RU2747181C1 - Method for creating support structure of pavement - Google Patents

Abstract

FIELD: road construction.SUBSTANCE: invention relates to the field of road construction and can be used in new construction or repair of highways, runways of airfields, helicopter and other sites on soft soils in wetlands, as well as on shifting sandy soils of deserts and sea coasts. The method of creating the support structure of the pavement includes an incremental-phased installation of layers of pavement. According to the method, the first stage presupposes that a base layer is laid on the ground, on top of which a layer is applied in the form of a segmented non-monolithic assembly of osteomorphic blocks with convex-concave surfaces made of lightweight foam concrete, on which road surface is then laid. The lower base layer is laid on a drainage base made of geotextile. Another separating drainage layer made of geotextile is laid between the supporting base, which is made of high-strength cellular polymer concrete, and a segmented non-monolithic layer made of concrete osteomorphic blocks with convex-concave surfaces. Then the second segmented non-monolithic layer of osteomorphic blocks with convex-concave surfaces is mounted. This layer is made of polymer material. The blocks are connected to each other according to the principle of topological self-interlocking. Monitoring sensors are installed inside the layer.EFFECT: creation of a road surface of increased strength and durability in conditions of soft soils and permafrost.1 cl, 8 dwg, 2 tbl

Description

The invention relates to the field of road construction and can be used for new construction or repair of highways, runways of airfields, helicopter and other sites, in conditions of soft soils in wetlands, as well as on moving sandy soils of deserts and sea coasts.

There is a known method of road surface construction (patent for invention of the Russian Federation No. 2318947, publ. 03/10/2008), including laying on the road base a combined crack-breaking layer, which includes an elastic membrane, and on top of it - a reinforcing geogrid of high strength, and subsequent laying on top a combined fracture-interrupting layer of a bearing coating made of an asphalt concrete mixture. The combined crack-breaking layer is laid on a pre-prepared road base, the preparation of which provides for its division into a number of separate composed elements both in length and width, followed by their compaction and landing on the ground of the subgrade, and as an elastic membrane in the composition of the combined crack-breaking layer, a leveling layer was introduced, consisting of an asphalt concrete mixture with a complex organic binder, the composition of which is selected in accordance with the brittleness temperature, equal to the minimum temperature of the coldest days of the operation area, while the reinforcing geogrid is made of glass material with a low degree of deformability, close to the deformability of the bearing coating ... The preparation of the road base for new construction or with a slight degree of destruction of the old road surface is carried out in the form of dividing into blocks with side sizes of 1.5 - 2.5 m.With a strong degree of destruction of the old road surface, the preparation of the road base is carried out in the form of dividing it into fragments with element sizes 200 - 250 mm.

The disadvantages of this method are the uneven distribution of the damping load on the base of the pavement, as well as the need for its compaction, which negatively affects the soils of a weak base

There is a known method for the construction of road pavements (patent for invention of the Russian Federation No. 2351702, publ. 10.04.2009), including a three-stage laying of layers of clothing and consisting in the fact that at the first stage, the upper part of the roadbed made of improved stable soil, consisting of mixtures of sand, ash and slag, coal mining waste and slag-alkali binder containing fiber. At the second stage, two layers of a polymer canvas are laid across the road with overlapping edges one on top of the other, after which one or two layers of a base made of fiber-reinforced concrete of increased strength are laid on a slag-alkaline binder, on the surface of which a thin layer of wear-resistant concrete is applied, followed by a rough knurling on its surface, after that, at the final stage, a two-layer coating is laid, which is covered with a thin layer of wear from a solution containing an ash-mineral mixture and a slag-alkaline binder to eliminate the roughness of the road.

The disadvantages of this method are the uneven distribution of the damping load on the base of the pavement, as well as the low strength and durability of the pavement in conditions of weak soils and permafrost.

