Polyurethane mixture compound pavement structure and design method thereof

Abstract

The invention relates to a polyurethane mixture compound pavement structure and a design method thereof, and belongs to the technical field of civil engineering. The pavement structure comprises a polyurethane gravel concrete wearing layer, a multi-gravel polyurethane concrete bearing layer, a bonding layer and an asphalt mixture lower surface layer from a surface layer to a bottom layer, the fatigue limit strain of the multi-gravel polyurethane concrete bearing layer is larger than the layer bottom tensile strain in a design load, and the shear strength of a whole formed by the multi-gravel polyurethane concrete bearing layer, the bonding layer and the asphalt mixture lower surface layer is larger than the interlayer shear stress in the design load. According to the pavement structure and the design method, material characteristics and mechanical characteristics of the polyurethane mixture are fully considered, operability is high, and the designed pavement structure is reasonable, low in cost, good in durability and capable of meeting use requirements of different working conditions; the method can effectively make up for the problem that the polymer mixture pavement structure is lack of theories or is difficult to adapt to existing standards in the design process.

Description

Technical Field

[0001] The invention belongs to the technical field of civil engineering, and in particular relates to a polyurethane mixture composite pavement structure and a design method thereof. Background Art

[0002] The strength, stability and durability of polyurethane mixtures mixed and cured at room temperature are better than those of conventional asphalt mixtures, and are more in line with the needs of green development. However, the material cost of full-thickness polyurethane mixture pavements is relatively high, limiting their widespread application.

[0003] Chinese patent CN116312883B discloses a polyurethane pavement structure design method. The polyurethane pavement structure is composed of a base layer, a multifunctional layer, a polyurethane mixture layer and an anti-skid wear layer from bottom to top. The polyurethane mixture layer is provided with an anti-fatigue load-bearing layer and an anti-rutting layer. By obtaining the traffic load design parameters of the polyurethane pavement structure, the dynamic modulus of each structural layer in the polyurethane pavement structure at the highest temperature of the road surface in the paving area is obtained by a dynamic modulus test. According to the proposed thickness of the polyurethane mixture layer in the polyurethane pavement structure, based on the elastic layered system theory, the thickness of the polyurethane mixture layer is calculated to be just less than the limit strain threshold. The design thickness of the polyurethane mixture layer is determined.

[0004] Chinese patent CN116334971A discloses a single-component polyurethane drainage, anti-cracking and anti-rutting pavement paving structure and method. A drainage, anti-cracking flexible base layer of a multi-void, large-particle, single-component polyurethane mixture is laid on a cement-stabilized gravel base layer, the lower layer uses an asphalt mixture, the middle surface layer uses a polyurethane mixture to resist rutting, and the upper layer uses an asphalt mastic gravel mixture.

[0005] Chinese patent CN116240768A discloses a paving structure and paving method of a single-component polyurethane noise reduction pavement. The specific pavement structure is that the surface layer is a polyurethane mixture anti-skid wear layer, the lower layer is a polyurethane mixture OGFC noise reduction drainage layer, the lower layer is a large-size asphalt macadam mixture drainage and anti-cracking layer, and the bottom layer is an SBS modified asphalt mixture anti-fatigue layer.

