Semi-rigid base layer double-layer continuous paving process with compaction control

Abstract

The invention discloses a semi-rigid base layer double-layer continuous paving process with compaction control. The process comprises the following steps: acquiring related design data; inputting the design data into the lower layer compactness control model to obtain a rolling construction combination scheme; continuously paving a semi-rigid mixture on the bearing base surface to form a lower layer structure; performing preset construction on the paved lower-layer structure according to a rolling construction combination scheme; continuously paving the second layer of semi-rigid mixture before the initial setting time of the lower-layer structure to obtain an upper-layer structure; according to the rolling construction combination scheme, the double-layer structure is subjected to overall rolling through a combined type compaction technology; and after compacting, covering a permeable geotextile and sprinkling water for maintenance. According to the method, the technology is economical, environmentally friendly and capable of improving efficiency, the problem that the compaction degree of the lower layer is difficult to effectively and reasonably control during double-layer continuous paving of the semi-rigid base layer is solved, technical parameter guidance is provided for the compaction degree of the lower layer structure, the construction time can be shortened, and the construction quality and the construction efficiency can be improved.

Description

Technical Field

[0001] This invention relates to the field of road engineering, specifically to a double-layer continuous paving process for a semi-rigid base course with compaction control. Background Technology

[0002] In my country, more than 95% of asphalt pavement base courses, especially expressways, use semi-rigid base courses. Therefore, promoting the application of semi-rigid base double-layer continuous paving technology can save curing time, improve construction efficiency, save on the curing process of the lower base course, and save on construction costs. It is a construction technology with significant effects.

[0003] Due to limitations in the tonnage and reliability of construction equipment, early construction methods strictly restricted the double-layer continuous paving technique for semi-rigid base courses. However, with socio-economic development and equipment advancements, existing construction equipment, under good process control, can guarantee the quality of double-layer continuous paving base courses. Currently, for double-layer continuous paving of semi-rigid base courses, the compaction degree of the lower layer and the upper layer upon completion can be detected and effectively controlled. However, after the upper layer is completed, the lower layer inevitably undergoes a re-compaction process. The effect of upper layer compaction on improving the compaction degree of the lower layer has not yet been studied, especially how to determine the required compaction degree of the lower layer based on the upper layer compaction process. This remains an unresolved issue and has become a significant factor hindering the widespread application of the double-layer continuous paving technique for semi-rigid base courses. Summary of the Invention

[0004] To address the aforementioned problems, this invention aims to provide a semi-rigid base double-layer continuous paving process with compaction control.

[0005] To achieve this technical objective, the present invention provides a two-layer continuous paving process for a semi-rigid base course with compaction control, the specific steps of which are as follows:

[0006] S1. Subgrade treatment: Conduct flatness testing on the subgrade and repair subgrade defects to form a bearing base surface that meets the design elevation, and obtain relevant design data;

[0007] S2. Input the design data into the lower layer compaction control model to obtain the rolling construction combination scheme; the relevant design data includes the design compaction degree B1 and design paving thickness h1 of the lower layer structure, and the design compaction degree B2 and design paving thickness h2 of the upper layer structure.

[0008] After the upper layer is compacted, the compaction degree of the lower layer structure satisfies the following formula:

[0009] λ1' = λ1 + ζημλ2;

[0010] Where: λ1' is the final compaction degree of the lower layer after the upper layer is compacted, which must be greater than or equal to B1; λ1 is the final compaction degree of the lower layer before the upper layer is compacted, i.e., the preset value; ζ is the first correction coefficient for the thickness of the upper layer; η is the second correction coefficient for the thickness of the upper layer; μ is the compaction correction coefficient for the upper layer; λ2 is the preset compaction degree of the upper layer after the upper layer is compacted, which must be greater than or equal to B2; λ1 can be calculated according to the above formula; the lower layer compaction degree control model can output the compaction construction combination scheme according to the design requirements of λ1' and λ2;

[0011] S3. Sub-layer paving: Semi-rigid mixture is continuously paved on the bearing base to form the sub-layer structure;

[0012] S4. Perform pre-construction of the paved substructure according to the compaction construction combination scheme. After completion, check the pre-compaction degree C1 of the substructure. If C1 is less than or equal to the preset value λ1, proceed to the next step.

