CN114059407B - High-bearing-capacity roadbed design method with gradually increasing modulus - Google Patents
High-bearing-capacity roadbed design method with gradually increasing modulus Download PDFInfo
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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
- E01C1/00—Design or layout of roads, e.g. for noise abatement, for gas absorption
- E01C1/002—Design or lay-out of roads, e.g. street systems, cross-sections ; Design for noise abatement, e.g. sunken road
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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
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- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
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- G06F30/13—Architectural design, e.g. computer-aided architectural design [CAAD] related to design of buildings, bridges, landscapes, production plants or roads
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- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
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Abstract
The invention discloses a high-bearing-capacity roadbed design method with gradually increased modulus, which relates to the technical field of roadbeds and comprises the following steps: determination of the soil-based rebound modulus E according to the Highway base design Specification JTGD30-2015 0 The method comprises the steps of carrying out a first treatment on the surface of the Based on the mechanical index requirement of road surface design on the rebound modulus of the top surface of the roadbed, the comprehensive rebound modulus E of the top of the roadbed is drawn 0C According to the principle of progressive increment of modulus from bottom to top, the filling materials selected by the roadbed structure combination are drawn; based on the theory of a multilayer elastic lamellar system, calculating the rebound modulus E of the top of the roadbed according to the principle of equivalent pressure strain of the top of the roadbed 0C The thickness of the filler layer meets the requirement; and (3) simulating the settlement of the roadbed in the design period by using finite element software ABAQUS simulation analysis, judging whether the settlement meets the settlement requirement of the top surface of the roadbed, and if not, adjusting the roadbed structure until the settlement requirement is met. The invention realizes high bearing of the roadbed, can obviously reduce settlement after roadbed construction, and solves the problem of unreasonable roadbed modulus value.
Description
Technical Field
The invention relates to the technical field of road foundations, in particular to a high-bearing-capacity roadbed design method with gradually increasing modulus.
Background
The roadbed is the foundation of the pavement, the bearing capacity and deformation of the roadbed have important influence on the pavement structure, and the stability and durability of the roadbed have important influence on the roadbed. The comprehensive rebound modulus of the roadbed is graded in the JTGD30-2015 of the existing roadbed design rule of highway and the JTGD50-2017 of the asphalt pavement design rule of highway, the highest requirement on the rebound modulus of the roadbed is 70MPa, and the requirement on the rebound modulus of the road is generally weaker, so that the value of the comprehensive rebound modulus of the Fang Duilu-base road surface design is smaller, the design thickness of the road surface is overlarge, and the waste of road building materials is caused; on the other hand, the road construction side can pay no attention to the construction quality of the roadbed, the roadbed is caused to leave the potential defect of overlarge settlement after construction, the pavement can be left empty, and then the pavement is evolved into the diseases such as empty, cracks and the like, the service quality of the pavement is reduced, and the service life of the pavement is shortened.
The higher the bearing capacity of the roadbed is, the stress on the pavement structure is favorable, the service life of the pavement can be prolonged, and the service performance of the pavement is ensured. If the roadbed is hierarchically structured, the roadbed is subjected to structural combination design, the roadbed is subjected to high-bearing design, and the comprehensive rebound modulus of the roadbed is finally obtained and is used as an important parameter index for road surface structural combination and checking calculation, on the one hand, the reasonable value of the comprehensive rebound modulus of the roadbed is clear, and on the other hand, the construction quality of the roadbed is controlled, so that the research of a high-bearing-capacity roadbed design method with gradually increased modulus is very necessary.
Disclosure of Invention
Aiming at the needs and the shortcomings of the prior art development, the invention provides a high-bearing-capacity roadbed design method with gradually increasing modulus.
