CN113062148B - High-speed railway bed surface layer thickness flexibility design method - Google Patents
High-speed railway bed surface layer thickness flexibility design method Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01B—PERMANENT WAY; PERMANENT-WAY TOOLS; MACHINES FOR MAKING RAILWAYS OF ALL KINDS
- E01B1/00—Ballastway; Other means for supporting the sleepers or the track; Drainage of the ballastway
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
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Abstract
The invention discloses a method for flexibly designing the thickness of a surface layer of a high-speed railway bed, which comprises the following steps: s1, surveying and researching the construction site condition; s2, screening asphalt mixture materials and proportions, and sampling fillers to obtain material related parameters; s3, establishing a three-dimensional full scale numerical calculation model according to the material parameters and the recommended geometric structure parameters, optimizing the thickness of the surface layer of the foundation bed according to the allowable stress value at the bottom of the foundation bed, and calibrating the thicknesses of the asphalt supporting layer and the surface layer of the foundation bed; s4, constructing an indoor full-scale model according to the structural layer parameters after the numerical model optimization, setting a loading head, embedding a pressure sensor, verifying the optimized structure, and continuously debugging to meet the requirements; and S5, after confirming the design scheme, compiling a design parameter comparison table of the surface layer thickness of the foundation bed. The method for designing the surface thickness of the high-speed railway foundation bed provided by the invention has strong flexibility, can strengthen the bearing capacity of the integral lower structure of the track, prolongs the service life of the track, and generates considerable economic and environmental benefits.
Description
Technical Field
The invention relates to the technical field of high-speed railway design and construction, in particular to a flexible design method for the surface layer thickness of a high-speed railway asphalt concrete paved track structure bed.
Background
High speed railways and heavy haul railways are two major directions in the development of global railways. Therefore, railway understructures are required to have good waterproof, vibration damping, durability, maintainability, and the like. The traditional cement-based ballastless track is directly paved on the surface layer of the flexible graded broken stone foundation bed, has the advantages of high integral rigidity, strong vibration, easiness in cracking, poor water resistance and difficulty in maintenance, the elastic modulus of a concrete material is large, the poisson ratio is small, and the attenuation of the dynamic load of a train in a concrete road bed plate is relatively slow. Meanwhile, all the current design specifications of China have unified regulations on the thickness of structural layers such as a high-speed railway ballast bed, a foundation bed and the like, and in actual engineering, due to the difference of foundation conditions of a roadbed and the difference of field external environments, the thickness of a lower structural layer of a railway can be flexibly designed to a certain extent, so that materials are saved and the construction cost is reduced on the premise of meeting the safety and smoothness in actual operation.
The asphalt mixture is used as a typical viscoelastic material, a transition layer can be formed between a roadbed bed and a concrete base plate, and the waterproof dense asphalt concrete can be used as a waterproof layer of the roadbed, is favorable for improving the deformation resistance of the roadbed, controlling the permanent deformation of a track structure and keeping the stability of the geometric conditions of the track structure, reduces diseases, prolongs the maintenance period and saves manpower and material resources for maintenance. Meanwhile, asphalt mixtures such as Hot Mix Asphalt (HMA), Epoxy Modified Asphalt (EMA), waste rubber modified asphalt (CRMA), and the like are also being widely studied and tested in the field of railway construction. Therefore, the asphalt material with viscoelasticity advantage is taken as the material of the high-speed railway track bed or the reinforced foundation bed, the attenuation of the dynamic load of the train and the protection of the roadbed are facilitated, the railway track bed is controlled to further adjust the lower basic structure layer, so that the thickness of the surface layer of the roadbed is optimized, a feasible and reliable technical reference is provided for the design and construction of the high-speed railway asphalt track bed in China in future, the bearing capacity of the lower structure of the track is reinforced to a certain extent, the service life of the track is prolonged, the maintenance requirement is reduced, and the gap of the current domestic research in the field is hopefully filled.
Disclosure of Invention
In order to solve the technical problems, the invention provides a flexible design method for the surface layer thickness of a high-speed railway foundation bed, aiming at the defects that the prior high-speed railway track bed slab has high rigidity and the related design specifications are too uniform for the thickness of a structural layer.
