阅读说明：本技术 高速铁路沥青级配碎石基床及其施工方法 (Asphalt graded broken stone foundation bed for high-speed railway and construction method thereof ) 是由 蔡德钩 叶阳升 姚建平 楼梁伟 石越峰 杨国涛 魏少伟 吕宋 耿琳 叶晓宇 张也 于 2020-03-12 设计创作，主要内容包括：本发明提供一种高速铁路沥青级配碎石基床的施工方法,其包括如下步骤：施工准备、透层沥青和/或粘层沥青洒布、沥青级配碎石的拌和、沥青级配碎石的运输、沥青级配碎石的摊铺、沥青级配碎石的压实与沥青级配碎石的养护。本发明还提供一种本发明的方法制得的高速铁路沥青级配碎石基床。通过本发明的施工方法制得的沥青级配碎石基床作为一种新的高速铁路路基结构形式,可节约路基填料,提高路基承载能力和防水排水能力,延长路基服役寿命,具有广阔的应用前景,并且具有显著的经济和社会效益。(The invention provides a construction method of a high-speed railway asphalt graded crushed stone foundation bed, which comprises the following steps: construction preparation, permeable asphalt and/or sticky asphalt distribution, asphalt graded broken stone mixing, asphalt graded broken stone transportation, asphalt graded broken stone paving, asphalt graded broken stone compaction and asphalt graded broken stone maintenance. The invention also provides a high-speed railway asphalt graded crushed stone foundation bed prepared by the method. As a new roadbed structure form of the high-speed railway, the asphalt graded broken stone foundation bed prepared by the construction method can save roadbed fillers, improve the bearing capacity and waterproof and drainage capacity of the roadbed, prolong the service life of the roadbed, has wide application prospect and has obvious economic and social benefits.)

1. A construction method of a high-speed railway asphalt graded crushed stone foundation bed comprises the following steps:

(1) preparation for construction

Rechecking the top surface elevation, the geometric dimension and the quality of the graded crushed stone on the surface layer of the foundation bed to ensure that the top surface elevation, the geometric dimension and the quality of the graded crushed stone on the surface layer of the foundation bed meet the regulations in the design Specifications for railway subgrades TB10001 and the design Specifications for high-speed railways TB 10621; then, hanging a construction lead or a guide beam for controlling the elevation of the top surface of the asphalt graded crushed stone;

(2) spreading of permeable asphalt and/or adhesive layer asphalt

When the design thickness of the asphalt graded broken stone is less than or equal to 10cm, designing, paving and compacting according to a layer of asphalt graded broken stone layer;

when the design thickness of the asphalt graded broken stone is more than 10cm, the asphalt graded broken stone is designed in a layered mode and paved and compacted in a layered mode;

distributing permeable asphalt between the graded crushed stone layer and the asphalt graded crushed stone layer on the surface layer of the foundation bed, and distributing adhesive layer asphalt between the asphalt graded crushed stone layers;

(3) mixing of asphalt graded crushed stone

Controlling the heating temperature of the asphalt to be 160-190 ℃, wherein the heating temperature of the aggregate is 10-30 ℃ higher than that of the asphalt; mixing the heated asphalt, the heated aggregate, the limestone powder and the asphalt reinforcing agent by using an intermittent mixer to form asphalt graded broken stone, and controlling the discharge temperature of the asphalt graded broken stone to be 170-195 ℃;

(4) transportation of asphalt graded crushed stone

A material transporting vehicle with the load of more than 12 tons is adopted to transport asphalt graded broken stones, and balanced loading is carried out when the material transporting vehicle is loaded from a mixer, so as to prevent coarse aggregate and fine aggregate from being separated;

(5) paving of asphalt graded broken stone

Paving by using a full-automatic asphalt paver, and preheating a screed plate of the paver to be more than 100 ℃ before paving; the temperature of the asphalt graded broken stone before paving is not lower than 160 ℃;

(6) compaction of asphalt graded macadam

Compacting by adopting initial pressure, re-pressure and final pressure according to a mode of combining a steel wheel road roller and a tire type road roller;

(7) maintenance of asphalt graded crushed stone

And after the spreading layer of the asphalt graded broken stone is completely and naturally cooled and the surface temperature of the asphalt graded broken stone is lower than 50 ℃, the traffic can be opened.

