Soil stabilization and strengthening technology “ANT. Soil stabilizers in domestic road and airfield construction Technology of soil road stabilization

When developing the Road Classification of Stabilizers, the accumulated domestic and foreign experience in the use of chemical additives (stabilizers) and binders to improve soil properties in road construction was taken into account. However, in relation to the domestic practice of road construction, it is necessary to clearly distinguish between two parallel, but fundamentally different technologies: soil stabilization technology and soil stabilization technology.

stabilization technology differs in that clay soils are treated only with those types of stabilizers that do not contain binders as structure-forming elements, i.e. according to the General classification (see figure), they should include cationic (cationic), anionic (anionic), universal and nanostructured stabilizers.

With stabilization technology changes to positive side almost the entire complex of water-physical properties of clay soil. This increases its hydrophobicity. By reducing the filtration coefficient, its water permeability decreases. The heaving and swelling of soils are also reduced, up to complete exclusion. The height of the capillary rise and their optimal humidity decrease with a simultaneous increase in the maximum density with standard compaction (GOST 22733-2002).

stabilization technology should be recommended for use for soils laid in the working layer of the subgrade, since the most intensive processes of the water-thermal regime (WTR) and moisture transfer mainly affect the upper part of the earthen density of the road structure. At the same time, the stabilization of soils of the working layer will not only have a positive effect on the WTR, but will also make it possible to lay local muddy soils that were not previously suitable for use in this element of the road structure, by raising their water-physical characteristics in terms of water permeability (GOST 25584-90), heaving (GOST 28622-90), swelling (GOST 24143-80) and soaking (GOST 5180-84) to the required values.

Complex stabilization technology differs in that clay soils are treated with structured stabilizers (see Figure 1), i.e. those that contain a binder in their composition, or any other stabilizers in an amount not exceeding 2% by weight of the soil, or all other types of stabilizers are used , according to their General classification (see Figure 1, Figure 2), but with additional application of a binder to the soil in the same quantities.

Complex stabilization technologies clay soils, in addition to improving their water-physical properties, it contributes to the formation of rigid crystallization bonds, which has a positive effect on increasing the physical and mechanical characteristics of soils, and primarily such as shear strength and deformation modulus.

An increase in the strength and deformation characteristics of complexly stabilized clay soils makes it possible to use them not only for the working layer, but also for roadsides, as well as soil bases for pavements and coatings of local (rural) roads. An increase in the amount of binder used in soil treatment in excess of 2% by weight, while maintaining the amount of stabilizer additives introduced into the soil (up to 0.1% by weight), transforms soil stabilization technology into soil stabilization technology, which, taking into account the presence of additives, should be characterized as a technology for complex soil strengthening .

The presence of stabilizer additives in the fortified clay soil, firstly, leads to a decrease in the required binder consumption and, secondly, makes it possible to increase the frost and crack resistance of the fortified soils.

Complexly strengthened soils, as well as reinforced soils, should be used as bases in pavement structures in accordance with GOST 23558-94.

Taking into account the above, the Road classification of stabilizers (see Figure 2) is compiled according to the target functions of soil treatment with additives. This means that depending on the final function of the stabilized and soil treated, a certain type of soil treatment is selected, taking into account the properties of the soil in terms of pH and the type of stabilizer compatible with this soil.

Also, according to the function of soil properties, the assignment of the obtained material to the required structural element of the pavement and subgrade of the highway is determined. Therefore, the applied nature of the Road Classification of Stabilizers is expressed in its functional orientation, i.e. it clearly reflects the purpose and scope of the stabilizer in the road structure. Therefore, the following main target functions are distinguished:

First function- hydrophobization of soil in the working layer.

Second function- Structurization (together with hydrophobization) of the soil in the foundations of pavement.

Third function- increasing the frost and crack resistance of reinforced soils in the structural layers of pavement.

All the selected target functions of the process of affecting the soil with stabilizer additives are implemented using a similar technology; the curtain is based on the combination of soil with additives and its compaction at optimal moisture content.

