WO2024092998A1

WO2024092998A1 - Saturated-water vibrating compaction construction process for graded crushed stone

Info

Publication number: WO2024092998A1
Application number: PCT/CN2022/142583
Authority: WO
Inventors: 白银战
Original assignee: 中国港湾工程有限责任公司
Priority date: 2022-11-01
Filing date: 2022-12-28
Publication date: 2024-05-10
Also published as: CN115787386A

Abstract

A saturated-water vibrating compaction construction process for graded crushed stone, comprising: carrying out checking and accepting and finishing on a base course; carrying out mixing proportion design and tests on graded crushed stone so as to determine a mixing proportion, the coefficient of loose paving and a paving method; performing survey and setting out on the base course which has been qualified in checking and accepting; preparing crushed-stone raw materials according to the mixing proportion determined by the tests, adding the crushed-stone raw materials to a mixing machine and mixing same to obtain a mixture; and paving the mixture on the surface of the base course according to the coefficient of loose paving and the paving method which are determined by the tests, and compacting same, wherein a compacting method comprises first carrying out static compaction, repairing and leveling, then carrying out vibration rolling, fully sprinkling water to the rolled mixture until saturation, and repeatedly rolling same until the water flows away from gaps and said graded crushed-stone layer satisfies the requirement of the degree of compaction. Therefore, the process can enable graded crushed stone to be applied to airport road surface courses, the degree of compaction reaching 100%, and the airport road surface courses having flat and compact surfaces and being free of loosening and segregation.

Description

Construction technology of graded crushed stone saturated watertight vibration

Technical Field

The present invention relates to the technical field of road base construction, and more specifically to a graded crushed stone saturated water-tight vibration construction process.

Background technique

The base of pavement structures such as roads, airport runways, and storage yards usually have graded crushed stone, cement stabilized crushed stone, cement stabilized soil, etc. At present, for airport runways, cement stabilized crushed stone is usually used as the pavement structure base in China. Compared with the cement stabilized crushed stone base, the graded crushed stone base has a lower cost and is not limited by the initial setting of cement during construction. The difficulty of rolling and surface preparation is much lower than that of cement stabilized crushed stone base, so it is still used in many places.

However, if the graded crushed stone base layer is compacted according to the conventional moisture content control and layered compaction method, its compaction degree is difficult to approach or reach 100%, and quality problems such as unqualified compaction degree, loose surface, peeling, etc. often occur during the construction of graded crushed stone. The loose surface has a great influence on the subsequent sweeping and oil penetration construction, and it is difficult to meet the design requirements of the airport runway under heavy load.

Summary of the invention

An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

Another object of the present invention is to provide a construction process for saturated water-tight vibration of graded crushed stone, which can enable the graded crushed stone to be applied to the airport pavement base with a compaction degree of 100%. At the same time, the surface of the airport pavement base is flat and dense without looseness or segregation.

In order to achieve these purposes and other advantages according to the present invention, a saturated water-tight vibration construction process for graded crushed stone is provided, which comprises:

Acceptance and repair of the underlying layer;

Carry out mix design and testing of graded crushed stone to determine mix ratio, loose paving coefficient and paving method;

Measure and set out on the qualified underlying layer;

Prepare crushed stone raw materials according to the mix ratio determined by the test, and place the crushed stone raw materials in a mixing machine for mixing to obtain a mixed material;

According to the loose paving coefficient and paving method determined by the test, the mixture is spread on the surface of the underlying layer and then compacted. The compaction method includes: static pressing first, repairing and leveling, and then vibration rolling. The compacted mixture is then fully watered until saturated, and then the rolling is repeated until the water flows out of the gaps and the graded gravel layer reaches the compaction requirement.

Preferably, when the graded crushed stone layer is applied to the airport pavement base, the mixing ratio of the crushed stone raw materials is: when the sieve hole size is 50 mm, the crushed stone passing rate is 100wt%, when the sieve hole size is 37 mm, the crushed stone passing rate is 95-100wt%, when the sieve hole size is 25 mm, the crushed stone passing rate is 70-95wt%, when the sieve hole size is 19 mm, the crushed stone passing rate is 55-85wt%, when the sieve hole size is 4.75 mm, the crushed stone passing rate is 30-60wt%, when the sieve hole size is 0.6 mm, the crushed stone passing rate is 12-30wt%, and when the sieve hole size is 0.075 mm, the crushed stone passing rate is 0-8wt%;