2. The method of claim 1, wherein the construction preparation in step (1) further comprises ensuring the following construction conditions: the construction is not carried out under the conditions of strong wind and rain with the temperature lower than 10 ℃, 5 grades and above.

3. The method according to claim 1, wherein the amount of the spread of the asphalt for tack coat in the step (2) is 0.3 to 0.6L/m²；

Preferably, the spreading amount of the permeable asphalt in the step (2) is 0.7-2.0L/m²；

Preferably, after the permeable asphalt in the step (2) is spread, the traffic is closed, and after the permeable asphalt is fully permeated and the moisture is evaporated, the asphalt graded broken stone is paved within 48 hours;

preferably, the sticky layer asphalt in the step (2) is sprayed on the day of paving the asphalt graded broken stone, and after the sticky layer asphalt is demulsified and the water evaporation is finished, the paving of the asphalt graded broken stone is followed;

preferably, when the asphalt graded broken stone in the step (2) is designed according to one layer, the asphalt graded broken stone with the specification of AGCS-16 is selected; when the asphalt graded broken stones in the step (2) are designed in a layered mode, the first layer is the asphalt graded broken stones with the specification of AGCS-16 from top to bottom, and the other layers are the asphalt graded broken stones with the specification of AGCS-20 or AGCS-25 respectively and independently.

4. The method as claimed in claim 1, wherein the production cycle per disc of the batch mixer in the step (3) is not less than 45s, and the dry mixing time is not less than 10 s.

5. The method as claimed in claim 1, wherein the spreading speed of the spreading machine in the step (5) is controlled to be 1-3 m/min.

6. The method according to claim 1, wherein the total mass of the steel-wheel road roller in the step (6) is not less than 12t, the vibration frequency is 35-50 Hz, and the amplitude is 0.3-0.8 mm;

preferably, the total mass of the tyre-type road roller in the step (6) is not less than 25t, the pressure of each tyre is not less than 15kN, the inflation pressure of the tyre in a cold state is not less than 0.55MPa, the air pressure of the heated tyre is not less than 0.6MPa, and the air pressure of each tyre is approximately the same.

7. The method according to claim 1, wherein the primary pressing in the step (6) comprises static pressing of a steel wheel roller for 2-4 times, and the internal temperature of the asphalt graded broken stone at the beginning of the primary pressing is not lower than 150 ℃; and the static pressure rolling speed of the steel wheel road roller is 2-3 km/h.

8. The method of claim 1, wherein the re-compacting in step (6) comprises 4-6 times of steel wheel roller compaction and 4-8 times of tire roller compaction; the vibration and compression rolling speed of the steel wheel road roller is 3-5 km/h; the rolling speed of the rubber-tyred road roller is 3-6 km/h; the repressing is carried out closely after the initial pressure is finished.

9. The method of claim 1, wherein the final compaction in step (6) comprises hydrostatic pressing of the steel-wheel roller for 2-4 times; the static pressure rolling speed of the steel wheel road roller is 3-6 km/h; the surface temperature of the asphalt graded crushed stone after the final pressure is finished is not lower than 90 ℃.

10. A high speed railway asphalt graded crushed stone foundation bed prepared by the method of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of high-speed railway roadbed structures. Specifically, the invention relates to a high-speed railway asphalt graded crushed stone foundation bed and a construction method thereof.