The difference in the physical and mechanical properties of the soil mixture depends on the type and quantitative ratios of the stabilizer and binder in the soil and the type of the latter. Therefore, the following main features have been chosen as the basis for dividing the most general and broad concept of "Soil treatment with additives".

Class: It is determined by the depth of impact and the degree of change in the structural and physical and mechanical characteristics of the pound.

View: It is determined by the type of additives and their quantitative ratio, with the help of which the required level of change in the physical and mechanical characteristics of the pound is realized.

Subspecies: It is determined by the conditions of compatibility in a pound mixture of the sign of the charge of the stabilizer ions and the type of pounds by pH (acid, alkaline, neutral).

The developed Road Classification of Stabilizers considers only those materials and additives, as well as the types and varieties of soils that are most widely used and have a positive effect. practical experience. The initial product in the Road Classification are stabilizers, the types of which correspond to their General Classification (see figure).

Stabilizers should be used for processing at optimal moisture content: soils with a plasticity number from 1 to 22, with a content of sand particles of at least 40% by weight and a yield strength WL of not more than 50%, as well as all varieties of coarse clastic and sandy soils containing in their composition of silty and clay particles in an amount of at least 15% by mass, with a content of easily soluble salts - sulfates - not more than 2% by mass, chlorides - not more than 4% by mass, humus - not more than 2% by mass and gypsum impurities - not more than 10%.

Normative references:

• GOST 29213-91 (ISO 896-77) Surfactants. Terms and Definitions
• GOST 25584-90 Soils. Methods for laboratory determination of the filtration coefficient
• GOST 24143-80 Soils. Methods for laboratory determination of swelling and shrinkage characteristics
• GOST 23161-78 Soils. Method for laboratory determination of the characteristics of subsidence.
• GOST 25100-95 Soils. Classification
• GOST 5180-84 Soils. Methods for laboratory determination of physical characteristics
• GOST 22733-2002 Soils. Method for laboratory determination of maximum density

Soil stabilization is the most profitable and efficient way to build dirt roads inside settlements, populated areas, settlements, cottage settlements in the case when the use of full-fledged asphalt roads or highways is not financially efficient.

Soil stabilization technology is as follows:

Step 1.

Road planning. It is necessary to take measures related to ensuring proper drainage with the installation of drainage ditches and ditches. Eliminate possible stagnation of water near the subgrade, reducing its penetration into autumn period; level down ground water by means of drainage.

Step 2

Determination of the composition of the soil. For the construction of structural layers of pavement and strengthening of roadsides, it is allowed to use both natural soils and imported soils. Soil is delivered using imported soils. In this case, it is necessary to fulfill the following requirements before starting soil stabilization work:

• delivery of soil in the amount necessary for the construction of a structural layer of pavement or roadside reinforcements;
• distribution of soil and its leveling over the entire width of the prepared subgrade or shoulder
• rolling of the leveled layer to a density of 0.85-0.90 of the maximum density according to the standard compaction method.

Soil selection and stabilizer consumption.

• determination of the granulometric composition of the soil intended for use;
• if necessary, adjusting the granulometric composition of the soil mixture by mixing the existing soil with soil of a different granulometric composition;
• determination of the maximum density and optimal moisture content of the soil treated with the stabilizer;
• determination of strength characteristics in accordance with the requirements of GOST 12801-98;
• determination of moisture resistance and water resistance;
• determination of the need for a stabilizer per 1 m2 and in general for a site with the same soil.

Step 3

Mixing of composites.

Preparation of the stabilizer solution. The solution is obtained by diluting the stabilizer in the working container, with stirring the resulting solution for 10 ... 15 minutes. The concentration of the stabilizer solution is set depending on the current soil moisture and its optimal moisture determined by the modified Proctor method for soil samples treated with a stabilizer.