[0006] The above-mentioned pavement applies polyurethane mixture to 2~3 layers of structure with relatively large thickness, such as anti-fatigue layer, base layer and wear layer. The cost of pavement structure materials is still relatively high and is only suitable for special scenarios. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a polyurethane mixture composite pavement structure and a design method thereof, which adopts a single-layer polyurethane mixture load-bearing layer structure and a suitable interlayer treatment scheme to obtain a polyurethane mixture composite pavement structure with low cost and good durability.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions: In the first aspect, a polyurethane mixture composite pavement structure comprises, from the surface layer to the bottom layer: a polyurethane crushed stone concrete wearing layer, a multi-crushed stone polyurethane concrete bearing layer, a bonding layer and an asphalt mixture lower layer; The raw materials for preparing the bonding layer include polyurethane binder and polyurethane concrete with multiple crushed stones; The fatigue limit strain of the multi-gravel polyurethane concrete load-bearing layer is greater than the layer bottom tensile strain in the design load, and the shear strength of the whole composed of the multi-gravel polyurethane concrete load-bearing layer, the bonding layer and the asphalt mixture lower layer is greater than the interlayer shear stress in the design load; The raw materials for preparing the polyurethane crushed stone concrete wearing layer include crushed stone, mineral powder and polyurethane binder in a predetermined set; The raw materials for preparing the multi-crushed stone polyurethane concrete load-bearing layer include crushed stones, mineral powder and polyurethane binder in a predetermined assembly.

[0009] In a second aspect, the design method of the polyurethane mixture composite pavement structure comprises the following steps: S1. Preparing a polyurethane crushed stone concrete wearing layer according to crushed stones of set gradation, and setting the amount of polyurethane in the polyurethane crushed stone concrete wearing layer; S2, preparing a multi-crushed stone polyurethane concrete load-bearing layer according to crushed stones of set gradation, setting the amount of polyurethane in the multi-crushed stone polyurethane concrete load-bearing layer, and detecting its fatigue limit strain; S3, designing a first pavement structure including a multi-crushed stone polyurethane concrete load-bearing layer, an asphalt mixture lower layer and a semi-rigid base layer of different thicknesses from top to bottom, and calculating the bottom tensile strain of the multi-crushed stone polyurethane concrete load-bearing layer in different first pavement structures and the interlayer shear stress of the first pavement structure; S4, preparing a plurality of second pavement structures including a multi-crushed stone polyurethane concrete load-bearing layer, a bonding layer and an asphalt mixture lower layer, and conducting an interlayer inclined shear test to obtain the maximum interlayer shear stress of each of the different second pavement structures; S5. Select the proportion and thickness of the pavement structure in which the bottom tensile strain of the middle layer in S3 is less than the fatigue limit strain in S2, and the maximum interlayer shear stress in S4 is less than the interlayer shear stress in S3, perform structural verification, and obtain the polyurethane mixture composite pavement structure.

[0010] The beneficial effects of the present invention are: The present invention proposes a polyurethane mixture composite pavement structure and a design method thereof. The pavement structure and design method fully consider the material properties and mechanical characteristics of the polyurethane mixture, combine the multi-gravel polyurethane concrete load-bearing layer and the lower layer of the asphalt mixture through an adhesive layer, and reduce the amount of the polyurethane layer while obtaining excellent performance. The operability is strong, the designed pavement structure is reasonable, the cost is low, the durability is good, and the use requirements of different working conditions can be met. In addition, the design method in the present invention focuses on the performance of the multi-gravel polyurethane concrete load-bearing layer and its connecting layer, which can effectively make up for the lack of theory / difficulty in applying existing standards in the design process of the polymer mixture pavement structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0012] Figure 1 It is a structural schematic diagram of the polyurethane mixture composite pavement structure in Example 1 of the present invention.

[0013] Figure 2 It is a verification result diagram obtained by S5 in Example 1 of the present invention, wherein (a) is the verification result of road surface deflection, (b) is the verification result of shear stress between polyurethane mixture and asphalt mixture layers, (c) is the verification result of tensile strain at the bottom of asphalt mixture layer, (d) is the verification result of tensile stress at the bottom of base layer, and (e) is the verification result of vertical compressive strain on the top surface of roadbed.

[0014] In the figure: the distances or sizes between parts are exaggerated to show the positions of various parts, and the schematic diagram is for reference only.

