RU2767638C1 - Method for construction of base of aerodrome and road pavements from substandard soils - Google Patents

Abstract

FIELD: agriculture.

SUBSTANCE: invention relates to construction of bases of rigid and non-rigid aerodrome and road surfaces in conditions of absence of crushed stone and gravel materials, coarse-grained sands or other standard nonfrost-heaving soil materials, suitable for creation of heat-insulating embankment, non-deformable during freezing and thawing. Method of construction of base of aerodrome and road pavements from substandard soils includes laying of soil layer, introduction of binder into it and their mixing with road mills, soil compaction, which is then subjected to fragmentation. Formation of the base is carried out in layers until the design thickness is achieved. Surface layer of soil is treated with bitumen emulsion. Following particular cases of the construction method are presented. Compaction of soil is carried out with rollers on pneumatic wheels, and soil fragmentation — with a lattice roller. Compaction of the lower layer is additionally carried out with cam rollers with ballast, after which, without temporary interruption, repeated compaction is carried out with rollers on pneumatic wheels until reaching 30–40 % of strength. Or soil compaction is carried out with rollers on pneumatic wheels weighing 25±4 t with pressure of 0.4 MPa. It is possible to carry out soil fragmentation with a lattice roller weighing 30±4 t with cell size making range of 3÷5 cm, or soil fragmentation is carried out without temporary interruption, after compaction with rollers until the layer of design strength is achieved. As binder, it is possible to use cement and/or polycement binders. Surface layer is compacted with two-slope or single-slope incline. In certain cases, the method may additionally include a preliminary excavation installation to the design depth, wherein the excavated soil, with the exception of the vegetal layer, is used for the base arrangement. In certain cases, the method may comprise preliminary filling of the lower layers on the natural soil base with a thickness corresponding to the design marks of the sole of the artificial base, and subsequent laying of the primary layer of soil to be reinforced.

EFFECT: increasing bearing capacity, crack resistance, frost heaving resistance and service life of artificial aerodrome or road surface.

11 cl

Description

The invention relates to road and transport construction and can be used in the construction of foundations for rigid and non-rigid airfield and road surfaces in the absence of crushed stone and gravel materials, coarse sands or other conditioned non-porous soil materials suitable for creating a thermally insulating embankment that does not deform during freezing and thawing.

TERMS AND DEFINITIONS

UNCONDITIONAL GROUND. Soil that does not meet the requirements of road construction standards for a particular layer of the road structure in terms of composition and condition. The use of such soil for construction is allowed only if special structural and technological measures are taken (Methodological recommendations for designing the subgrade of public roads from local thawed and frozen waterlogged clay and peat soils in areas of permafrost distribution. ODM 218.2.094-2018 INDUSTRY ROAD METHODOLOGICAL DOCUMENT https://docs.cntd.ru/document/550918191

The problem of the lack of conditioned non-rocky soils with a high filtration coefficient is very relevant for Russia, especially for its Arctic part. Delivery of crushed stone and gravel materials to these remote regions with poor transport infrastructure is extremely expensive.

A known method of building pavement, including grinding the soil - the foundation of the road, introducing a binder into the crushed soil, compacting the mixture obtained and keeping the compacted mixture in the air in natural conditions. The soil is crushed to a depth of 10-30 cm, a 0.12-0.30% aqueous solution of technical lignosulfonate is introduced into the crushed soil by irrigation with a solution volume of 3-6 l / m ² of the soil surface, the moistened soil is compacted with a mechanized roller weighing 25-40 t in 10-15 passes, keeping the compacted mixture in air is carried out at 18-25°C for 3-5 days to a soil moisture content of 7-9%. Then, hydroprotection is carried out in the form of a two-layer asphalt concrete pavement: the first layer of 7-8 cm thick of asphalt concrete with a crushed stone content of not more than 40% is compacted with a smooth-roller roller weighing 10-18 tons (8-10 passes), the second layer of asphalt-sand concrete with a thickness of 5-8 cm followed by compaction with a smooth-roller roller weighing 10-18 tons (8-10 passes) (RF patent No. 2495181 for the invention "METHOD OF CONSTRUCTION OF PATHWAYS", IPC E01C 3/04,, publ. 2013.10.10). The disadvantage of this method is the need to use crushed stone materials, which makes the use of the method in the conditions of the Arctic part of Russia inefficient.

