CN112376349A - Long-life flexible base asphalt pavement structure - Google Patents
Long-life flexible base asphalt pavement structure Download PDFInfo
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- CN112376349A CN112376349A CN202011327964.9A CN202011327964A CN112376349A CN 112376349 A CN112376349 A CN 112376349A CN 202011327964 A CN202011327964 A CN 202011327964A CN 112376349 A CN112376349 A CN 112376349A
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C7/00—Coherent pavings made in situ
- E01C7/08—Coherent pavings made in situ made of road-metal and binders
- E01C7/32—Coherent pavings made in situ made of road-metal and binders of courses of different kind made in situ
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C3/00—Foundations for pavings
- E01C3/04—Foundations produced by soil stabilisation
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C7/00—Coherent pavings made in situ
- E01C7/08—Coherent pavings made in situ made of road-metal and binders
- E01C7/18—Coherent pavings made in situ made of road-metal and binders of road-metal and bituminous binders
- E01C7/26—Coherent pavings made in situ made of road-metal and binders of road-metal and bituminous binders mixed with other materials, e.g. cement, rubber, leather, fibre
- E01C7/262—Coherent pavings made in situ made of road-metal and binders of road-metal and bituminous binders mixed with other materials, e.g. cement, rubber, leather, fibre with fibrous material, e.g. asbestos; with animal or vegetal admixtures, e.g. leather, cork
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
- C04B2111/0075—Uses not provided for elsewhere in C04B2111/00 for road construction
Abstract
The invention discloses a long-life flexible base asphalt pavement structure, and belongs to the technical field of pavement structures. The pavement structure includes from last to down in proper order: the thickness of the upper surface layer of the asphalt concrete is 3-6 cm; the thickness of the high-modulus and anti-rutting type asphalt concrete middle surface layer is 6-12 cm; the thickness of the high-modulus asphalt concrete lower surface layer is 8-16 cm; the anti-fatigue asphalt concrete layer is 4-6 cm thick; the graded broken stone base layer is 10-16 cm thick; the thickness of the strengthened graded broken stone subbase layer is 12-18 cm; and improving the soil layer of the roadbed. The long-life flexible base asphalt pavement structure solves the inherent reflection crack defect existing in the structure, reduces the consumption of non-renewable resource crushed stone aggregates from the aspects of environment and resources, and overcomes the problems of unclear service life design and service state evaluation of the asphalt pavement.
Description
Technical Field
The invention belongs to the technical field of pavement structures, and particularly relates to a long-life flexible base asphalt pavement structure.
Background
Asphalt pavement is a kind of pavement which is made up by mixing mineral material with asphalt material, and the asphalt binder can raise the ability of paving granules to resist running and damage of natural factors to pavement, and can make the pavement smooth, dustless, impervious and durable, so that it is a high-grade pavement which is most extensively used in road construction.
The semi-rigid base asphalt pavement is the main structural form of the expressway in China at present, and although the semi-rigid base asphalt pavement is widely applied, the semi-rigid base asphalt pavement has the defects that the semi-rigid base asphalt pavement is difficult to overcome: 1. because the inorganic binder stabilizes the dry shrinkage and warm shrinkage behaviors of the base layer, a large amount of cracks are generated in the use process, so that the modulus of the structure is inconsistent with the value in the design process; 2. cracks of the base layer are reflected upwards to the asphalt surface layer, so that a large number of transverse cracks appear; 3. the porosity difference between the asphalt layer and the inorganic binder stable base layer is easy to cause water damage and the like at the bottom of the asphalt layer. Although part of diseases can make the structure continue to serve by a timely maintenance means, when the structure reaches the service life, the structure is damaged in the full depth range, and the economic benefit in the full life cycle is poor.
Disclosure of Invention
In order to solve at least one of the above technical problems, according to an aspect of the present invention, there is provided a long-life flexible base asphalt pavement structure, comprising, in order from top to bottom:
the thickness of the upper surface layer of the asphalt concrete is 3-6 cm;
the thickness of the high-modulus and anti-rutting type asphalt concrete middle surface layer is 6-12 cm;
the thickness of the high-modulus asphalt concrete lower surface layer is 8-16 cm;
the anti-fatigue asphalt concrete layer is 4-6 cm thick;
the graded broken stone base layer is 10-16 cm thick;
the thickness of the strengthened graded broken stone subbase layer is 12-18 cm;
and improving the soil layer of the roadbed.
