CN113250010A - Large-particle-size asphalt macadam flexible ballast bed and construction method thereof - Google Patents
Large-particle-size asphalt macadam flexible ballast bed and construction method thereof Download PDFInfo
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- CN113250010A CN113250010A CN202110424617.6A CN202110424617A CN113250010A CN 113250010 A CN113250010 A CN 113250010A CN 202110424617 A CN202110424617 A CN 202110424617A CN 113250010 A CN113250010 A CN 113250010A
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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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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B26/00—Compositions of mortars, concrete or artificial stone, containing only organic binders, e.g. polymer or resin concrete
- C04B26/02—Macromolecular compounds
- C04B26/26—Bituminous materials, e.g. tar, pitch
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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
- E01B1/001—Track with ballast
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
- C04B2111/0075—Uses not provided for elsewhere in C04B2111/00 for road construction
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Abstract
The invention discloses a large-particle-size asphalt macadam flexible ballast bed and a construction method thereof, and belongs to the technical field of railway ballast beds. The large-particle-size asphalt macadam flexible ballast bed comprises a macadam ballast layer and a foundation bed which are arranged from top to bottom, and further comprises a large-particle-size asphalt macadam bottom ballast layer which is arranged between the macadam ballast layer and the foundation bed, wherein the large-particle-size asphalt macadam bottom ballast layer comprises the following components in parts by mass: 12-37 parts of 20-25mm coarse aggregate; 21-53 parts of 10-20mm coarse aggregate; 4-24 parts of 5-10mm coarse aggregate; 14-42 parts of 0-5mm fine aggregate; 0-6 parts of a filler; 2.5-3.5 parts of asphalt; 0.1-0.6 part of special additive. According to the invention, the large-particle-size asphalt macadam is laid on the bottom ballast layer, so that the bearing capacity and stability are stronger, the residual deformation of the track bed under the repeated action of the train load can be effectively reduced, the sinking of the track bed is reduced, the stability of the track bed is ensured, and the large-particle-size asphalt macadam mixture can uniformly distribute the dynamic stress generated by the train load to the surface layer of the foundation bed, improve the stress behavior of the foundation bed structure and improve the integrity of the foundation structure at the lower part of the track.
Description
Technical Field
The invention belongs to the technical field of railway ballast beds, and particularly relates to a large-particle-size asphalt macadam flexible ballast bed and a construction method thereof.
Background
The roadbed is used as the foundation of a railway track, the smoothness, the uniformity and the long-term stability of the roadbed are crucial to ensuring the safe operation of a high-speed train, the ballast pulverization and the sinking rate of the ballast bed with insufficient elasticity are accelerated under the action of heavy load, more than 90% of the settlement of the ballast track is caused by the sinking of the ballast bed according to incomplete statistics, and 80% of maintenance and repair work of the ballast track is carried out around the improvement of the ballast bed or other track diseases caused by the ballast bed diseases.
At present, the waterproof sealing layer of the high-speed railway roadbed in China mainly adopts a cement-based material, and due to the characteristics of large brittleness, poor deformation adaptability and the like of the cement-based material, the waterproof sealing layer is easy to crack irregularly, the waterproof effect of the waterproof sealing layer is greatly reduced, a series of problems such as roadbed frost heaving, slurry pouring, mud pumping and the like are caused, and the service state of the track structure is further degraded.
Through retrieval, the Chinese patent publication number: CN 104278598A; the publication date is as follows: 14 days 1 month 2015; the waterproof sealing layer is positioned between the pavement surface lines of a high-speed railway and at the road shoulder and comprises special modified asphalt, a special reinforcing agent, aggregate and filler, the thickness of the waterproof sealing layer is 35-100 mm, the bonding strength of the waterproof sealing layer and the concrete is not lower than 0.2MPa, the interface shear strength of the waterproof sealing layer and the concrete is not lower than 0.2MPa, the asphalt binder is special modified asphalt meeting PG70-34, and the total consumption of the reinforcing agent and the special modified asphalt in the self-compacting asphalt concrete is 7.0-10.0%. Compared with the existing waterproof sealing layer in a cement-based material form, the waterproof sealing layer composition of the application has the advantages that the seepage-proofing performance and the ageing resistance are improved to a certain extent, but in the waterproof sealing layer structure of the application, the consumption of special modified asphalt is high, the engineering cost is high, and the high-temperature stability is poor.