The technical scheme provided by the invention is as follows:
a high-speed railway bed surface layer thickness flexibility design method is suitable for an asphalt concrete flexible paving plate type track structure and comprises the following steps:
s1, surveying and investigating hydrology, geological conditions, climatic conditions, environmental temperature and the like of a construction site;
s2, according to the on-site investigation, the material selection and the mix proportion design are carried out on the asphalt mixture, the representative fillers of each structural layer of the on-site roadbed are sampled, and the indoor material test is carried out to obtain the relevant parameters of the materials;
s3, establishing a three-dimensional full-scale numerical calculation model according to material parameters obtained by indoor tests and geometric structure parameters recommended by the existing specifications, optimizing the thickness of the surface layer of the foundation bed by combining the allowable stress value of the bottom of the foundation bed in the high-speed railway design specifications, and calibrating the thickness of the improved asphalt supporting layer and the corresponding thickness of the surface layer of the foundation bed;
s4, constructing an indoor full-scale model according to the structure layer parameters optimized by the numerical model, setting a loading head, embedding a pressure sensor, verifying whether the optimized structure can meet the requirement on the allowable stress of the bottom of the foundation bed or not, and continuously debugging to meet the requirement, wherein the load size and the frequency are consistent with those in S3;
and S5, after confirming the design scheme, compiling a design parameter comparison table of the surface layer thickness of the high-speed railway bed corresponding to different substrate conditions, environmental temperatures, overlying materials and thickness dimensions.
Further, the asphalt concrete pavement slab type track structure sequentially comprises a substrate, a foundation bed bottom layer, a foundation bed surface layer, a permeable layer, an asphalt concrete supporting layer, an adhesive layer geotextile and a track slab from bottom to top.
Further, the material selection of the asphalt mixture in the step S2 needs to be determined according to the investigation condition in S1, the related material tests include dynamic triaxial creep tests and DSC tests, and the required material parameters include mechanical parameters and thermodynamic parameters of each structural layer.
Further, the method of step S3 is as follows: firstly, designing thicknesses of track slabs and structural layers of a surface layer and a bottom layer of a traditional roadbed according to on-site engineering and geological conditions of a construction site researched and developed in S1 by combining with the design specifications of the existing high-speed railway, selecting a proper asphalt supporting layer thickness, and establishing a geometric model of an asphalt concrete paved ballastless track by using finite element software or combining with discrete element coupling; then, obtaining modeling material parameters required by the numerical model according to the field sampling and material experiment in S2, and inputting the parameters into the model; then selecting proper boundary conditions and loading conditions, and determining constraint conditions; and finally, carrying out mesh division on the model.
Furthermore, the finite element software includes, but is not limited to, general finite element software such as ABAQUS and ANSYS, and professional finite element software such as MIDAS, etc., and the three-dimensional or two-dimensional shell model is built by coupling the finite elements and the discrete elements.
Further, in step S3, the load loading mode of the numerical model adopts fixed point excitation loading.
Further, the thickness of the structural layer of the numerical calculation model established in step S3 is preliminarily determined according to the existing specifications, where the asphalt supporting layer (stress diffusion thickness) is H, the bed surface layer is D, and the bed bottom dynamic stress is σ.
Further, the allowable stress at the bottom of the foundation bed in the step S3 and the step S4 is determined according to the dynamic-static stress ratio of the high-speed railway subgrade at 0.2, a proper safety factor can be selected to ensure absolute safety of the structure, and the static stress is obtained according to the uniform load of the high-speed train and the track on the road base surface in the high-speed railway design specification (TB 10621-2014).
Further, the structure layer size optimized in step S3 is that the asphalt supporting layer (stress diffusion thickness) is HiThe surface layer of the foundation bed is Di', when the ratio of the dynamic and static stresses at the bottom of the foundation bed is 0.2, the dynamic stress is recorded as sigmaiAnd the stress diffusion thickness is calibrated to be H after the conversion of the safety coefficientiThe thickness of the surface layer of the foundation bed is Di' the structure has a bed bottom allowable stress, denoted as [ sigma ]i]Then according to HiAnd [ sigma ]i]Inverse calculation of the bed surface thickness DiAnd obtaining a function relation between the surface layer of the foundation bed and the thickness of the stress diffusion layer and the bottom stress of the foundation bed as follows: di＝f(Hi,σi) And obtaining the result from the numerical model output. The safety factor refers to railway roadbed design specifications, and can also be obtained according to a large amount of field test data (the traditional railway roadbed data is used as a reference).