Background

The main foundation bed structure of the high-speed railway in China mainly comprises a foundation bed surface layer and a foundation bed bottom layer, wherein the foundation bed surface layer is I-type or II-type graded broken stones of the railway, and cement can be added into the graded broken stones if the frost heaving prevention of the railway bed is considered; the bed bottom layer was made up of A, B sets of packing.

The asphalt graded broken stone consists of asphalt, coarse aggregate, fine aggregate, limestone powder, asphalt reinforcing agent and the like, and has the characteristics of good water resistance, bearing capacity, cracking resistance and fatigue resistance. The asphalt graded broken stone is paved on the surface of the foundation bed surface layer in a full-section way and is used as a part of the foundation bed surface layer, so that the stress state and the waterproof and drainage capacity of the foundation bed structure can be improved, the optimization of the high-speed railway roadbed structure is realized, roadbed filling materials are saved, the service performance of the high-speed railway roadbed is improved, the service life of the high-speed railway roadbed is prolonged, and the asphalt graded broken stone has remarkable economic and social benefits.

The compaction quality of the asphalt graded broken stone and the temperature control in the whole construction process directly influence the service performance and the service life of the asphalt graded broken stone foundation bed. The main factors influencing the compaction effect of the asphalt graded broken stones comprise the matching combination of temperature control and compaction machinery in the whole construction process. If the construction temperature of each link is too high, the asphalt graded broken stone is aged, and the service life of the asphalt graded broken stone is influenced; if the construction temperature of each link is too low, the viscosity of the asphalt material is high, so that the asphalt graded broken stone is difficult to compact to a target void ratio (design void ratio), and the performance requirement of indoor mixing ratio can not be met. Therefore, the construction temperature of each link of the asphalt graded broken stone needs to be reasonably controlled, and the aging of the asphalt graded broken stone is avoided while the construction workability is ensured. In addition, according to the characteristics of the asphalt graded crushed stone material, it is important to clearly control the compaction work required for compacting to a target void ratio (designed void ratio) or a target compaction degree, reasonably select a compaction machine, and determine a combination mode of the compaction machine.

Therefore, it is urgently needed to provide a high-speed railway asphalt graded crushed stone foundation bed structure and form a matched construction method to ensure the construction quality and the implementation effect of the foundation bed structure.

Disclosure of Invention

The invention aims to provide a construction method for ensuring the construction quality and the use effect of a high-speed railway asphalt graded broken stone foundation bed.

The above object of the present invention is achieved by the following means.

In the context of the present invention, the term "aggregate" refers to granules comprising fine aggregates and coarse aggregates which act as a framework and a filler in the mix, including crushed stone, gravel, machine-made sand, stone chips, sand and the like. The coarse aggregate is crushed stone with the particle size of more than 2.36mm, crushed gravel, screened gravel, slag and the like; the fine aggregate refers to natural sand, artificial sand (including machine-made sand), stone chips and the like with the particle size of less than 2.36 mm.

In the context of the present invention, the term "asphalt reinforcing agent" may be a commercially available asphalt reinforcing agent, preferably the "aggregate interface reinforcing agent for asphalt concrete" disclosed in patent application No. 201711236017.7, which is incorporated herein by reference in its entirety. The asphalt reinforcing agent is prepared from the following components in percentage by weight: 10-50% of elastomer, 30-50% of synthetic resin, 5-30% of fusion oil, 0-0.5% of color master batch and 0.25-1.25% of antioxidant. The elastomer is one or more of styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer and polystyrene butadiene copolymer. The synthetic resin is one or more of petroleum resin, polyethylene resin and polystyrene resin. The fusion oil is one or more of kerosene, lubricating engine oil and diesel oil. The color master is resin pigment. The antioxidant is rosin pentaerythritol ester. The preparation method of the asphalt reinforcing agent comprises the following steps: sequentially adding the elastomer, the synthetic resin, the color master and the antioxidant into a stirrer for stirring, then adding the fusion oil for continuously stirring uniformly, and standing for 24 hours at normal temperature; uniformly mixing and melting the mixture by a screw machine at the temperature of 110-180 ℃, extruding and molding the mixture, and cooling and cutting the mixture to form a cylindrical granular product.

