Technogenic soils are natural soils and soils that have undergone change and displacement as a result of human production and economic activities. Such material is also called artificial soil. It is made for industrial needs, as well as for the improvement of urban areas.
Purpose of artificial soil
Technogenic soils are often used as a foundation for residential, engineering and industrial buildings. Also, railway embankments and earthen dams are constructed from this material.
As a rule, construction volumes on man-made soils are measured in hundreds of billions of cubic meters.
Engineering-geological properties of the soil
The characteristics of soil are determined by the composition of its parent rock or the waste generated during its processing. Also, the engineering-geological properties of technogenic soil can be determined by the nature of human impact on it. So that specialists can accurately determine the characteristics of the minedbuilding 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 building foundations) is separated into a separate class.
Classification of technogenic soils consists of several groups:
- 1 group: rocky, frozen and dispersed. You can distinguish them by the nature of the structural bonds.
- 2 group: connected, rocky, unconnected, not rocky and icy. They differ in strength from each other.
- 3 group: natural formations that have changed during their natural occurrence in the earth, as well as natural displaced formations that have been changed as a result of physical and physico-chemical impact. Also, the experts include bulk and alluvial soils that have been changed as a result of thermal exposure to the third group.
Also, the class of technogenic soils is determined by dividing it into types and species. Subdivided according to the material composition, name, effect, origin, formation condition and other conditions. Many experts believe that the existing classification of technogenic bulk soils has a number of shortcomings and requires some clarification.
Cultural layers
Cultural layers are called formations of a peculiar composition, due to the geological conditions of the area where the material occurs. It is determined by the nature of economic activity. Such technogenic soil has a heterogeneous composition along the vertical and area. ATin the modern world, it is actively used in construction.
To extract the cultural layer, which lies several hundred meters deep in the earth, it is required to develop a method of engineering and geological survey. During such work, engineers will be required to organize places for the collection of construction debris, as well as domestic and industrial waste. It is worth considering that carrying out such work on the territory of old cemeteries and animal burial grounds is strictly prohibited by Russian law.
Displaced natural formations
Natural displaced formations are called soils that were removed from their natural occurrence, and then subjected to partial industrial processing. This building material is formed from dispersed cohesive and non-cohesive soils.
Rocky and semi-rocky rocks are first crushed on machines, and then they are moved already as dispersed coarse-grained soils. The same applies to 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 systematically and unplannedly dumped. 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 and geological features of technogenic soils used in the construction of embankments and dumps include:
- Violation of the rock structure in the body of the embankment as a result of a decrease in the strength of the building material.
- Soil fractionation and self-flattening of slopes.
- Change in durability. Shear resistance increases due to compaction or decreases due to heavy moisture.
- The formation of pore pressure mounds in water-saturated soils, which increases the risk of landslides.
Depending on the lithological composition, experts divide 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 backfilling. In this case, fine fractions are usually concentrated in the upper part of the embankment, and large fractions in the lower. This happens as a result of the use of building materials of different 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 an embankment, engineers must take into account the incomplete compaction of the soil mass, which is assessed after shear testing.
The maximum density of man-made soil, which is used for the construction of embankments, is reached after several years and depends on the type of material used. For example, sandy loamsoils 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. Sandy loam embankments and sands of medium and fine fractions are compacted within 2-6 years.
Alluvial soil
Alluvial technogenic soil is created with the help of hydromechanization using a pipeline system. During the construction process, specialists carry out organized and unorganized alluviums. The first are necessary for engineering and construction purposes. They are built already with predetermined properties. With the help of such structures, dense layers of sand, dams and dams, designed for an average water pressure, are washed.
Unorganized alluvium is used to move soil rocks to free up land for further work, such as the extraction of natural building materials and other minerals.
The construction of earthworks and the release of territories by hydromechanization includes several stages:
- Hydraulic mining of ground rocks using hydraulic monitors and suction dredgers.
- Hydrotransportation of mined material through distribution and main pipelines.
- Organization of alluvium of technogenic soil into earthworks or free territories, which should serve to accommodate the extracted rock.
Properties of alluvial building material
Engineering and geological properties of alluvial soils are determined by their composition andphysical and 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 alluvium 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 where building materials are mined. 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 matter in the alluvial soil determines the time of acquisition of its physical and mechanical properties. During the washing process, the mixture is divided into fractions. Large particles are concentrated for the most part near the outlet of the slurry, in the place where the slope zone is formed. Fine sand particles are located in the intermediate zone, and fine, consisting mainly of clay, form the pond zone.
Engineers share several stages in the formation of alluvial soil properties:
- Consolidation of building material, which occurs as a result of gravitational influence on it. There is also intense water loss. It is during this period that the main process of self-compaction takes place. This process usually does not take more than a year.
- Soil strengthening occurs due to sand compression. Between small particles of building material, dynamic stability increases. This process takes from one to three years.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 technogenic soil
All ongoing work during backfilling and alluvium for the further construction of structures should be carried out only with strict geotechnical control, which is carried out by an experienced engineering staff. The building material must be evaluated at once by several indicators, such as the degree of uniformity of the embankment, the content of organic substances in it, physical and mechanical properties, and so on. Also, geologists 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 finalized in several ways:
- Consolidate with heavy machinery (rollers, rammers, vibrators).
- Reinforce embankment with concrete piles and slabs.
- Strengthen the structure with directed explosions.
- Produce deep soil stabilization.
- Cut through a building to reinforce it with supports.
If heavy rainfall periodically occurs at construction sites, builders need tocarry out constructive measures that will be aimed at increasing the strength of the entire structure, including roads and buildings. It is necessary to carry out measures to strengthen the foundation to prevent uneven deformation of the concrete.