There is a known method of erecting pavement (patent for invention of the Republic of Kazakhstan No. 22792, publ. 16.08.2010), in which the base of soil, sand and / or crushed stone is covered with a geotextile cloth made of nonwoven material, on which a carrier layer is applied, the edges of the cloth are wrapped upward, forming a supporting frame and placing on it a geomembrane made of a polymer film, on which plates with through channels are laid and connected to each other in a section with a reinforcing cable using fasteners, while in the upper part of some plates, holes are preliminarily made, connected to the channels, for tensioning and joining the reinforcing cable.

This method does not provide a significant increase in the strength and durability of the road in conditions of soft soil and permafrost. In addition, it provides for the use of conventional, but often difficult to access materials (soil, sand, gravel, crushed stone, etc.) to form the road base, which, moreover, do not fully ensure the construction of a road surface that evenly distributes and dampens the load on the base of the pavement, and does not show resistance to erosion and flooding, which are significant factors in the destruction of roads in conditions of weak soils and permafrost.

There is a method of erecting pavements (materials of the V-th International Scientific and Practical Conference "Innovations and Prospects for the Development of Mining Engineering and Electromechanics: IPDME-2017". V. Yu. Piirainen, Yu. Estrin. A new concept of road construction in oil-producing regions of Western Siberia. St. Petersburg: St. Petersburg Mining University, April 23-24, 2017 p.,), Taken as a prototype. According to which the layer-by-layer formation of the road pavement is carried out from: waterproof rubberized roll substrate, which serves as a load-bearing base; a backing layer made of lightweight building materials, such as aerated concrete; and an asphalt or other road surface laid on the above-described abutment base. The support layer is a non-monolithic assembly of separate osteomorphic blocks with convex-concave surfaces, impregnated with a rubber-like material, such as bitumen.

The disadvantages of this method include the formation of one support layer from separate osteomorphic blocks, which takes over and distributes both the internal vertical load from the soil and the external vertical load and shear stress from the side of passing vehicles and temperature fluctuations of the environment, which excludes, if necessary, reliable operation of built-in sensors for monitoring the current state of the road in real time, and, accordingly, the implementation of the "smart road" concept.

The technical result of the proposed solution is the creation of a road surface of increased strength and durability in conditions of soft soils and permafrost.

The technical result is achieved by the fact that the lower bearing layer is laid on a drainage base made of geotextile, and between the bearing base, which is made of high-strength cellular polymer concrete and a segmented non-monolithic layer of concrete osteomorphic blocks with convex-concave surfaces, another separating drainage layer of geotextile is laid, then a second segmented non-monolithic layer of osteomorphic blocks with convex-concave surfaces is mounted, which is made of polymeric material, the blocks are connected to each other according to the principle of topological self-interlocking, monitoring sensors are installed inside the layer. Surface bending sensors, temperature sensors, pressure sensors, humidity sensors, gamma background sensors are used as monitoring sensors.

The method is illustrated by the following figures:

fig. 1 is a diagram of the arrangement of the layers of the pavement;

fig. 2 - the appearance of a layer of topologically self-interlocking segmented osteomorphic blocks;

fig. 3 is a graph of the dependence of the track depth on the number of cycles of the applied load in the roadway;

fig. 4 - experimental sandwich assembly, segmented;

fig. 5 - experimental sandwich assembly, monolithic-segmented;

fig. 6 is a diagram of inclinometer turn during the rise / fall of the pavement layer;

fig. 7 is a block diagram of the use of geosynthetics when performing road works, where:

1 - soil;

2 - separating drainage layer;

3 - bearing base;

4 - a layer of osteomorphic concrete blocks;

5 - a layer of osteomorphic plastic blocks;

6 - road surface;

7 - formwork;

8 - measuring sensors;

fig. 8 shows the results of calculations with a concentrated load in the center of the experimental assembly of three geometry options.