[0013] S5. Upper layer paving: The upper layer structure is obtained by continuously paving the second layer of semi-rigid mixture before the initial setting time of the lower layer structure.

[0014] S6. Continuous compaction: The double-layer structure is compacted as a whole using a combined compaction process according to the rolling construction combination scheme. After all rolling operations are completed, the compaction degree C2 of the upper layer structure is tested. If C2 is greater than or equal to the design compaction degree A2, the next step is carried out.

[0015] S7. Curing and shaping: After compaction, cover with permeable geotextile and sprinkle with water for curing.

[0016] Preferably, the pre-construction process in step S4 includes one or more compaction processes such as non-compacting, initial compaction, secondary compaction, and rolling compaction.

[0017] The combined compaction process in step S6 includes four stages: initial compaction, secondary compaction, rolling and pressing, and finishing with a smooth wheel.

[0018] Preferably, step S2 also includes the verification and selection of the compaction construction combination scheme; after the construction is completed according to the compaction construction combination scheme, the on-site compaction degree A1 of the lower layer structure is immediately tested. After the upper layer covers and compacts the lower layer, the on-site compaction degree A2 of the upper layer structure is tested; the compaction degree deviation is calculated. If the lower layer compaction degree deviation is: β1=ABS(A1-λ1)≤1% and β2=ABS(A2-λ2)≤0.5%, then the compaction construction combination scheme is considered to have met the predetermined requirements, and the lower layer structure can achieve the predetermined λ1' compaction degree, where ABS indicates the absolute value; otherwise, the compaction construction combination scheme should be adjusted, that is, the design paving thickness h1 of the lower layer structure, or the design paving thickness h2 of the upper layer structure, or the combination of mechanical equipment, or the compaction process should be readjusted. After adjustment, the test section is paved again until the requirements are met.

[0019] Preferably, the semi-rigid mixture of the lower structure in step S3 contains cement-stabilized crushed stone or cement-stabilized gravel, with a cement content of 3-6% and a paving thickness h1 of 15-25cm; the paving thickness of the upper structure in step S5 is 10-28cm, and the total thickness of the two layers is controlled to be 25-50cm.

[0020] Preferably, in steps S4 and S6, the initial compaction is carried out using a steel wheel roller for static compaction, with 1-3 passes; the secondary compaction is carried out using a vibratory roller for vibratory compaction, with 3-6 passes; the tumbling compaction is carried out using a rubber-tired roller for tumbling compaction, with 2-3 passes; and finally, the finishing is carried out using a smooth-drum roller for finishing, with 1 pass.

[0021] When vibratory rollers are used for vibratory compaction, they adopt a high-frequency, low-amplitude vibration mode with a vibration frequency of 35-45Hz and an amplitude of 0.3-0.8mm. The overlap width of the compaction wheel tracks is ≥1 / 3 of the wheel width.

[0022] Preferably, the base treatment in step S1 includes cement-soil stabilization treatment of the roadbed, with a treatment depth ≥30cm, compaction degree ≥95%, and deflection value ≤0.5mm.

[0023] Preferably, the paving equipment in steps S3 and S4 includes a first paver and a second paver arranged in series, with the distance between the two machines controlled at 5-10m and the paving speed matched at 1.5-3m / min;

[0024] The first paver is equipped with an adjustable thickness scraper device with a scraper elevation angle adjustment range of 5-15°. The second paver is equipped with an ultrasonic thickness monitoring module to provide real-time feedback on paving thickness deviation to the control terminal.

[0025] Preferably, in step S7, the curing period is ≥7 days, during which the surface is kept moist; the daily watering frequency is ≥3 times, and the watering amount is controlled at 0.5-1.5 kg / m²; vehicles are prohibited from passing through during the curing period.

[0026] As an option, a quality inspection step is also included. After the curing is completed, a falling weight deflectometer is used to test the overall deflection value. The representative deflection value is required to be less than or equal to the design allowable value, and the extreme value at a single point is not more than twice the representative value.

