CN112668075A - Mechanical response analysis method for permeable pavement structure under vehicle load effect - Google Patents
Mechanical response analysis method for permeable pavement structure under vehicle load effect Download PDFInfo
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Abstract
The invention relates to a mechanical response analysis method for a permeable pavement structure under the action of vehicle load. The mechanical response analysis method of the permeable pavement structure under the action of the vehicle load comprises the following steps: establishing a three-dimensional finite element pavement model of a permeable cement pavement structure; analyzing different positions of the pavement model to determine a critical load position; determining the contact state between layers by adjusting the friction coefficient between the interfaces of the pavement models; carrying out finite element analysis on a three-dimensional finite element pavement model of the pavement structure to obtain the influence of the parameter change of the pavement structure layer on the mechanics of the pavement structure; and (3) calculating by adopting parameter combinations in the uniform design table to obtain load stress, and performing regression analysis by utilizing regression software according to the calculation result to obtain a calculation formula of the driving load fatigue stress generated by the pervious cement concrete layer at the critical load position. The invention provides reference for the design of the sponge urban permeable pavement structure.
Description
Technical Field
The invention belongs to the technical field of pavement pavements, and particularly relates to a mechanical response analysis method for a permeable pavement structure under the action of vehicle load.
Background
The concept of "sponge city" was first proposed in "2012 low carbon city and regional development science and technology forum". The sponge city means that the city can rapidly permeate into the ground when raining like a sponge, can release the water stored in rainy seasons when dry, and solves the urban problem through city self-regulation.
The construction of a sponge city can not be separated from a sponge body. The urban land features conforming to the characteristics of the sponge body comprise water systems such as rivers, lakes and the like, and urban supporting facilities such as green belts, gardens, permeable ground and the like. Rainwater falls onto the sponge body and can quickly seep to the ground, and the natural ground surface has the functions of storing, purifying and recycling the rainwater, so that various urban diseases are reduced. The permeable road pavement is an important measure in sponge city construction, and covers urban roads, urban green land and square roads, residential road, urban road and other urban roads at all levels. Due to the particularity of the permeable pavement structure, the characteristics of the structure and the material of the permeable pavement structure are greatly different from those of the original road pavement. In the process of research on water permeable pavement, the state issues technical specifications of water permeable brick pavement, water permeable asphalt pavement, water permeable cement concrete pavement and the like in succession, and can guide the construction of water permeable pavement of urban roads to a certain extent.
In recent years, pervious cement concrete pavements have received increasing national attention, and some concrete technical meetings, partial building projects or construction projects decide to use porous cement concrete. Sponge urban road permeable pavement should satisfy the intensity requirement that the road required of driving at first, and secondly should satisfy can effective water permeability requirement. The strength is directly related to the bearing capacity of the road surface, which formally limits the use of various pervious concrete materials on various grades of roads and main roads of cities. Therefore, strength is a key factor and index for the mix design of pavement materials. In engineering practice construction, the strength requirements of the permeable paving materials are different due to different traffic grades and load grades of the paving road sections. The strength of the permeable paving material is lower than that of the common paving material, so that the strength characteristics and the strength capability of various paving structures are determined by establishing model analysis.
Disclosure of Invention
In order to achieve the purpose, the invention provides a mechanical response analysis method of a permeable pavement structure under the action of vehicle load.