[0015] Among them, 1. Polyurethane crushed stone concrete wearing layer; 2. Multi-crushed stone polyurethane concrete bearing layer; 3. Asphalt mixture lower layer; 4. Semi-rigid base layer; 5. Soil base. DETAILED DESCRIPTION It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0016] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0017] A polyurethane mixture composite pavement structure, comprising from the surface layer to the bottom layer: a polyurethane crushed stone concrete wearing layer, a multi-crushed stone polyurethane concrete bearing layer, a bonding layer and an asphalt mixture lower layer; The bonding layer is prepared from polyurethane binder and multi-gravel polyurethane concrete, which is used to effectively connect the multi-gravel polyurethane concrete load-bearing layer and the asphalt mixture lower layer, resist interlayer shear stress, and use the asphalt mixture lower layer to effectively strengthen the multi-gravel polyurethane concrete load-bearing layer, thereby obtaining a more cost-effective pavement structure, which is suitable for conventional high-grade pavement requirements; The fatigue limit strain of the multi-gravel polyurethane concrete load-bearing layer is greater than the layer bottom tensile strain in the design load, and the shear strength of the whole composed of the multi-gravel polyurethane concrete load-bearing layer, the bonding layer and the asphalt mixture lower layer is greater than the interlayer shear stress in the design load; The raw materials for preparing the polyurethane crushed stone concrete wearing layer include crushed stone, mineral powder and polyurethane binder in a predetermined set; The raw materials for preparing the multi-crushed stone polyurethane concrete load-bearing layer include crushed stones, mineral powder and polyurethane binder in a predetermined assembly.

[0018] Optionally, in the bonding layer, the polyurethane binder is prepared in an amount of 0.3~0.5L / m2 as a polyurethane bonding layer; the multi-gravel polyurethane concrete is prepared in an amount of 3~5kg / m2 as a multi-gravel polyurethane concrete non-stick wheel layer.

[0019] Optionally, the polyurethane binder is a single-component moisture-curing finished polyurethane binder.

[0020] Optionally, the raw materials for preparing the polyurethane crushed stone concrete wearing layer include 0-3 mm crushed stone, 3-5 mm crushed stone, 5-8 mm crushed stone, mineral powder and polyurethane binder in a mass ratio of (15-25): (6-10): (60-70): (4-8): (5-6).

[0021] Optionally, the raw materials for preparing the multi-gravel polyurethane concrete load-bearing layer include 0-3 mm gravel, 3-5 mm gravel, 5-8 mm gravel, mineral powder and polyurethane binder in a mass ratio of (20-35): (20-30): (30-45): (4-8): (5-6), and the multi-gravel polyurethane concrete in the bonding layer is the same as the raw materials for preparing the multi-gravel polyurethane concrete load-bearing layer.

[0022] Optionally, the lower layer of the asphalt mixture adopts a suspended dense structure, wherein the mineral material, mineral material gradation and oil-to-stone ratio comply with the relevant provisions of the Technical Specifications for Highway Asphalt Pavement Construction (JTG F40-2004).

[0023] Optionally, the thickness of the polyurethane crushed stone concrete wearing layer is 1.5-2.5 cm.

[0024] Optionally, the thickness of the multi-gravel polyurethane concrete load-bearing layer is 5 to 15 cm.

[0025] Optionally, the thickness of the lower layer of the asphalt mixture is 5 to 15 cm.

[0026] Optionally, the polyurethane mixture composite pavement structure further includes a semi-rigid base layer located below the lower layer of the asphalt mixture, and the thickness of the semi-rigid base layer is 30 to 60 cm.