The method of erecting a pavement includes a step-by-step laying of layers of clothing. At the first stage, a separating drainage layer 2 of geotextile is laid on the soil 1 (Fig. 1). On this layer, the supporting base 3 of the pavement is laid, which is made of composite aerated concrete. Next, lay another separating drainage layer 2. Next, lay a support layer of osteomorphic concrete blocks 4. On top of the layer of osteomorphic concrete blocks 4, lay another support layer of osteomorphic plastic blocks 5. On top, lay a pavement 6 (Fig. 1).

The separating drainage layer 2 is a woven fabric made of synthetic geotextile that prevents moisture from penetrating into the body of the pavement from the ground, and at the same time drains the upper layers of the pavement from moisture coming from the external environment.

The load-bearing base 3 of the pavement is a monolithic layer made of composite cellular concrete with high strength and low volumetric weight, which is poured onto the separating drainage layer 2, using lightweight plastic formwork 7, and does not require compaction, the effect of which on soft soil has a negative effect ... The thickness of this layer depends on the planned loads and is calculated at the design stage. On average, the thickness is from 0.3 to 0.5 m.Calculations of road structures with typical loads show that an equivalent layer of composite aerated concrete has a strength 3 - 4 times greater than a layer of the same thickness made of bulk materials (sand, gravel , crushed stone).

The layer of osteomorphic concrete blocks 4 plays the role of the main support layer, which is assembled from topologically self-interlocking osteomorphic concrete blocks (Fig. 2), laid on the principle of self-interlocking in conventional pavement technologies. The layer of osteomorphic concrete blocks 4 takes on the load and relieves the stresses transmitted to it from the supporting base 3, which act from the side of the soil as a result of its swelling. The layer of osteomorphic concrete blocks 4 is at the same time a supporting base for the layer of osteomorphic plastic blocks 5, which receives and dampens the load from moving vehicles and from external temperature changes. The layer of osteomorphic plastic blocks 5 is mounted similarly to the layer of osteomorphic concrete blocks 4 according to the principle of topological self-engagement.

The layer of osteomorphic concrete blocks 4 and the layer of osteomorphic plastic blocks 5 represent a non-monolithic segmented structure of archimates, that is, materials with a given internal architecture, at a larger scale than the microstructural one. An important property of materials of this class and structures made from them is their non-monolithic nature and segmented structure, which consists of separate blocks of a certain shape, oriented in relation to each other in a special way. These include osteomorphic blocks, self-interlocking of which is ensured due to the convex-concave shape of their contact surfaces; the blocks are connected to each other according to the principle of topological self-interlocking. The geometry of the blocks is such that after their assembly, none of the many elementary blocks can be removed from the structure, and due to the "mosaic" of the material, its resistance to destruction is significantly increased. In fact, self-wedging of individual structural elements occurs similarly to the assembly of arches and domes from bricks with tapered surfaces, with the only difference that in the case of assembly from osteomorphic blocks, wedging occurs simultaneously in all directions. This property plays a key role in the construction of the pavement, as it allows you to create layers that are sufficiently rigid in several planes, withstanding repeated dynamic loads from vehicle traffic and cyclic heaving of soils.

In the layer of osteomorphic plastic blocks 5, independent or combined in groups of measuring sensors 8, for example, surface bending angle sensors (inclinometers) and / or temperature sensors, and / or pressure sensors, and / or a humidity sensor, and / or a sensor are built in a certain order gamma background and others. In this case, the sensors 8 can be combined into groups containing several measuring sensors for different purposes. Sensors 8 can be made in a single housing, powered by a battery, the charge of which is enough to ensure operation for, for example, 10 years. The angles of inclination of the layer of osteomorphic plastic blocks 5 are measured with an accuracy of 0.1 angular degree, temperature - with an accuracy of one degree C, pressure - with an accuracy of 10% of the nominal set for these operating conditions, humidity - with an accuracy of 5% of the nominal set for given operating conditions, the level of gamma background - with an accuracy of 20% of the nominal, established for these operating conditions. The measurement data is transmitted to the track monitoring system via a wireless communication channel based on the LoRaWAN protocol. The sensor system 8 is built into the layer of osteomorphic plastic blocks 5 at the stage of its laying and cannot be repaired, retaining its operability for at least 10 years, after which the layer of osteomorphic plastic blocks 5 can be replaced as part of the planned repair of the pavement. Installation of each sensor body 8 is performed in special grooves that are pre-created in a group of adjacent elements of the layer of osteomorphic plastic blocks 5. Measurements taken from the distributed system of sensors 8 allow on a permanent basis to remotely monitor the condition of the pavement along the entire length of the roadway or multifunctional pavement. In those parts of the roadway where the measured indicators go beyond the a priori established boundaries, an operational inspection is carried out with the possibility of reconstructing the problem part of the pavement. It is also important that the layer of osteomorphic plastic blocks 5 retains its properties even if some of the elementary blocks of its structure are destroyed for any reason.