The invention discloses a mechanical response analysis method of a permeable pavement structure under the action of vehicle load, which adopts the technical scheme that:
the mechanical response analysis method of the permeable pavement structure under the action of vehicle load comprises the following steps:
establishing a three-dimensional finite element pavement model of a permeable cement pavement structure;
analyzing different positions of the pavement model to determine a critical load position;
determining the contact state between layers by adjusting the friction coefficient between the interfaces of the pavement models;
carrying out finite element analysis on a three-dimensional finite element pavement model of the pavement structure to obtain the influence of the parameter change of the pavement structure layer on the mechanics of the pavement structure;
calculating by adopting parameter combinations in a uniform design table to obtain load stress, and performing regression analysis by utilizing regression software according to a calculation result to obtain a calculation formula of the driving load fatigue stress generated by the pervious cement concrete layer at a critical load position:
wherein: sigmapDriving load fatigue stress (MPa) generated by a surface layer drainage type and a base layer drainage type permeable cement concrete pavement structure layer at a critical load position; sigmap' -full-penetration type permeable cement concrete pavement structure layer critical loadFatigue stress (MPa) of the running load generated at the position; p-axle load (kN); h isp-pervious cement concrete layer thickness (cm); ep-pervious cement concrete layer modulus (MPa); h isc-cement concrete layer thickness (cm); h isj-base layer thickness (cm); ej-base modulus (MPa); e0-modulus of the ground (MPa).
As a further improvement of the technical scheme, a pavement model is established by adopting an elastic layered system theory, and the pavement model is subjected to convergence analysis to determine the size of the pavement model.
As a further improvement of the technical scheme, the middle part, the corners, the middle parts of the longitudinal edges and the middle parts of the transverse edges of the pavement model are analyzed, and the middle parts of the longitudinal edges are determined to be critical load positions.
As a further improvement to the technical scheme, for the surface layer drainage type and base layer drainage type permeable cement concrete pavement structure layers, the changes of road sign deflection, the tensile stress of the bottom surface of the upper layer, the tensile stress of the bottom surface of the lower layer, the tensile stress of the bottom surface of the base layer and the compressive strain of the top surface of the pavement are obtained by changing the thickness of the upper layer, the modulus of the upper layer, the thickness of the lower layer, the thickness of the base layer, the modulus of the base layer and the modulus of the foundation by using a finite element pavement model.
As a further improvement to the technical scheme, for the fully permeable type permeable cement concrete pavement structure layer, the maximum tensile stress of the permeable cement concrete bottom, the deflection of the road surface, the tensile stress of the base bottom and the compressive strain of the road top are obtained by changing the thickness of the permeable cement concrete pavement layer, the modulus of the permeable cement concrete pavement layer, the thickness of the base layer, the modulus of the base layer and the modulus of the foundation by using the finite element pavement model.
The invention provides a mechanical response analysis method for a permeable pavement structure under the action of vehicle load, which has the following beneficial effects compared with the prior art:
according to the mechanical response analysis method for the permeable pavement structure under the action of the vehicle load, a reasonable calculation model is selected, a reasonable finite element model geometric dimension is selected, an unfavorable position is determined, a load is applied, and the most unfavorable interlayer contact condition is determined. By analyzing the finite element model of the pavement structure and applying regression software to carry out regression, a calculation formula of the parameters of the permeable cement pavement structure layer for the mechanical response of the pavement structure and the driving load fatigue stress generated by the permeable cement concrete layer at the critical load position is obtained. At present, domestic research on water permeability cement pavements is basically carried out on water permeable materials, and a real system for researching a water permeability cement pavement structure is unavailable. Compared with the prior art, the method has the advantages that the three-dimensional finite element model of the pavement structure is established, the parameters of the permeable cement pavement structure layer are analyzed through the finite element model to realize the mechanical response of the permeable cement pavement structure layer to the pavement structure, the regression is carried out on the result through the application of regression software, the calculation formula of the driving load fatigue stress generated by the permeable cement concrete layer at the critical load position is obtained, and the reference is provided for the design of the permeable pavement structure of the sponge city.