[0027] The design method of the polyurethane mixture composite pavement structure comprises the following steps: S1. Preparing a polyurethane crushed stone concrete wearing layer according to crushed stones of set gradation, and setting the amount of polyurethane in the polyurethane crushed stone concrete wearing layer; S2, preparing a multi-crushed stone polyurethane concrete load-bearing layer according to the crushed stone of the set gradation, setting the amount of polyurethane in the multi-crushed stone polyurethane concrete load-bearing layer, and detecting its fatigue limit strain and dynamic modulus; S3, designing a first pavement structure including a multi-crushed stone polyurethane concrete load-bearing layer, an asphalt mixture lower layer and a semi-rigid base layer of different thicknesses from top to bottom, and calculating the bottom tensile strain of the multi-crushed stone polyurethane concrete load-bearing layer in different first pavement structures and the interlayer shear stress of the first pavement structure; S4, preparing a plurality of second pavement structures including a multi-crushed stone polyurethane concrete load-bearing layer, a bonding layer and an asphalt mixture lower layer, and conducting an interlayer inclined shear test to obtain the maximum interlayer shear stress of each of the different second pavement structures; S5. Select the proportion and thickness of the pavement structure in which the bottom tensile strain of the middle layer in S3 is less than the fatigue limit strain in S2, and the maximum interlayer shear stress in S4 is less than the interlayer shear stress in S3, perform structural verification, and obtain the polyurethane mixture composite pavement structure.

[0028] Optionally, in S1, the amount of polyurethane in the polyurethane crushed stone concrete wearing layer is set according to the test results of the Marshall specimen curing time, the flying loss rate, the freeze-thaw splitting strength and the splitting tensile strength.

[0029] Optionally, in S2, the amount of polyurethane in the multi-crushed stone polyurethane concrete load-bearing layer is set according to the test results of Marshall specimen curing time, scattering loss rate, freeze-thaw splitting strength, splitting tensile strength, fatigue limit strain and dynamic modulus; the test result of fatigue limit strain is used to verify the tensile strain of the bottom layer in S5, and the dynamic modulus is used as an input parameter of the pavement structure model in the load response index calculation process in S3.

[0030] Optionally, in S3, based on the "Highway Asphalt Pavement Design Code" (JTG D50-2017) and the mechanical properties of polyurethane crushed stone concrete, indicators such as road surface deflection, layer bottom tensile strain, interlayer shear stress, base layer bottom tensile stress and roadbed top surface vertical compressive strain of the first pavement structure are evaluated as load response indicators of different pavement structures.

[0031] Optionally, in S3, an orthogonal test is used to perform a range analysis to obtain the recommended thickness of each structural layer.

[0032] Optionally, in S4, the variables of different second pavement structures include: the spreading amount of polyurethane binder and the spreading amount of multi-crushed stone polyurethane concrete; and screening the bonding layer component ratio of the optimal layer from the combinations of different spreading amounts.

[0033] Optionally, in S5, the working conditions selected for structure verification include: standard load at normal temperature, overload at normal temperature, standard load at high temperature and overload at high temperature. Under the set working conditions, indicators such as road surface deflection, layer bottom tensile strain, interlayer shear stress, road surface deflection and base layer bottom tensile stress are calculated to verify whether they meet the requirements of "Highway Asphalt Pavement Design Specification" (JTG D50-2017).

[0034] Example 1 A polyurethane mixture composite pavement structure, such as Figure 1 As shown, from the surface layer to the bottom layer, it includes: a polyurethane crushed stone concrete wearing layer 1, a multi-crushed stone polyurethane concrete bearing layer 2, a bonding layer and an asphalt mixture lower layer 3; The bonding layer is located between the multi-gravel polyurethane concrete load-bearing layer 2 and the asphalt mixture lower layer 3, and includes a polyurethane bonding layer in an amount of 0.3-0.5L / m2 and a multi-gravel polyurethane concrete in an amount of 3-5kg / m2; The fatigue limit strain of the multi-gravel polyurethane concrete load-bearing layer 2 is greater than the layer bottom tensile strain in the design load, and the shear strength of the whole composed of the multi-gravel polyurethane concrete load-bearing layer 2, the bonding layer and the asphalt mixture lower layer 3 is greater than the interlayer shear stress in the design load.