Further, the bed bottom allowable stress safety factor in the step S3 and the step S4 is
Further, the positions of the pre-embedded pressure sensors in the indoor full-scale model test in the step S4 are the top of the asphalt supporting layer, the top of the surface layer of the foundation bed, the bottom of the surface layer of the foundation bed and the bottom of the bottom layer of the foundation bed on the cross section under the rail, and the positions of the embedded temperature gauge are the top of the surface layer of the foundation bed, the bottom of the surface layer of the foundation bed and the bottom of the bottom layer of the foundation bed.
Further, the field test in step S4 is to recheck the optimized parameters of the structural layer in step S3, measure the dynamic stress value of the bottom of the actual structural bed according to the pressure sensor, and verify that the function D is used in step S3i＝f(Hi,σi) Optimizing whether the obtained structure meets the requirement, and if so, confirming the design scheme; if not full ofIf yes, the thickness H of the stress diffusion layer in step S3 is changediFurther adjusting the thickness D of the surface layer of the foundation bediObtaining a new functional relation, and then carrying out full-scale model test rechecking until the requirements are met; meanwhile, if the working condition of the engineering standard section changes, so that the existing design is no longer applicable, the steps from S1 to S4 need to be performed again to complete the calibration under the new working condition.
Further, the step S5 is to compile a parameter comparison table of the high-speed railway bed surface layer thickness, including the bed surface layer thicknesses corresponding to different base conditions, environmental temperatures, overlying materials and structural layer thickness dimensions, as the design calibration of the structure and material of the engineering standard section.
Further, the method is suitable for engineering construction standard sections with foundation conditions of good overall stability and good supporting strength and rigidity, and the foundation is required to be processed according to corresponding specifications if the method is used for special road sections, and meanwhile, the method is designed according to local conditions by selecting appropriate asphalt concrete materials and asphalt supporting layer thicknesses. Different structural layer geometries and material designs exist in different standard sections according to different actual engineering geological states and climatic conditions.
The invention has the beneficial effects that:
according to the design method for the thickness of the surface layer of the high-speed railway foundation bed, the structure can disperse the load of the upper train on the premise of ensuring the high smoothness of the high-speed railway track, the downward transmission of the dynamic load of the train is weakened, the coordination matching between the track supporting layer and the lower foundation layer is formed, and the design flexibility is high. On the other hand, the thickness of the surface layer of the foundation bed determined by the method can effectively adjust the thickness of the structural layer of the surface layer of the original roadbed or optimize the grade of the filler of the surface layer of the foundation bed while weakening the vibration and the noise generated by the dynamic load of the train, thereby strengthening the bearing capacity of the integral substructure of the track, prolonging the service period of the track and reducing the maintenance requirement. In addition, the invention can select the asphalt layer material and the thickness according to the external environment and the substrate condition according to the local conditions, and select the substrate surface layer according to the environment, the asphalt layer material and the thickness; meanwhile, for different standard sections of the same project, the structural layer thickness and the asphalt concrete material suitable for each standard section are selected according to different substrate conditions and regional environment differences so as to obtain the optimal matching effect. The invention is expected to generate considerable economic and social benefits, promotes the development of novel ballastless track paving structure and material, and promotes the development of the track engineering industry
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a design flow chart of the design method for flexibility of the surface thickness of the high-speed railway bed of the invention;
FIG. 2 is a schematic diagram of a structural layer of an asphalt concrete paved track;
FIG. 3 is a schematic diagram of the arrangement positions of the indoor full-scale test section pressure sensor and the thermometer and the loading device.
Detailed Description
In order to clearly understand the technical features, objects and effects of the present invention, the detailed description of the present invention will be made with reference to the accompanying drawings, which are merely illustrative of the specification and drawings, and the values of the parameters are merely referred to.
Example 1
As shown in fig. 1, the method for designing the flexibility of the surface thickness of the high-speed railway bed according to the present invention comprises the following steps:
and S1, surveying and researching the hydrology, geological conditions, climatic conditions, environmental temperature and the like of the construction site.