The invention relates to a high bearing capacity roadbed design method with gradually increasing modulus, which solves the technical problems and adopts the following technical scheme:
a design method of a high bearing capacity roadbed with gradually increasing modulus comprises the following implementation contents:
step S1, determining the rebound modulus E of the soil base according to JTGD30-2015 of the highway subgrade design rule, wherein the roadbed structure combination comprises the soil base, the lower embankment, the upper embankment and the roadbed 0 ；
S2, based on mechanical index requirements of road surface design on the rebound modulus of the top surface of the roadbed, the comprehensive rebound modulus E of the top of the roadbed is drawn 0C According to the principle of progressive increment of modulus from bottom to top, at least one filler of plain soil, emulsified asphalt solidified soil, emulsified asphalt improved soil, cement improved soil, curing agent improved soil, graded broken stone and low-dose cement stabilized broken stone is respectively selected for preparing soil foundation, lower embankment, upper embankment and roadbed of roadbed structure combination;
step S3, calculating the rebound modulus E of the roadbed top based on the multilayer elastic layered system theory according to the principle of roadbed top pressure strain equivalence 0C The thickness of the filler layer meets the requirement;
and S4, applying finite element software ABAQUS to simulate analysis, simulating the settlement of the roadbed structure combination in the design period, judging whether the settlement requirement of the roadbed top surface is met, and if the settlement requirement is not met, adjusting the roadbed structure combination until the settlement requirement is met.
Optionally, the thickness of the roadbed in the roadbed structure combination is 0.5m-1.5m.
Further alternatively, in the roadbed structure combination, the soil base, the lower embankment, the upper embankment and the roadbed respectively comprise 1-4 layers of fillers, and the thickness of the single-layer filler is 15cm-30cm.
Further alternatively, the roadbed structure combination is concerned, wherein the ratio of the modulus of the upper layer filler to the modulus of the adjacent lower layer filler is 1.5-2.
Further alternatively, in the roadbed structure combination, the thickness of the single-layer filler is 15cm-25m when the roadbed adopts graded broken stone or low-dose cement stabilized broken stone.
Further alternatively, step S2 is performed to develop the comprehensive modulus of resilience E at the top of the subgrade 0C Firstly, according to the principle of progressive increment of modulus from bottom to top, the filling materials selected by soil foundation, lower embankment, upper embankment and road bed in the roadbed structure combination are planned, and then the dynamic rebound modulus of the filling material layer is calculated by referring to JTGD30-2015 annex A of the highway roadbed design rule, and the concrete process is as follows:
(1) Preparing a sample by taking soil on site or remolding soil indoors to obtain a sample with the diameter of 150mm plus or minus 2mm, the height of 300mm plus or minus 2mm or the diameter of 100mm plus or minus 2mm and the height of 200mm plus or minus 2 mm;
(2) The sample is sleeved with rubber membranes and is arranged on the instrument base, and permeable stones are placed up and down;
and (3) mounting a displacement sensor: mounting LVDT or displacement sensors at the bottom and top of the sample for measuring displacement;
(3) Opening a drain valve, applying certain confining pressure around a sample, then pre-loading, applying pulse load, and taking the load and displacement of the last five times as calculated dynamic rebound modulus;
(4) The dynamic modulus of resilience is calculated as follows,
wherein M is R Representing dynamic rebound modulus and sigma of roadbed soil 0 -axial stress amplitude, ε 0 -axial strain amplitude.
Further optionally, step S3 is performed to calculate the thickness of the filler layer, which specifically includes the following steps:
step S3.1, according to the sketchThe dynamic rebound modulus of the roadbed structure combination and the packing layer to obtain the mechanical parameters of the packing layer; then according to the principle of multilayer elastic lamellar system theory and roadbed top pressure strain equivalent, designing the layer number and layer thickness of roadbed structure combination, and calculating the comprehensive rebound modulus of all the filler layers based on the dynamic rebound modulus of the filler layers, namely roadbed top rebound modulus E 0C ；
S3.2, selecting a structural design layer from packing layers contained in the roadbed, and simultaneously calculating the top compressive strain of the planned roadbed structural combination;
step S3.3, combining the calculated roadbed structure with the top compressive strain and the comprehensive rebound modulus E 0C The compressive strain was compared:
(a) If the compressive strain at the top of the roadbed structure combination is greater than the comprehensive rebound modulus E 0C The structural design layer is thinned by pressing down the strain, and each time the structural design layer is thinned by 1cm, the structural design layer is iterated in sequence until the compressive strain at the top of the roadbed structure combination is just close to and larger than the comprehensive rebound modulus E 0C The lower strain is applied to the substrate and the substrate is subjected to a lower strain,
(b) If the pressure strain at the top of the roadbed structure combination is smaller than the comprehensive rebound modulus E 0C The structural design layer is thickened under the downward compressive strain, each thickening is 1cm, and the steps are iterated in sequence until the compressive strain at the top of the roadbed structure combination is just close to and larger than the comprehensive rebound modulus E 0C And (3) lower strain.