The flexible base asphalt pavement can overcome diseases such as reflection cracks and the like from the source, when the asphalt layer reaches a certain thickness, the tensile strain of the bottom of the asphalt layer is small enough, so that the asphalt layer is not subjected to fatigue damage and becomes a permanent structure, in addition, the main diseases of the structure only occur on the surface layer, and because the modulus of the flexible base layer is low, the maximum shear stress level of the middle part of the surface layer is smaller than that of the semi-rigid base asphalt pavement structure, the track resistance of the structure is more favorable; in the whole life cycle, only maintenance means such as renovation or overlay addition and the like are needed to repair possible diseases on the surface layer, although the manufacturing cost in the early stage is higher than that of a semi-rigid base asphalt pavement structure, the asphalt layer bottom does not generate fatigue cracks, and the structure is a permanent pavement structure theoretically; in addition, the main materials of the structure of the scheme are only asphalt mixture and graded broken stone, so that the asphalt mixture and the graded broken stone can be recycled to the maximum extent, and the economic benefit in the whole life cycle is good.
Furthermore, in the flexible base asphalt pavement, the base layer is usually made of graded broken stones; the graded broken stone is a discrete aggregate base layer, has certain deformation coordination capacity, and can reduce the influence of the uneven settlement of the roadbed on the surface flatness and the surface layer stress state; graded macadam, however, is a typical non-linear bulk material whose modulus value increases with increasing stress levels; therefore, in the depth range, the modulus of the graded broken stone layer is gradually reduced layer by layer, and the scheme aims at the characteristic that the graded broken stone layer is divided into a graded broken stone base layer and a reinforced graded broken stone subbase layer so as to improve the quality of the graded broken stone.
When the rigidity of the roadbed is insufficient, the generated uneven settlement influences the smoothness of the surface, influences the comfort or safety of driving, and even causes local cracking of the surface; therefore, this embodiment adopts the road bed to improve the soil layer, can rationally control rigidity and the homogeneity of road bed department, has very profitable influence to the holistic bearing capacity of structure, durability etc..
According to the long-life flexible base asphalt pavement structure provided by the embodiment of the invention, optionally, the upper surface layer of the asphalt concrete is a dense-graded asphalt mixture or an asphalt mastic broken stone mixture.
According to the long-life flexible base asphalt pavement structure provided by the embodiment of the invention, optionally, the high-modulus rutting-resistant asphalt concrete middle surface layer is a hard asphalt mixture or a high-modulus modified asphalt mixture.
The high-modulus anti-rutting asphalt concrete middle surface layer formed by matching the dense-graded asphalt mixture or the asphalt mastic macadam mixture with the high-modulus anti-rutting asphalt concrete middle surface layer formed by matching the hard asphalt mixture or the high-modulus modified asphalt mixture can effectively reduce the stress level of the upper surface layer, delay the development of shear fatigue cracks from top to bottom and avoid plastic flow of the surface layer at high temperature.
According to the long-life flexible base asphalt pavement structure disclosed by the embodiment of the invention, optionally, the dynamic stability of the surface layer in the high-modulus and anti-rutting asphalt concrete at 60 ℃ is more than or equal to 10000 times/mm; the dynamic stability at 70 ℃ is more than or equal to 5000 times/mm; the dynamic modulus at 20 ℃ is more than or equal to 12000 MPa.
This scheme has carried out the injecing of lower limit value to high-modulus anti rutting type asphalt concrete middle surface layer dynamic stability and dynamic modulus under the different temperatures, and in this application, well surface course structure is main anti rutting layer, and higher dynamic stability and dynamic modulus promote the influence to overall structure's high temperature stability and are showing.
According to the long-life flexible base layer asphalt pavement structure disclosed by the embodiment of the invention, optionally, the high-modulus asphalt concrete lower surface layer is a high-modulus modified asphalt mixture.
The high-modulus asphalt concrete lower surface layer formed by the high-modulus modified asphalt mixture is matched with the asphalt concrete upper surface layer formed by the dense-graded asphalt mixture or the asphalt mastic stone mixture and the high-modulus anti-rutting asphalt concrete middle surface layer formed by the hard asphalt mixture or the high-modulus modified asphalt mixture, so that the problem of middle surface layer bottom fatigue caused by singly improving the modulus of the middle surface layer or excessively low modulus of the lower surface layer can be effectively prevented, and the matched middle and lower surface layers are sequentially anti-rutting and stress dissipation in the structure.