In this embodiment, the pile number of the engineering full-scale section is K0+000 to K20+436, wherein the K0+000 to K12+516 scale section is in a temperate zone, the geological condition is good, the K12+517 to K20+436 scale section is in a high-freezing frozen soil zone, the water content of the roadbed soil body is higher, and the groundwater level is higher. The construction of the temperature zone of the standard sections K0+000 to K12+516 is only taken as an example for explanation.
As shown in fig. 2, in this embodiment, the asphalt concrete is used as a stress diffusion layer of the high-speed railway, and the overall structure includes, from bottom to top, a base, a bed bottom layer, a bed surface layer, a permeable layer, an asphalt concrete pavement layer, an adhesive geotextile, and a concrete track slab.
And S2, according to the on-site investigation, carrying out material selection and mix proportion design on the asphalt mixture, sampling the on-site roadbed filler, carrying out an indoor material test, and obtaining related material parameters.
In the embodiment, for the standard section K0+000 to K12+516, a common matrix asphalt mixture can be selected as an asphalt concrete supporting layer material, and an indoor dynamic triaxial creep test and a DSC test are performed to obtain a dynamic modulus parameter and a thermodynamic parameter of the matrix asphalt mixture; meanwhile, the roadbed soil body sampled on site is tested to obtain soil-based material parameters with good mechanical properties, and the thermodynamic parameters of each structural layer of the standard section are shown in table 1.
TABLE 1 sections K0+000 to K12+516 thermodynamic design parameters (recommendations)
S3, establishing a numerical calculation model according to the parameters of the indoor test materials and the parameters of the existing standard geometric structure, optimizing the thickness of the surface layer of the foundation bed by combining the allowable stress value of the bottom of the foundation bed in the design standard of the high-speed railway, and calibrating the thickness of the improved asphalt bearing layer and the thickness of the corresponding surface layer of the foundation bed.
In this embodiment, the established numerical calculation model is an ABAQUS finite element model, and the thickness of the structural layer is designed according to the field engineering and geological conditions of the construction site investigated in S1 in combination with the existing high-speed railway design specifications for the track slab and the structural layers of the surface layer and the bottom layer of the conventional roadbed, and the appropriate thickness of the asphalt supporting layer is selected to establish a geometric model of the asphalt concrete paved ballastless track; then, based on the field sampling and material experiment in S2, the modeling material parameters required for the numerical model are obtained and input into the model.
In this embodiment, the structure of the established numerical model and the parameters of the mechanical material are shown in table 2. According to the actual geological and engineering foundation conditions on site, the local climate, temperature and humidity environment is researched, on the premise that foundation treatment meets the requirements of the current railway roadbed design specification, the overall stability of the roadbed is good, and the foundation condition with good supporting strength and rigidity is ensured, an initial asphalt supporting layer (stress diffusion thickness) is selected to be H150 mm, the surface layer of the roadbed is D' 400mm, and the loading mode of the model adopts fixed-point excitation loading to simulate the running of high-speed trains with different design running speeds (if the local environmental conditions or the engineering geological conditions change, such as alpine regions, collapsible loess regions and the like, the materials and the initial thickness values of the asphalt concrete supporting layer need to be additionally designed). According to a simplified form of uniform load distribution of a roadbed train and a track in design Specifications of high-speed railways (TB10621-2014), a static stress value which is increased along with the depth under the roadbed is calculated, and a dynamic stress value at the bottom of a model roadbed is output, wherein the dynamic stress at the bottom of the roadbed is sigma, and the requirement that the ratio of the dynamic stress to the static stress at the bottom of the roadbed is less than or equal to 0.2 is met. Then, the allowable dynamic stress value of the bed bottom is converted according to the allowable safety factor, the safety factor can be 1.25, the allowable dynamic stress of the bed bottom is [ sigma ] ═ sigma/1.25, and at this time, the required bed surface layer thickness D under the allowable stress is inversely calculated.