[0035] The raw materials for preparing the polyurethane crushed stone concrete wearing layer 1 include 0-3 mm crushed stone, 3-5 mm crushed stone, 5-8 mm crushed stone, mineral powder and polyurethane binder in a mass ratio of 17:8:63.5:6:5.5; The raw materials for preparing the multi-gravel polyurethane concrete load-bearing layer 2 include 0-3 mm gravel, 3-5 mm gravel, 5-8 mm gravel, mineral powder and polyurethane binder in a mass ratio of 18:30:40:7:5; The asphalt mixture lower layer 3 is an AC-20 mixture that complies with the Technical Specifications for Highway Asphalt Pavement Construction (JTG F20-2004).

[0036] The thickness of the polyurethane crushed stone concrete wearing layer 1 is 1.5-2.5 cm.

[0037] The thickness of the multi-gravel polyurethane concrete load-bearing layer 2 is 5-15 cm.

[0038] When preparing the bonding layer, firstly, a polyurethane binder is spread on the surface of the lower layer 3 of the asphalt mixture in a set amount, and then a multi-gravel polyurethane concrete is spread in a set amount (since spreading a small amount of multi-gravel concrete can prevent the paver from sticking to the wheels during paving, it is a non-wheel-stick layer. During construction, the material can be directly taken from the paver and spread, which is more convenient). Then, a multi-gravel polyurethane concrete load-bearing layer 2 is prepared on the upper surface of the multi-gravel polyurethane concrete, so as to obtain a bonding layer that plays the role of connecting the multi-gravel polyurethane concrete load-bearing layer 2 and the lower layer 3 of the asphalt mixture.

[0039] The thickness of the lower layer 3 of the asphalt mixture is 5-15 cm.

[0040] The polyurethane mixture composite pavement structure also includes a semi-rigid base layer 4 located below the asphalt mixture lower layer, the semi-rigid base layer 4 includes a cement-stabilized gravel mixture layer, and the thickness of the semi-rigid base layer 4 is 30-60 cm; below the semi-rigid base layer is a soil base 5.

[0041] The design method of the polyurethane mixture composite pavement structure of this embodiment includes the following steps: S1. Use basalt aggregate with SAC-8 grading, design and verify the mineral grading according to "Design and Construction of SAC Series of Multi-Crushed Stone Asphalt Concrete", use Marshall specimen curing time of 4d, scattering loss rate less than 15%, freeze-thaw splitting strength ratio greater than 85%, splitting tensile strength greater than 3MPa as indicators to determine the amount of polyurethane in the wearing layer of polyurethane crushed stone concrete.

[0042] S2. Use gravel with SAC-20 grading, design and verify the aggregate grading according to the Design and Construction of SAC Series of Gravel Asphalt Concrete, and use the Marshall specimen curing time of 4 days, the scattering loss rate of less than 15%, the freeze-thaw splitting strength ratio of more than 80%, and the splitting tensile strength of more than 2MPa as indicators to determine the amount of polyurethane in the gravel polyurethane concrete bearing layer; and according to the provisions of T0738-2011 and T0739-2011 in the Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering (JTG E20-2011), the four-point bending fatigue test and dynamic modulus test of the gravel polyurethane concrete bearing layer are carried out to obtain its fatigue limit strain value and dynamic modulus value.

[0043] Among them, the fatigue limit strain value is used for verification in S5, and the dynamic modulus value is used as an input parameter of the pavement structure load response model in S3.

[0044] S3. Use L9 (33) orthogonal experimental design table to design the first pavement structure of different thicknesses (the first pavement structure includes: multi-gravel polyurethane concrete bearing layer 2, asphalt mixture lower layer 3 and semi-rigid base layer 4, no bonding layer is required). According to the data in Table 1, use Design Expert software to perform three-factor three-level orthogonal design of semi-rigid base polyurethane mixture pavement.

[0045] Table 1

[0046] The response surface test results obtained by three-dimensional simulation using Abaqus software include: tensile strain at the bottom of asphalt mixture layers (i.e. tensile strain at the bottom of structural layers), shear stress between polyurethane mixture and asphalt mixture layers, road surface deflection, tensile stress at the bottom of base layer and vertical compressive strain on the top surface of roadbed.