On one hand, the invention provides a construction method of a high-speed railway asphalt graded crushed stone foundation bed, which comprises the following steps:

(1) preparation for construction

Rechecking the top surface elevation, the geometric dimension and the quality of the graded crushed stone on the surface layer of the foundation bed to ensure that the top surface elevation, the geometric dimension and the quality of the graded crushed stone on the surface layer of the foundation bed meet the regulations in the design Specifications for railway subgrades TB10001 and the design Specifications for high-speed railways TB 10621; then, hanging a construction lead or a guide beam for controlling the elevation of the top surface of the asphalt graded crushed stone;

(2) spreading of permeable asphalt and/or adhesive layer asphalt

When the design thickness of the asphalt graded broken stone is less than or equal to 10cm, designing, paving and compacting according to a layer of asphalt graded broken stone layer;

when the design thickness of the asphalt graded broken stone is more than 10cm, the asphalt graded broken stone is designed in a layered mode and paved and compacted in a layered mode;

distributing permeable asphalt between the graded crushed stone layer and the asphalt graded crushed stone layer on the surface layer of the foundation bed, and distributing adhesive layer asphalt between the asphalt graded crushed stone layers;

(3) mixing of asphalt graded crushed stone

Controlling the heating temperature of the asphalt to be 160-190 ℃, wherein the heating temperature of the aggregate is 10-30 ℃ higher than that of the asphalt; mixing the heated asphalt, the heated aggregate, the limestone powder and the asphalt reinforcing agent by using an intermittent mixer to form asphalt graded broken stone, and controlling the discharge temperature of the asphalt graded broken stone to be 170-195 ℃;

(4) transportation of asphalt graded crushed stone

A material transporting vehicle with the load of more than 12 tons is adopted to transport asphalt graded broken stones, and balanced loading is carried out when the material transporting vehicle is loaded from a mixer, so as to prevent coarse aggregate and fine aggregate from being separated;

(5) paving of asphalt graded broken stone

Paving by using a full-automatic asphalt paver, and preheating a screed plate of the paver to be more than 100 ℃ before paving; the temperature of the asphalt graded broken stone before paving is not lower than 160 ℃;

(6) compaction of asphalt graded macadam

Compacting by adopting initial pressure, re-pressure and final pressure according to a mode of combining a steel wheel road roller and a tire type road roller;

(7) maintenance of asphalt graded crushed stone

And after the spreading layer of the asphalt graded broken stone is completely and naturally cooled and the surface temperature of the asphalt graded broken stone is lower than 50 ℃, the traffic can be opened.

Preferably, in the method of the present invention, the construction preparation in the step (1) further includes ensuring the following construction conditions: the construction is not carried out under the conditions of strong wind and rain with the temperature lower than 10 ℃, 5 grades and above.

Preferably, in the method of the present invention, the spreading amount of the asphalt for the sticky layer in the step (2) is 0.3 to 0.6L/m²。

Preferably, in the method of the present invention, the amount of the through-layer asphalt to be spread in the step (2) is 0.7 to 2.0L/m²。

Preferably, in the method of the present invention, after the permeable asphalt in the step (2) is spread, the traffic is closed, and after the permeable asphalt is fully penetrated and the moisture evaporation is completed, the asphalt graded crushed stone is paved within 48 hours.

Preferably, in the method of the present invention, the sticky asphalt in step (2) is spread on the day of paving the asphalt graded broken stone, and after the sticky asphalt is demulsified and the water evaporation is completed, the paving of the asphalt graded broken stone is followed.