Disclosure of Invention
In order to solve at least one of the above technical problems, according to an aspect of the present invention, there is provided a large-particle-size asphalt macadam flexible ballast bed, including a macadam ballast layer and a foundation bed which are arranged from top to bottom, and further including a large-particle-size asphalt macadam ballast layer which is arranged between the macadam ballast layer and the foundation bed, wherein the large-particle-size asphalt macadam ballast layer includes the following components in parts by mass:
12-37 parts of 20-25mm coarse aggregate;
21-53 parts of 10-20mm coarse aggregate;
4-24 parts of 5-10mm coarse aggregate;
14-42 parts of 0-5mm fine aggregate;
0-6 parts of a filler;
2.5-3.5 parts of asphalt;
0.1-0.6 part of special additive.
According to the large-particle-size asphalt macadam flexible track bed, the large-particle-size asphalt macadam bottom ballast layer is adopted as the waterproof sealing layer between the gravel ballast layer and the foundation bed, and the large-particle-size asphalt macadam mixture prepared from the components in the scheme can resist large plasticity and shearing deformation, improves the high-temperature stability of an asphalt pavement, and has good anti-rutting and structural bearing performances; through reasonable grading design, the large-particle-size asphalt macadam flexible ballast bed has good waterproof, antifreezing and durability properties; in the scheme, the large-particle-size aggregates have more usage and correspondingly have less usage of asphalt, so that the construction cost is reduced, the development direction of cracks in the mixture is changed to a certain extent due to the large-particle-size aggregates, the development of the cracks is hindered, the cracking time is delayed, and the fatigue life is prolonged; the large-particle-size crushed stone bottom ballast layer is high in internal heat storage capacity, heat is not easy to dissipate and dissipate, construction in cold seasons is facilitated, and the construction period is prolonged.
Most of the existing surface layer structures for replacing graded broken stone foundation beds are medium-particle type AC graded asphalt concrete waterproof sealing layers, the asphalt consumption cannot be lower than 5% of the total mass, otherwise, the thickness of the asphalt film is insufficient, the performance of the whole waterproof sealing layer can be greatly reduced, in the large-particle-size asphalt broken stone bottom ballast layer, through the grading design, the large-particle-size aggregate is more, the filler consumption is reduced, the asphalt consumption can be reduced on the premise of not reducing the thickness of the asphalt film, the final asphalt consumption can be reduced to be lower than 4% of the total mass, the construction cost is effectively reduced, and the performance is ensured.
According to the large-particle-size asphalt macadam flexible ballast bed provided by the embodiment of the invention, optionally, the thickness of the macadam ballast layer is 150-300 mm;
the thickness of the large-particle-size asphalt macadam bottom ballast layer is 100-200 mm;
the side slope of the ballast bed is 1: 1.5.
In the scheme, the maximum nominal particle size of the large-particle-size asphalt macadam bottom ballast layer is 25-31.5 mm, the thickness of the large-particle-size asphalt macadam bottom ballast layer is designed to be 100-200 mm, the design specification is met, the convenience in rolling and compacting are considered, the thickness is not smaller than 2.5% -3% of the maximum nominal particle size after compaction, the large-particle-size asphalt macadam bottom ballast layer with the thickness can play a good mechanical property, and the function of protecting the structure can be better played than that of a macadam ballast, so that the thickness of the macadam ballast layer is properly reduced during design, and the thickness of the layer is smaller than that of the macadam ballast layer in the existing ballast bed structure.
According to the scheme, the ballast layer at the bottom of the large-particle-size asphalt macadam with good mechanical property and durability is used for partially replacing macadam ballasts in the high-speed rail, the supporting function of the ballast layer at the upper part can be improved, the stress diffusion effect is increased, the deformation protection effect on the roadbed soil is enhanced, and the bearing capacity of the roadbed is improved.
According to the large-particle-size asphalt macadam flexible ballast bed provided by the embodiment of the invention, optionally, the amount of the special additive in the ballast layer at the bottom of the large-particle-size macadam is 5% -9% of the mass of asphalt.