Among them, the weight proportion of crushed stone raw materials passing through the 0.075mm sieve hole in the crushed stone raw materials passing through the 0.6mm sieve hole does not exceed 60%; the weight proportion of needle-shaped and flaky crushed stone raw materials in the crushed stone raw materials with a particle size greater than 4.75mm does not exceed 15%, and the needle-shaped and flaky crushed stone raw materials are defined in the test method in ASTM D 693 standard; the abrasion value of the crushed stone raw materials is tested in accordance with the ASTM C131 test procedure, and the result is not greater than 35%; the sodium sulfate firmness of the crushed stone raw materials is tested in accordance with the ASTM C 88 test procedure, and after 5 test cycles, the loss value is less than 5%.

Preferably, the process of mixing the crushed stone raw materials to obtain the mixture specifically includes: placing the crushed stone raw materials in a mixing station, using the mixing station to forcibly mix the mixture, and adding water during mixing according to the optimal moisture content of the crushed stone raw materials that meet the grading requirements ±2%, and the optimal moisture content of the crushed stone raw materials that meet the grading requirements is determined by a heavy compaction test.

Preferably, before spreading the mixture on the surface of the underlying layer, the surface of the underlying layer is first wetted by sprinkling water.

Preferably, before the mixed material is transported from the mixing station to the paving construction site, the surface of the truck bed of the transport vehicle is first wetted by spraying water.

Preferably, the process of measurement and layout on the qualified underlying layer includes: setting a pile every 10m, conducting leveling measurement, driving a guide control line bracket 50cm outside the paving edge line, the position of the guide control line bracket corresponds to the center line pile number, the spacing between the guide control line brackets is 10m, and adjusting the height of the cross bar of the guide control line bracket according to the elevation of the top surface of the underlying layer, the design thickness, the loose laying coefficient obtained from the test and the fixed value, and setting it to the elevation of the guide control line during paving, the elevation of the guide control line = elevation of the top surface of the underlying layer + loose laying coefficient × designed compacted thickness of the graded gravel layer + fixed value, and the fixed value is the height difference between the conductor and the ironing plate of the paving equipment.

Preferably, after the graded crushed stone layer reaches the compaction requirement, it is also repaired and jointed, and finally accepted.

Preferably, the compaction degree of the graded crushed stone layer is measured by a sand filling method.

Preferably, in the compaction method, static compaction is first performed once, followed by repair and leveling, and then vibration rolling is performed four times.

The present invention includes at least the following beneficial effects: when graded crushed stone is applied to the airport pavement base, the compaction degree should reach 100%. If it is constructed according to the conventional layered compaction method, its compaction degree is difficult to reach 100%. The saturated water-tight vibration compaction process provided by the present application successfully solves this technical problem. At the same time, since the graded crushed stone is saturated with water during the compaction process, there is no need to consider the quality problems such as looseness and peeling of the base surface caused by excessive surface water loss of the graded crushed stone base during the compaction process.

Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a saturated water-tight vibration process for graded crushed stone according to an embodiment of the present invention;

FIG2 is a perspective schematic diagram of the pavement of the Hambantota Airport in Sri Lanka according to an embodiment of the present invention;

FIG3 is a close-up schematic diagram of the pavement of the Hambantota Airport in Sri Lanka according to an embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

The following takes the pavement base of Hambantota Airport in Sri Lanka as an example to illustrate the graded crushed stone saturated watertight vibration construction process. The pavement design of Hambantota Airport in Sri Lanka is based on the AC150/5320-6E specification of the Federal Aviation Administration of the United States "Airport Pavement Design and Evaluation". According to the requirements of the specification, graded crushed stone is used in the airport pavement base, and the compaction degree should reach 100%, and the CBR value should not be less than 100%.

If the graded gravel base is constructed according to the conventional layered compaction method, its compaction degree is difficult to reach 100%. This is the technical difficulty of this construction. After many experiments and demonstrations, the technical research team of the project department finally came up with the saturated watertight compaction method and successfully solved this technical problem.

As shown in FIG1 , the saturated water-tight vibration construction process of graded crushed stone specifically includes the following steps:

S1. Construction preparation;

Specifically include:

1. Technical and data preparation;

(1) Prepare a construction plan and obtain approval from the owner;

(2) Organize personnel to conduct detailed training and briefing;

(3) Construction commencement report: Submit the "Graded gravel base construction commencement report" to the owner. The gravel base construction can only be carried out after approval.