Soil crushing carried out various types road machines in order to obtain a homogeneous grain composition of the mixture in accordance with the requirements of clause 6.4.SNiP. 3.06.03-85 The best crushing of the soil is achieved when its moisture content is 3-5% less than the optimum and the density is 0.85-0.90 of the maximum, determined by the standard compaction method. At low natural soil moisture, moistening to the specified degree is carried out 6-12 hours before the start of crushing. At high natural humidity, the soil is dried by repeated mixing in dry windy or sunny weather to a moisture content of 2-4% less than optimal. The soil is considered crushed if it contains no more than 25% of lumps larger than 5.0 mm. In this case, the content of lumps larger than 10.0 mm should not exceed 10.0%.

Step 4

Rolling and compaction.

Profiling surfaces of the stabilized layer are produced in two passes of a motor grader along one track with the creation of a transverse slope of the structural layer of pavement from stabilized soil equal to the transverse slope of the carriageway. The cross slope of the shoulder should exceed the cross slope of the carriageway by 1-2%.

Compaction of treated and profiled soil. Produced by self-propelled vibrating or oscillating rollers weighing at least 10 tons. The lower layers of the structural layer of the pavement can be compacted with self-propelled vibratory cam rollers, but upper layer must be rolled with smooth vibrating or oscillating rollers weighing at least 15 tons.

Notes.

1. The speed of the roller during compaction should be 3.5-6.5 m/min (the first two passes), for the remaining passes the maximum value of the working speed is assigned. The first two passes are carried out with the vibration (oscillation) mode turned off.
2. The number of passes of the roller and the speed of its movement are set according to the results of the test compaction. Approximately 12-18 passes of the roller on one track are required for compaction.
3. The degree of density of the stabilized layer must be at least the maximum standard according to the Proctor method modified in accordance with GOST 22733-2002.

Soil stabilization

TO category:

About road construction machines

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Soil stabilization

The soils used in road construction have certain limiting strength indicators, i.e., they are able to carry a certain amount of load from moving vehicles.

In recent years, it has been developed new method increasing the strength of soils by adding additives of binders - cement, lime, bitumen, tar. This method is called soil stabilization. binders. Soils strengthened by this method are used for the construction of road bases for permanent asphalt concrete pavements and for the construction of lightweight pavements instead of asphalt concrete pavements. The cost of building bases and pavements from stabilized soil is 3.5-5 times cheaper than the construction of crushed stone bases or asphalt concrete pavements. A base layer of stabilized soil 30 cm thick is equal in strength to a layer of crushed stone 18-20 cm thick; a light pavement of stabilized soil 15-20 cm thick is equal to the strength of an asphalt concrete pavement 6-10 cm thick.

Previously, road surfaces were constructed in the form of a cobblestone pavement (cobblestone highway) or by laying a layer of crushed stone 6-15 cm thick, rolled by carriage wheels or road rollers (graveled stone or "white" highway). With the development of automobile traffic, the strength of these highways turned out to be insufficient.

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The main reason for the rapid destruction of white highways by car wheels is the weak connection of individual gravel with each other.

In addition, due to the high speeds of vehicles, new requirements are imposed on the roads - evenness of the surface, dustlessness and good grip with tires.

The increase in the cohesion of crushed stone in the coating is achieved by introducing organic binders into the thickness of the coating - bitumen or tar, which increases the strength and durability of the road. The presence of binder materials in the coating allows you to evenly roll its surface with rollers, bind dust and thus remove dust from the road and improve tire grip. The organic binder coats the mineral particles with a thin film and binds them together.

A white highway treated with bitumen or tar becomes black and therefore such coatings are called "black".

Soil stabilization can be carried out both on local and imported soils. For stabilization, sandy loam and loam are the most suitable. When stabilizing soils, the upper plant layer (sod) with the roots of grasses and shrubs must be removed, since voids form when the vegetation particles rot.

Soil stabilization consists of the following main operations: - preparation of a strip of soil; – loosening and grinding of soil; - distribution of binder material; - mixing of crushed soil with a binder material; - watering and final mixing with water of crushed soil, mixed with a powdered binder when stabilized with cement or lime; – strip compaction, stabilized soil.