Drawings
FIG. 1 is a flow chart of a method for analyzing the mechanical response of a permeable pavement structure under the action of vehicle load according to the present invention;
FIG. 2 is a graphical representation of the mechanical response of the permeable pavement structure under vehicle loading for analysis of the pavement structure elastomer;
FIG. 3 is a finite element pavement model and a grid division diagram in the mechanical response analysis method of the permeable pavement structure under the vehicle load;
FIG. 4 is a graph showing the influence of the modulus of the upper layer on the road surface index in the mechanical response analysis method of the permeable pavement structure under the vehicle load;
FIG. 5 is a graph showing the influence of the upper layer thickness on the pavement index in the method for analyzing the mechanical response of the permeable pavement structure under the action of vehicle load according to the present invention;
FIG. 6 is a graph showing the influence of the thickness of the lower layer on the road surface index in the mechanical response analysis method of the permeable pavement structure under the vehicle load;
FIG. 7 is a graph illustrating the influence of the base layer thickness on the pavement index in the mechanical response analysis method of the permeable pavement structure under the vehicle load;
FIG. 8 is a graph illustrating the effect of the base modulus on the pavement index in the mechanical response analysis method of the permeable pavement structure under the vehicle load;
FIG. 9 is a graph showing the effect of the modulus of the foundation on the road surface index in the mechanical response analysis method of the permeable pavement structure under the vehicle load;
FIG. 10 is a graph showing the influence of the thickness of the surface layer on the road surface index in the mechanical response analysis method of the permeable pavement structure under the vehicle load;
FIG. 11 is a graph showing the effect of surface layer modulus on pavement index in the mechanical response analysis method of the water permeable pavement structure under vehicle load;
FIG. 12 is a graph illustrating the effect of the base modulus on the pavement index in the mechanical response analysis method of the permeable pavement structure under the vehicle load;
FIG. 13 is a graph illustrating the effect of the base layer thickness on the pavement index in the mechanical response analysis method of the water permeable pavement structure under the vehicle load;
FIG. 14 is a graph showing the effect of the modulus of the foundation on the road surface index in the mechanical response analysis method of the permeable pavement structure under the vehicle load;
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
According to the specific embodiment of the mechanical response analysis method of the permeable pavement structure under the action of the vehicle load, the finite element numerical calculation method is used as a powerful tool for mechanical analysis of the pavement structure, so that complex analytic derivation can be avoided, various linearity and nonlinearity of a road material can be simulated, any wheel load mode can be applied more easily, and the finite element method is applied more and more widely. Most of internationally known finite element software such as ANSYS, MCS, PATRAN and the like has good experience, convenient use and comprehensive functions, and has important application value in the wide fields of engineering checking calculation, simulation and the like under the support of strong hardware conditions. Therefore, a finite element ANSYS is adopted to establish a model to simulate the stress conditions of different road surface structures.
In this example, the theory of elastic layer system is used. The elastic layered system theory adopts a layered foundation model according to the structural level and the material property under the surface layer, and compared with the elastic foundation theory, the elastic layered system theory can simulate the real situation of the pavement structure more truly, and can reduce errors generated in the calculation process. The elastic layered system consists of several elastic layers, each of which has certain thickness and the lowest layer is elastic semi-spatial body. The structural layers of different thickness and material make up the pavement structure composite elastomer, as shown in fig. 2.
The theory of elastic lamellar systems assumes the following assumptions:
(1) each structural layer is continuous, completely elastic, homogeneous and isotropic, and displacement and deformation are small;
(2) the bottommost layer is infinite in the horizontal direction and the vertical direction, the thickness of each structural layer on the bottommost layer is finite, and the bottommost layer is infinite in the horizontal direction;
(3) stress, deformation and displacement of each structural layer are zero at an infinite distance in the horizontal direction and at an infinite depth of the bottommost layer;
(4) the interlayer contact condition is that the stress and the displacement are continuous, or only the vertical stress and the displacement between the layers are continuous without frictional resistance;
(5) the dead weight is not counted.
1. Establishment of finite element model
The method comprises the steps of modeling by adopting a typical structure of a surface drainage type pervious cement concrete pavement additionally paved with a pervious asphalt functional layer, determining the size of the model by carrying out convergence analysis on the model, simulating the pervious cement concrete pavement by adopting a cuboid structure with the length and the width of 6m multiplied by 5.4m respectively, and taking the depth of a foundation to be 7m, wherein the x axis, the z axis and the y axis are respectively the driving direction, the transverse direction and the depth direction. The arrangement of each structural layer of the surface drainage type permeable cement concrete pavement is shown in table 1. The finite element model and meshing are shown in FIG. 3.