[0027] The beneficial effects of this invention are that the method of this application can help promote the application of this process that can significantly and effectively improve construction efficiency, solve the problem of difficulty in effectively and reasonably controlling the compaction degree of the lower layer in the continuous double-layer paving of semi-rigid base, provide technical parameter guidance for the compaction degree of the lower layer structure, reduce construction time, and improve construction quality and efficiency. Attached Figure Description

[0028] Figure 1 This is a flowchart of the present invention;

[0029] Figure 2 This is a flowchart of an embodiment of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] like Figure 1-2 As shown, a specific embodiment of the present invention is a two-layer continuous paving process for a semi-rigid base course with compaction control. The specific steps are as follows:

[0033] S101. Base treatment: The flatness of the subgrade is tested and defects are repaired to form a bearing base surface that meets the design elevation, and relevant design data is obtained; the base treatment includes cement-soil stabilization treatment of the subgrade, with a treatment depth ≥30cm, compaction degree ≥95%, and deflection value ≤0.5mm.

[0034] S102. Input the design data into the lower layer compaction control model to obtain the rolling construction combination scheme; the relevant design data includes the design compaction degree B1 and design paving thickness h1 of the lower layer structure, and the design compaction degree B2 and design paving thickness h2 of the upper layer structure.

[0035] After the upper layer is compacted, the compaction degree of the lower layer structure satisfies the following formula:

[0036] λ1'=λ1+ζημλ2; (1)

[0037] Among them: ζ=k1h1+a; η=k2h2+b; μ=-k3λ1+d;

[0038] Wherein λ1'—final compaction of the lower structure after the upper layer is compacted, which must be greater than or equal to B1; λ1—final compaction of the lower structure before the upper layer is compacted, i.e., the preset value; ζ—first correction coefficient for the thickness of the upper structure; η—second correction coefficient for the thickness of the upper structure; μ—compaction correction coefficient for the upper structure; λ2—preset compaction degree of the upper structure after the upper layer is compacted, which must be greater than or equal to B2.

[0039] Where k1, k2, and k3 are correction coefficients, k1 = 0.5 ± 0.1, k2 = 0.4 ± 0.1, and k3 = 0.00359; a, b, and d are constants, a = 1.2 ± 0.1, b = 1.0 ± 0.1, and d = 0.38094. λ1 can be calculated using the above formula; the lower layer compaction control model can output compaction construction combination schemes based on the design requirements of λ1' and λ2.

[0040] S103, Lower layer paving: Semi-rigid mixture is continuously paved on the bearing base to form a lower layer structure; the semi-rigid mixture of the lower layer structure contains cement-stabilized crushed stone or cement-stabilized gravel, the cement content is 3-6%, and the paving thickness h1 of the lower layer structure is 15-25cm.

[0041] S104. Perform pre-compaction on the paved substructure according to the compaction construction combination scheme. After completion, check the pre-compaction degree C1 of the substructure. If C1 is less than or equal to the preset value λ1, proceed to the next step. Pre-compaction includes one or more compaction processes such as non-compaction, initial compaction, secondary compaction and rubbing.

[0042] S105. Upper layer paving: The upper layer is obtained by continuously paving the second layer of semi-rigid mixture before the initial setting time of the lower layer; the paving thickness of the upper layer is 10-28cm, and the total thickness of the two layers is controlled to be 25-50cm.

[0043] S106. Continuous compaction: The double-layer structure is compacted as a whole using a combined compaction process according to the rolling construction combination scheme. After all rolling operations are completed, the final compaction degree C2 of the upper layer structure is tested. If C2 is greater than or equal to the design compaction degree A2, the next operation is carried out. The combined compaction process includes four stages: initial compaction, secondary compaction, rolling, and finishing with a smooth wheel.