[0047] Design-Expert software was used to perform variance analysis and regression model variance analysis on the road surface deflection, shear stress between polyurethane mixture and asphalt mixture layers, tensile strain at the bottom of asphalt mixture layer, tensile stress at the bottom of base layer, and vertical compressive strain on the top of roadbed. The predicted pavement structure includes: the thickness of the multi-gravel polyurethane concrete bearing layer is 5 cm, the thickness of the lower layer of asphalt mixture is 9 cm, and the thickness of cement stabilized gravel base (semi-rigid base) is 40 cm. The calculation indicators obtained by fitting include: road surface deflection is 1.350*10-4m, the shear stress between polyurethane mixture and asphalt mixture is 0.158MPa, the tensile strain at the bottom of asphalt mixture layer is 0.2368, the tensile stress at the bottom of base layer is 0.0372MPa, and the vertical compressive strain on the top of roadbed is 0.409. The design indicators calculated by Abaqus are close to the fitting results, indicating that the thickness value obtained here is appropriate.

[0048] Based on the simulation results and considering the different traffic load requirements, the thickness of the multi-gravel polyurethane concrete load-bearing layer of the polyurethane mixture composite pavement can fluctuate in the range of 4-6cm, the thickness of the asphalt mixture lower layer can fluctuate in the range of 8-11cm, and the thickness of the semi-rigid base layer can fluctuate in the range of 36-44cm.

[0049] Among them, the tensile strain at the bottom of the layer (also known as the tensile strain at the bottom of the structural layer) refers to the tensile force between the multi-gravel polyurethane concrete load-bearing layer 2 and the asphalt mixture layer 3 below. When the tensile strain at the bottom of the structural layer is less than the ultimate strain of the material itself, theoretically the structural layer can withstand countless loads without damage, effectively ensuring the durability of the structure.

[0050] The interlayer shear stress refers to the maximum shear stress between the multi-gravel polyurethane concrete bearing layer 3 and the asphalt mixture lower layer 4. When the maximum interlayer shear stress is less than the shear strength of the composite specimen, shear failure will not occur between the structural layers, effectively ensuring the structural stability.

[0051] Road surface deflection can be used as an indicator to evaluate the deformation resistance and bearing capacity of polyurethane mixture pavement, reflecting the level of overall stiffness of the pavement structure.

[0052] The tensile stress at the bottom of the base layer is used to limit the occurrence of base fatigue and cracking damage.

[0053] The vertical compressive strain on the top surface of the roadbed refers to the degree of deformation of the roadbed surface due to the vertical extrusion when it is subjected to vehicle load or other loads.

[0054] S4. Prepare a variety of second pavement structures including a multi-crushed stone polyurethane concrete load-bearing layer, a bonding layer and an asphalt mixture lower layer, conduct interlayer inclined shear tests, and obtain the maximum interlayer shear stress of different second pavement structures.

[0055] Specifically, it includes: using a 5 cm thick rutting plate test mold (other molds of set shapes can also be used to facilitate molding and testing) to mold the lower layer of the asphalt mixture, and demolding after curing for 2 days to obtain the asphalt mixture rutting plate; loading the asphalt mixture rutting plate into a 10 cm thick composite rutting test mold, and coating the bonding layer material according to the set technical requirements; filling the multi-gravel polyurethane concrete load-bearing layer in S2 on the surface of the bonding layer material, and demolding and cutting after curing for 4 days to obtain a test piece with a size of 6 cm * 6 cm * 10 cm; carrying out an interlayer inclined shear test, and selecting the optimal bonding layer based on the maximum interlayer shear strength; the optimal bonding layer obtained includes: a polyurethane bonding layer with a dosage of 0.4L / m2 and a multi-gravel polyurethane concrete with a dosage of 4kg / m2.