TABLE 1 road finite element model Structure and parameters
| Sequence of layers | Horizon | Material | Thickness/cm | modulus/MPa | Poisson ratio mu |
| 1 | Functional layer | Permeable asphalt mixture | 4 | 800 | 0.25 |
| 2 | Surface layer | Pervious cement |
30 | 27000 | 0.15 |
| 3 | Base layer | |
30 | 1800 | 0.2 |
| 4 | Soil foundation | Soil for soil | 700 | 40 | 0.35 |
In order to analyze the adverse condition of the stress of the road surface, the condition that the road surface is damaged under the action of vehicle load is simulated, and the indexes determined and analyzed and investigated are deflection, layer bottom bending tensile stress, roadbed top surface compression strain, shearing stress and the like.
(ii) deflection
The road surface deflection is the vertical deformation generated on the road surface under the action of load, and is the most intuitive and simplest index for reflecting the whole bearing capacity of the road surface and the condition of use. The deformation is the accumulated result of the deformation of each structural layer and soil foundation of the pavement, so that the deformation reflects the mechanical properties of all the structural layers and the soil foundation of the pavement to a certain extent. And the data show that the maximum value of the road surface settlement occurs at the wheel load center under the action of the vehicle load, and the maximum value is not greatly different from the road surface deflection and has consistent variation trend.
Bottom bending tensile stress of layer II
According to the maximum tensile stress theory (first strength theory) in material mechanics, whatever the stress state the material is in, as long as brittle fracture occurs, the common reason for this is that the maximum tensile stress in the cell body reaches the maximum tensile stress at which the material breaks in single-row tension, i.e., the strength limit. The cement concrete slab has larger rigidity, and under the load action, the slab bottom is under tensile stress, and simultaneously the asphalt layer and the semi-rigid base layer are made of materials with better compression resistance and weak tensile stress, so that the asphalt layer bottom tensile stress, the base layer bottom tensile stress and the concrete layer bottom tensile stress under the action of the single-shaft double-wheel set are adopted as calculation indexes.
Thirdly, the pressure strain of the top surface of the roadbed
The lowest layer of the pavement structure is a soil foundation which bears the vehicle load transferred by the surface layer and the gravity of the upper structure. If the roadbed strength is insufficient or a defect occurs, the roadbed strength is reflected on the pavement, and uneven settlement, structural rutting and the like occur. The foreign road asphalt pavement design method mostly adopts the compressive strain of the top surface of the roadbed as an important index for pavement design, and can reflect the integral strength and pavement performance of the soil foundation. The soil foundation is taken as an elastic half-space foundation model, the modulus of resilience E is taken as a rigidity index of the soil foundation, but no corresponding deformation index exists, and the research inspects the compressive strain of the top surface of the roadbed so as to ensure the strength of the soil foundation.
Shear stress
When the internal force of the pavement is larger than the allowable unidirectional tensile yield limit of the material, the pavement can be subjected to shear failure. According to the maximum shear stress theory (third strength theory) in material mechanics, the maximum shear stress is the main factor causing the material to yield. That is, the material will yield no matter what stress state the material is in, as long as the maximum shear stress reaches that of the uniaxial tension. Under the repeated action of loads of vehicles and natural factors, the asphalt surface layer generates larger shear stress near wheels, and when the generated shear stress exceeds a yield limit, the mixture moves along a shear plane, and finally the pavement structure is damaged.
2. Determining model dimensions
In order to ensure that the division of the grids is more convenient while the calculation accuracy can be ensured by considering the size of the model, the structure of the permeable asphalt pavement is simulated by adopting a cuboid structure with the length and the width of 6m multiplied by 6m respectively through carrying out convergence analysis on the model, the depth of the foundation is 6m, and the x axis, the z axis and the y axis are respectively in the driving direction, the transverse direction and the depth direction. The geometric model generated by using ANSYS software, as shown in fig. 2, is calculated by enlarging the ground.