According to the long-life flexible base layer asphalt pavement structure disclosed by the embodiment of the invention, optionally, the dynamic modulus of the high-modulus asphalt concrete lower surface layer at 20 ℃ is more than or equal to 12000 MPa.
The lower surface layer is the most main stress diffusion layer in the structure of this application, improves the dynamic modulus on this layer, can accelerate the dissipation of stress, can effectively solve the permanent deformation of grading rubble layer, the inhomogeneous settlement scheduling problem of road bed, consequently, this scheme has carried out the injecing of lower limit value to its dynamic modulus.
According to the long-life flexible base asphalt pavement structure provided by the embodiment of the invention, optionally, the anti-fatigue asphalt concrete layer is a dense-graded asphalt mixture or an asphalt mastic broken stone mixture.
The anti-fatigue asphalt concrete layer of the dense-graded asphalt mixture or the asphalt mastic macadam mixture stroke of the scheme is matched with the upper, middle and lower layers of the composition structure, so that the problem that the layer-by-layer fatigue performance is not enough below the layer due to the improvement of the structural modulus can be effectively avoided, the independent anti-fatigue layer of the scheme is arranged at the bottom of the layer, the structure can be effectively guaranteed not to generate fatigue cracks from bottom to top, and the requirement of a long-life pavement is met.
According to the long-life flexible base asphalt pavement structure provided by the embodiment of the invention, the reinforced graded broken stone subbase is optionally composed of the following materials: coarse aggregate, fine aggregate, cement, an additive and a fiber material; the additive is one of a water reducing agent, a crack inhibitor or a shrinkage reducing agent; the fiber material is one of glass fiber, polyester fiber or steel fiber.
In the scheme, the traditional single graded broken stone base structure is improved into a structure matched with the graded broken stone base and the reinforced graded broken stone subbase, so that the problem that the structural modulus is gradually reduced along with the depth due to the stress-dependent constitutive relation of the traditional graded broken stone layer is solved; the advantages of the flexible base layer can be fully exerted by combining the two, and the stability and durability of the long-life pavement are effectively guaranteed.
Further, in the scheme, the reinforced graded broken stone subbase layer is composed of the following materials: 730 parts of coarse aggregate, 260 parts of fine aggregate, 8 parts of cement, 1 part of additive and 1 part of fiber, wherein the using amount of the cement is not more than 1 percent of the total amount of the reinforced graded broken stone subbase, and the cement with low grade and small hydration heat, namely small dry shrinkage, is adopted, the finally formed reinforced graded broken stone subbase can improve the strength of the graded broken stone layer, and is not easy to generate dry shrinkage and temperature shrinkage cracking to cause rapid decay of modulus, and the condition that the modulus of the graded broken stone layer is reduced with depth can be effectively solved.
According to the long-life flexible base asphalt pavement structure provided by the embodiment of the invention, optionally, the dynamic modulus of the reinforced graded broken stone subbase is 800-1200 MPa.
According to the long-life flexible base asphalt pavement structure of the embodiment of the invention, the roadbed modified soil layer is optionally formed by modifying soil in which cement or lime is doped in the roadbed soil layer.
The scheme improves the soil layer at the roadbed, cement or lime is doped into the existing soil layer of the roadbed for improvement, and more specifically, the roadbed improved soil layer is divided into an improved soil roadbed, an improved soil upper embankment and an improved soil lower embankment from top to bottom, wherein the improved soil roadbed is formed by adding 8 mass percent of lime or 6 mass percent of cement into the roadbed soil layer at the improved soil roadbed; the improved soil upper embankment and the improved soil lower embankment are formed by adding 6 mass percent of lime or 4 mass percent of cement into the corresponding roadbed soil layer; through the road bed improvement soil layer of this scheme, guarantee roadbed structure's stability, avoid overall structure because the inhomogeneous deformation of road bed takes place to destroy.
Furthermore, the equivalent resilience modulus of the top surface of the roadbed improved soil layer is more than or equal to 150 MPa.
By limiting the lower limit value of the equivalent modulus of resilience of the top surface of the foundation improvement soil layer, the stress distribution of the whole structure can be improved, and the stability and durability of the structure at the position can be improved.