Table 2 numerical model structural layer parameters (recommendations)
| Component part | Material | Unit cell | Size of structural layer (m) | E(MPa) | υ | Density (kg/m)3) | Damping |
| Rail for railway vehicle | Steel | Entity | - | 206000 | 0.25 | 7850 | 0.015 |
| Track plate | Cement concrete | Entity | 0.19 (Width: 2.4) | 36000 | 0.16 | 2500 | 0.03 |
| Supporting layer | Asphalt concrete | Entity | Variation (Width: 3.0) | 4000 | 0.35 | 2400 | 0.09 |
| Bed surface layer | Graded broken stone | Entity | Variations in | 250 | 0.3 | 1800 | 0.035 |
| Bottom layer of foundation bed | Medium sand | Entity | 2.3 | 200 | 0.35 | 2000 | 0.039 |
| Soil foundation | Clay | Entity | 5.0 | 110 | 0.4 | 1800 | 0.035 |
In this example, the thickness of the asphalt concrete supporting layer in the numerical model is adjusted to be H1200mm, simulating the loading size and frequency of the fixed-point excitation load at the same time, and adjusting the surface layer thickness of the foundation bed to D1', the dynamic stress of the bottom of the foundation bed just meets the requirement that the ratio of the dynamic stress to the static stress is less than or equal to 0.2 at the moment, and D is recorded1' numerical value and dynamic stress value of bed bottom σ1Calculating to obtain the corresponding allowable stress [ sigma ] of the bottom of the foundation bed1]Then, the bed surface thickness D at the time of dynamic stress attenuation to the allowable stress is back-calculated again1(ii) a Continuously adjusting the thickness of the asphalt concrete supporting layer to be H2＝250mm，Adjusting the surface thickness of the foundation bed to D2', the dynamic stress of the bottom of the foundation bed just meets the requirement that the ratio of the dynamic stress to the static stress is less than or equal to 0.2 at the moment, and D is recorded2' numerical value and dynamic stress value of bed bottom σ2Calculating to obtain the corresponding allowable stress [ sigma ] of the bottom of the foundation bed2]Then, the bed surface thickness D at the time of dynamic stress attenuation to the allowable stress is back-calculated again2(ii) a And by analogy, continuously adjusting the thickness of the asphalt concrete supporting layer until the thickness of the asphalt layer is increased to 400mm (the existing data show that the optimal thickness of the asphalt supporting layer is 200-350mm, and the upper limit value can be adjusted according to subsequent research), then encrypting the thickness adjustment change value of the asphalt supporting layer, for example, increasing the thickness according to 10mm, further obtaining the encrypted optimized thickness of the surface layer of the foundation bed, and correspondingly recording the optimized thickness H of the asphalt supporting layeriBed surface thickness DiAnd dynamic stress sigma of the bed bottomiAt this time, because of σiThat is, the dynamic and static stress ratio is 0.2 corresponding to the dynamic stress value of the bottom of the foundation bed, [ sigma ]i]For the bitumen-bearing layer is HiThe surface layer of the foundation bed is DiThe allowable stress of the bottom of the foundation bed can obtain the functional relation between the thickness of the surface layer of the foundation bed, the thickness of the supporting layer and the dynamic stress of the bottom of the foundation bed: di＝f(Hi,σi)(i＝1,2,3…)。
S4, constructing an indoor full-scale model according to the structural layer parameters optimized by the numerical model, setting a loading head, embedding a pressure sensor, verifying whether the optimized structure can meet the requirement on the allowable stress of the bottom of the foundation bed, and continuously debugging to meet the requirement, wherein the load size and the frequency are consistent with those in S3;
in this embodiment, the thickness H of the asphalt supporting layer optimized in step S3 is usediBed surface thickness DiAn indoor full-scale model (i is 1,2,3 …) is built, the size of a model excavation soil box and the embedding positions of embedded components are shown in fig. 3, the embedding positions of the pressure sensors are the top of an asphalt supporting layer, the top of a foundation bed surface layer, the bottom of the foundation bed surface layer and the bottom of the foundation bed bottom layer of an under-rail section, and the embedding positions of the thermometers are the top of the foundation bed surface layer, the bottom of the foundation bed surface layer and the bottom of the foundation bed bottom layer. Using a counter-force system and a distribution beam, using twoThe loading head simulates the effect of a bogie on the rail. Taking a CR400AF motor train unit as a basic basis, and taking 17t of dead axle weight. The two loading heads are respectively connected with a vibration exciter to obtain excitation loads, and the distance between the two loading heads is 2.5m, so that the loading frequency is utilized to adjust the phase difference between the two excitation loads to simulate different train speeds.