2. Preparation of equipment and materials;

(2.1) Material test preparation;

(1) Be familiar with design requirements, acceptance standards and construction specifications, organize all construction personnel to conduct technical briefings on process operations and quality standards, and debug and familiarize themselves with various mechanical operations at the front and back ends.

(II) Select qualified crushed stone in accordance with the design and specification requirements, take samples in time for the required tests and report to the owner for inspection. The specific requirements are as follows:

a. The source of aggregates must be approved by the engineer and must be clean, solid, durable crushed stone particles that are roughly the same as the sample. Pebbles and crushed pebbles are not allowed;

b. Aggregates can be mixed with fine sand, stone powder, or other similar binders or fillers approved by other suppliers. The mixture should be uniform and meet the requirements of the technical specifications;

c. The mixture must be capable of being compacted into a dense and stable base and must not contain vegetable matter, clay lumps, easily decomposable or breakable or other harmful matter.

(2.2) Preparation of stockpile site;

The stockpile yard is selected near the mixing station, and a temporary stockpile silo is set up at the mixing station. Raw materials of various specifications in the stockpile silo are separated by isolation walls.

(2.3) Preparation of mechanical equipment;

(1) Large equipment;

1) Mixing equipment: A WCB-500 graded gravel mixing station is installed at the mixing site. After the equipment arrives at the site, it is installed and debugged, and calibrated by the measurement department. It can only be used after inspection that all indicators meet the requirements. A loader is configured in the mixing station silo for loading and preparing materials;

2) Transportation equipment: 15 dump trucks with a load capacity of more than 15 tons will be equipped according to the mixing capacity and transportation road conditions. The number will be adjusted according to the construction progress and on-site needs;

3) Paving equipment: The model of the paving machine brought to the site is DTU95 produced by Sany Heavy Industry;

4) Rolling equipment: One 26T single-wheel vibratory roller and one 22T single-wheel vibratory roller, and one small tamping machine are used for construction;

5) Sprinkler equipment: two sprinkler trucks, with more to be added as needed;

6) Other mechanical equipment: one land grader, mainly used for repairing the underlying layer. One generator, backup power generation equipment for the mixing station;

The above machine operators all hold valid operation certificates and are fully aware of the working performance of their own machines and vehicles. Before the trial mixing of the mixture, relevant certificates are issued, and the owner's engineer will debug and verify the working performance of the mixing plant and mechanical equipment to ensure that the aggregate gradation and moisture content of the mixture meet the requirements of the technical specifications, so that all processes are under control.

(ii) small equipment;

A batch of small tools such as shovels, wheelbarrows, wire ropes, etc.

(2.3) Site laboratory preparation;

Laboratory construction is divided into three aspects, namely: establishment of quality management system for construction site laboratories, laboratory hardware construction, and rational allocation and quality education of personnel.

1) Laboratory quality system: including the organizational structure, responsibilities, procedures, processes and resources for implementing quality management.

2) Laboratory hardware construction: including the degree of sophistication of test instruments, the quantity and quality of equipment and instruments.

3) Laboratory technical staff: 1 technical supervisor and 8 operators are equipped to ensure the basic needs of grassroots construction and on-site testing.

(2.4) Measurement preparation;

1) Carefully check the drawings before carrying out the layout work;

2) Surveyors must be certified, instruments must be calibrated in advance, and the working performance of the instruments must be recalibrated before setting out;

3) Conduct joint testing of the measurement and control network and submit the retest results to the owner’s engineer for approval;

4) Stake out the road centerline and roadside line. After staking out, the measurement results must be reviewed again to ensure that the measurement results are accurate; these points will serve as control points for the base layer in the future;

5) Another joint measurement should be made before the last layer of gravel is laid.

(2.5) Site preparation;

(1) Preparation of underlying strata;

Actively carry out the acceptance and repair work of the underlying layer to provide a good on-site space for the base construction, and pay attention to the following points.

1) The lower bearing layer to be accepted must meet the specified requirements, and its longitudinal and transverse slopes, flatness, compaction, longitudinal elevation, etc. must meet the assessment requirements, otherwise the lower bearing layer must be reprocessed before the base construction.

2) Before the graded gravel mixture is put on the road, make a final inspection of the underlying layer, remove all loose soil and debris on the on-site working surface, and keep it flat.