The special additive is mainly used for enhancing the high-temperature deformation resistance and fatigue durability of the mixture, the special additive is prepared by blending and processing high-molecular polymers such as waste tire rubber powder, polyethylene waste, SBS and SIS through a double-screw extruder, and is added as a direct feeding material in the preparation process of the mixture, the appearance of the special additive is dark gray or black, the diameter of the special additive is 2-5 mm, and the density of the special additive is about 0.95-1.10 g/mm3In the softening range of 130 toThe mixing amount is 5-9% of the asphalt dosage at 150 ℃, and the high-temperature deformation resistance and fatigue durability of the mixture can be greatly improved by adding the asphalt in the range.
According to the large-particle-size asphalt macadam flexible ballast bed provided by the embodiment of the invention, optionally, in the bottom ballast layer of the large-particle-size macadam, the content of needle-shaped particles of coarse aggregate is not more than 15%, the aggregate crushing value is not more than 26%, and the adhesion with asphalt is not lower than 5 grade.
According to the large-particle-size asphalt macadam flexible track bed provided by the embodiment of the invention, optionally, in the ballast layer at the bottom of the large-particle-size macadam, the angularity of fine aggregates is more than 50%, and the sand equivalent value is not less than 60%.
According to the large-particle-size asphalt macadam flexible ballast bed provided by the embodiment of the invention, optionally, in the large-particle-size macadam bottom ballast layer, the filler is limestone mineral powder, the water content is not more than 1%, the hydrophilic coefficient is less than 1, and the plasticity index is less than 4%.
According to the scheme, the coarse aggregate is rolled hard rock, the fine aggregate is hard rock aggregate produced by a counterattack type or hammer crusher, and the coarse aggregate, the fine aggregate and the filler are required to be screened according to the requirements in order to ensure the performance of the prepared mixture.
According to the large-particle-size asphalt macadam flexible track bed provided by the embodiment of the invention, optionally, in the ballast layer at the bottom of the large-particle-size macadam, asphalt is rubber powder-SBS composite modified asphalt, the penetration degree is 5-8 cm, and the elastic recovery rate is not less than 70%.
The asphalt in the scheme is prepared by adopting modified asphalt compounded by rubber powder and SBS and adopting a high-temperature screw extrusion desulfurization process, so that the rubber powder is firstly desulfurized and degraded, the rubber powder particles are thinned by destroying the crosslinked structure of the rubber powder particles, the rubber component is converted from a solid state to a viscous state, the mixing and melting of the rubber powder particles at a molecular level in the asphalt are conveniently realized, the rubber powder particles are more finely dispersed in the asphalt, and the physical swelling effect of the rubber component is fully exerted, so that the rubber powder-SBS composite modified asphalt with larger waste rubber mixing amount and more stable and excellent performance is prepared.
Further, the grading design is carried out by adopting a coarse aggregate framework embedding and extruding method, so that the coarse aggregates are mutually embedded and extruded in the asphalt mixture to form a framework structure, the coarse aggregates and the coarse aggregates are divided by the grain diameter of 10mm, the coarse aggregates are designed by adopting a grading embedding and extruding method, and the fine aggregates are calculated by referring to the design method of a Bailey method, so that the proportion of each grade of aggregates is obtained.
According to another aspect of the invention, a construction method of a large-particle size asphalt macadam flexible ballast bed is provided, which comprises the following steps:
firstly, treating the surface of a foundation bed: cleaning the surface of the foundation bed and spraying 1.3-1.5 kg/m2The hydrophobic anti-freezing emulsified asphalt is used for sealing the traffic for 24 hours until the asphalt is fully permeated;
secondly, processing the mixture of the large-particle-size asphalt macadam bottom ballast layer: mixing by adopting an intermittent mixer, firstly adding coarse aggregate and fine aggregate into the intermittent mixer, then adding a special additive, after dry mixing for 15s, sequentially adding filler and asphalt for mixing again, wherein the total mixing time is not less than 120s, and the discharging temperature is kept at 170-185 ℃;
thirdly, transporting materials: transporting the mixed mixture to a construction site;
fourthly, paving: the paver moves at a constant speed of not more than 2m/min, the loose paving coefficient is 1.2-1.3, and the paving temperature is not lower than 170 ℃;
fifthly, rolling:
primary pressing, namely, adopting a steel wheel road roller to follow a paver to advance for static pressure once, retreat for vibration pressure once, and then reciprocate for vibration pressure 2-3 times, wherein the primary pressing temperature is controlled at 150-160 ℃;
re-pressing, namely rolling back and forth for 2-3 times at a speed of 3-4 km/h by adopting a rubber-tyred roller;
compacting for 2 times by adopting a vibratory roller and the same process, and then carrying out static pressure once by using a rubber-wheel roller, wherein the temperature is not lower than 110 ℃ after the final pressing is finished;
sixthly, finishing construction: and after the construction is finished, the traffic is closed until the temperature of the ballast layer at the bottom of the large-particle-size gravel is naturally cooled to 50 ℃, and then the gravel ballast layer is paved.