Compared with the existing semi-rigid asphalt pavement, the long-life flexible base asphalt pavement structure disclosed by the invention solves the inherent reflection crack defect existing in the prior art, reduces the consumption of non-renewable resource crushed stone aggregates from the aspects of environment and resources, and overcomes the problem that the service life design and service state evaluation of the asphalt pavement are not clear.
Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
(1) according to the long-life flexible base asphalt pavement structure, the anti-fatigue layer is introduced, so that the possibility of fatigue cracking at the bottom of the asphalt layer can be further reduced, and the service life of the structure is further ensured;
(2) the long-life flexible base asphalt pavement structure of the invention puts forward the requirements on the modulus of the middle surface layer and the lower surface layer, can improve the anti-rutting performance of the structure, and the middle and lower surface layers with high modulus can further reduce the tensile strain level of the anti-fatigue layer, thereby prolonging the service life of the structure again;
(3) according to the long-life flexible base asphalt pavement structure, the conventional graded broken stone layer is divided into two layers, and the lower layer is treated to a certain degree, on one hand, due to the addition of trace and low-grade cement and the addition of additional materials such as anti-cracking agents, fibers and the like, the strength of the graded broken stone base layer is improved to some extent, and the rapid decay of the modulus is not easy to occur due to drying shrinkage and thermal shrinkage cracking, so that the problem that the modulus of the graded broken stone layer is reduced gradually along with the depth can be solved; on the other hand, due to the improvement of the modulus of the graded broken stone base layer, the stress level of the base layer on the graded broken stone is increased compared with that of a typical structure, and the rigidity of the layer is further improved; in addition, the scheme of matching the graded broken stone base layer with the reinforced graded broken stone subbase layer can further reduce the tensile strain of the asphalt layer base;
(4) the long-life flexible base asphalt pavement structure of the invention puts forward a definite requirement on the treatment of the roadbed, obviously reduces the possibility of rutting of the structural structure, and improves the comfort and safety of driving and the durability of the whole structure.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly described below, and it is apparent that the drawings in the following description only relate to some embodiments of the present invention and are not limiting on the present invention.
FIG. 1 shows a schematic representation of the long life flexible base asphalt pavement structure of the present invention;
FIG. 2 shows a graph comparing the vertical stress of example 1 with that of comparative example 1;
FIG. 3 shows a shear stress comparison of example 1 and comparative example 1;
FIG. 4 shows a graph comparing the vertical stress of example 3 with that of comparative example 2;
FIG. 5 shows a shear stress comparison of example 3 and comparative example 2;
reference numerals:
1. an upper asphalt concrete layer; 2. a high-modulus anti-rutting asphalt concrete middle surface layer; 3. a high modulus asphalt concrete lower surface layer; 4. an anti-fatigue asphalt concrete layer; 5. grading a crushed stone base layer; 6. strengthening the graded broken stone subbase; 7. and improving the soil layer of the roadbed.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention.
Comparative example 1
This comparative example is a structural style of traditional bituminous paving, and its component structure from top to bottom is by: the road surface comprises an upper surface layer, a middle surface layer, a lower surface layer, a graded broken stone base layer, a graded broken stone subbase layer and a roadbed, wherein parameters such as thickness, modulus, Poisson ratio and the like of each layer are shown in the following table:
| material | Thickness/m | modulus/MPa | Poisson ratio |
| SMA-13 | 0.04 | 11000 | 0.25 |
| SUP-20 | 0.08 | 10000 | 0.25 |
| SUP-25 | 0.16 | 11000 | 0.25 |
| Graded broken stone base | 0.12 | 400 | 0.35 |
| Graded broken stone subbase | 0.12 | 300 | 0.35 |
| Road bed | 60 | 0.40 |
The middle and lower surface materials of the comparative example have no special high modulus requirement, no anti-fatigue layer is arranged, the graded broken stone subbase layer is not subjected to strengthening treatment, and the roadbed soil material is not subjected to improvement treatment.