In this embodiment, the bed bottom dynamic stress measured by the build full-scale model at (i ═ 1,2,3 …) is used as a function D of the numerical model calibrationi＝f(Hi,σi) Whether the obtained structure meets the standard design requirement or not, and if so, confirming the design scheme; if not, the process returns to step S3 to change the thickness H of the stress diffusion layer in the numerical modeliFurther adjusting the thickness D of the surface layer of the foundation bediAnd obtaining a new functional relation, and rechecking the indoor full-scale test again until the standard requirement is met.
In this embodiment, when entering the K12+517 to K20+436 construction segment, the existing design is no longer applicable, and a site survey needs to be performed again, and since the segment is located in a severe cold area, modified asphalt concrete is selected to improve the low-temperature performance of an asphalt supporting layer, for example, waste rubber modified asphalt concrete may be selected, and the thermodynamic parameter design of the material of each structural layer of the segment is shown in table 3. Meanwhile, as the freezing and thawing depth of the soil body in the plateau area is large, the mechanical parameters of the roadbed structure layer are changed, so that the mechanical parameters of the numerical model and the indoor full-scale model structure layer in S3 and S4 are influenced, and the standard section needs to be calibrated again by repeating the steps S1 to S4.
TABLE 3 thermodynamic design parameters (recommended) in paragraphs K12+517 through K20+436
And S5, after confirming the design scheme, compiling a parameter comparison table of the surface layer thickness of the high-speed railway bed corresponding to different substrate conditions, environmental temperatures, overlying materials and thickness dimensions.
In the embodiment, the compiled parameter comparison table of the surface layer thickness of the high-speed railway bed is used for calibrating the structure and material design of the engineering standard section, and the different standard sections of the engineering have different material and thickness designs of all the whole structure layers of the asphalt concrete pavement track due to different working conditions.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
While the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A method for designing the flexibility of the surface layer thickness of a high-speed railway foundation bed is characterized in that the method is suitable for an asphalt concrete paved plate type track structure and comprises the following steps:
s1, surveying and investigating the hydrology, geological conditions, climatic conditions and environmental temperature of a construction site;
s2, according to the on-site investigation, the material selection and the mix proportion design are carried out on the asphalt mixture, the representative fillers of each structural layer of the on-site roadbed are sampled, and the indoor material test is carried out to obtain material parameters;
s3, establishing a three-dimensional full-scale numerical calculation model according to material parameters obtained by an indoor material test and geometric structure parameters recommended by the existing specification, optimizing the thickness of the surface layer of the foundation bed by combining the allowable stress value of the bottom of the foundation bed in the high-speed railway design specification, and calibrating the thickness of the improved asphalt concrete supporting layer and the corresponding thickness of the surface layer of the foundation bed;
s4, calculating the parameters of the optimized structural layer of the model according to the full scale value, constructing an indoor full scale model, setting a loading head, embedding a pressure sensor, verifying whether the optimized structure can meet the requirement on the allowable stress of the bottom of the foundation bed or not, and continuously debugging to meet the requirement, wherein the load size and the frequency are consistent with those in S3;
and S5, after confirming the design scheme, compiling a design parameter comparison table of the surface layer thickness of the high-speed railway bed corresponding to different substrate conditions, environmental temperatures, overlying materials and thickness sizes thereof.
2. The method of claim 1, wherein: the asphalt concrete pavement slab type track structure sequentially comprises a base, a foundation bed bottom layer, a foundation bed surface layer, a permeable layer, an asphalt concrete supporting layer, an adhesive geotechnical cloth and a track slab from bottom to top.
3. The method of claim 1, wherein: the material selection of the asphalt mixture in the step S2 needs to be determined according to the investigation condition in the step S1, the indoor material test comprises a dynamic triaxial creep test and a DSC test, and the required material parameters comprise mechanical parameters and thermodynamic parameters of each structural layer.
4. The method according to claim 1, wherein the method of step S3 is as follows: firstly, designing thicknesses of track slabs and structural layers of a surface layer and a bottom layer of a traditional roadbed according to on-site engineering and geological conditions of a construction site researched and developed in S1 by combining with the existing high-speed railway design specifications, selecting a proper asphalt supporting layer thickness, and establishing a numerical calculation model of an asphalt concrete pavement slab type track structure by using a finite element or combining with discrete element coupling; then, according to the on-site sampling and the indoor material test in S2, obtaining the modeling material parameters required by the full-scale numerical calculation model, and inputting the parameters into the model; selecting proper boundary conditions and loading conditions, determining constraint conditions, and loading by adopting fixed-point excitation in a loading mode; and finally, carrying out mesh division on the model.