When the layer thickness of the roadbed structure combination is designed in the step S3.1, the layer thickness shall meet the requirement of the JTG/T3610-2019 on the thickness of the filler layer in the roadbed structure combination, and if not, the designed layer number and layer thickness of the roadbed structure combination shall be adjusted until the requirements of the strain and the thickness are met at the same time.
Optionally, when the roadbed structure combination is drawn, the modulus of each layer of filler in the roadbed structure combination is subjected to humidity adjustment, and the reduction of the modulus by the dry-wet cycle and the freeze-thawing cycle is considered; when humidity adjustment is carried out, the humidity adjustment coefficients of different fillers are specifically referred to as JTGD30-2015 in the highway subgrade design Specification.
The high-bearing-capacity roadbed design method with gradually increasing modulus has the following beneficial effects compared with the prior art:
the invention realizes high bearing capacity of the roadbed, can obviously reduce settlement after roadbed construction, and solves the problem of unreasonable roadbed modulus value during pavement design; the invention also obviously improves the design level and the deformation of the roadbed, can obviously improve the bearing capacity and the stability of the roadbed, provides solid support for durable asphalt pavement, and greatly improves the construction quality and the service level of the roadbed.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a schematic diagram of the settlement result of the top surface of the roadbed 15 years after the simulation operation of the expressway according to the first embodiment of the present invention;
fig. 3 is a schematic diagram of the settlement result of the top surface of the roadbed 15 years after the simulation operation of the expressway according to the second embodiment of the present invention.
Detailed Description
In order to make the technical scheme, the technical problems to be solved and the technical effects of the invention more clear, the technical scheme of the invention is clearly and completely described below by combining specific embodiments.
Embodiment one:
taking the engineering of the foundation of the yellow-colored region of the highway with the robust section as an example.
The total amount of the silt in the yellow and flood zone of the roadbed engineering of the robust section is 300 masterpieces, wherein the first masterpiece is 80 masterpieces, the second masterpiece is 170 masterpieces, and the third masterpiece is 60 masterpieces. The powder soil in the yellow flood area has single particle size, and the fine particle soil is relatively lacking, so that the fine particle soil is difficult to achieve an ideal compact state after being compacted, capillary gaps of the fine particle soil are developed, and migration and aggregation of moisture can soften roadbed due to overlarge water content, so that various engineering problems are induced. If the technology of changing and filling is adopted, the land is damaged, the engineering cost is improved, the existing roadbed filler is fully utilized, the foundation is specially designed for the foundation of the yellow soil region under the premise of ensuring the engineering progress, the integral rigidity of the foundation is improved, the settlement after construction is reduced, and the construction problem to be overcome in Lu Jiduan high-speed construction is solved.
The embodiment provides a high bearing capacity roadbed design method with gradually increasing modulus, which comprises the following implementation contents:
in the high-speed roadbed design of the steps S1 and Lu Jiduan, the roadbed structure combination comprises a soil base, a lower embankment, an upper embankment and a roadbed, and the rebound modulus E of the soil base is determined according to JTGD30-2015 of the highway roadbed design rule 0 =25 MPa, the soil base bearing capacity is weak. According to the design requirement of the roadbed with high bearing capacity, the rebound modulus at the top of the roadbed is up to 120MPa, and the roadbed needs to be comprehensively designed.
S2, based on mechanical index requirements of road surface design on the rebound modulus of the top surface of the roadbed, the comprehensive rebound modulus E of the top of the roadbed is drawn 0C 120MPa should be reached.