In the scheme, the first step ensures the cohesiveness and the water tightness of the foundation bed and the large-particle-size asphalt macadam bottom ballast layer, cleans the surface of the foundation bed and ensures the rough and clean surface of the foundation bedNo floating soil and sundries, meets the requirements of cleanliness and flatness, and sprays 1.3-1.5 kg/m2The purpose of the hydrophobic anti-icing emulsified asphalt is to control the emulsified asphalt to permeate into the surface layer of the foundation bed to be not more than 5mm and not to form an oil film on the surface;
when the mixture is prepared in the second step, because the coarse and fine aggregates are separated greatly, the coarse aggregates are more and the asphalt dosage is less, in order to enable all particles to be coated with the asphalt, the total mixing time is ensured to be not less than 120s, in the mixing process, the heating temperature of the asphalt is controlled to be 160-190 ℃, because the fine aggregates in the large-particle-size asphalt macadam are less, in order to prevent overheating during heating, the heating temperature of the aggregates is controlled to be 180-200 ℃, the discharging temperature is kept to be 170-185 ℃, and the abandoning temperature is 195 ℃;
step three, when the mixture is transported, a large-scale dump truck with the volume of more than 30t is adopted for transporting, a separant is coated before loading every day to prevent fine aggregate accumulation and oil spots from forming, emergency braking is avoided as much as possible in the transporting process to reduce the segregation of the asphalt macadam, a skip car needs to move back and forth to be loaded in multiple piles when the transport car loads, the two ends and the middle part are firstly arranged to reduce the segregation of the asphalt macadam, the transport car needs to be provided with covering tarpaulin, and cotton quilts are used when the air temperature is low to reduce the heat loss of the asphalt macadam in the transporting process;
paving in a full-width paving mode, erecting wood baffles on two sides of a paving area during paving, limiting the asphalt macadam, and preventing the asphalt macadam from being scattered outside the construction area to influence the construction quality; the loose paving coefficient is controlled to be 1.2-1.3 because the large-particle-size asphalt macadam mixture has a large particle size, two layers of paving are needed, a lower layer structure is damaged when a second layer is paved, and the large-particle-size asphalt macadam adopts a framework embedding and extruding structure, so that the loose paving coefficient is properly improved in order to avoid more coarse aggregate crushing and mixture segregation, and the occurrence of coarse aggregate crushing and mixture segregation can be effectively reduced by controlling the loose paving coefficient to be 1.2-1.3;
in the rolling process, discontinuous watering is carried out when the steel wheel roller rolls to ensure that the wheel is not stuck, in order to avoid that the wheel is firstly sprinkled with rapeseed oil when the rubber wheel roller rolls, and watering is carried out for replacement when the temperature of the tire rises, and in the construction process, small rollers or impact rammers can be manually adopted for rolling in areas which are difficult to operate such as cable troughs, water collecting wells and other large rollers; and during final compaction, compacting twice by adopting the same process as that of the steel wheel roller, wherein each compaction comprises advancing static pressure once, retreating vibration pressure once and reciprocating vibration pressure for 2-3 times.
According to the construction method of the large-particle-size asphalt macadam flexible ballast bed provided by the embodiment of the invention, optionally, the mixture obtained in the second step is tested, and the required performance meets the following requirements for subsequent construction:
the porosity is not more than 4%;
marshall stability is not less than 5 KN;
the dynamic stability at 50 ℃ is not lower than 2400 times/mm;
low temperature bending test failure should be no less than 2800 mu epsilon;
the freeze-thaw splitting strength ratio and the residual stability are not less than 80%;
100kPa, 10Hz, and the dynamic modulus at 15 ℃ is more than 6000 Mpa;
10Hz, 15 ℃, 500 mu epsilon fatigue life more than 20 ten thousand times;
the water seepage rate is not more than 0 mL/min.