A known method of construction of pavements and bases of roads and airfields, including crushing the soil to be strengthened, introducing cement into it, mixing, introducing water, mixing the mixture and compacting it. Next, the compacted mixture is kept under natural conditions for 24-36 hours at an ambient temperature of 21-23°C. Then the reinforced soil is additionally treated with water at the rate of 6-12 l / m, the layer is crushed until at least 25% by weight of particles 1.25 - 0.315 mm in size is obtained in the mixture and the mixture is finally compacted (CSSZ author's certificate No. 1636497 for the invention Method of erecting coatings and bases of highways and airfields, IPC E01C 3/04, publ. 03/23/1991). The known method is laborious, in addition to soil and cement, a lot of water is required, and the fortified soil must be maintained in natural conditions for 24-36 hours at an ambient temperature of 21-23°C. And this is not always possible, that is, the method can be carried out only in the warm season. The disadvantage of this method is that only the surface layer is subjected to fragmentation, while the lower part remains a monolithic rigid layer, which is subject to cracking, which leads to the appearance of reflected cracks on the surface. The inability to control the fractional composition of the resulting material, increased abrasion, dustiness and surface destruction due to climatic factors makes this method inapplicable in the construction of an airfield pavement.

A known method of repairing road sections from dusty, watered soils. The known method provides for the strengthening of "heavy" oil dusty, watered soils while ensuring the industrial and environmental safety of the developed routes and adjacent natural objects. When carrying out road repairs after thawing of the embankment, subsidence of crushed stone preparation, asphalt concrete (concrete) pavement, boreholes are drilled with a motor drill with a depth of 0.7 ... 1.2 m, a diameter of 63 ... 108 mm. Heated, low-viscosity "heavy" oil is pumped into wells at a pressure exceeding domestic pressure by 20 ... 80%, crushed stone is added and the asphalt concrete pavement is restored. In cases of repair of road sections destroyed by frost heaving (heaving mounds), a motor drill is used to drill holes with a depth exceeding the seasonal freezing of the soils of the road embankment. Then, heated oil is pumped into the wells under excessive pressure and the crushed stone preparation, asphalt concrete pavement are restored (RF patent No. 2456399 for the invention METHOD FOR REPAIRING ROAD SECTIONS FROM SILKY, WATERED SOILS, IPC E01C 3/04, publ. 2012.07.20). The known method is laborious and costly.

A known method of hydrophobization and stabilization of soils, which consists in profiling, subsequent grinding of the soil with a soil cutter, subsequent mixing of the soil with a cutter with the addition of cement, processing the soil-cement mixture with a water repellent agent based on the natural mineral montmorillonite, altering the treated soil-cement mixture with a cutter, compacting with heavy vibratory rollers to the maximum degree and subsequent the opening of the movement, and the composition for stabilizing the soil contains water, cement and a mineral additive, montmorillonite concentrate is introduced as a mineral additive in the following ratio, wt. %: cement - 5-7%; montmorillonite concentrate (R-SO3H, where R is a hydrocarbon) - 4%; water, and the mass fraction of water is a variable value depending on soil moisture (see RF patent No. 2662737, IPC E01C 7/36, E02D 3/12, publ. 04/04/2018). The disadvantage of this method is the creation of a homogeneous array of the coating and the base, which by its properties is related to hard coatings, while the absence of expansion joints during operation will cause cracking, and as a result, the formation of potholes. In addition, a small amount of montmorillonite concentrate on the road construction market makes it economically inexpedient to widely use it in mass road construction.

The closest in terms of essential features to the claimed method is a method for constructing a pavement base, including milling the soil, introducing a binder and water into it, mixing, subsequent compaction of the soil, treating the soil with a bitumen emulsion, re-loosening and grinding the material of the surface layer of the initially compacted mixture, with In addition, the bitumen suspension is added to the composition from the re-loosened initially compacted layer, the resulting mixture is additionally crushed and mixed and re-compacted (RF patent No. ). The disadvantage of the known method is that only the top layer is subjected to repeated loosening. The monolithic rigid layer in the lower part is subject to thermal cracking, which causes reflected cracks in the upper, treated with bituminous binder, part of the pavement, which reduces the strength and service life of the pavement.

The task to be solved by the claimed technical solution is the development of a method for constructing a strong durable base of the airfield and road pavement from substandard soils that is not subject to seasonal deformations, cracking of the base and coatings.

The technical result achieved as a result of solving the problem is to increase the bearing capacity, crack resistance, heaving resistance and service life of the pavement of an artificial airfield or road surface.

The specified technical result is achieved by the fact that the method of building the base of airfield and road pavements from substandard soils includes milling the soil, introducing a binder into it, compacting the soil and treating the soil with a bitumen emulsion. In this case, the soil after compaction is subjected to fragmentation, the formation of the base is carried out in layers, until the design thickness is reached, and only the surface layer is treated with a bitumen emulsion.