Strip preparation consists in removing the turf layer and roots of stumps and shrubs and in planning the strip with backfilling of local depressions and cutting off mounds and bumps.

At the same time, the subgrade is profiled and side ditches are cut. Strip preparation work is carried out by bulldozers and, if necessary, rooters, as well as graders or motor graders.

If local soils are stabilized, then the corresponding subgrade strip is subjected to loosening and grinding. If stabilization is not carried out on local soil, then the necessary soil is brought from the near-traoss quarry by scrapers, tractor trailers or dump trucks, the brought soil is distributed and planned on the subgrade and then it is loosened and crushed.

It is advisable to loosen dense, heavy sandy loam and loam with trailed tractor plows and harrows.

Light soils are loosened by trailed tractor cutters, which then crush the loosened soil. Loosening and grinding are carried out by several passes of machines along the processed strip.

The more intensively the soil is crushed, the better and more evenly it mixes with the binder and the stronger the stabilized layer is obtained. In normally crushed soil, the number of particles 3-5 mm in size should not exceed 3-5% by weight, which is checked by special samples.

cement stabilization

Cement or lime is brought to the job site in cement trucks or dump trucks and manually spread with shovels evenly over the treated strip immediately before dry mixing. Special machines for the distribution of cement and lime are not yet manufactured.

The soil is dry mixed with a binder, then watered with water from an asphalt distributor, after which it is finally mixed with several passes of a trailed cutter and compacted with rolling.

Stabilization with bitumen or tar

Bitumen or tar is brought and poured with an asphalt distributor immediately before mixing so that the binder does not cool down.

The soil with the binder is mixed with several passes of the trailed cutter and compacted with rolling.

The stabilized layer is compacted with a D-219 pneumatic tire roller on a trailer to a car or a wheeled tractor. Towing the roller by a caterpillar tractor is unacceptable due to damage to the strip surface by caterpillar spurs.

This technology was invented by ANT-Engineering LLC in 2006. To date, more than 150 km of roads of various categories have been built in Russia and abroad. Highways built using ANT technology are operated in all climatic zones: from the desert to the Arctic Circle.

The main element of the technology is the preparation “Soil and organic-mineral mixture stabilizer “ANT” (eng. - “ant”). It is used both independently for soil stabilization, and together with inorganic or organic binders for strengthening.

The principle of operation of the soil stabilizer "ANT"

The ANT soil stabilizer is a Russian product and is produced in the city of Volzhsky, Volgograd region. It is a complex organic preparation. Its action is aimed at carrying out redox reactions in the soil. Produces a directed oxidative reaction by exposing the surface of the soil particle to molecular oxygen, as well as in the cement (if used). As a result, the formation of new oxides of chemical elements contained in the soil occurs. Then, the previously attached oxygen is separated, and a reverse reduction reaction occurs, which leads to the formation of new crystalline compounds in the soil between its particles.

This reaction completely repeats the processes of formation of sedimentary rocks in the earth's crust. If we had the opportunity to increase the load during compaction of the treated soil by more than 5 times, then we would be able to obtain reinforced soils with a strength grade of over M200. But, unfortunately, modern technology and methods of road works do not allow us to achieve these results.

In addition, the stabilizer contains surfactants in its composition, which makes it possible to achieve the maximum coefficient of soil compaction, and, consequently, obtaining a material with less presence of capillaries. This allows you to significantly reduce the water absorption of stabilized and fortified soils.

5 key benefits

1. High physical and mechanical properties.

Soils reinforced with Stabilizer "ANT", have high physical and mechanical properties and fully comply with the requirements of GOST 23558-94 "Crushed stone-gravel-sand mixtures and soils treated with inorganic binders for road and airfield construction."

For example, during construction highways V of the technical category of the transitional type, it is sufficient to install one layer of reinforced soil with a thickness of h = 15 cm. This structural layer is designed for traffic with an axle load of up to 8TC. The total modulus of elasticity on the surface of this layer will be more than 150 MPa.