Compared with the prior art, the invention at least has the following beneficial effects:
(1) according to the invention, the large-particle-size asphalt macadam is paved on the ballast layer at the bottom of the ballast track bed of the ballast track, and the asphalt macadam has stronger bearing capacity and stability, can effectively reduce the residual deformation of the track bed under the repeated action of train load, reduces the sinking of the track bed, and ensures the integrity and stability of the track bed;
(2) the large-particle-size asphalt macadam mixture of the bottom ballast layer is a viscoelastic material with mechanical strength, durability and construction convenience, has good load diffusion capacity, can uniformly distribute dynamic stress generated by train load to the surface layer of the foundation bed, improves the stress behavior of the foundation bed structure, and improves the integrity of the foundation structure at the lower part of the track;
(3) the large-particle-size asphalt macadam bottom ballast layer has good mechanical properties, has a better protection effect on a foundation bed compared with a macadam ballast, can reduce the pavement thickness of the ballast bed by 10-20 cm by partially replacing the macadam ballast, and realizes the integral optimization of the structure;
(4) the bottom ballast layer is well graded, and compared with the traditional compact asphalt concrete, the asphalt consumption is lower, so that the construction cost is greatly reduced;
(5) the large-particle-size asphalt macadam mixture can be paved with a larger thickness at one time, so that the construction speed of the project is improved, the equipment investment is reduced, the construction cost of the project is reduced, in addition, the heat storage capacity in the asphalt layer is high, the heat is not easy to dissipate, the construction in cold seasons is facilitated, and the construction period is prolonged;
(6) the ballast layer at the bottom of the large-particle-size asphalt macadam has small void ratio, can well play the waterproof and anti-permeability capacity, reduce the occurrence of roadbed soil diseases, and ensure the firmness and stability of a roadbed, thereby improving the service state of the roadbed.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly described below, and it is apparent that the drawings in the following description only relate to some embodiments of the present invention and are not limiting on the present invention.
FIG. 1 shows a schematic view of a large particle size bituminous macadam flexible track bed of the present invention;
reference numerals:
1. a ballast layer of a gravel road; 2. a foundation bed; 3. a large-particle-size asphalt macadam bottom ballast layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments.
As shown in fig. 1, the large-particle-size asphalt macadam bottom ballast layer 3 of the embodiment is arranged between the crushed stone ballast layer 1 and the surface layer of the foundation bed 2, the slope of the side slope of the foundation bed is controlled to be 1:1.5 for facilitating drainage, the bonding strength and the shear strength between the large-particle-size asphalt macadam bottom ballast layer 3 and the surface layer of the foundation bed 2 are not lower than 0.2MPa, and the asphalt performance is not lower than PG 78-22.
Example 1
In this embodiment, the ballast layer 3 with the large-particle-size crushed stone bottom comprises the following components in parts by mass:
20 parts of 20-25mm coarse aggregate;
21 parts of 10-20mm coarse aggregate;
4 parts of 5-10mm coarse aggregate;
14 parts of 0-5mm fine aggregate;
1 part of limestone mineral powder;
2.5 parts of asphalt;
0.1 part of special additive.
For the construction site, the specific construction method of the embodiment is as follows:
firstly, treating the surface of a foundation bed: cleaning the surface of the foundation bed and spraying 1.3kg/m2The hydrophobic anti-freezing emulsified asphalt is used for sealing the traffic for 24 hours until the asphalt is fully permeated;
secondly, processing the mixture of the large-particle-size asphalt macadam bottom ballast layer: mixing by adopting an intermittent mixer, firstly adding coarse aggregate and fine aggregate into the intermittent mixer, then adding a special additive, after dry-mixing for 15s at 180 ℃, sequentially adding limestone mineral powder and asphalt, and mixing again at 160 ℃, wherein the total mixing time is 125s, and the discharging temperature is 170 ℃;
thirdly, transporting materials: transporting the mixed mixture to a construction site;
fourthly, paving: the paver advances at a constant speed of not more than 2m/min, the loose paving coefficient is 1.2, and the paving temperature is not lower than 170 ℃;
fifthly, rolling:
primary pressure, wherein a steel wheel road roller is adopted to closely follow a paver to advance for static pressure once, retreat for vibration pressure once, and then reciprocate for vibration pressure 2 times, and the primary pressure temperature is controlled at 150 ℃;
re-pressing, namely performing back-and-forth rolling for 2 times at the speed of 3km/h by adopting a rubber-tyred roller;
compacting for 2 times by adopting a vibratory roller and the same process, and then carrying out static pressure once by using a rubber-wheel roller, wherein the temperature is not lower than 110 ℃ after the final pressing is finished;
sixthly, finishing construction: and after the construction is finished, the traffic is closed until the temperature of the large-particle-size gravel bottom ballast layer 3 is naturally cooled to 50 ℃, and then the gravel ballast layer 1 is paved.