5. The method of claim 1, wherein: the thickness of the structural layer of the numerical calculation model established in step S3 is preliminarily determined according to the existing specification, where the asphalt supporting layer, i.e., the stress diffusion layer, has a thickness of H, the surface layer of the foundation bed has a thickness of D, and the bottom dynamic stress of the foundation bed has a value of σ.
6. The method of claim 1, wherein: and (4) the allowable stress at the bottom of the foundation bed in the step S3 and the step S4 is determined according to the dynamic-static stress ratio of the high-speed railway subgrade of 0.2, a proper safety factor is selected to ensure absolute safety of the structure, and the static stress is obtained according to the uniform load of the high-speed train and the track on the road foundation surface in the high-speed railway design Specification (TB 10621-2014).
7. The method of claim 1, wherein: the optimized structure layer size in the step S3 is an asphalt supporting layer, i.e., a stress diffusion layer, and the thickness is HiThe thickness of the surface layer of the foundation bed is Di' when the ratio of the dynamic and static stresses at the bottom of the foundation bed is 0.2, the dynamic stress is recorded as sigmaiAnd the thickness of the stress diffusion layer is calibrated to be H after the conversion of the safety coefficientiThe thickness of the surface layer of the foundation bed is Di' the structure has a bed bottom allowable stress, denoted as [ sigma ]i]Then according to HiAnd [ sigma ]i]Inverse calculation of the bed surface thickness DiAnd obtaining the functional relation among the thickness of the surface layer of the foundation bed, the thickness of the stress diffusion layer and the bottom stress of the foundation bed as follows: di＝f(Hi,σi) The data are obtained by outputting a full-scale numerical calculation model; the conversion method of the safety coefficient comprises the following steps:
8. the method of claim 1, wherein: the positions of the pre-embedded pressure sensors in the indoor full-scale model test in the step S4 are the top of an asphalt supporting layer of the cross section under the rail, the top of a surface layer of the foundation bed, the bottom of the surface layer of the foundation bed and the bottom of a bottom layer of the foundation bed, and the positions of the embedded temperature meters are the top of the surface layer of the foundation bed, the bottom of the surface layer of the foundation bed and the bottom of the bottom layer of the foundation bed.
9. The method of claim 7, wherein: the indoor full-scale model test in the step S4 is to recheck the optimized parameters of the structural layer in the step S3, measure the dynamic stress value of the bottom of the actual structural bed according to the pressure sensor and verify the function D in the step S3i＝f(Hi,σi) Optimizing whether the obtained structure meets the requirements, and if so, confirming the design scheme; if not, the thickness H of the stress diffusion layer in step S3 is changediFurther adjusting the thickness D of the surface layer of the foundation bediObtaining a new functional relation, and then carrying out indoor full-scale model test rechecking until the requirements are met; meanwhile, if the working condition of the engineering standard section changes, so that the existing design is no longer applicable, the steps from S1 to S4 need to be performed again to complete the calibration under the new working condition.
10. The method of claim 1, wherein: and step S5, compiling a parameter comparison table of the surface layer thickness of the high-speed railway foundation bed, wherein the parameter comparison table comprises the surface layer thicknesses of the foundation bed corresponding to different foundation conditions, environment temperatures, overlying materials and thickness sizes thereof, and is used for calibrating the structure and material design of the engineering standard section, and the conditions of different structure layer geometries and material designs exist in different standard sections according to the difference of actual engineering geological states and climatic conditions.
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| GB2226504B (en) * | 1988-12-05 | 1992-06-24 | Rossler Elfriede | A track bed for model railway track |
| DE19500443A1 (en) * | 1995-01-10 | 1996-07-18 | Groetz Georg | Track system for rail-bound vehicles |
| DE10319298A1 (en) * | 2003-04-29 | 2004-11-18 | Gsg Knape Gleissanierung Gmbh | Construction method for permanent way for railways, with construction of track bed incorporating antifreeze layer, sub base, concrete sub base, and thin asphalt layer to compensate for unevenness |
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