3) For the underlying layer with holes, first fill and compact it carefully with the same material. The loose areas should be loosened and supplemented with the same material, mixed, shaped and watered, and re-compacted to meet the compaction requirements.

4) Before paving the base layer, the surface of the underlying layer can be appropriately sprinkled with water to moisten the surface according to the site conditions.

5) During road surface construction, high fill embankments may undergo settlement, and settlement observations must be made on the underlying layers.

(2) Temporary roads;

Carry out temporary road repairs and daily maintenance.

(3) Temporary drainage system;

Make good temporary drainage ditch and other drainage facilities, improve the temporary drainage system, and prevent rainwater from soaking the graded gravel working surface.

S2, construction of test section;

1) Test section location;

10 days before the formal construction of the graded crushed stone base, a test section with an area of not less than 300 square meters shall be paved on site approved by the owner's engineer. The shoulder section (between two navigation lights) between runway 2200 and 3000 shall be selected to pave the test section first;

2) rolling test;

First, test with layer thickness of 20cm and loose laying coefficient of 1.25. Optimization and adjustment can be made during the test. Compactness test can be carried out by sand injection method, and various original data can be recorded until the compaction meets the corresponding compaction standard.

3) Experimental results;

The following parameters are determined through the construction of the test section: whether the construction mix ratio of materials is reasonable; the loose paving coefficient of materials; standard construction method; paving speed; method for controlling the moisture content of the mixture; combination of compaction machinery, rolling method and compaction sequence as well as speed and number of passes; coordination and cooperation of mixing, transportation, paving and rolling machinery; inspection method after compaction; length of the daily working section; standardized management and optimized construction organization.

4) Test time;

The owner's engineer shall be notified 48 hours before the construction of the test area. If the preparation work cannot be completed in time due to bad weather and equipment failure, the owner's engineer shall be notified verbally or in writing to obtain consent.

S3. Measure and set out on the qualified underlying layer;

A pile is set up every 10m for leveling measurement, and the guide control line bracket is driven into the paving edge line 50cm away. The position of the guide control line bracket corresponds to the center line pile number. The spacing between the guide control line brackets is 10m. According to the top surface elevation of the underlying layer, the design thickness, the loose laying coefficient obtained from the test and the fixed value (10cm), the height of the cross bar of the guide control line bracket is adjusted and set to the elevation of the guide control line during paving. The elevation of the guide control line = the top surface elevation of the underlying layer + the loose laying coefficient × the designed compacted thickness of the graded gravel layer + the fixed value. The fixed value is the height difference between the conductor and the ironing plate of the paving equipment.

S4. Prepare crushed stone raw materials according to the mix ratio determined by the test, and place the crushed stone raw materials in a mixing machine for mixing to obtain a mixed material;

(1) The requirements for the gradation of the crushed stone base are shown in the following table:

The materials should be well graded from coarse to fine, and the design batching specifications required in the above table should be strictly followed, and the deviation should be controlled within the allowable range;

The percentage of material passing the 0.075 mm sieve must not exceed 60% of the percentage passing the 0.60 mm sieve;

The content of needle and flake crushed stone with a particle size greater than 4.75 mm shall not exceed 15% by weight. The test method for distinguishing needle and flake crushed stone shall comply with the definition of ASTM D 693;

If the gravel abrasion value is tested according to the ASTM C131 test procedure, the result shall not be greater than 35%;

If the sodium sulfate strength of crushed stone is tested according to ASTM C 88 test procedure, the loss value should be less than 5% after 5 test cycles;

If tested according to ASTM D 4318 test procedure, the liquid limit of fine aggregate with a particle size less than 0.42 mm should be no greater than 25 and the plastic limit should be no greater than 4; according to ASTM 2419 test of the sand equivalent value of this particle size level, the test result should be greater than 35%;

According to the test procedure ASTM 1833, the CBR value of the 4-day saturated test sample is tested, and the result is not less than 100%. The test sample is a construction mix ratio sample;

According to the test requirements of ASTM D 4791, the needle and flake content should be less than 30%.

(2) Mixing

(I) The mixing of graded crushed stone base material adopts the centralized factory mixing method. The mixer is a set of WCB-500 graded crushed stone mixer, with an average output of 500t per hour. The equipment should be fully debugged before mixing. The debugging of the mixing equipment is divided into two steps: the first step is to debug the aggregate gradation, that is, without adding water, determine the mixing ratio of various crushed stones; the second step is to debug the mixture, that is, add water to the crushed stone and adjust the water content to meet the requirements of the design mix ratio.