The thickness of the crushed stone ballast layer 1 is 150mm, and the thickness of the large-particle-size asphalt crushed stone bottom ballast layer is 200 mm.
The large particle size bituminous macadam mixture of this example is graded as follows:
TABLE 1 grading Table for large-particle-size bituminous macadam mixture in example 1
The road performance evaluation test is carried out on the large-particle-size asphalt macadam mixture, and the obtained results are shown in the following table:
table 2, example 1 evaluation table for road performance of large-particle-size bituminous macadam mixture
After the construction is finished, the construction position is checked, and the results are as follows:
table 3, table of the detection results of the completion of the construction in example 1
Example 2
In this embodiment, the ballast layer 3 with the large-particle-size crushed stone bottom comprises the following components in parts by mass:
37 parts of 20-25mm coarse aggregate;
53 parts of 10-20mm coarse aggregate;
24 parts of 5-10mm coarse aggregate;
42 parts of 0-5mm fine aggregate;
6 parts of limestone mineral powder;
3.5 parts of asphalt;
0.6 part of special additive.
For the construction site, the specific construction method of the embodiment is as follows:
firstly, treating the surface of a foundation bed: cleaning the surface of the foundation bed and spraying 1.5kg/m2The hydrophobic anti-freezing emulsified asphalt is used for sealing the traffic for 24 hours until the asphalt is fully permeated;
secondly, processing the mixture of the large-particle-size asphalt macadam bottom ballast layer: mixing by adopting an intermittent mixer, firstly adding coarse aggregate and fine aggregate into the intermittent mixer, then adding a special additive, after dry-mixing for 15s at 200 ℃, sequentially adding limestone mineral powder and asphalt, and mixing again at 190 ℃, wherein the total mixing time is 140s, and the discharging temperature is 185 ℃;
thirdly, transporting materials: transporting the mixed mixture to a construction site;
fourthly, paving: the paver advances at a constant speed of not more than 2m/min, the loose paving coefficient is 1.3, and the paving temperature is not lower than 170 ℃;
fifthly, rolling:
primary pressure, wherein a steel wheel road roller is adopted to closely follow a paver to advance for static pressure once, retreat for vibration pressure once, and then reciprocate for vibration pressure 3 times, and the primary pressure temperature is controlled at 160 ℃;
re-pressing, namely rolling for 3 times in a reciprocating way at the speed of 4km/h by adopting a rubber-tyred roller;
compacting for 2 times by adopting a vibratory roller and the same process, and then carrying out static pressure once by using a rubber-wheel roller, wherein the temperature is not lower than 110 ℃ after the final pressing is finished;
sixthly, finishing construction: and after the construction is finished, the traffic is closed until the temperature of the large-particle-size gravel bottom ballast layer 3 is naturally cooled to 50 ℃, and then the gravel ballast layer 1 is paved.
The thickness of the crushed stone ballast layer 1 is 300mm, and the thickness of the large-particle-size asphalt crushed stone bottom ballast layer is 100 mm.
The large particle size bituminous macadam mixture of this example is graded as follows:
TABLE 4 grading table of large-particle-size bituminous macadam mixture in example 2
The road performance evaluation test is carried out on the large-particle-size asphalt macadam mixture, and the obtained results are shown in the following table:
table 5, example 2 road performance evaluation table for large particle size bituminous macadam mixture
After the construction is finished, the construction position is checked, and the results are as follows:
table 6, example 2 construction completion detection result table
Example 3
In this embodiment, the ballast layer 3 with the large-particle-size crushed stone bottom comprises the following components in parts by mass:
12 parts of 20-25mm coarse aggregate;
33 parts of 10-20mm coarse aggregate;
18 parts of 5-10mm coarse aggregate;
10 parts of 0-5mm fine aggregate;
5 parts of limestone mineral powder;
2.9 parts of asphalt;
0.3 part of special additive.