Preferably, soil compaction is carried out by rollers on pneumatic wheels, and soil fragmentation is carried out by a lattice roller.

It is also preferable that the compaction of the lower layer is additionally carried out by cam rollers with ballast, after which, without a temporary break, re-compaction is carried out by rollers on pneumatic wheels until 30-40% strength is reached.

It is also preferable that soil compaction is carried out by rollers on pneumatic wheels weighing 25 ± 4 tons with a pressure of 0.4 MPa.

It is also preferable that the fragmentation of the soil is carried out with a lattice roller weighing 30 ± 4 tons with a cell size in the range of 3 ÷ 5 cm,

It is preferable that the fragmentation of the soil is carried out without a temporary break, after compaction by rollers until the design strength is gained by the layer.

Preferably, cement and/or polycement binders are used as the binder.

Preferably, the surface layer is compacted with a gable or single slope.

It is preferable that the surface layer of the base be treated with a bituminous emulsion without soil mixing.

In some cases, the method may additionally include a preliminary excavation to the design depth, while the selected soil, with the exception of the vegetation layer, is used to construct the foundation.

In some cases, the method may include preliminary dumping of the lower layers on a natural soil base with a thickness corresponding to the design marks of the sole of the artificial base, and subsequent laying of the primary layer of soil to be strengthened.

A comparative analysis of the claimed invention with the prototype showed that in all cases of execution, it differs from the known, closest technical solution:

- soil fragmentation after its compaction;

- layer-by-layer formation of the base until the design thickness is reached;

- processing only the surface layer with bituminous emulsion.

In preferred cases, the invention differs from the known, closest technical solution:

- soil compaction by rollers on pneumatic wheels;

- soil fragmentation by a lattice roller;

- additional compaction of the lower layer with cam rollers with ballast, followed by repeated compaction with rollers on pneumatic wheels until 30-40% strength is reached;

- soil compaction by self-propelled rollers weighing 25 ± 4 tons on pneumatic wheels;

- soil fragmentation by a lattice roller weighing 30 ± 4 tons with a cell size in the range of 3 ÷ 5 cm;

- fragmentation of the soil without a temporary break after compaction with rollers until the layer reaches the design strength;

- using cement and/or polycement binders as a binder;

- compaction of the surface layer with a gable or single slope;

- processing the surface layer of the base with a bituminous emulsion without mixing the soil;

- an additional preliminary excavation device to the design depth using the selected soil, with the exception of the vegetation layer, for the construction of the foundation.

- preliminary filling of the lower layers on a natural soil base with a thickness corresponding to the design marks of the sole of the artificial base, and subsequent laying of the primary layer of soil to be strengthened.

Soil fragmentation after compaction; layer-by-layer formation of the base until the design thickness is reached ensures the creation of a homogeneous crack-resistant base. Treatment of the surface layer with a bituminous emulsion provides its waterproofing from atmospheric moisture, imparts hydrophobic properties and increases the service life of the coating. As a result of the application of the developed method, substandard soils (silty sands, sandy loams and loams) form a base that is close in its properties to crushed stone of sedimentary rocks, characterized by high bearing capacity, crack resistance, heaving resistance and a high filtration coefficient. Soil fragmentation by a lattice roller weighing 30 ± 4 tons with a cell size ranging from 3 to 5 cm ensures soil fragmentation into microblocks of a given size, which eliminates the formation of dusty fine fractions and increases the bearing capacity of the layer, since microblocks form a spatial structure similar to brickwork. The compaction of the lower layer with ballasted cam rollers forms soil-cement micropiles pressed into the underlying layer, which "turn on" the lower unreinforced layers of the base, increasing the bearing capacity of the layer being built.

In the preferred embodiment, the method of constructing the base of airfield and road pavements from substandard soils includes: layer-by-layer milling of the soil, the introduction of a cement and/or poly-cement binder into it, compaction of the soil with rollers weighing 25 ± 4 tons on pneumatic wheels, soil fragmentation with a lattice roller weighing 30 ± 4 tons with a cell size in the range of 3÷5 cm, until the design thickness is reached. Soil fragmentation is carried out without a temporary break, after compaction with rollers until the design strength is gained by the layer. The bottom layer of the base, after compaction with rollers on pneumatic wheels, is additionally compacted with cam rollers with ballast, after which, without a temporary break, they are re-compacted with rollers on pneumatic wheels until 30-40% strength is reached. The last surface layer of the soil is compacted with a gable or single slope, after which it is treated with a bitumen emulsion without mixing the soil. In the case of the construction of an airfield or road surface in a recess, a recess is preliminarily arranged to the design depth, while the selected soil, with the exception of the vegetation layer, is used to construct a reinforced foundation. On permafrost soils (PMG), the installation of coatings in the excavation is not recommended.