According to the principle of progressive increment of modulus from bottom to top, the subgrade structure combination is drawn up and comprises: soil base +4% cement improved soil +6% cement improved soil + emulsified asphalt improved soil, table 1 below:
TABLE 1 initial roadbed structure combination
| Roadbed structure combination | Roadbed filling material | Filling thickness (m) | Layer number of filling |
| Road bed | Emulsified asphalt improving soil | ||
| Embankment for |
6% cement improved soil | ||
| |
4% cement improved soil | ||
| Soil foundation | Plain soil |
Based on the planned roadbed structure combination, referring to JTGD30-2015 annex A of the highway roadbed design specification, the dynamic rebound modulus of the filler layer is calculated, and the concrete process is as follows:
(1) Preparing a sample by taking soil on site or remolding soil indoors to obtain a sample with the diameter of 150mm plus or minus 2mm, the height of 300mm plus or minus 2mm or the diameter of 100mm plus or minus 2mm and the height of 200mm plus or minus 2 mm;
(2) The sample is sleeved with rubber membranes and is arranged on the instrument base, and permeable stones are placed up and down;
and (3) mounting a displacement sensor: mounting LVDT or displacement sensors at the bottom and top of the sample for measuring displacement;
(3) Opening a drain valve, applying certain confining pressure around a sample, then pre-loading, applying pulse load, and taking the load and displacement of the last five times as calculated dynamic rebound modulus;
(4) The dynamic modulus of resilience is calculated as follows,
wherein M is R Representing dynamic rebound modulus and sigma of roadbed soil 0 -axial stress amplitude, ε 0 -axial strain amplitude.
Based on the formulated roadbed structure combinations, the dynamic rebound modulus of the filler layer is as follows in table 2:
TABLE 2 results of robust section high speed subgrade filler parameter test
Step S3, calculating the rebound modulus E of the roadbed top based on the multilayer elastic layered system theory according to the principle of roadbed top pressure strain equivalence 0C The filler layer thickness meeting the requirements is specifically operated as follows:
s3.1, obtaining mechanical parameters of the filler layer according to the formulated roadbed structure combination and the dynamic rebound modulus of the filler layer; then according to the principle of multilayer elastic lamellar system theory and roadbed top pressure strain equivalent, designing the layer number and layer thickness of roadbed structure combination, and calculating the comprehensive rebound modulus of all the filler layers based on the dynamic rebound modulus of the filler layers, namely roadbed top rebound modulus E 0C . At this time, the thickness of the layer should meet the requirement of JTG/T3610-2019 on the thickness of the filler layer in the roadbed structure combination, if not, the designed roadbed structure combination layer number and layer thickness should be adjusted until the requirements of strain and thickness are met at the same time.
And S3.2, selecting a structural design layer from filler layers contained in the roadbed, and simultaneously calculating the top compressive strain of the planned roadbed structural combination.
Step S3.3, combining the calculated roadbed structure with the top compressive strain and the comprehensive rebound modulus E 0C The compressive strain was compared:
(a) If the compressive strain at the top of the roadbed structure combination is greater than the comprehensive rebound modulus E 0C The selected structural design layer is thinned by pressing down strain, and each time the structural design layer is thinned by 1cm, the structural design layer is iterated in sequence until the top of the roadbed structure combinationCompressive strain is just near and greater than the combined modulus of elasticity E 0C The lower strain is applied to the substrate and the substrate is subjected to a lower strain,
(b) If the pressure strain at the top of the roadbed structure combination is smaller than the comprehensive rebound modulus E 0C The structural design layer is thickened under the downward compressive strain, each thickening is 1cm, and the steps are iterated in sequence until the compressive strain at the top of the roadbed structure combination is just close to and larger than the comprehensive rebound modulus E 0C And (3) lower strain.
Based on step S3, the final formulation results of the roadbed structure combinations are as follows in table 3:
TABLE 3 final subgrade structure composition
| Roadbed structure combination | Roadbed filling material | Filling thickness (m) | Layer number of filling |
| Road bed | Emulsified asphalt improving soil | 0.8 | 4 |
| Embankment for |
6% cement improved soil | 0.7 | 3 |
| |
4% cement improved soil | 0.7 | 3 |
| Soil foundation | Plain soil | - | - |
Step S4, a planning scheme based on roadbed structure combination: the method comprises the steps of (1) applying finite element software ABAQUS simulation analysis to simulate the settlement of a roadbed structure combination in the design period to judge whether the roadbed structure combination meets the settlement requirement of the top surface of the roadbed, and if not, further adjusting the roadbed structure combination scheme until the requirement is met.