Before mixing, the test personnel shall measure the aggregate gradation and aggregate moisture content. If the construction is carried out in the rainy season, the frequency of moisture content measurement shall be increased, and the construction mix ratio and the actual amount of water added during mixing shall be calculated. Considering that the moisture content will be lost during mixing, transportation, paving, shaping, rolling and other processes, the amount of water used for mixing can be appropriately increased according to the weather, transportation distance and construction progress, so that the moisture content of the mixed material after mixing is slightly greater than the optimal moisture content by 0.5-1% (determined by the test). In the morning, when the temperature is low, there is no wind and the transportation distance is short, the moisture content of the mixed material is close to the optimal moisture content. At noon, when the temperature is high, there is wind and the transportation distance is long, the moisture content of the mixed material should be higher than the optimal moisture content. When implementing mixing, it is necessary to ensure that all preparations in the back field and the front field are ready before starting mixing production.

(II) When mixing the graded crushed stone base mixture, the materials shall be loaded in strict accordance with the mix ratio design requirements approved by the owner's engineer. The materials shall be sent from the silo to the mixing silo via a belt conveyor. At the same time, water shall be added according to the mix ratio requirements. After mixing, the materials shall be sent to the storage silo by a belt conveyor to wait for loading. The mixing quality shall be jointly controlled by the laboratory attendant and the machine operator. The person in charge of each control shall strictly select the aggregate specifications and quantity of each silo according to the mix ratio notice provided by the laboratory. The amount of various aggregates and water used during mixing shall be accurate to ensure that the gradation of the mixture meets the design requirements and that the materials discharged are uniform and there is no separation of coarse and fine materials. When loading the graded crushed stone base mixture, in order to reduce segregation, the materials shall be loaded three times: front, back and middle, and a special person shall be arranged to be responsible for the command.

(III) Daily discharge inspection:

(1) Water content;

(2) Aggregate gradation;

(3) Mixture segregation phenomenon.

(IV) Mixing precautions:

(1) Accurate ingredients;

(2) The water content is slightly greater than the optimum water content;

(3) Mix evenly;

(4) The mixture is tested in a timely manner.

(V) Personnel arrangement during mixing process: 2 operators in each mixing plant, responsible for the operation of the mixing station; 4 inspectors at the mixing station, responsible for the inspection of each silo at the mixing station; 1 person to test the moisture content of the mixture gradation; 1 person to direct the loading.

(VI) Transportation

The graded crushed stone mixture is transported by dump trucks of 15 tons or more. When the transportation distance is long, there is wind or the temperature is high at noon, the mixture on the material truck is covered with tarpaulin to prevent water loss. The transportation capacity is adjusted in time according to the mixer capacity, transportation distance, paving capacity, etc. The transportation vehicles must ensure that there are three vehicles waiting to unload in front of the paver, and no less than three vehicles waiting to load at the mixing station. The number of vehicles, drivers, and driving routes are uniformly implemented the day before paving. According to the production quantity required by the construction section of the front field, sufficient transportation vehicles are equipped to ensure continuous operation of the construction section.

Before transporting the mixture from the mixing station to the paving construction site, sprinkle water on the surface of the transport vehicle's bed to moisten it. The transport vehicle must be in good condition to ensure that the mixture is transported at the optimal moisture content.

Regularly maintain the transportation roads to ensure that the roads are smooth and unobstructed and to prevent the mixture from segregating during transportation.

S5. According to the loose paving coefficient and paving method determined by the test, the mixture is spread on the surface of the underlying layer and then compacted. The compaction method includes: first static compaction once, repairing and leveling, then vibration rolling 4 times, and then fully watering the rolled mixture until saturation, and then repeating the rolling until the water flows out of the gaps and the graded gravel layer reaches the compaction requirement.

Specifically, the mixture was spread using a DTU95 paver produced by Sany Heavy Industry. During paving, the sensor used a steel wire rope to control the elevation and thickness. Before paving, the surface of the underlying layer was properly sprinkled with water and moistened, and the operation of each part of the paver was checked every day to see if it was normal. Before the paver started, the ironing plate was padded with wooden boards so that the elevation of the ironing plate was the loose elevation of the paving layer. To reduce the deformation of the ironing plate, each paver ironing plate must be padded at least three places.