The layer of osteomorphic plastic blocks 5 is made of high-strength polymer material and is replaceable. This layer serves for the primary distribution of traffic loads and is a layer that can change during the repair of roads or multifunctional sites.

The total thickness of the layer of osteomorphic concrete blocks 4 and the layer of osteomorphic plastic blocks 5 varies depending on the planned load on the road and can be from 0.10 to 0.15 m.The thickness must be sufficient to support and distribute the maximum weight of vehicles that will be allowed use the road. The elementary blocks of the layer of osteomorphic concrete blocks 4 and the layer of osteomorphic plastic blocks 5 are made by 3D printing.

The road surface 6, for example, made of asphalt concrete, is intended for direct contact with the wheels of vehicles or other sources of static or dynamic load, is a removable layer subject to planned replacement or local restoration. The top layer of asphalt concrete must be at least 0.05 m and can reach 0.13 - 0.15 m, depending on the planned loads on the road.

The method is illustrated by the following examples. An example of the effective use of the drainage layer used in the proposed solution is diagram of the use of geosynthetics when performing road works (Fig. 7), as well as a graph of the dependence of the track depth on the number of cycles of the applied load in the roadbed, reinforced

geosynthetic material (figure 3). Geosynthetics do an excellent job of extending pavement life.

The conceptual idea was tested on a mock-up of the base of the pavement assembled from concrete and polystyrene blocks into a single layered structure impregnated with a rubber-like polymer material.

The development of the segments of the experimental design was carried out using the method of computer simulation. In the AutoCAD program with a three-dimensional computer-aided design system, the search and construction of models of topological self-interlocking blocks were carried out, which were "assembled" further into a three-layer canvas, fixed at the edges with a fixing frame. In total, four types of mathematical models of elementary blocks were considered and built: two - of the LEGO type and one each - Plato's bodies and osteomorphic blocks.

Further, three-layer assemblies from these blocks were checked for the properties of solid mechanics in the ANSYS finite element analysis software system. At the same time, an identical monolithic structure was calculated for comparison. Each assembly was compared according to three calculation options:

- evenly distributed load (20 tons) over the entire plane of the assembly under study;

- concentrated load (20 tons) in the center of the assembly under study;

- clockwise torsion relative to the center of the end face (torque - 200 kN).

Aerated concrete and expanded polystyrene were chosen as assembly materials for calculations, which, to one degree or another, are already used in road construction and are most suitable for comparative experiments.

The first calculation results showed a clear advantage of the sandwich structures over the monolith, while the osteomorphic assembly (Fig. 2) turned out to be the most durable, and therefore it was chosen for the subsequent optimization of the block sizes and further prototyping.

The search and construction of the convex-concave shape of the osteomorphic block was carried out using elementary commands of the AutoCAD program in accordance with the conditions of sequential self-engagement during assembly.

To select the optimal geometry of the assembly element (block), various options for the ratio of dimensions along the coordinate axes were considered, one of which in the horizontal plane corresponded to the "golden ratio" (2.0x1.2258x1.0). It was this option that showed the best result in the calculations. FIG. 8 shows the results of calculations with a concentrated load in the center of the experimental assembly of three geometry options.