Embodiment two:
take a highway-approaching example. The highway is immersed in the highway, which is an important section of 'nine-longitudinal five-transverse one-ring seven-link' in the regulation scheme of the highway network in Shandong province (2014-2030), the whole line adopts the standard of the bidirectional six-lane highway, the design speed is 120km/h, the total length is about 292 km, and the total investment amount is 348.2 hundred million yuan. Wherein, the total engineering quantity of the roadbed is more than 15000 square meters and is divided into four standard segments. The foundation soil for the high-speed main line is mainly made of powdery clay, has the engineering problems of looseness, low bearing capacity, difficult consolidation and the like, is partially immersed in saline soil foundation at high speed, and can fully utilize the existing roadbed filler to fill roadbed and reduce post-construction sedimentation, thus becoming the engineering technical problem to be solved in the process of being immersed in the high-speed construction.
The embodiment provides a high bearing capacity roadbed design method with gradually increasing modulus, which comprises the following implementation contents:
in the step S1, the roadbed structure combination comprises a soil base, a lower embankment, an upper embankment and a roadbed, and the rebound modulus E of the soil base is determined according to JTGD30-2015 of the highway roadbed design rule 0 =28 Mpa, the soil base bearing capacity is weak. According to the roadbed with high bearing capacityThe design requirement is that the rebound modulus at the top of the roadbed should reach 140MPa, and the roadbed needs to be comprehensively designed.
S2, based on mechanical index requirements of road surface design on the rebound modulus of the top surface of the roadbed, the comprehensive rebound modulus E of the top of the roadbed is drawn 0C 140MPa should be reached.
According to the principle of progressive increment of modulus from bottom to top, the subgrade structure combination is drawn up and comprises: soil base +6% cement improved soil +0.4% srx curative improved soil + graded crushed stone as shown in table 4 below:
TABLE 4 initial roadbed structure combination
Based on the planned roadbed structure combination, referring to JTGD30-2015 annex A of the highway roadbed design specification, the dynamic rebound modulus of the filler layer is calculated, and the concrete process is as follows:
(1) Preparing a sample by taking soil on site or remolding soil indoors to obtain a sample with the diameter of 150mm plus or minus 2mm, the height of 300mm plus or minus 2mm or the diameter of 100mm plus or minus 2mm and the height of 200mm plus or minus 2 mm;
(2) The sample is sleeved with rubber membranes and is arranged on the instrument base, and permeable stones are placed up and down;
and (3) mounting a displacement sensor: mounting LVDT or displacement sensors at the bottom and top of the sample for measuring displacement;
(3) Opening a drain valve, applying certain confining pressure around a sample, then pre-loading, applying pulse load, and taking the load and displacement of the last five times as calculated dynamic rebound modulus;
(4) The dynamic modulus of resilience is calculated as follows,
wherein M is R Representing dynamic rebound modulus and sigma of roadbed soil 0 -axial stress amplitude, ε 0 -axial strain amplitude.
Based on the formulated roadbed structure combinations, the dynamic rebound modulus of the filler layer is as follows in table 5:
table 5 results of the high speed subgrade filler parameter test
Step S3, calculating the rebound modulus E of the roadbed top based on the multilayer elastic layered system theory according to the principle of roadbed top pressure strain equivalence 0C The filler layer thickness meeting the requirements is specifically operated as follows:
s3.1, obtaining mechanical parameters of the filler layer according to the formulated roadbed structure combination and the dynamic rebound modulus of the filler layer; then according to the principle of multilayer elastic lamellar system theory and roadbed top pressure strain equivalent, designing the layer number and layer thickness of roadbed structure combination, and calculating the comprehensive rebound modulus of all the filler layers based on the dynamic rebound modulus of the filler layers, namely roadbed top rebound modulus E 0C . At this time, the thickness of the layer should meet the requirement of JTG/T3610-2019 on the thickness of the filler layer in the roadbed structure combination, if not, the designed roadbed structure combination layer number and layer thickness should be adjusted until the requirements of strain and thickness are met at the same time.
And S3.2, selecting a structural design layer from filler layers contained in the roadbed, and simultaneously calculating the top compressive strain of the planned roadbed structural combination.