Comparative example 2
This comparative example is another structural style of the conventional asphalt pavement, and the composition structure thereof is composed of, from top to bottom: the road surface comprises an upper surface layer, a middle surface layer, a lower surface layer, a graded broken stone base layer, a graded broken stone subbase layer and a roadbed, wherein parameters such as thickness, modulus, Poisson ratio and the like of each layer are shown in the following table:
| material | Thickness/m | modulus/MPa | Poisson ratio |
| SMA-13 | 0.06 | 11000 | 0.25 |
| SUP-20 | 0.12 | 10000 | 0.25 |
| SUP-25 | 0.16 | 11000 | 0.25 |
| Graded broken stone base | 0.16 | 400 | 0.35 |
| Graded broken stone subbase | 0.18 | 300 | 0.35 |
| Road bed | 60 | 0.40 |
The middle and lower surface materials of the comparative example have no special high modulus requirement, no anti-fatigue layer is arranged, the graded broken stone subbase layer is not subjected to strengthening treatment, and the roadbed soil material is not subjected to improvement treatment.
Example 1
The long-life flexible base asphalt pavement structure of the embodiment is as shown in fig. 1, and comprises the following components:
the asphalt concrete upper surface layer 1 is made of SMA-13;
the high-modulus anti-rutting asphalt concrete middle surface layer 2 is made of SUP-20 materials;
the high modulus asphalt concrete lower surface layer 3 is made of SUP-25 materials;
the anti-fatigue asphalt concrete layer 4 is made of AC-10;
a graded crushed stone base 5;
a reinforced graded crushed stone subbase 6;
and a roadbed-modified soil layer 7 consisting of a modified soil bed containing 6% of cement, a modified soil upper embankment containing 4% of cement, and a modified soil lower embankment containing 4% of cement.
The thickness, modulus, poisson's ratio, etc. of each layer are shown in the following table:
| material | Thickness/m | modulus/MPa | Poisson ratio |
| SMA-13 | 0.04 | 11000 | 0.25 |
| SUP-20 | 0.08 | 12000 | 0.25 |
| SUP-25 | 0.16 | 12000 | 0.25 |
| AC-10 | 0.04 | 10000 | 0.25 |
| GradingMacadam base course | 0.12 | 400 | 0.35 |
| Reinforced graded broken stone base | 0.12 | 1000 | 0.35 |
| 6% cement improved road bed | 1.20 | 250 | 0.40 |
| 4% cement improved embankment on soil (compactness is more than or equal to 94%) | 0.80 | 200 | 0.40 |
| 4% cement improved embankment under soil (compactness is more than or equal to 93%) | 1.20 | 180 | 0.40 |
| Foundation | 60 | 0.40 |
The vertical stress calculated by the theory of elastic lamellar system is shown in figure 2. It can be seen that the vertical stress of the base layer in the example 1 is slightly increased compared with that in the comparative example 1, so that the total stress of the graded broken stone base layer 5 is increased, the modulus of the base layer is further improved, and the base layer is very beneficial to the whole structure; in addition, although the compressive stress of the top surface of the roadbed in example 1 is greater than that of comparative example 1, the compressive strain level is very low, only 56.34 mu epsilon, due to the increased roadbed strength, while the compressive strain of the top surface of the roadbed in comparative example 1 is 148 mu epsilon.
The shear stress calculated by the theory of the elastic lamellar system is shown in figure 3. It can be seen that, in example 1, the base layer modulus is higher, and the shear stress level near the middle surface layer is higher than that in comparative example 1, but because this example adopts the middle and lower surface layer material with high modulus and rutting resistance, the rutting resistance of the structure is greatly improved to be enough to cope with the stress change, and in addition, compared with comparative example 1, the shear stress level of the asphalt surface layer bottom in example 1 is lower, so that the shear fatigue of the surface layer bottom can be effectively prevented.
The maximum values of the tensile stress of the asphalt layer under the action of the 100kN standard axis in the example 1 and the comparative example 1 are 29.88 mu epsilon and 47.35 mu epsilon respectively according to the theory calculation of the elastic layer system. According to the calculation method in the current Chinese standard road asphalt pavement design Standard (JTG D50-2017), the times of the allowable action of the asphalt layer bottom are 4.882 multiplied by 10 respectively7Sub and 2.263X 107Second, example 1 shows at least a 2-fold increase in life over the comparative example.
Example 2
The long-life flexible base asphalt pavement structure of the embodiment is as shown in fig. 1, and comprises the following components:
the asphalt concrete upper surface layer 1 is made of SMA-13;
the high-modulus anti-rutting asphalt concrete middle surface layer 2 is made of SUP-20 materials;
the high modulus asphalt concrete lower surface layer 3 is made of SUP-25 materials;
the anti-fatigue asphalt concrete layer 4 is made of AC-10;
a graded crushed stone base 5;
a reinforced graded crushed stone subbase 6;
and a roadbed-modified soil layer 7 consisting of a modified soil bed containing 6% of cement, a modified soil upper embankment containing 4% of cement, and a modified soil lower embankment containing 4% of cement.
