography of the site and the climate at the place of extraction of the building material. Also, experts take into account the condition and properties of the foundation of the alluvial structure built from this rock.
Composition of alluvial soil
The composition of organic substances in the alluvial soil determines the time of acquisition of its physical and mechanical properties. In the process of washing, the mixture is divided into fractions. Large particles are concentrated mainly near the release of the slurry, in the place where the mowing zone is formed. Fine sand particles are located in the intermediate zone, while fine particles, consisting mainly of clay, form the pond zone.
Engineers share several stages of the formation of properties of alluvial soils:
- Compaction of building material, which occurs as a result of gravitational impact on it. Intensive water loss also occurs. It is during this period that the main process of self-compaction occurs. This process, as a rule, does not take more than a year.
- Hardening of the soil occurs due to the compression of sand. Between small particles of building material, dynamic stability increases. This process takes from one to three years.
- The stabilization state is formed due to the formation of cementation bonds, which are not afraid of water flows. At the final stage of this process, alluvial sands are significantly strengthened. The duration of stabilization of the structure is achieved for ten years or more.
Construction of buildings on industrial soil
All ongoing work during the filling and washing of the soil for the further construction of structures should be carried out only with strict geotechnical control, which is carried out by an experienced engineering staff. Building material should be evaluated at once by several indicators, such as the degree of homogeneity of the embankment, the content of organic substances in it, physical and mechanical properties, etc. Also, geological engineers need to find out the ability of the soil to generate various gases, such as methane, as well as carbon dioxide. The formation of these substances occurs as a result of the decomposition of organic substances.
If it turns out that the embankment does not have sufficient strength, which is required for further construction, the constructed object must be modified in several ways:
- Seal with heavy equipment (rollers, rammers, vibrating machines).
- Strengthen the embankment with concrete piles and slabs.
- Strengthen the structure by means of directional explosions.
- Perform deep soil strengthening.
- Cut through the structure to strengthen it with supports.
If heavy rainfall periodically occurs at construction sites, builders need to take constructive measures that will be aimed at increasing the strength of the entire structure, including roads, buildings. It is necessary to carry out measures to strengthen the foundation in order to prevent uneven deformation of concrete.