During paving operations, the speed of the paver is determined according to the mixing capacity and transportation capacity. It is strictly forbidden to stop the paver to wait for materials, so as to maintain the continuity of paving and improve the flatness. The paving speed of the paver is 1.5-2m/min. When paving the mixture, the minimum paving speed should be 1.5m/min to reduce the phenomenon of stopping to wait for materials.

During the paving process, a dedicated person will direct the transport vehicle to stop 20 to 30 cm in front of the paver to prevent collision with the paver. The paver will push the unloading vehicle forward and unload while moving forward. The vehicle cannot brake during unloading. The unloading speed should be coordinated with the paving speed. A dedicated person will direct the unloading. When the transport vehicle turns around on the underlying layer, it must be done at the designated place to reduce damage to the underlying layer. At the same time, be careful not to collide with the guide control wire to avoid affecting the elevation accuracy control of the paving layer.

During paving operations, designated on-site technicians will track and control the elevation and thickness of the paved base layer, and fine-tune the paver sensors based on the test results to ensure compliance with design and specification requirements and to ensure construction quality.

After the paver spreads, a dedicated person shall be assigned to eliminate the segregation of coarse and fine aggregates, promptly remove local coarse aggregate "nests", and fill them with newly mixed materials. If there is too much coarse aggregate, a dedicated person shall be assigned to fill the gaps with newly mixed fine aggregates in a timely manner.

After the mixture is spread, the edges of the road surface should be trimmed and shaped, and compacted with relevant tools (such as a shovel) to ensure that the edges are straight, smooth and dense.

When paving, the joints of the upper and lower layers should be staggered by no less than 3m.

Specifically, the compaction and rolling of the mixture will be carried out by a 26T single steel wheel vibratory roller and a 22T single steel wheel vibratory roller.

After the mixture is spread and shaped, it is rolled immediately. The rolling length should be 50 to 80 meters. The rolling sections should be clearly layered, with obvious boundary marks and continuous rolling. The principle of static pressure should be followed for both initial and final pressure to reduce deformation and improve surface density and flatness.

The rolling sequence is to use a 22T grade roller for static rolling once, weak vibration rolling twice, and strong vibration rolling twice. Then use a sprinkler truck to fully sprinkle water on the compacted mixture until it is saturated. Then use a 26T grade roller to repeat strong vibration rolling until the water flows out of the gaps and the graded gravel layer reaches the compaction requirement. Finally, use a 26T grade roller for static rolling once to make the surface dense and free of wheel marks.

Rolling method: After paving and forming, the roller is used for rolling. The rolling direction is parallel to the center line of the road. For straight sections, rolling is carried out from the shoulder to the center. For super-high sections, rolling is carried out from the inside to the outside, so that the longitudinal extension and the cross slope meet the design requirements. The roller rolls in a step-like manner. At the joint of the two rolling sections, the roller rolls at a 45-degree angle. During normal rolling, the wheel tracks overlap by 1/2 of the wheel width. The rear wheel must exceed the joint of the two sections. When the rear wheel rolls the full width of the road surface, it is considered one pass. Rolling is carried out until the required compaction degree and no wheel tracks are left. The rolling speed of the roller is preferably 1st gear for the first two passes, and 2nd gear can be used afterwards. High-speed rolling is absolutely not allowed. Rolling procedure: static pressure ~ weak vibration ~ strong vibration ~ static pressure. Record the number of rolling times on site. Both sides of the road surface should be rolled 1 to 2 more times. The speed of the roller should be 1.5 to 1.7 km/h during steady pressure, 1.8 to 2.2 km/h during vibration pressure, and 1.5 to 1.7 km/h during final pressure.

It is strictly forbidden for the roller to "turn around" or brake suddenly on the completed or rolling road section to ensure that the surface of the graded gravel base is not damaged.

Treatment of blind corners: In corners and other places where rollers cannot compact, small tamping machines will be used for compaction, and manual compaction will be used in small areas.

Flatness control: During the construction process, the bumps at the joints are manually shoveled away, and the flatness is checked with a 4.8-meter ruler. Those that do not meet the requirements are immediately processed to eliminate the unevenness between the rolling sections. The leveling should be done carefully, with the purpose of scraping off the protruding parts and manually sweeping them out of the working surface in time. The scraped materials should not be used as the leveling layer for the local concave parts, that is, "only shoveling is allowed, not filling the concave". In some serious cases, when the pits need to be leveled, they should be manually dug into a rectangular surface (depth of not less than 10cm), filled with the same mixture, manually leveled and compacted, and then uniformly rolled to form.