Preferably, in the method of the present invention, when the asphalt graded crushed stone in the step (2) is designed according to one layer, the asphalt graded crushed stone with the specification of AGCS-16 is selected; when the asphalt graded broken stones in the step (2) are designed in a layered mode, the first layer is the asphalt graded broken stones with the specification of AGCS-16 from top to bottom, and the other layers are the asphalt graded broken stones with the specification of AGCS-20 or AGCS-25 respectively and independently.

In the present invention, the Asphalt Graded Crushed Stone can be classified into three specifications of AGCS-25, AGCS-20 and AGCS-16, wherein AGCS represents Asphalt Graded Crushed Stone (AGCS), and the numerical value represents nominal maximum particle size of aggregate in mm. For example, AGCS-16 represents an asphalt graded crushed stone having an aggregate nominal maximum particle size of 16 mm.

Preferably, in the method of the present invention, the production cycle per disc of the batch mixer in the step (3) is not less than 45s, and the dry mixing time is not less than 10 s.

Preferably, in the method of the invention, the spreading speed of the spreading machine in the step (5) is controlled to be 1-3 m/min.

Preferably, in the method of the invention, the total mass of the steel-wheel road roller in the step (6) is not less than 12t, the vibration frequency is 35-50 Hz, and the amplitude is 0.3-0.8 mm.

Preferably, in the method of the present invention, the total mass of the tyre roller in step (6) is not less than 25t, the pressure of each tyre is not less than 15kN, the tyre inflation pressure in a cold state is not less than 0.55MPa, the air pressure after tyre heating is not less than 0.6MPa, and the air pressure of each tyre is substantially the same.

Preferably, in the method, the preliminary pressing in the step (6) comprises the step of carrying out static pressing on a steel wheel road roller for 2-4 times, wherein the internal temperature of the asphalt graded macadam at the beginning of the preliminary pressing is not lower than 150 ℃; and the static pressure rolling speed of the steel wheel road roller is 2-3 km/h.

Preferably, in the method of the present invention, the re-pressing in step (6) includes 4-6 times of vibration pressing of a steel-wheel road roller, and 4-8 times of compacting of a rubber-tyred road roller; the vibration and compression rolling speed of the steel wheel road roller is 3-5 km/h; the rolling speed of the rubber-tyred road roller is 3-6 km/h; the repressing is carried out closely after the initial pressure is finished.

Preferably, in the method of the present invention, the final pressing in step (6) includes static pressing of a steel-wheel roller for 2-4 times; the static pressure rolling speed of the steel wheel road roller is 3-6 km/h; the surface temperature of the asphalt graded crushed stone after the final pressure is finished is not lower than 90 ℃.

In another aspect, the invention provides a high-speed railway asphalt graded crushed stone foundation bed prepared by the method.

The invention has the following beneficial effects:

(1) the asphalt graded broken stone is ensured to be molded on site to a target void ratio (design void ratio), a target compaction degree is achieved, and the compaction effect of the asphalt graded broken stone is ensured.

(2) The molding quality such as the flatness, the thickness, the gradient and the like of the asphalt graded broken stone can meet the requirements.

(3) The performances of water resistance, bearing and the like of the asphalt graded broken stone are ensured to meet the design requirements.

(4) The construction method can be used for guiding the construction of the asphalt graded broken stone foundation bed of the high-speed railway, standardizing the process flow and perfecting the quality control system.

(5) As a new roadbed structure form of the high-speed railway, the asphalt graded broken stone foundation bed prepared by the construction method can save roadbed fillers, improve the bearing capacity and waterproof and drainage capacity of the roadbed, prolong the service life of the roadbed, has wide application prospect and has obvious economic and social benefits.

Detailed Description

The present invention is described in further detail below with reference to specific embodiments, which are given for the purpose of illustration only and are not intended to limit the scope of the invention.

The construction method of the asphalt graded broken stone foundation bed mainly comprises the following steps: construction preparation, permeable asphalt and/or sticky asphalt distribution, asphalt graded broken stone mixing, asphalt graded broken stone transportation, asphalt graded broken stone paving, asphalt graded broken stone compaction and asphalt graded broken stone maintenance.