For the construction site, the specific construction method of the embodiment is as follows:
firstly, treating the surface of a foundation bed: cleaning the surface of the foundation bed and spraying 1.4kg/m2The hydrophobic anti-freezing emulsified asphalt is used for sealing the traffic for 24 hours until the asphalt is fully permeated;
secondly, processing the mixture of the large-particle-size asphalt macadam bottom ballast layer: mixing by adopting an intermittent mixer, firstly adding coarse aggregate and fine aggregate into the intermittent mixer, then adding a special additive, after dry-mixing for 15s at 190 ℃, sequentially adding limestone mineral powder and asphalt, and mixing again at 180 ℃, wherein the total mixing time is 130s, and the discharging temperature is 180 ℃;
thirdly, transporting materials: transporting the mixed mixture to a construction site;
fourthly, paving: the paver advances at a constant speed of not more than 2m/min, the loose paving coefficient is 1.3, and the paving temperature is not lower than 170 ℃;
fifthly, rolling:
primary pressure, wherein a steel wheel road roller is adopted to closely follow a paver to advance for static pressure once, retreat for vibration pressure once, and then reciprocate for vibration pressure 3 times, and the primary pressure temperature is controlled at 160 ℃;
re-pressing, namely rolling for 3 times in a reciprocating way at the speed of 4km/h by adopting a rubber-tyred roller;
compacting for 2 times by adopting a vibratory roller and the same process, and then carrying out static pressure once by using a rubber-wheel roller, wherein the temperature is not lower than 110 ℃ after the final pressing is finished;
sixthly, finishing construction: and after the construction is finished, the traffic is closed until the temperature of the large-particle-size gravel bottom ballast layer 3 is naturally cooled to 50 ℃, and then the gravel ballast layer 1 is paved.
The thickness of the crushed stone ballast layer 1 is 200mm, and the thickness of the large-particle-size asphalt crushed stone bottom ballast layer is 150 mm.
The large particle size bituminous macadam mixture of this example is graded as follows:
TABLE 7 grading table for large-particle-size bituminous macadam mixture in example 3
The road performance evaluation test is carried out on the large-particle-size asphalt macadam mixture, and the obtained results are shown in the following table:
TABLE 8 and EXAMPLE 3 evaluation table for road performance of large-particle-size bituminous macadam mixture
After the construction is finished, the construction position is checked, and the results are as follows:
TABLE 9 TABLE 3 examination result table for construction completion
Comparative example
In the comparative example, the bottom ballast layer is composed of the following components in parts by mass:
10-20mm coarse aggregate: 5 portions of
5-10mm coarse aggregate: 18 portions of
3-5mm fine aggregate: 5 portions of
0-3mm fine aggregate: 8 portions of
Limestone mineral powder: 2 parts of (1);
asphalt: 3.5 parts of
Special additive: 0.1 part
The construction method is the same as that in the prior art.
The bottom ballast layer of the comparative example adopts the improved AC-16 asphalt mixture, belongs to the medium-grain compact asphalt concrete, and is used as a waterproof sealing layer, and the performances such as the anti-permeability, the deformation adaptability and the like are greatly improved compared with the traditional cement-based material.
The road performance evaluation test is carried out on the bottom ballast layer material, and the obtained results are shown in the following table:
TABLE 10 road performance evaluation table for ballast layer material at bottom of comparative example
Through comparison of the comparative example and the examples 1, 2 and 3, the large-particle size asphalt-crushed stone mixtures of the examples 1, 2 and 3 have more excellent high and low temperature performance and water damage resistance than the materials of the comparative example, the consumption of asphalt in the examples 1, 2 and 3 is very low, the construction cost is lower, and the results of the test tables show that the construction of the examples 1, 2 and 3 can meet various standard requirements and the service state is good.
The examples described herein are merely illustrative of the preferred embodiments of the present invention and do not limit the spirit and scope of the present invention, and various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the design concept of the present invention shall fall within the protection scope of the present invention.
Claims (9)
1. The large-particle-size asphalt macadam flexible ballast bed comprises a macadam ballast layer and a foundation bed which are arranged from top to bottom, and is characterized by further comprising a large-particle-size asphalt macadam bottom ballast layer arranged between the macadam ballast layer and the foundation bed, wherein the large-particle-size asphalt macadam bottom ballast layer comprises the following components in parts by weight:
12-37 parts of 20-25mm coarse aggregate;
21-53 parts of 10-20mm coarse aggregate;
4-24 parts of 5-10mm coarse aggregate;
14-42 parts of 0-5mm fine aggregate;
0-6 parts of a filler;
2.5-3.5 parts of asphalt;
0.1-0.6 part of special additive.