The method is carried out as follows.

On a natural prepared soil base or a layer of intact mohopeat (in the case of construction on permafrost soils), the lower layers are dumped with a thickness corresponding to the design marks of the sole of the artificial base of the pavement structure. A primary layer of soil 15-20 cm thick to be strengthened is laid on the prepared and compacted surface of the embankment, it is leveled and mixed with cement or polymer-cement binder by road cutters. The resulting layer is subjected to primary compaction by road rollers on pneumatic wheels (rollers 25 ± 4 tons, pressure 0.3-0.4 MPa). Then, without a temporary break, with cam rollers with ballast (cam pressure on the ground is 6 MPa), after which compaction is repeated with rollers on pneumatic wheels weighing 25 ± 4 tons. layer. As a result, after gaining strength, a lower layer of a reinforced base is obtained with micropiles formed by pressing soil cement by the cams of a cam roller into the underlying layer, and a layer of soil cement fragmented by a lattice roller into microblocks ranging in size from 3x3 to 5x5 cm, depending on the cell size of the lattice roller.

After gaining 30-40% of the strength of the arranged layer, a layer of soil 15 cm thick is applied to it, leveled, mixed with a road milling machine with a cement or polymer cement binder and compacted with rollers on pneumatic wheels (25 ± 4 tons, pressure 0.3-0.4 MPa). After reaching the design density, without a temporary break, processing is carried out with a lattice roller weighing 30 ± 4 tons. This procedure is repeated until the design thickness of the reinforced base of the airfield or road pavement is reached. The surface of the final formed base layer, having a gable or single slope, is treated with a bitumen emulsion to impart hydrophobic properties to the base layer and increase the service life. On top of the arranged base, it can be laid as a rigid one. and soft cover. In this case, the base layer will not form reflected cracks in the coating.

In the case of the installation of an airfield or road surface in the excavation, all the above named procedures are performed after the excavation to the design depth, the selected soils, with the exception of the vegetation layer, are stored and used for the construction of the reinforced base layer. On permafrost soils (PMG), the installation of coatings in the excavation is not recommended.

As a result of applying the proposed method from substandard soils: silty sands, sandy loams and loams, a base layer is formed, similar in its properties to crushed stone of sedimentary rocks, characterized by high bearing capacity, crack resistance, heaving resistance and high filtration coefficient.

An airfield or road surface of a rigid or non-rigid type arranged over such a base layer will have durability, will not be subject to cracking, frost heaving and temperature subsidence during thawing.

Claims (11)

1. A method for constructing the base of airfield and pavement pavements from substandard soils, including laying a layer of soil, introducing a binder into it and mixing them with road cutters, followed by compaction of the soil layer, which is then subjected to fragmentation, and the formation of the base is carried out in layers until the design thickness is reached, and the surface the soil layer is treated with a bituminous emulsion. 2. The method according to p. 1, characterized in that the compaction of the soil is carried out by rollers on pneumatic wheels, and the fragmentation of the soil is carried out by a lattice roller. 3. The method according to p. 2, characterized in that soil compaction is carried out by rollers on pneumatic wheels weighing 25 ± 4 tons with a pressure of 0.4 MPa. 4. The method according to claim 2, characterized in that the lower layer is additionally compacted with cam rollers with ballast, after which, without a temporary break, re-compacting is carried out with rollers on pneumatic wheels until 30-40% strength is reached. 5. The method according to p. 4, characterized in that the lower layer is compacted by cam rollers with ballast with a cam pressure on the ground equal to 6 MPa. 6. The method according to claim 2, characterized in that soil fragmentation is carried out with a lattice roller weighing 30 ± 4 tons with a cell size in the range of 3 ÷ 5 cm. 7. The method according to p. 1, characterized in that the fragmentation of the soil is carried out without a temporary break, after compaction with rollers until a layer of design strength is gained. 8. The method according to p. 1, characterized in that cement and/or polymer cement binders are used as a binder. 9. The method according to p. 1, characterized in that the surface layer is compacted with a gable or single slope. 10. The method according to claim. 1, characterized in that it additionally includes a preliminary excavation to the design depth, while the selected soil, with the exception of the vegetation layer, is used to build the foundation. 11. The method according to claim 1, characterized in that it includes preliminary backfilling of the lower layers on a natural soil base with a thickness corresponding to the design marks of the sole of the artificial base, followed by laying the primary layer of soil to be strengthened.