1. Preparation for construction

Before asphalt graded broken stone construction, a roadbed deformation observation device, a cable trough, a drainage ditch, a water collecting well, a contact net support, a pre-buried pipeline, a pre-buried cable and the like are treated and protected.

Before the asphalt graded broken stone is constructed, the top surface elevation, the geometric dimension and the quality of the graded broken stone on the surface layer of the foundation bed are rechecked, and the standard of the design Specification of railway subgrade TB10001 and the design Specification of high-speed railway TB10621 is met.

And after rechecking is qualified, performing construction lofting on the asphalt graded broken stones. And hanging a construction lead or a guide beam for controlling the elevation of the top surface of the asphalt concrete, and rechecking the elevation. The construction can not be carried out under the conditions of strong wind and rain with the temperature lower than 10 ℃, 5 grades and above.

2. Spreading permeable asphalt and/or adhesive layer asphalt

When the design thickness of the asphalt graded broken stone is less than or equal to 10cm, designing according to one layer, and paving, compacting and the like according to one layer; when the thickness exceeds 10cm, designing according to two layers, and paving, compacting and the like in a layering manner; when the asphalt graded broken stone is designed into two layers, the adhesive layer asphalt must be sprayed between the asphalt graded broken stone layers, and the adhesive layer asphalt can be uniformly sprayed by adopting an asphalt spraying vehicle or a manual asphalt spraying machine, and the recommended spraying amount of the adhesive layer asphalt is 0.3-0.6L/m²。

Before the permeable layer asphalt and/or the sticky layer asphalt are/is scattered, scum of the graded broken stone layer is cleaned, and structures such as a cable trough, a water collecting well, a contact net support foundation and the like are shielded to avoid pollution.

The permeable asphalt is sprayed uniformly by an asphalt spraying vehicle at one time, when the leakage is missed, manual spraying is needed, when the redundant permeable asphalt does not permeate into the surface layer of the foundation bed, coarse sand is needed to be spread on the part, and proper rolling is needed. The recommended spreading amount of the permeable asphalt is 0.7-2.0L/m²。

After the permeable asphalt is spread, the traffic is closed, and after the permeable asphalt is fully permeated and the water is evaporated (usually, the water is evaporated for 24 hours), the asphalt graded broken stone is paved within 48 hours.

The adhesive layer asphalt is preferably sprayed on the day of paving the asphalt graded broken stone, and after demulsification and water evaporation are finished, the adhesive layer asphalt is closely paved with the asphalt graded broken stone to ensure that the adhesive layer asphalt is not polluted.

Description of the drawings:

the permeable asphalt is as follows: in order to ensure that the asphalt graded gravel layer and the graded gravel layer are well combined, a thin layer which penetrates into the surface of the graded gravel layer to a certain depth and is formed by spraying emulsified asphalt on the graded gravel layer. The sticky layer asphalt is as follows: a thin layer of bituminous material distributed to enhance the bond between the bituminous graded gravel layer and the bituminous graded gravel layer.

3. Mixing of asphalt graded crushed stone

The asphalt graded broken stone is preferably produced by adopting an intermittent mixer, the number of cold storage bins of the intermittent mixer meets the requirement of the mixing ratio, is not less than 5-6, and the intermittent mixer is provided with equipment for adding an asphalt reinforcing agent.

The heating temperature of the asphalt is 160-190 ℃, and the heating temperature of the aggregate is 10-30 ℃ higher than that of the asphalt.

The mixing time of the asphalt graded broken stone is determined according to the trial mixing, and the degree of uniformly coating aggregate with the asphalt is taken as the degree. The production cycle of each plate of the batch mixer is not less than 45s, wherein the dry mixing time is not less than 5-10 s.

The discharge temperature of the asphalt graded broken stone is 170-195 ℃. The discharge temperature is over 200 ℃, the asphalt graded broken stone which is produced by the steps of whitening materials, agglomerating into blocks and seriously separating coarse and fine aggregates is discarded.