[0056] S5. Select the ratio and thickness of the pavement structure in which the bottom tensile strain of the middle layer in S3 is less than the fatigue limit strain in S2, and the maximum interlayer shear stress in S4 is less than the interlayer shear stress in S3. Then use Abaqus finite element software to perform structural verification under four working conditions: normal temperature standard load, normal temperature overload, high temperature standard load and high temperature overload. Finally, a polyurethane mixture composite pavement structure that meets the conditions is obtained. The four working conditions can reflect various situations in the use of the pavement.

[0057] Among them, normal temperature standard load refers to the road condition of 20℃ and 0.7MPa, normal temperature overload refers to the road condition of 20℃ and 0.9MPa, high temperature standard load refers to the road condition of 50℃ and 0.7MPa; high temperature overload refers to the road condition of 50℃ and 0.9MPa. The verification indicators are the same as those in S3, including: road surface deflection, shear stress between polyurethane mixture and asphalt mixture layers, tensile strain at the bottom of asphalt mixture layer, tensile stress at the bottom of base layer and vertical compressive strain on the top surface of roadbed.

[0058] The specific pavement structure is: polyurethane wearing layer + 6cm multi-gravel polyurethane concrete bearing layer + 9cm asphalt mixture lower layer + 42cm semi-rigid base layer; Figure 2 The calculation results are shown in the figure. In the figure, the x-axis direction represents the longitudinal direction of the road lane, and the distance from the x-axis represents the distance from the longitudinal extension direction of the road model. Figure 2 (a) in the figure is the verification result of road surface deflection. Figure 2 (b) is the calculation result of the shear stress between the polyurethane mixture and the asphalt mixture. Figure 2 (c) in the figure is the verification result of the tensile strain at the bottom of the asphalt mixture layer. Figure 2 (d) in the figure is the verification result of the tensile stress at the bottom of the base layer. Figure 2 (e) in the figure is the verification result of the vertical compressive strain on the top surface of the roadbed. All verification results meet the design requirements, and the design of the polyurethane mixture composite pavement structure is completed.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A polyurethane mixture composite pavement structure, characterized in that: From the surface to the bottom layer, it includes: polyurethane crushed stone concrete wearing layer, multi-crushed stone polyurethane concrete bearing layer, bonding layer and asphalt mixture bottom layer; The raw materials for preparing the bonding layer include polyurethane binder and polyurethane concrete with multiple crushed stones; The fatigue limit strain of the multi-gravel polyurethane concrete load-bearing layer is greater than the layer bottom tensile strain in the design load, and the shear strength of the whole composed of the multi-gravel polyurethane concrete load-bearing layer, the bonding layer and the asphalt mixture lower layer is greater than the interlayer shear stress in the design load; The raw materials for preparing the polyurethane crushed stone concrete wearing layer include crushed stone, mineral powder and polyurethane binder in a predetermined set; The raw materials for preparing the multi-crushed stone polyurethane concrete load-bearing layer include crushed stones, mineral powder and polyurethane binder in a predetermined assembly.

2. The polyurethane mixture composite pavement structure according to claim 1, characterized in that: The raw materials for preparing the polyurethane crushed stone concrete wearing layer include 0-3 mm crushed stone, 3-5 mm crushed stone, 5-8 mm crushed stone, mineral powder and polyurethane binder in a mass ratio of (15-25): (6-10): (60-70): (4-8): (5-6); Optionally, the raw materials for preparing the multi-gravel polyurethane concrete load-bearing layer include 0-3 mm gravel, 3-5 mm gravel, 5-8 mm gravel, mineral powder and polyurethane binder in a mass ratio of (20-35): (20-30): (30-45): (4-8): (5-6), and the multi-gravel polyurethane concrete in the bonding layer is the same as the raw materials for preparing the multi-gravel polyurethane concrete load-bearing layer; Optionally, the lower layer of the asphalt mixture adopts a suspended dense structure.