Step S3.3, combining the calculated roadbed structure with the top compressive strain and the comprehensive rebound modulus E 0C The compressive strain was compared:
(a) If the compressive strain at the top of the roadbed structure combination is greater than the comprehensive rebound modulus E 0C The structural design layer is thinned by pressing down the strain, and each time the structural design layer is thinned by 1cm, the structural design layer is iterated in sequence until the compressive strain at the top of the roadbed structure combination is just close to and larger than the comprehensive rebound modulus E 0C The lower strain is applied to the substrate and the substrate is subjected to a lower strain,
(b) If the pressure strain at the top of the roadbed structure combination is smaller than the comprehensive rebound modulus E 0C The selected structural design layer is thickened under the downward compressive strain, each time is thickened by 1cm, and the layers are sequentially overlappedInstead, until the compressive strain at the top of the roadbed structure assembly is just close to and greater than the integrated modulus of resilience E 0C And (3) lower strain.
Based on step S3, the final formulation results of the roadbed structure combinations are as follows in table 6:
table 6 final formulated roadbed structure combinations
Step S4, a planning scheme based on roadbed structure combination: the method comprises the steps of (1) applying finite element software ABAQUS simulation analysis to simulate the settlement of a roadbed structure combination in the design period to judge whether the roadbed structure combination meets the settlement requirement of the top surface of the roadbed, and if not, further adjusting the roadbed structure combination scheme until the requirement is met.
In the execution of the first and second embodiments, it should be noted that: when the roadbed structure combination is formulated, the modulus of each layer of filler in the roadbed structure combination is subjected to humidity adjustment, and the reduction of the modulus by dry-wet circulation and freeze thawing circulation is considered; when humidity adjustment is carried out, the humidity adjustment coefficients of different fillers are specifically referred to as JTGD30-2015 in the highway subgrade design Specification.
In conclusion, the high bearing capacity roadbed design method with gradually increasing modulus realizes high bearing capacity of the roadbed, can obviously reduce settlement after roadbed construction, and solves the problem of unreasonable roadbed modulus value during pavement design; the invention also obviously improves the design level and the deformation of the roadbed, can obviously improve the bearing capacity and the stability of the roadbed, provides solid support for durable asphalt pavement, and greatly improves the construction quality and the service level of the roadbed.
The foregoing has outlined rather broadly the principles and embodiments of the present invention in order that the detailed description of the invention may be better understood. Based on the above-mentioned embodiments of the present invention, any improvements and modifications made by those skilled in the art without departing from the principles of the present invention should fall within the scope of the present invention.
Claims (8)
1. A design method of a high bearing capacity roadbed with gradually increasing modulus is characterized by comprising the following implementation contents:
step S1, determining the rebound modulus E of the soil base according to JTGD30-2015 of the highway subgrade design rule, wherein the roadbed structure combination comprises the soil base, the lower embankment, the upper embankment and the roadbed 0 ；
S2, based on mechanical index requirements of road surface design on the rebound modulus of the top surface of the roadbed, the comprehensive rebound modulus E of the top of the roadbed is drawn 0C According to the principle of progressive increment of modulus from bottom to top, the soil foundation, the lower embankment, the upper embankment and the roadbed of the roadbed structure combination are respectively prepared by selecting at least one filler from plain soil, emulsified asphalt solidified soil, emulsified asphalt improved soil, cement improved soil, curing agent improved soil, graded broken stone and low-dose cement stabilized broken stone, and then the dynamic rebound modulus of the filler layer is calculated by referring to JTGD30-2015 annex A of highway roadbed design Specification;
step S3, calculating the rebound modulus E of the roadbed top based on the multilayer elastic layered system theory according to the principle of roadbed top pressure strain equivalence 0C The filler layer thickness meeting the requirements is specifically operated as follows:
s3.1, obtaining mechanical parameters of the filler layer according to the formulated roadbed structure combination and the dynamic rebound modulus of the filler layer; then according to the principle of multilayer elastic lamellar system theory and roadbed top pressure strain equivalent, designing the layer number and layer thickness of roadbed structure combination, and calculating the comprehensive rebound modulus of all the filler layers based on the dynamic rebound modulus of the filler layers, namely roadbed top rebound modulus E 0C ，
S3.2, selecting a structural design layer from filler layers contained in the roadbed, simultaneously calculating the top compressive strain of the planned roadbed structural combination,
step S3.3, combining the calculated roadbed structure with the top compressive strain and the comprehensive rebound modulus E 0C The compressive strain was compared:
(a) If the compressive strain at the top of the roadbed structure combination is greater than the comprehensive rebound modulus E 0C The structural design layer is thinned by pressing down the strain, and each time the structural design layer is thinned by 1cm, the structural design layer is iterated in sequence until the compressive strain at the top of the roadbed structure combination is just close to and larger than the comprehensive rebound modulus E 0C The lower strain is applied to the substrate and the substrate is subjected to a lower strain,
(b) If the pressure strain at the top of the roadbed structure combination is smaller than the comprehensive rebound modulus E 0C The structural design layer is thickened under the downward compressive strain, each thickening is 1cm, and the steps are iterated in sequence until the compressive strain at the top of the roadbed structure combination is just close to and larger than the comprehensive rebound modulus E 0C Lower strain;
and S4, applying finite element software ABAQUS to simulate analysis, simulating the settlement of the roadbed structure combination in the design period, judging whether the settlement requirement of the roadbed top surface is met, and if the settlement requirement is not met, adjusting the roadbed structure combination until the settlement requirement is met.