2. Low consumption, as well as its low estimated cost.

The consumption is 0.007% of the mass of the soil. When carrying out road construction work, 1 liter per 7.5 m 3 of the future layer is required. For the construction of 1 km of a motorway of category IV–V, i.e. device 6000m 2 layers of reinforced soil, 15cm thick, the stabilizer consumption will be 120 liters, the estimated cost, respectively, is 312,000 rubles or 52 rubles / m 2.

3. Simplification of the processes of stabilization and strengthening of soils.

Namely:

• lack of maintenance of hardened soils;
• the possibility of resuming the movement of vehicles immediately after the compaction of the layer;
• no need for expansion joints.

4. UsabilitySoil stabilizer "ANT"both alone and together with inorganic and organic binders.

When using the Stabilizer together with cement, the strength properties of reinforced soils increase by more than 30% relative to control samples without it.

When used together with bitumen emulsions or foamed bitumen, there is a better distribution of the binder throughout the volume of the soil, an increase in the adhesion of binder particles to the soil and a subsequent increase in the physical and mechanical properties of reinforced soils.

5. Complete environmental safety.

Stabilizer "ANT" does not have any negative effect on environment and is 100% environmentally friendly. When carrying out road construction works, it is not required to provide technical personnel with additional means of protection. Also, it does not have a negative impact on the components of machines and mechanisms.

Scope of soil stabilizer "ANT"

arrangement of foundations for motor roads of category I–V, non-rigid and rigid types;

road surfaces IV - V category of transitional type;

stabilization of the sole and the working layer of the subgrade;

as an additive when strengthening soils with organic or complex binders.

Independently Stabilizer "ANT" can be used in the stabilization of clay soils with a plasticity number from 1 to 17 (sandy loam, loam, clay). Stabilized soils can be used to stabilize the sole or working layer of the subgrade, as well as the construction of the lower layers of the bases.

To obtain reinforced soils, it is necessary to add cement in an amount of 2% -5% by weight of the soil. The rate of cement consumption depends on the type of soil, climate zone and the required strength properties of the reinforced soil. For work, it is possible to use sandy loam, loam, sand and gravel mixtures, low-strength stone materials, waste from crushing stone materials and concrete.

Usage Soil stabilizer "ANT", together with organic or complex binders, it allows to reduce the consumption of binders and increase the strength characteristics of reinforced soils. In addition to the ongoing redox reaction in the soil, the ANT Stabilizer will increase the adhesion of the bituminous binder to the soil, as well as evenly distribute it throughout the entire volume of the soil.

Consumption rate

The required amount of Stabilizer is 0.007% by weight of the soil. When carrying out road works, 1 liter of stabilizer per 7.5 m 3 of the future structural layer is taken as the rate of its consumption.

Consumption rate soil stabilizer "ANT" for every 1000m 2 of construction layer, depending on layer thickness

Soil stabilizer "ANT" is used in the form of an aqueous solution. The required amount of water is calculated based on the natural moisture content of the soil and the optimum during compaction. Also provide for a correction for the amount of water per climatic conditions, type of soil, amount of cement used, etc. In practice, the dissolution ratio of the stabilizer with water ranges from 1:250 to 1:1000.

Road construction options

Road works can be carried out using various options equipment equipment.

Self propelled recyclers. With their help during work shift make the device of a constructive layer from the strengthened soils, the area over 5000 sq.m. The treated soil mixture is prepared directly on the road, in one pass. The aqueous solution is dosed into the rotor, and its consumption is controlled by the machine's on-board computer. The distribution of cement is carried out before the passage of the recycler.

When using technogenic soils, it is possible to prepare the mixture on specialized soil-mixing or concrete-mixing plants. Treated soil is laid using an asphalt paver (best results in terms of geometry) or a motor grader. The speed of work production depends directly on the productivity of mixing plants.

The preparation of the treated soil is also carried out using agricultural cutters and harrows. The penetration into the ground should be 30% higher than the calculated thickness of the structural layer. The best results are achieved when using horizontal attachment mills driven by the tractor's stub shaft. In practice, the speed of work per shift is 1000 m 2 or more.