[0044] S107. Curing and Shaping: After compaction, cover with permeable geotextile and water for curing. The curing period is ≥7 days, during which the surface should be kept moist; the watering frequency during the curing period is ≥3 times per day, and the watering amount is controlled at 0.5-1.5 kg / m². Vehicles are prohibited from passing through during the curing period. It also includes a quality inspection step. After curing, a falling weight deflectometer is used to test the overall deflection value. The representative deflection value must be ≤ the design allowable value, and the extreme value at a single point must not exceed twice the representative value.

[0045] The initial compaction of the rolling construction is carried out by static compaction with a steel wheel roller, with 1-3 passes; the secondary compaction is carried out by vibratory compaction with a vibratory roller, with 3-6 passes; the tumbling compaction is carried out by tumbling compaction with a rubber-tired roller, with 2-3 passes; and finally, the surface finishing is carried out by a smooth-drum roller, with 1 pass.

[0046] When vibratory rollers are used for vibratory compaction, they adopt a high-frequency, low-amplitude vibration mode with a vibration frequency of 35-45Hz and an amplitude of 0.3-0.8mm. The overlap width of the compaction wheel tracks is ≥1 / 3 of the wheel width.

[0047] The paving equipment includes a first paver and a second paver arranged in series, with the distance between the two machines controlled at 5-10m and the paving speed matched at 1.5-3m / min; the first paver is equipped with an adjustable thickness scraper device, and the scraper elevation angle adjustment range is 5-15°; the second paver is equipped with an ultrasonic thickness monitoring module to provide real-time feedback on the paving thickness deviation to the control terminal. When the total thickness of the two layers is less than 40cm and the thickness of the upper layer is less than 25cm, the compaction degree can be directly calculated by formula (1); when the total thickness of the two layers is greater than or equal to 40cm, or the thickness of the upper layer is greater than or equal to 25cm, it is best to further verify and optimize the compaction construction combination scheme to ensure that the predetermined compaction degree can be achieved. It also includes the verification and selection of the compaction construction combination scheme; after the construction is completed according to the compaction construction combination scheme. The test shall be conducted in accordance with the method of T 0921-2019 of the "Specifications for Field Testing of Highway Subgrade and Pavement" (JTG 3450-2019). The field compaction degree A1 of the lower layer shall be tested immediately. After the upper layer covers and compacts the lower layer, the field compaction degree A2 of the upper layer shall be tested.

[0048] Calculate the compaction deviation. If the compaction deviation of the lower layer satisfies: β1=ABS(A1-λ1)≤1%, β2=ABS(A2-λ2)≤0.5%, then the rolling construction combination scheme is considered to have met the predetermined requirements, and the lower layer structure can achieve the predetermined λ1' compaction degree. Here, ABS indicates the absolute value, and ABS is an abbreviation for "absolute value".

[0049] Otherwise, the compaction construction combination scheme should be adjusted, that is, the design paving thickness h1 of the lower layer structure or the design paving thickness h2 of the upper layer structure should be readjusted, or the combination of mechanical equipment or the compaction process should be adjusted. After adjustment, the test section should be paved again and step S7 should be repeated until the requirements are met.

[0050] Example 1

[0051] A double-layer continuous paving process was used for pavement construction on a certain highway. A method for controlling the compaction degree of the lower layer in a semi-rigid base double-layer continuous paving process is described, characterized by the following steps:

[0052] Step S201: Preliminarily determine the rolling combination of the upper and lower layers and the equipment configuration of the semi-rigid base continuous paving process test section, and initially determine the construction thickness of the upper layer of the semi-rigid base as h1 and the construction thickness of the lower layer of the semi-rigid base as h2;

[0053] Step S202: Determine the compaction degree that should be controlled for each layer of the base course according to the following formula (1): λ1'=λ1+ζημλ2;

[0054] Among them: ζ=0.5h1+1.2; η=0.4h2+1.0; μ=-0.00359λ1+0.38094;

[0055] Step S203: Calculate the compaction deviation. If the compaction deviation of the lower structure meets the following conditions: β1=ABS(A1-λ1)≤1% and β2=ABS(A2-λ2)≤0.5%, then the rolling construction combination scheme is considered to meet the predetermined requirements and the lower structure can achieve the predetermined λ1' compaction. Otherwise, the compaction process should be adjusted, that is, the construction thickness of the upper and lower layers of the double-layer continuous paving, the combination of mechanical equipment, or the rolling process should be readjusted. After adjustment, the test section should be paved again and the compaction of the upper and lower layers should be tested until the requirements are met.