2. The method for designing a roadbed with high bearing capacity, which is gradually increased in modulus according to claim 1, wherein the thickness of the roadbed in the roadbed structure combination is 0.5m-1.5m.
3. The method for designing the roadbed with high bearing capacity, which is gradually increased in modulus according to claim 2, wherein in the roadbed structure combination, the soil foundation, the lower embankment, the upper embankment and the roadbed respectively comprise 1-4 layers of fillers, and the thickness of the single-layer filler is 15cm-30cm.
4. A method of designing a high load bearing subgrade having a progressive increase in modulus according to claim 3, in which the ratio of the modulus of the upper layer of packing to the modulus of the adjacent lower layer of packing in said subgrade structure combination is 1.5 to 2.
5. The method for designing a roadbed with high bearing capacity, which is gradually increased in modulus according to claim 3, wherein in the roadbed structure combination, when graded broken stone or low-dose cement stabilized broken stone is selected as a roadbed, the thickness of a single-layer filler is 15cm-25m.
6. The method for designing a roadbed with high bearing capacity, which is gradually increased in modulus according to claim 3, wherein the step S2 is performed, and the dynamic rebound modulus of the filler layer is calculated by referring to appendix a of JTGD30-2015 of the highway roadbed design specification, which comprises the following steps:
(1) Preparing a sample by taking soil on site or remolding soil indoors to obtain a sample with the diameter of 150mm plus or minus 2mm, the height of 300mm plus or minus 2mm or the diameter of 100mm plus or minus 2mm and the height of 200mm plus or minus 2 mm;
(2) The sample is sleeved with rubber membranes and is arranged on the instrument base, and permeable stones are placed up and down;
and (3) mounting a displacement sensor: mounting LVDT or displacement sensors at the bottom and top of the sample for measuring displacement;
(3) Opening a drain valve, applying certain confining pressure around a sample, then pre-loading, applying pulse load, and taking the load and displacement of the last five times as calculated dynamic rebound modulus;
(4) The dynamic modulus of resilience is calculated as follows,
wherein M is R Representing dynamic rebound modulus and sigma of roadbed soil 0 -axial stress amplitude, ε 0 -axial strain amplitude.
7. The method for designing the roadbed with the high bearing capacity, which is gradually increased in modulus according to claim 6, is characterized in that when the layer thickness of the roadbed structure combination is designed in the step S3.1, the layer thickness shall meet the requirements of the JTG/T3610-2019 on the thickness of the filler layer in the roadbed structure combination, and if not, the designed layer number and the layer thickness of the roadbed structure combination shall be adjusted until the requirements of the strain and the thickness are met at the same time.
8. The method for designing the roadbed with the high bearing capacity, which is gradually increased in modulus, according to claim 1, is characterized in that when the roadbed structure combination is formulated, the modulus of each layer of filler in the roadbed structure combination is subjected to humidity adjustment, and the reduction of the modulus by a dry-wet cycle and a freeze-thawing cycle is considered; when humidity adjustment is carried out, the humidity adjustment coefficients of different fillers are specifically referred to as JTGD30-2015 in the highway subgrade design Specification.
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