Further, laboratory tests of the combined three-layer structure were carried out on concrete specimens with dimensions of 200x80x40 with a segmented inner layer of polystyrene impregnated with silicone. The test results showed significant advantages of sandwich assemblies with outer layers of self-interlocking osteomorphic blocks (Fig. 4) compared to monolithic-segmented (Fig. 5)

Based on the test results, the tensile strength in bending was calculated (table 1) according to the formula:

,

,

Where:

R _outg - bending tensile strength, kgf / cm ² ;

F- maximum load, kgf;

l - distance between supports during testing, cm;

b is the sample width, cm;

The calculation results are shown in the table.

Table 1 - Results of calculations of experimental specimens in tension in bending Design l,
cm b,
cm h,
cm F,
Kgs R _exile ,
kgf / cm ² monolithic
segmented 10 eight four 250 19.5 segmented 10 eight four 550 42.9

The twofold increase in the strength of the experimental segmented structure is fully consistent with preliminary computer calculations and confirms the correctness of the conceptual idea.

An example of one of the key elements of the proposed solution is a system for monitoring road surface deformations using measuring sensors. For this, tilt angle measurement sensors (inclinometers) are installed in the layer of osteomorphic plastic blocks. During the operation of the road surface, its deformations may occur (subsidence, swelling, rutting, etc.). In this case, inclinometers placed in the layer of osteomorphic plastic blocks perceive deformations and change their angular position. Information about the change in the inclination angle is transmitted via wireless communication channels to the track monitoring system, where the increments of the inclination angles specified in angular degrees are recalculated into the linear displacement values specified in millimeters.

FIG. 5 shows an illustration of the turn of inclinometers during deformation of the pavement layer.

Table 2 shows the relationship between the pitch of the inclinometers, the amount of rise / fall of the pavement layer (mm) and the angle of rotation of the inclinometers (angular minutes).

Table 2 - Change in the angle of inclination of the inclinometer from the magnitude of the rise / fall of the soil Step
installations
sensors (m) Rise / subsidence of soil (mm) 1.0 4.0 10.0 20.0 50.0 100.0 Tilt angle of inclinometers (arc.min) 0.5 13.7 55.0 137.5 275.3 692.2 1414.6 1.0 6.8 27.5 68.7 137.5 344.3 692.2 2.0 3.4 13.7 34.4 68.8 171.9 344.4

Thus, the rise / fall of the pavement by 1 mm when placing inclinometers with a step of 1 m leads to a change in their angle of inclination by 6 ... 7 arc minutes. When carrying out measurements once a day, the capacity of the power sources will be enough to ensure operability for at least 10 years.

Thus, the proposed method for the construction of road pavements makes it possible to increase the strength and durability of roads or other sites in conditions of weak soils and permafrost, as well as significantly reduce the material costs for their construction. This circumstance is especially important in conditions of road construction, when the usual materials for the formation of the support base are soil, sand, gravel, crushed stone, etc. are difficult to access.

Claims (2)

1. A method of erecting a support base of a pavement, including a phased installation of layers of clothing, in which, at the first stage, a supporting layer is laid on the ground, on top of which a layer is applied in the form of a segmented non-monolithic assembly of osteomorphic blocks with convex-concave surfaces made of lightweight foam concrete, on which is then laid with a road surface, characterized in that the lower supporting layer is laid on a drainage base made of geotextile, and another separating drainage is laid between the supporting base, which is made of high-strength cellular polymer concrete, and a segmented non-monolithic layer of concrete osteomorphic blocks with convex-concave surfaces. a layer of geotextile, then a second segmented non-monolithic layer of osteomorphic blocks with convex-concave surfaces is mounted, which is made of polymer material, the blocks are connected to each other according to the principle of topological self-interlocking, a sensor is installed inside the layer iki monitoring. 2. The method according to claim 1, characterized in that surface bending sensors, temperature sensors, pressure sensors, humidity sensors, gamma background sensors are used as monitoring sensors.

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