3. The polyurethane mixture composite pavement structure according to claim 1, characterized in that: The thickness of the polyurethane crushed stone concrete wearing layer is 1.5-2.5 cm; Optionally, the thickness of the multi-gravel polyurethane concrete load-bearing layer is 5 to 15 cm; Optionally, the thickness of the lower layer of the asphalt mixture is 5 to 15 cm; Optionally, in the adhesive layer, the polyurethane binder is 0.3-0.5 L / m 2 The polyurethane adhesive layer is prepared in an amount of 3-5 kg / m 2 The amount of is prepared as a multi-gravel polyurethane concrete non-stick wheel layer; Optionally, the polyurethane mixture composite pavement structure further includes a semi-rigid base layer located below the lower layer of the asphalt mixture; Optionally, the thickness of the semi-rigid base layer is 30 to 60 cm.

4. A method for designing a polyurethane mixture composite pavement structure according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Preparing a polyurethane crushed stone concrete wearing layer according to crushed stones of set gradation, and setting the amount of polyurethane in the polyurethane crushed stone concrete wearing layer; S2, preparing a multi-crushed stone polyurethane concrete load-bearing layer according to crushed stones of set gradation, setting the amount of polyurethane in the multi-crushed stone polyurethane concrete load-bearing layer, and detecting its fatigue limit strain; S3, designing a first pavement structure including a multi-crushed stone polyurethane concrete load-bearing layer, an asphalt mixture lower layer and a semi-rigid base layer of different thicknesses from top to bottom, and calculating the bottom tensile strain of the multi-crushed stone polyurethane concrete load-bearing layer in different first pavement structures and the interlayer shear stress of the first pavement structure; S4, preparing a plurality of second pavement structures including a multi-crushed stone polyurethane concrete load-bearing layer, a bonding layer and an asphalt mixture lower layer, and conducting an interlayer inclined shear test to obtain the maximum interlayer shear stress of each of the different second pavement structures; S5. Select the proportion and thickness of the pavement structure in which the bottom tensile strain of the middle layer in S3 is less than the fatigue limit strain in S2, and the maximum interlayer shear stress in S4 is less than the interlayer shear stress in S3, perform structural verification, and obtain the polyurethane mixture composite pavement structure.

5. The design method of the polyurethane mixture composite pavement structure according to claim 4, characterized in that: In S1, the amount of polyurethane in the wearing layer of polyurethane crushed stone concrete is set according to the test results of the curing time, fly scatter loss rate, freeze-thaw splitting strength and splitting tensile strength of the Marshall specimen.

6. The design method of the polyurethane mixture composite pavement structure according to claim 4, characterized in that: In S2, the amount of polyurethane in the bearing layer of the multi-crushed stone polyurethane concrete was set according to the test results of the curing time, fly scatter loss rate, freeze-thaw splitting strength, splitting tensile strength, fatigue limit strain and dynamic modulus of the Marshall specimens.

7. The design method of the polyurethane mixture composite pavement structure according to claim 4, characterized in that: In S3, the road surface deflection, layer bottom tensile strain, interlayer shear stress, base layer bottom tensile stress and roadbed top surface vertical compressive strain indicators of the first pavement structure are evaluated.

8. The design method of the polyurethane mixture composite pavement structure according to claim 4, characterized in that: In S3, orthogonal test was used to perform range analysis to obtain the recommended thickness of each structural layer.

9. The design method of the polyurethane mixture composite pavement structure according to claim 4, characterized in that: In S4, the variables of different second pavement structures include: the spreading amount of polyurethane binder and the spreading amount of polyurethane concrete with multiple crushed stones; and the bonding layer component ratio of the optimal layer is screened from the combinations of different spreading amounts.

10. The design method of the polyurethane mixture composite pavement structure according to claim 4, characterized in that: In S5, the working conditions selected for structural verification include: normal temperature standard load, normal temperature overload, high temperature standard load, and high temperature overload.

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