3. Vehicle load loading and boundary conditions
The double-circle uniform load is simplified into a rectangular uniform load, the side length is 20 multiplied by 20cm, the grounding pressure is 0.625MPa, and the axial load distance is 18 cm. The direction of the vehicle is the x direction, the y direction is the transverse direction of the road surface, and the z direction is the depth direction of the road subgrade. The boundary conditions are as follows: the displacement of the foundation in the horizontal direction is restrained respectively around the foundation, and the pavement slab is not restrained around the foundation.
In order to ensure the bearing capacity of the pavement, different positions of the plate body are analyzed, and the typical positions of the pervious cement concrete are the plate middle part, the plate corners, the longitudinal edge middle part and the transverse edge middle part respectively, so that the positions with unfavorable stress are determined. The load adopts BZZ-100 standard axle load, and the road surface structure parameters are shown in Table 2.
TABLE 2 results for different positions of the standard load application plate
And for the tensile stress of the bottom of the permeable cement concrete layer, determining the central part of the longitudinal edge as the most unfavorable loading position, namely the critical loading position.
Simulating the contact state between layers by adjusting the friction coefficient between the interfaces, completely continuing the layers and coupling all degrees of freedom of nodes on the interfaces; for complete smoothness between layers, only the vertical degrees of freedom of the nodes on the interface are coupled. The results of the stress analysis of the different interlaminar states are shown in Table 3.
TABLE 3 stress analysis results of different interlaminar states
The results of the calculation are compared and analyzed in table 3, and it is found that the flexural tensile stress, the maximum shear stress and the tensile stress of the pervious cement concrete layer of the pervious asphalt mixture layer of the road surface in the smooth state are all increased significantly. Therefore, the interlayer contact conditions of the structures of the pervious cement concrete pavement and the pervious asphalt pavement are determined to be an absolute smooth state and an interlayer continuous state respectively.
Influence of surface layer drainage type and base layer drainage type permeable cement concrete pavement structure layer parameters on pavement structure mechanical response
The surface drainage type permeable cement concrete pavement is suitable for various light load new construction and reconstruction of urban roads. According to relevant contents and requirements in the research data and technical regulations of the pervious cement concrete pavement, the finite element structure and parameters of the surface drainage type pervious cement concrete pavement are recommended, and are shown in the table 4.
In order to prevent the surface aggregate of the surface drainage type permeable cement concrete pavement from peeling off, a permeable asphalt mixture thin layer is laid on the pavement surface to serve as a functional layer, so that the phenomenon of ash falling or particle peeling off of the permeable cement concrete pavement can be effectively prevented. The section mainly analyzes the influence of seven index changes of the surface drainage type permeable cement concrete pavement axle weight, the permeable cement concrete surface layer thickness, the permeable cement concrete base layer modulus, the cement concrete layer thickness, the base layer modulus and the foundation modulus on different factors such as the cement concrete layer bottom tensile stress, the permeable cement concrete layer bottom maximum tensile stress, the road surface deflection, the roadbed top surface compressive strain, the base layer bottom surface tensile stress and the like.
The surface drainage type pervious cement concrete pavement finite element structure (the thickness can be changed according to the specific bearing requirement and drainage requirement) and parameters are recommended, as shown in table 4:
TABLE 4 finite element structure and parameters of surface-layer drainage type pervious cement concrete pavement
| Sequence of layers | Horizon | Material | Thickness of | modulus/MPa | Poisson ratio mu |
| 1 | Upper surface layer | Pervious cement concrete class A | /10 | 27000 | 0.15 |
| 2 | Lower surface layer | Cement concrete | 15 | 30000 | 0.15 |
| 3 | Base layer | |
30 | 1800 | 0.2 |
| 4 | Soil foundation | Soil for soil | 700 | 40 | 0.35 |
And analyzing the influence of the six index changes of the road surface structure layer parameters on the mechanical response of the road surface structure. The mechanical response indexes of the pavement structure are increased along with the increase of the axle load, and the change trend along with other parameter indexes is shown in the following graph. The abscissa represents the parameters of each layer, and the ordinate represents the percentage of a certain index quantity under the corresponding parameter to the maximum value of the index quantity. The analysis results are shown in fig. 4 to 9.