The thickness, modulus, poisson's ratio, etc. of each layer are shown in the following table:
| material | Thickness/m | modulus/MPa | Poisson ratio |
| SMA-13 | 0.03 | 11000 | 0.25 |
| SUP-20 | 0.06 | 12000 | 0.25 |
| SUP-25 | 0.08 | 12000 | 0.25 |
| AC-10 | 0.04 | 10000 | 0.25 |
| Graded broken stone base | 0.10 | 400 | 0.35 |
| Reinforced graded broken stone base | 0.12 | 800 | 0.35 |
| 6% cement improved road bed | 1.20 | 250 | 0.40 |
| 4% cement improved embankment on soil (compactness is more than or equal to 94%) | 0.80 | 200 | 0.40 |
| 4% cement improved embankment under soil (compactness is more than or equal to 93%) | 1.20 | 180 | 0.40 |
| Foundation | 60 | 0.40 |
Through the theoretical calculation of an elastic layered system, the tensile strain at the bottom of the fatigue control layer in the embodiment 2 is 55 mu epsilon, the condition that the tensile strain is less than 65 mu epsilon in the permanent pavement concept is met, and the condition that the tensile strain meets the standard of the long-service-life pavement can be preliminarily judged.
According to a calculation method in the current specification of the design of the asphalt pavement of the highway (JTG D50-2017) in China, the fatigue strain of the bottom of the asphalt layer is taken as the basisThe number of fatigues for which the permissible action is 1.305X 10 can be obtained7And secondly, the standard of light traffic under the conventional condition is met.
Based on a formula for calculating the permanent deformation of the asphalt layer according to the specification, the calculated permanent deformation of the asphalt layer is 15.13mm, and the standard of the current specification in China is met.
Example 3
The flexible basic unit bituminous paving structure of long-life of this embodiment constitutes as follows:
the asphalt concrete upper surface layer 1 is made of SMA-13;
the high-modulus anti-rutting asphalt concrete middle surface layer 2 is made of SUP-20 materials;
the high modulus asphalt concrete lower surface layer 3 is made of SUP-25 materials;
the anti-fatigue asphalt concrete layer 4 is made of AC-10;
a graded crushed stone base 5;
a reinforced graded crushed stone subbase 6;
and a roadbed-modified soil layer 7 consisting of a modified soil bed containing 6% of cement, a modified soil upper embankment containing 4% of cement, and a modified soil lower embankment containing 4% of cement.
The thickness, modulus, poisson's ratio, etc. of each layer are shown in the following table:
| material | Thickness/m | modulus/MPa | Poisson ratio |
| SMA-13 | 0.06 | 11000 | 0.25 |
| SUP-20 | 0.12 | 12000 | 0.25 |
| SUP-25 | 0.16 | 12000 | 0.25 |
| AC-10 | 0.06 | 10000 | 0.25 |
| Graded broken stone base | 0.16 | 400 | 0.35 |
| Reinforced graded broken stone base | 0.18 | 1200 | 0.35 |
| 6% cement improved road bed | 1.20 | 250 | 0.40 |
| 4% cement improved embankment on soil (compactness is more than or equal to 94%) | 0.80 | 200 | 0.40 |
| 4% cement improved embankment under soil (compactness is more than or equal to 93%) | 1.20 | 180 | 0.40 |
| Foundation | 60 | 0.40 |
Through theoretical calculation of an elastic layered system, the maximum values of the tensile stress of the bottom of the asphalt layer under the action of a 100kN standard shaft in example 3 and comparative example 2 are 20.63 mu epsilon and 31.68 mu epsilon respectively, and the times of the allowable action of the bottom of the asphalt layer are 2.361 multiplied by 10 respectively according to the calculation method in the existing Chinese standard road asphalt pavement design specification (JTG D50-2017)8Sub and 4.270X 107Second, it can be seen that both meet the requirements of extra heavy traffic, but example 3 has at least a 5-fold improvement in life over comparative example 2; if comparative example 2 can meet the design life requirement of 15 years after specific surface maintenance, the structure of example 3 will theoretically have a life of more than 100 years, which is a structure with considerable economic benefits.