[0056] Step S204: The base layer is set to be 36cm thick and a double-layer continuous paving construction process is adopted, which can save time and ensure the bonding effect between layers;

[0057] Table 1: Compaction Scheme Comparison Table

[0058] Step S205: The preset compaction degree λ2 of the upper structure is initially set to 99%. Based on experience, the estimated value of the field compaction degree of the lower structure under different rolling combinations is determined, and the final compaction degree λ1' of the lower structure is calculated according to formula (1). The results are shown in Table 1.

[0059] Based on Table 1, this application can calculate and predict the compaction degree of the underlying structure. With parameter guidance, it can select a suitable rolling process combination to ensure that the compaction degree of the underlying structure meets the design requirements, thereby reducing unnecessary process costs while ensuring the construction quality of the underlying layer.

[0060] The method described in this application can help promote the application of this technology, which is beneficial to the country and the people, saves resources, is environmentally friendly, and improves efficiency. It solves the problem of effectively and reasonably controlling the compaction degree of the lower layer in the continuous double-layer paving of semi-rigid base courses, provides technical parameter guidance for the compaction degree of the lower layer structure, and can reduce construction time and improve construction quality and efficiency.

[0061] Example 2

[0062] A highway construction project requires the rapid installation of two semi-rigid base layers within a 500-meter area, with a very tight construction schedule. See the table below.

[0063] Table 2: Comparison of the proposed solution with traditional solutions

[0064] Traditional construction methods require layer-by-layer compaction testing, especially ensuring the lower layer's compaction meets requirements before constructing the upper structure. This impacts construction time. The method described in this application, however, directly yields a two-layer compaction process based on the required compaction level, saving testing time and achieving better results.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent substitutions, and improvements made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A double-layer continuous paving process for a semi-rigid base course with compaction control, characterized in that, The specific steps are as follows: S1. Subgrade treatment: Conduct flatness testing on the subgrade and repair subgrade defects to form a bearing base surface that meets the design elevation, and obtain relevant design data; S2. Input the design data into the lower layer compaction control model to obtain the rolling construction combination scheme; the relevant design data includes the design compaction degree B1 and design paving thickness h1 of the lower layer structure, and the design compaction degree B2 and design paving thickness h2 of the upper layer structure. After the upper layer is compacted, the compaction degree of the lower layer structure satisfies the following formula: λ1' = λ1 + ζημλ2; Where: λ1' is the final compaction degree of the lower layer after the upper layer is compacted, which must be greater than or equal to B1; λ1 is the final compaction degree of the lower layer before the upper layer is compacted, i.e., the preset value; ζ is the first correction coefficient for the thickness of the upper layer; η is the second correction coefficient for the thickness of the upper layer; μ is the compaction correction coefficient for the upper layer; λ2 is the preset compaction degree of the upper layer after the upper layer is compacted, which must be greater than or equal to B2; λ1 can be calculated according to the above formula; the lower layer compaction degree control model can output the compaction construction combination scheme according to the design requirements of λ1' and λ2; S3. Sub-layer paving: Semi-rigid mixture is continuously paved on the bearing base to form the sub-layer structure; S4. Perform pre-construction of the paved substructure according to the compaction construction combination scheme. After completion, check the pre-compaction degree C1 of the substructure. If C1 is less than or equal to the preset value λ1, proceed to the next step. S5. Upper layer paving: The upper layer structure is obtained by continuously paving the second layer of semi-rigid mixture before the initial setting time of the lower layer structure. S6. Continuous compaction: The double-layer structure is compacted as a whole using a combined compaction process according to the rolling construction combination scheme. After all rolling operations are completed, the compaction degree C2 of the upper layer structure is tested. If C2 is greater than or equal to the design compaction degree A2, the next step is carried out. S7. Curing and shaping: After compaction, cover with permeable geotextile and sprinkle with water for curing.