As can be seen from fig. 4 to 9, the thickness and modulus of the upper layer of the surface-layer drainage type permeable cement concrete pavement have a weak influence on each index, while the thickness of the lower layer of the cement concrete pavement has the greatest influence on each index, i.e., the thickness of the lower layer has an important influence on the fatigue fracture of the pavement; the increase of the base layer thickness has a relatively obvious effect on the reduction of each index, along with the increase of the base layer thickness, the tensile stress of the bottom surface of the base layer tends to be stable, the increase of the base layer modulus has an unobvious effect on the reduction of each index, and the influence on the base layer is very adverse, so that the base layer modulus is not suitable to be too high. Comprehensively considering, the thickness of the upper layer of the pervious cement concrete is more than 10cm, and the specific thickness is selected according to the drainage requirement. The thickness value of the lower surface layer of the cement concrete is more than 12cm, the thickness value of the base layer is more than 32cm, and the economic efficiency and the application are comprehensively considered. The influence on each index is weaker after the modulus of the foundation exceeds 50 MPa.
The basic water storage and drainage type permeable cement concrete pavement is composed of permeable cement concrete A types, permeable cement concrete B types and framework gap type inorganic binder stabilization types, and is basically the same as the surface drainage type permeable cement concrete pavement in structure, except that the structural layer moduli of the permeable cement concrete pavement are different, and the structural layer material pairs are shown in table 5.
TABLE 5 comparison of the parameters of the surface layer drainage type and the base layer drainage type pervious cement concrete pavement material
As can be seen from the analysis results of fig. 4 to 9, the influence of the variation of the modulus of the permeable cement concrete layer and the modulus of the base layer on each index of the road surface is small, so that the base layer water storage and drainage type permeable cement concrete road surface can refer to the analysis result of the surface layer drainage type permeable cement concrete road surface, and the analysis is not performed independently.
Influence of structural layer parameters of fully-permeable water-permeable cement concrete pavement on mechanical response of pavement structure
The full-permeable pervious cement concrete pavement can be used for roads with not heavy traffic loads, such as sidewalks, non-motor vehicle lanes, urban district park roads, parking lots, squares and the like, and the road foundation soil needs to have certain water permeability. If the roadbed soil can not meet the requirements, an anti-filtration isolation layer is arranged between the base layer and the soil foundation to exclude rainwater outside the roadbed.
The finite element structure (thickness can be changed according to specific bearing requirements and drainage requirements) and parameters of the full-penetration type permeable cement concrete pavement are recommended, and are shown in table 6.
TABLE 6 finite element structure and parameters of full-penetration type permeable cement concrete pavement
| Sequence of layers | Horizon | Material | Thickness of | modulus/MPa | Poisson ratio mu |
| 1 | Surface layer | Pervious cement |
22 | 27000 | 0.15 |
| 2 | Base layer | Graded broken |
25 | 350 | 0.3 |
| 3 | Soil foundation | Soil for soil | 700 | 40 | 0.35 |
Analyzing the influence of five index changes of the permeable cement concrete surface layer thickness, the permeable cement concrete surface layer modulus, the base layer thickness, the base layer modulus and the foundation modulus on the mechanical response indexes of the road surface structure, such as the maximum tensile stress of the permeable cement concrete bottom, the deflection of the road surface, the tensile stress of the base layer bottom, the compressive strain of the roadbed top surface and the like. The mechanical response indexes of the pavement structure are increased along with the increase of the axle load, and the change trend along with other parameter indexes is shown in the following graph. The abscissa represents the parameters of each layer, and the ordinate represents the percentage of a certain index quantity under the corresponding parameter to the maximum value of the index quantity. As shown in fig. 10-14.