The permanent deformation of the asphalt layer was calculated according to the calculation method in the current specification of the design of road asphalt pavement (JTG D50-2017) in our country, and the permanent deformation of example 3 was 10.89mm, while the permanent deformation of the comparative example was 13.77mm, both of which met the standards of the current specification.
The vertical stress calculated by the theory of elastic lamellar system is shown in figure 4. It can be seen that the vertical stress of the base layer in the example 3 is slightly increased compared with that in the comparative example 2, so that the full stress of the graded broken stone base layer 5 is increased, the modulus of the base layer is further improved, and the base layer is very beneficial to the whole structure; in addition, although the compressive stress of the top surface of the roadbed in example 3 is greater than that of the comparative example, the compressive strain level is low, only 37 mu epsilon, due to the increased roadbed strength, while the compressive strain of the top surface of the roadbed in comparative example 2 is 103 mu epsilon. Therefore, in theory, the problem of uneven settlement of the roadbed caused by the load action is almost impossible in the embodiment 3.
The shear stress calculated by the theory of the elastic lamellar system is shown in figure 5. It can be seen that example 3 has higher shear stress level near the middle layer than comparative example 2 due to higher modulus of the base layer, but the rutting resistance of the structure is greatly improved to cope with the stress change due to the high modulus of the middle and lower surface layer materials adopted in example 3. In addition, compared with comparative example 2, the reduction amount of the shear stress level of the asphalt surface layer bottom in example 3 is considerable, the shear fatigue of the surface layer bottom can be effectively prevented, and the fatigue crack of the lower part of the structure is further prevented.
The examples described herein are merely illustrative of the preferred embodiments of the present invention and do not limit the spirit and scope of the present invention, and various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the design concept of the present invention shall fall within the protection scope of the present invention.
Claims (10)
1. The utility model provides a flexible basic unit bituminous pavement structure of long-life, its characterized in that, the pavement structure includes from last to down in proper order:
the thickness of the upper surface layer of the asphalt concrete is 3-6 cm;
the thickness of the high-modulus and anti-rutting type asphalt concrete middle surface layer is 6-12 cm;
the thickness of the high-modulus asphalt concrete lower surface layer is 8-16 cm;
the anti-fatigue asphalt concrete layer is 4-6 cm thick;
the graded broken stone base layer is 10-16 cm thick;
the thickness of the strengthened graded broken stone subbase layer is 12-18 cm;
and improving the soil layer of the roadbed.
2. The long life flexible base asphalt pavement structure of claim 1, wherein: the upper surface layer of the asphalt concrete is dense-graded asphalt mixture or asphalt mastic broken stone mixture.
3. The long life flexible base asphalt pavement structure of claim 1, wherein: the surface layer of the high-modulus anti-rutting asphalt concrete is a hard asphalt mixture or a high-modulus modified asphalt mixture.
4. A long life flexible base asphalt pavement structure as set forth in claim 3, wherein: the dynamic stability of the high-modulus anti-rutting asphalt concrete middle surface layer at 60 ℃ is more than or equal to 10000 times/mm; the dynamic stability at 70 ℃ is more than or equal to 5000 times/mm; the dynamic modulus at 20 ℃ is more than or equal to 12000 MPa.
5. The long life flexible base asphalt pavement structure of claim 1, wherein: the high-modulus asphalt concrete lower surface layer is a high-modulus modified asphalt mixture.
6. The long life flexible base asphalt pavement structure of claim 5, wherein: the dynamic modulus of the high-modulus asphalt concrete lower surface layer at 20 ℃ is more than or equal to 12000 MPa.
7. The long life flexible base asphalt pavement structure of claim 1, wherein: the anti-fatigue asphalt concrete layer is a dense-graded asphalt mixture or an asphalt mastic broken stone mixture.
8. The long life flexible base asphalt pavement structure of claim 1 wherein said graded stone sub-base is comprised of: coarse aggregate, fine aggregate, cement, an additive and a fiber material; the additive is one of a water reducing agent, a crack inhibitor or a shrinkage reducing agent; the fiber material is one of glass fiber, polyester fiber or steel fiber.
9. The long life flexible base asphalt pavement structure of claim 1, wherein: the dynamic modulus of the reinforced graded broken stone subbase layer is 800-1200 MPa.
10. The long life flexible base asphalt pavement structure of claim 1, wherein: the roadbed modified soil layer is formed by modified soil mixed with cement or lime in a roadbed soil layer.
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