2. The large-particle-size asphalt macadam flexible ballast bed according to claim 1, wherein:
the thickness of the ballast layer of the gravel road is 150-300 mm;
the thickness of the large-particle-size asphalt macadam bottom ballast layer is 100-200 mm;
the side slope of the ballast bed is 1: 1.5.
3. The large-particle-size asphalt macadam flexible ballast bed according to claim 2, wherein: in the large-particle-size crushed stone bottom ballast layer, the dosage of the special additive is 5-9% of the mass of the asphalt.
4. A large particle size bituminous macadam flexible ballast bed according to claim 3, wherein: in the large-particle-size gravel bottom ballast layer, the content of needle-shaped flaky particles of coarse aggregate is not more than 15%, the crushing value of the aggregate is not more than 26%, and the adhesion with asphalt is not lower than 5 grade.
5. A large particle size bituminous macadam flexible ballast bed according to claim 3, wherein: in the ballast layer at the bottom of the large-particle-size gravel, the angularity of a fine aggregate is more than 50%, and the sand equivalent value is not less than 60%.
6. A large particle size bituminous macadam flexible ballast bed according to claim 3, wherein: in the large-particle-size crushed stone bottom ballast layer, the filler is limestone mineral powder, the water content is not more than 1%, the hydrophilic coefficient is less than 1, and the plasticity index is less than 4%.
7. A large particle size bituminous macadam flexible ballast bed according to claim 3, wherein: in the ballast layer at the bottom of the large-particle-size gravel, the asphalt is rubber powder-SBS (styrene butadiene styrene) composite modified asphalt, the penetration degree is 5-8 cm, and the elastic recovery rate is not less than 70%.
8. A construction method of a large-particle-size asphalt macadam flexible ballast bed is characterized by comprising the following steps:
firstly, treating the surface of a foundation bed: cleaning the surface of the foundation bed and spraying 1.3-1.5 kg/m2The hydrophobic anti-freezing emulsified asphalt is used for sealing the traffic for 24 hours until the asphalt is fully permeated;
secondly, processing the mixture of the large-particle-size asphalt macadam bottom ballast layer: mixing by adopting an intermittent mixer, firstly adding coarse aggregate and fine aggregate into the intermittent mixer, then adding a special additive, after dry mixing for 15s, sequentially adding filler and asphalt for mixing again, wherein the total mixing time is not less than 120s, and the discharging temperature is kept at 170-185 ℃;
thirdly, transporting materials: transporting the mixed mixture to a construction site;
fourthly, paving: the paver moves at a constant speed of not more than 2m/min, the loose paving coefficient is 1.2-1.3, and the paving temperature is not lower than 170 ℃;
fifthly, rolling:
primary pressing, namely, adopting a steel wheel road roller to follow a paver to advance for static pressure once, retreat for vibration pressure once, and then reciprocate for vibration pressure 2-3 times, wherein the primary pressing temperature is controlled at 150-160 ℃;
re-pressing, namely rolling back and forth for 2-3 times at a speed of 3-4 km/h by adopting a rubber-tyred roller;
compacting for 2 times by adopting a vibratory roller and the same process, and then carrying out static pressure once by using a rubber-wheel roller, wherein the temperature is not lower than 110 ℃ after the final pressing is finished;
sixthly, finishing construction: and after the construction is finished, the traffic is closed until the temperature of the ballast layer at the bottom of the large-particle-size gravel is naturally cooled to 50 ℃, and then the gravel ballast layer is paved.
9. The construction method of the large-particle size asphalt macadam flexible ballast bed according to claim 8, wherein the mixture obtained in the second step is inspected, and the performance of the mixture is required to meet the following requirements for subsequent construction:
the porosity is not more than 4%;
marshall stability is not less than 5 KN;
the dynamic stability at 50 ℃ is not lower than 2400 times/mm;
low temperature bending test failure should be no less than 2800 mu epsilon;
the freeze-thaw splitting strength ratio and the residual stability are not less than 80%;
100kPa, 10Hz, and the dynamic modulus at 15 ℃ is more than 6000 Mpa;
10Hz, 15 ℃, 500 mu epsilon fatigue life more than 20 ten thousand times;
the water seepage rate is not more than 0 mL/min.
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