S6. After the graded gravel layer reaches the compaction requirement, it will be repaired and the joints will be treated before final acceptance.

Specifically, transverse joint treatment: the graded crushed stone base mixture that is not compacted on the day of the paver can be rolled together with the mixture to be paved the next day, but attention should be paid to the moisture content of this part of the mixture. When the moisture content is low, appropriate watering should be added to make its moisture content meet the specified requirements.

Longitudinal joint treatment: When rolling the longitudinal joint, leave about 20cm unrolled as the control elevation surface for the next paver to move. At the same time, the joint should overlap about 5cm. When the paver has paved the entire designed width of the working surface, the next rolling surface can be rolled. If the machine is shut down due to special circumstances, the entire paving surface should be rolled (including the reserved 20cm). When paving is restarted, the uncompacted and loose materials at the longitudinal joint should be shoveled away first, and the longitudinal joint should be shoveled into a vertical section. Then, water should be sprinkled to moisten the joint before new paving, leveling, and rolling work.

Treatment of the interface: When paving at the interface, first spread 20cm more on one surface. After leveling and compacting, scrape off the excess material on the interface and shovel the interface into a vertical section. Then sprinkle water to moisten the interface before paving, leveling and rolling the other surface.

Maintenance: After each section of the working surface is rolled and the compaction degree is tested by the sand filling method, it will be inspected and the upper layer will be constructed in time. If the upper layer cannot be constructed continuously, a special person will be assigned to perform maintenance. At the same time, traffic control will be implemented. Except for sprinkler trucks, other vehicles are prohibited from passing.

Through the above construction technology, the compaction degree of the graded crushed stone base of the pavement of Sri Lanka's Hambantota Airport reached 100%, and the CBR value reached 120%. The surface of the base was flat and dense, without looseness or segregation, fully meeting the requirements of the US Federal Aviation Administration's "Airport Pavement Design and Evaluation" AC 150/5320-6E specification.

Because graded crushed stone has micro-permeability, on the one hand, it can continuously discharge the infiltrated water within a certain period of time, so that it will not accumulate on the interface of the structural layer, and maintain the intact connection between the graded crushed stone base and the asphalt layer of the airport pavement above it; on the other hand, graded crushed stone will not have strong water permeability, so it will not cause a large amount of water to quickly infiltrate the roadbed, causing the roadbed soil to quickly reach supersaturation and soften, and quickly reduce the bearing capacity of the airport runway. In addition, the shrinkage coefficient of graded crushed stone is extremely small, almost zero, which can avoid the reflection cracks of the asphalt surface layer caused by the shrinkage of the semi-rigid base. In addition, graded crushed stone is a granular body, which does not transmit stress and displacement by itself. Therefore, it can dissipate and absorb the high stress and strain at the crack tip caused by changes in environmental factors, especially load and temperature changes, and completely absorb the strain energy at the crack tip under the action of external loads, eliminating the possibility of crack expansion in the asphalt surface layer. In addition, graded crushed stone has sufficient compressive and shear strength, meeting the requirements of being a pavement load-bearing layer.

On March 18, 2013, Sri Lanka's Hambantota International Airport was officially opened to traffic. As of today, it has been in operation for nearly two years, and the runway pavement is in good condition (as shown in Figures 2 and 3). After a design review, no early disease was found, and the design effect was achieved. Compared with the semi-rigid base, the graded crushed stone base saves about 30,000 tons of cement for the entire project and saves 19.8 million yuan in direct engineering costs.

Comparative Example:

During the construction of the test section, the mixture consistent with the above embodiment was used for conventional moisture content control and layered compaction construction, that is, layered paving and rolling, and the mixture was controlled at the optimal moisture content during each layer rolling. However, the final graded crushed stone base compaction degree can only reach 98% at most, which is difficult to meet the requirements of the Federal Aviation Administration's "Airport Pavement Design and Evaluation" AC 150/5320-6E specification.

Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

A graded crushed stone saturated watertight vibration construction process, characterized by comprising:

Acceptance and repair of the underlying layer;

Carry out mix design and testing of graded crushed stone to determine mix ratio, loose paving coefficient and paving method;

Measure and set out on the qualified underlying layer;

Prepare crushed stone raw materials according to the mix ratio determined by the test, and mix the crushed stone raw materials to obtain a mixed material;

According to the loose paving coefficient and paving method determined by the test, the mixture is spread on the surface of the underlying layer and then compacted. The compaction method includes: static pressing first, repairing and leveling, and then vibration rolling. The compacted mixture is then fully watered until saturated, and then the rolling is repeated until the water flows out of the gaps and the graded gravel layer reaches the compaction requirement.
The construction process of graded crushed stone saturated watertight vibration as claimed in claim 1 is characterized in that when the graded crushed stone layer is applied to the airport pavement base, the mixing ratio of the crushed stone raw materials is: when the sieve hole size is 50mm, the crushed stone passing rate is 100wt%, when the sieve hole size is 37mm, the crushed stone passing rate is 95-100wt%, when the sieve hole size is 25mm, the crushed stone passing rate is 70-95wt%, when the sieve hole size is 19mm, the crushed stone passing rate is 55-85wt%, when the sieve hole size is 4.75mm, the crushed stone passing rate is 30-60wt%, when the sieve hole size is 0.6mm, the crushed stone passing rate is 12-30wt%, and when the sieve hole size is 0.075mm, the crushed stone passing rate is 0-8wt%;

Among them, the weight proportion of crushed stone raw materials passing through the 0.075mm sieve hole in the crushed stone raw materials passing through the 0.6mm sieve hole does not exceed 60%; the weight proportion of needle-shaped and flaky crushed stone raw materials in the crushed stone raw materials with a particle size greater than 4.75mm does not exceed 15%, and the needle-shaped and flaky crushed stone raw materials are defined in the test method in ASTM D 693 standard; the abrasion value of the crushed stone raw materials is tested in accordance with the ASTM C131 test procedure, and the result is not greater than 35%; the sodium sulfate firmness of the crushed stone raw materials is tested in accordance with the ASTM C 88 test procedure, and after 5 test cycles, the loss value is less than 5%.
The graded crushed stone saturated watertight vibration construction process as described in claim 2 is characterized in that the process of mixing the crushed stone raw materials to obtain a mixture specifically includes: placing the crushed stone raw materials in a mixing station, using the mixing station to forcibly mix the mixture, and adding water during mixing according to the optimal water content ±2% of the crushed stone raw materials that meet the grading requirements, and the optimal water content of the crushed stone raw materials that meet the grading requirements is determined by a heavy compaction test.
The construction process of graded crushed stone saturated watertight vibration as described in claim 1 is characterized in that before the mixture is spread on the surface of the underlying layer, the surface of the underlying layer is first sprinkled with water to moisten it.
The construction process for saturated watertight vibration of graded crushed stone as described in claim 3 is characterized in that before the mixed material is transported from the mixing station to the paving construction site, the surface of the truck bed of the transport vehicle is first sprinkled with water to moisten it.
The construction process of graded crushed stone saturated watertight vibration as described in claim 1 is characterized in that the process of measuring and setting out on the qualified lower bearing layer includes: setting a pile every 10m, conducting leveling measurement, driving a guide control line bracket 50cm outside the paving edge line, the position of the guide control line bracket corresponds to the center line pile number, the spacing between the guide control line brackets is 10m, and adjusting the height of the cross bar of the guide control line bracket according to the elevation of the top surface of the lower bearing layer, the design thickness, the loose laying coefficient obtained from the test and the fixed value, and setting it to the elevation of the guide control line during paving, the elevation of the guide control line = the elevation of the top surface of the lower bearing layer + the loose laying coefficient × the designed compacted thickness of the graded crushed stone layer + the fixed value, and the fixed value is the height difference between the conductor and the ironing plate of the paving equipment.
The construction process of graded crushed stone saturated watertight vibration as described in claim 1 is characterized in that after the graded crushed stone layer reaches the compaction requirement, it is also repaired and jointed, and finally accepted.
The construction process for graded crushed stone saturated watertight vibration as described in claim 1 is characterized in that the compaction degree of the graded crushed stone layer is measured by a sand filling method.
The construction process of graded crushed stone saturated watertight vibration as described in claim 1 is characterized in that in the compaction method, static compaction is first performed once, repair and leveling are performed, and then vibration rolling is performed four times.