As can be seen from fig. 10 to 14, the decrease of each index is more significant by the increase of the surface layer thickness, the base layer thickness and the foundation modulus, and the influence of the surface layer thickness is the greatest, while the decrease of each index is not significant by the increase of the surface layer modulus and the base layer modulus, and the influence of the surface layer modulus and the base layer modulus is very adverse. Therefore, the fully-permeable water-permeable cement concrete pavement is recommended to adopt a low-modulus and high-thickness design and is suitable for low-bearing roads. The values of the surface layer thickness and the base layer thickness are above 20cm, and are reasonably selected according to economic factors. The influence on each index is weaker after the modulus of the foundation exceeds 60 MPa.
In order to analyze the influence of all factors of the full-penetration type pervious cement concrete pavement on load stress, the combination design of the scheme is carried out by uniformly designing a table, the influence factors are mainly shown in a table 7, and a table U (12) is used10) To perform the design.
TABLE 7 table of all the influencing factors in the uniform design and the value-taking table thereof
Table 8 uniform design calculation results
And performing regression analysis according to the calculation result, and obtaining a regression formula of the plate edge middle load stress by integrating calculation analysis of each layer of axle load, thickness and modulus on the plate edge middle load stress without considering the influence of temperature in the pavement structure. Regression software 1stopt is used for carrying out regression on the result, and a stress calculation formula can be obtained by adopting a Marquardt method and a general global optimization algorithm, wherein R20.999, meets the requirement.
In the formula: sigmap' -driving load fatigue stress (MPa) generated by the permeable cement concrete layer at the critical load position; p-axle load (kN); h isp-the thickness (cm) of the pervious cement concrete (class a) layer; ep-pervious cement concrete (class a) layer modulus (MPa); h isj-base layer thickness (cm); ej-base modulus (MPa); e0-modulus of the ground (MPa).
In order to analyze the influence of each factor of the surface drainage type and the base layer drainage type permeable cement concrete pavement structure layer on the load stress, the scheme is designed by uniformly designing a table, the influence factors are mainly shown in table 9, and a table U (12) is used10) To perform the design.
TABLE 9 influence factors in uniform design and value-taking table thereof
The columns 1, 2, 6, 7, 8, 9 and 10 in the uniform design table were selected according to the table for uniform design calculation, and the calculation results are shown in table 10.
TABLE 10 Uniform design calculation results
Regression software 1stopt is used for carrying out regression on the result, and a Marquardt method and a general global optimization algorithm are adopted to obtain a load stress application calculation formula, wherein R20.99, meets the requirement.
In the formula: sigmap-driving load fatigue stress (MPa) generated by the pervious cement concrete layer at the critical load level; p-axle load (kN); h isp-the thickness (cm) of the pervious cement concrete (class a) layer; ep-pervious cement concrete (class a) layer modulus (MPa); h isc-cement concrete layer thickness (cm). h isj-base layer thickness (cm); ej-base modulus (MPa); e0-modulus of the ground (MPa).
According to the mechanical response analysis method for the permeable pavement structure under the action of the vehicle load, a reasonable calculation model is selected, a reasonable finite element model geometric dimension is selected, an unfavorable position is determined, a load is applied, and the most unfavorable interlayer contact condition is determined. By analyzing the finite element model of the pavement structure and applying regression software to carry out regression, a calculation formula of the parameters of the permeable cement pavement structure layer for the mechanical response of the pavement structure and the driving load fatigue stress generated by the permeable cement concrete layer at the critical load position is obtained. At present, domestic research on water permeability cement pavements is basically carried out on water permeable materials, and a real system for researching a water permeability cement pavement structure is unavailable. Compared with the prior art, the method has the advantages that the three-dimensional finite element model of the pavement structure is established, the parameters of the permeable cement pavement structure layer are analyzed through the finite element model to realize the mechanical response of the permeable cement pavement structure layer to the pavement structure, the regression is carried out on the result through the application of regression software, the calculation formula of the driving load fatigue stress generated by the permeable cement concrete layer at the critical load position is obtained, and the reference is provided for the design of the permeable pavement structure of the sponge city.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.