In the construction of any coating, an initial calculation of its wear resistance and bearing capacity. Some methods are used for pedestrian areas, and a completely different approach is practiced in the creation of automotive coatings. A special base helps to counteract the stress that acts on under traffic flows. For its formation, soil stabilization is used, which involves the use of organic and inorganic materials.

General information about soil stabilization

The main purpose of this event is to create a solid foundation under the road or platform, which will not deform and spread during operation. The entire workflow can be divided into four stages. First of all, soil stabilization technology provides for the preparation of a material from which a kind of cushion will be created. Further, an active mixture is created from substances with the desired characteristics. Already at the place of use, with the help of special equipment, the mass is applied to the working area. The final stage involves the distribution and a kind of mixing of the substance with the base soil.

It is important to understand that this process in itself is only an intermediate stage in the implementation of the overall road and site construction project. When soil stabilization is completed, insulating or technical layers of the future coating are laid directly on the prepared base.

Material preparation

Most often, cement and lime bases are used. Sand and gravel can also be used as thinners - their concentration depends on the requirements for the future coating. In the construction and design of pavement, local soil should also be used. For example, if the soil is stabilized with lime, it would be appropriate to include stone materials that will create the necessary cushioning strength. Another thing is that such additions must first be crushed with special cutters. Directly at the backfill site, the stabilization mass will be approximately 10-20% of the local soil, which will serve as the basis for the road surface.

Creating a mixture

The specific recipe for the manufacture of the mixture is determined by the characteristics that must be obtained after completion of the work. For example, methods for stabilizing soils with a monolithic base involve achieving such coating qualities as shear resistance and increased elasticity. As part of such mixtures, the mentioned cement-lime combination is usually used, which is also diluted with active ash and local soil. However, its main difference is the complete exclusion of rubble. As a result, other important properties coatings, among which are capillary-interrupting functions and an increase in heat-insulating performance.

Technically, the mixing operation is performed by special dosing machines. Modern technology allows you to perform mixing, taking into account the indicators entered through the panel electronic control. The initial parameters, according to which the road soil is stabilized, are pre-documented in the laboratory. Further, the information obtained becomes the basis for developing a recipe and preparing a strengthening mixture.

Distribution of material on the surface

Before this stage, special distribution containers are prepared into which the mixture is loaded. At the same stage, various modifiers can be added, through which the basic qualities of the mass are improved. On the job site, the equipment evenly distributes doses based on cement and lime. Again, depending on the design requirements, soil stabilization can be performed with loosening elements, which will further provide a higher degree of compaction of the mass. In addition, auxiliary steps for preparing the mixture for distribution may be included before delivery. These can be the operations of working in, grinding and mixing the components of the mass. The possibilities of implementing these technological stages depend on the functions of a particular special equipment. Typically, multifunctional machines are used, provided with couplings with protective valves, which are disconnected when overloaded.

Working the stabilization mass into the ground

The procedure can be performed by special equipment or manually. The choice of technology depends on the possibility of carrying out an operation near a residential area, a parking lot, an airfield site, or in bad weather. Most often, tractors with a three-point hitch at the rear are used for the final introduction of the material. Cutters interact directly with the active mixture - the action resembles loosening followed by compaction. Depending on the design solution, according to which soil stabilization is implemented, the construction of roads at this stage may include additional operations. For example, the operator can also carry out the distribution of a water-emulsion binder component, which will also be worked into the soil as a separate active substance.

Conclusion

Arrangement technologies pavement special requirements are imposed on the formation of protective layers. The presence of high-quality insulation and drainage sprinkles allows you to protect the future road from many negative factors. In turn, the stabilization of the soil forms a kind of foundation, on which physical pressure subsequently falls. This seal must not only withstand stress, but also ensure the integrity of the overall structure of the coating. It is for this purpose that viscous components are added to the stabilizing mixtures. In a single complex with lime and cement, they create a solid, frost-resistant and permeable platform for a future road or site.