2. The double-layer continuous paving process for semi-rigid base course with compaction control according to claim 1, characterized in that: The pre-construction process in step S4 includes one or more compaction processes such as non-compacting, initial compaction, secondary compaction, and rolling compaction. The combined compaction process in step S6 includes four stages: initial compaction, secondary compaction, rolling and pressing, and finishing with a smooth wheel.

3. The double-layer continuous paving process for semi-rigid base course with compaction control according to claim 1, characterized in that: Step S2 also includes the verification and selection of the compaction construction combination scheme; after the construction is completed according to the compaction construction combination scheme, the on-site compaction degree A1 of the lower layer structure is immediately tested. After the upper layer covers and compacts the lower layer, the on-site compaction degree A2 of the upper layer structure is tested; the compaction degree deviation is calculated. If the lower layer compaction degree deviation is: β1=ABS(A1-λ1)≤1% and β2=ABS(A2-λ2)≤0.5%, then the compaction construction combination scheme is considered to have met the predetermined requirements, and the lower layer structure can achieve the predetermined λ1' compaction degree, where ABS indicates the absolute value; otherwise, the compaction construction combination scheme should be adjusted, that is, the design paving thickness h1 of the lower layer structure, or the design paving thickness h2 of the upper layer structure, or the mechanical equipment combination, or the compaction process should be readjusted. After adjustment, the test section is paved again until the requirements are met.

4. The double-layer continuous paving process for semi-rigid base course with compaction control according to claim 1, characterized in that: The semi-rigid mixture of the lower structure mentioned in step S3 includes cement-stabilized crushed stone or cement-stabilized gravel, with a cement content of 3-6% and a paving thickness h1 of 15-25cm. In step S5, the thickness of the upper structure is 10-28cm, and the total thickness of the two layers is controlled to be 25-50cm.

5. The double-layer continuous paving process for a semi-rigid base course with compaction control according to claim 2, characterized in that: In steps S4 and S6, the initial compaction is carried out using a steel wheel roller for static compaction, with 1-3 passes; the secondary compaction is carried out using a vibratory roller for vibratory compaction, with 3-6 passes; the tumbling compaction is carried out using a rubber-tired roller for tumbling compaction, with 2-3 passes; and finally, the finishing is carried out using a smooth-drum roller for finishing, with 1 pass. When vibratory rollers are used for vibratory compaction, they adopt a high-frequency, low-amplitude vibration mode with a vibration frequency of 35-45Hz and an amplitude of 0.3-0.8mm. The overlap width of the compaction wheel tracks is ≥1 / 3 of the wheel width.

6. The double-layer continuous paving process for semi-rigid base course with compaction control according to claim 1, characterized in that: The base treatment mentioned in step S1 includes cement-soil stabilization treatment of the roadbed, with a treatment depth ≥30cm, compaction degree ≥95%, and deflection value ≤0.5mm.

7. The double-layer continuous paving process for a semi-rigid base course with compaction control according to any one of claims 1-6, characterized in that: The paving equipment in steps S3 and S4 includes a first paver and a second paver arranged in series, with the distance between the two machines controlled at 5-10m and the paving speed matched at 1.5-3m / min; The first paver is equipped with an adjustable thickness scraper device with a scraper elevation angle adjustment range of 5-15°. The second paver is equipped with an ultrasonic thickness monitoring module to provide real-time feedback on paving thickness deviation to the control terminal.

8. The double-layer continuous paving process for a semi-rigid base course with compaction control according to any one of claims 1-6, characterized in that: In step S7, the curing period is ≥7 days, during which the surface should be kept moist; During the maintenance period, water should be sprayed ≥3 times per day, with the water volume controlled at 0.5-1.5 kg / m². Vehicles are prohibited from passing through during the maintenance period.

9. The double-layer continuous paving process for a semi-rigid base course with compaction control as described in claim 8, characterized in that: It also includes quality inspection steps. After the curing is completed, a falling weight deflectometer is used to test the overall deflection value. The representative deflection value must be less than or equal to the design allowable value, and the extreme value at a single point must not exceed twice the representative value.

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