4. Transportation of asphalt graded crushed stone

The asphalt graded broken stone is preferably transported by a large tonnage such as a material transporting vehicle with a load of more than 15 tons, and heat preservation, rain prevention and pollution prevention measures are adopted. A large-tonnage material conveying vehicle is adopted, so that the temperature loss in the transportation process is reduced, and the arrival temperature of the asphalt graded crushed stones is ensured.

When the material is loaded from the mixer to the material transporting vehicle, the vehicle position should be moved for many times to balance the loading and prevent the segregation of coarse and fine aggregates. The arrival temperature of the asphalt graded broken stone is not lower than 160 ℃.

5. Paving of asphalt graded broken stone

The asphalt graded broken stone is paved by adopting a full-automatic asphalt paver. Before construction, the screed of the asphalt paver is preheated to more than 100 ℃. The temperature of the asphalt graded broken stone before paving is not lower than 160 ℃. The paver should adopt an automatic leveling mode, the paver should work slowly, uniformly and continuously during paving, the paving speed should be controlled within 1-3 m/min, the speed cannot be changed randomly or stopped midway, and obvious segregation, waves, cracks and drag marks cannot be generated.

The paving mode is reasonably determined according to the paving section form, and when a plurality of pavers operate, the echelon operation is adopted. If the ballast track asphalt graded broken stone foundation bed is available, 2 spreading machines can be adopted for ladder operation, and the ballastless track asphalt graded broken stone foundation bed can be adopted for ladder operation of 3 spreading machines.

6. Compaction of asphalt graded macadam

The compaction of the asphalt graded broken stone can be divided into initial compaction, re-compaction and final compaction, and the compaction is carried out according to the combined mode of a steel wheel road roller and a tire type road roller.

The total mass of the steel wheel road roller is not less than 12t, the vibration frequency is 35-50 Hz, and the amplitude is 0.3-0.8 mm.

The total mass of the tyre type road roller is not less than 25t, the pressure of each tyre is not less than 15kN, the inflation pressure of the tyre in a cold state is not less than 0.55MPa, the tyre is not less than 0.6MPa after heating, and the air pressure of each tyre is approximately the same.

The initial pressing comprises 2-4 times of static pressure of the steel wheel road roller, the static pressure rolling speed of the steel wheel road roller is 2-3 km/h, and the internal temperature of the asphalt graded broken stone at the beginning of the initial pressing is not lower than 150 ℃.

The re-pressing comprises the steps that the steel wheel road roller vibrates for 4-6 times, and the vibration rolling speed of the steel wheel road roller is 3-5 km/h; compacting for 4-8 times by using a rubber-tyred roller, wherein the rolling speed of the rubber-tyred roller is 3-6 km/h; the repression is carried out closely after the initial pressure is finished.

And the final pressing comprises 2-4 times of static pressure of the steel wheel road roller, the static pressure rolling speed of the steel wheel road roller is 3-6 km/h, and the surface temperature of the asphalt graded broken stone after the re-pressing is finished is not lower than 90 ℃.

For the parts of the large road roller which are difficult to operate, a small vibration road roller or an impact rammer is adopted for rolling. The roller must not turn around, add water or stay on the non-rolled section. The road roller needs to slow down and slowly move when being started and stopped, and emergency braking and braking are not needed. The initial pressing, the re-pressing and the final pressing are all carried out at the highest temperature without generating pushing and cracks.

7. Maintenance of asphalt graded crushed stone

After the construction is completed, all the construction machines should exit from the finished operation area on the same day. Before traffic is not opened, any vehicles are prohibited from driving in, and no heavy objects can be placed on the surface.

And after the spreading layer of the asphalt concrete is completely and naturally cooled and the surface temperature of the asphalt concrete is lower than 50 ℃, the traffic can be opened.