Claims (5)
1. The mechanical response analysis method of the permeable pavement structure under the action of vehicle load is characterized by comprising the following steps of: the method comprises the following steps:
establishing a three-dimensional finite element pavement model of a permeable cement pavement structure;
analyzing different positions of the pavement model to determine a critical load position;
determining the contact state between layers by adjusting the friction coefficient between the interfaces of the pavement models;
carrying out finite element analysis on a three-dimensional finite element pavement model of the pavement structure to obtain the influence of the parameter change of the pavement structure layer on the mechanics of the pavement structure;
calculating by adopting parameter combinations in a uniform design table to obtain load stress, and performing regression analysis by utilizing regression software according to a calculation result to obtain a calculation formula of the driving load fatigue stress generated by the pervious cement concrete layer at a critical load position:
wherein: sigmapDriving load fatigue stress (MPa) generated by a surface layer drainage type and a base layer drainage type permeable cement concrete pavement structure layer at a critical load position; sigmap' -driving load fatigue stress (MPa) generated by a structural layer of the full-penetration type pervious cement concrete pavement at a critical load position; p-axle load (kN); h isp-pervious cement concrete layer thickness (cm); ep-pervious cement concrete layer modulus (MPa); h isc-cement concrete layer thickness (cm); h isj-base layer thickness (cm); ej-base modulus (MPa); e0-modulus of the ground (MPa).
2. The mechanical response analysis method for the water permeable pavement structure under the action of the vehicle load according to claim 1, characterized by comprising the following steps of: and establishing a road model by adopting an elastic layered system theory, carrying out convergence analysis on the road model, and determining the size of the road model.
3. The mechanical response analysis method for the water permeable pavement structure under the action of the vehicle load according to claim 2, characterized by comprising the following steps of: and analyzing the plate middle part, the plate corner, the longitudinal edge middle part and the transverse edge middle part of the pavement model, and determining that the longitudinal edge middle part is a critical load position.
4. The mechanical response analysis method for the water permeable pavement structure under the action of the vehicle load according to claim 1, characterized by comprising the following steps of: for the surface layer drainage type and base layer drainage type permeable cement concrete pavement structure layers, the changes of road sign deflection, upper layer bottom surface tensile stress, lower layer bottom surface tensile stress and pavement top surface compressive strain are obtained by changing the thickness of the upper layer, the modulus of the upper layer, the thickness of the lower layer, the thickness of the base layer, the modulus of the base layer and the modulus of the foundation by using a finite element pavement model.
5. The mechanical response analysis method for the water permeable pavement structure under the action of the vehicle load according to claim 1, characterized by comprising the following steps of: for a full-permeable cement concrete pavement structure layer, the changes of the maximum tensile stress of the permeable cement concrete bottom, the deflection of the road surface, the tensile stress of the base bottom and the compressive strain of the roadbed top are obtained by changing the thickness of the permeable cement concrete surface layer, the modulus of the permeable cement concrete surface layer, the thickness of the base layer, the modulus of the base layer and the modulus of the foundation by using a finite element pavement model.
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| JP2002371503A (en) * | 2001-06-19 | 2002-12-26 | Efui Sekkai Gijutsu Kenkyusho:Kk | Pavement service life prediction method in designing pavement and confirmation method therefor |
| CN103031788A (en) * | 2013-01-07 | 2013-04-10 | 天津市市政工程设计研究院 | Method for designing long-life composite pavement structure of underground road |
| CN110472337A (en) * | 2019-08-13 | 2019-11-19 | 南京林业大学 | Asphalt pavement structure force analysis method under different copulation state between laminates |
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| JP2002371503A (en) * | 2001-06-19 | 2002-12-26 | Efui Sekkai Gijutsu Kenkyusho:Kk | Pavement service life prediction method in designing pavement and confirmation method therefor |
| CN103031788A (en) * | 2013-01-07 | 2013-04-10 | 天津市市政工程设计研究院 | Method for designing long-life composite pavement structure of underground road |
| CN110472337A (en) * | 2019-08-13 | 2019-11-19 | 南京林业大学 | Asphalt pavement structure force analysis method under different copulation state between laminates |
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