A new and old splicing and widening construction method of asphalt pavement based on stepped excavation

Abstract

The present application relates to the technical field of building road construction widening, and more particularly to a new and old asphalt pavement splicing widening construction method based on stepped excavation, comprising: obtaining the material type of each step tread surface to determine the initial roughness grade, checking and adjusting the initial roughness grade based on the measured structure depth, determining the actual roughness grade of the tread surface, determining the roughness correction coefficient and the height correction coefficient according to the determined actual roughness grade of the tread surface and the step tread surface height, correcting the standard binder coating amount, determining the binder coating amount, and determining the re-pressing mode based on the binder coating amount, the filling material type and the step tread surface height. The present application improves the interlayer bonding reliability and compaction uniformity by scientifically designing the binder coating amount and differentially setting the compaction mode, and reduces the risk of voids, cracking and water seepage at the new and old roadbed splicing.

Description

Technical Field

[0001] This invention relates to the field of road construction and widening technology, and in particular to a construction method for widening asphalt pavement by splicing old and new pavements based on stepped excavation. Background Technology

[0002] With the continuous development of my country's social economy and the increasingly complete infrastructure system, existing road facilities are gradually becoming inadequate to meet current transportation needs. Old roads, especially in rural areas, generally suffer from insufficient road width, weak load-bearing capacity, and aging and damaged surfaces, creating numerous obstacles for subsequent widening and renovation projects. Widening and upgrading old roads is a crucial measure to improve regional traffic capacity and ensure the efficient transport of goods and personnel.

[0003] Chinese Patent Publication No. CN112624699B discloses a cold-state bonding agent for connecting new and old water-stabilized base courses for roads. The bonding agent consists of a powder and a liquid component. The powder is a mixture of cement, fine sand, red mud, fly ash, water-reducing agent, expanding agent, thickener, defoamer (I), thixotropic agent, and redispersible latex powder in a specific weight ratio. The liquid component is a mixture of chlorinated ether resin emulsion, water, defoamer (II), and stabilizer.

[0004] In existing technologies, the treatment of splicing interfaces lacks specificity. For steps of different levels with different performance and composition, there is no scientific basis for controlling the amount of adhesive applied, making it difficult to fully exert the bonding strength of the interface. The splicing interface is prone to debonding and cracking. At the same time, the material types and paving thicknesses of the various structural layers of the road surface vary greatly. Conventional construction uses fixed and uniform compaction process parameters, which cannot be adapted to the compaction control requirements of different levels, making it difficult to guarantee the compaction quality of each layer. Summary of the Invention

[0005] To address this, the present invention provides a construction method for widening and splicing new and old asphalt pavements based on stepped excavation, which overcomes the problems in the existing technology where the amount of adhesive applied is not scientifically controlled, the compaction method cannot be adapted to the compaction control requirements of different structural layers, and it is difficult to guarantee the compaction quality of each layer.

[0006] A construction method for widening and splicing asphalt pavements by step-excavation, comprising: Several steps were milled from bottom to top along the widened side of the old roadbed to obtain the tread material type and measured structural depth of each step to determine the actual roughness level of each step's tread. Based on the actual roughness grade of the tread surface and the corresponding step riser height, roughness correction coefficients and height correction coefficients are determined respectively to determine the amount of adhesive coating; The method of re-compression is determined based on the amount of adhesive applied, the type of filler material, and the thickness of the filler material.

[0007] Furthermore, the method for determining the actual grade of the tread surface roughness is as follows: The initial roughness level is determined based on the tread material type; The initial roughness grade is checked and adjusted based on the measured construction depth to obtain the actual surface roughness grade. The initial roughness level includes high roughness, medium roughness, and low roughness.

[0008] Furthermore, when the tread material is a granular material, the initial roughness level is determined to be high roughness; When the tread material is an inorganic binder stabilized material, the initial roughness level is determined to be medium roughness. When the tread material type is asphalt mixture, the initial roughness level is determined to be low roughness.

[0009] Furthermore, the verification and adjustment include, The measured construction depth is compared with the threshold range corresponding to the initial roughness level; If the measured construction depth falls within the threshold range corresponding to the current level, the original level is maintained; If the measured construction depth is greater than the maximum value of the threshold interval, then adjust to one level in the direction of high roughness; If the measured construction depth is less than the minimum value of the threshold range, then adjust to one level in the direction of lower roughness.

[0010] Furthermore, the threshold interval determination method includes, The interlaminar pull-out strength of multiple specimens with different construction depths under standard adhesive coating conditions was obtained; The construction depth corresponding to the first time the pull-out strength falls below the minimum design standard value is determined as the minimum value of the threshold interval. The construction depth corresponding to the first time the pull-out strength exceeds the minimum design standard value is determined as the maximum value of the threshold interval.

[0011] Furthermore, the roughness coefficient increases with the increase of the actual roughness grade of the tread surface; The height correction factor increases as the riser height of the step increases.

[0012] Furthermore, the re-compression method is determined based on the amount of adhesive applied, the type of filler material, and the thickness of the filler material, including: The initial compaction method is determined based on the type and thickness of the filling material; The initial re-pressing method is verified based on the amount of adhesive applied in order to determine the actual re-pressing method. The determination of the re-compaction method includes determining the re-compaction working mode, the number of re-compaction times and the speed of each re-compaction. The re-compaction working mode includes vibration compaction, rubbing compaction, and vibration-rubbing combined compaction.

[0013] Furthermore, the process of determining the initial re-compression method based on the type and thickness of the filling material includes, The working mode of secondary compaction is determined based on the type of filling material, and the number of secondary compaction cycles and the speed of each secondary compaction cycle are determined based on the thickness of the filling material.

[0014] Furthermore, the process of verifying the initial re-pressing method based on the amount of adhesive applied to determine the actual re-pressing method includes, Based on the determined number of re-compaction times and the single re-compaction speed, it is determined whether the re-compaction effect on the adhesive is satisfied. If the re-compaction effect on the adhesive is not satisfied, the number of re-compaction times and the single re-compaction speed are adjusted.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention obtains the tread material type corresponding to each level of step and comprehensively judges the tread roughness level by combining the measured structural depth. Based on the roughness level and the step riser height, the amount of adhesive is determined. Based on the type of filling material, the thickness of the filling material, and the amount of adhesive, the re-compaction method is adjusted. This establishes a scientific basis for controlling the amount of adhesive, avoiding the impact of insufficient local adhesive due to uniform spraying, which affects the interlayer bonding strength, or the slippage and water seepage caused by excessive adhesive, thus improving the bonding reliability of the splicing interface. At the same time, the re-compaction method is determined based on the type of filling material, the thickness of the filling material, and the amount of adhesive, so that each structural layer can obtain a compaction effect that matches its material characteristics and the amount of adhesive, improving the compaction uniformity and overall stability of the splicing area between the new and old roadbeds, thereby improving the structural integrity, crack resistance, and durability of the splicing part between the new and old pavements.

[0016] Furthermore, in determining the surface roughness state, this invention first establishes an initial roughness level using the material type, and then verifies and adjusts the level based on the texture depth, so that the roughness state can establish a correspondence with the actual interfacial bonding ability. Since different structural layer materials have different surface characteristics and binder adsorption capabilities, granular materials typically have larger pores and stronger mechanical interlocking capabilities, inorganic binder stabilized materials have relatively dense surfaces, and asphalt mixtures typically have an asphalt film covering the surface. Therefore, the material type can reflect the basic bonding characteristics of the interface. Simultaneously, the surface texture state of the same material will differ during long-term service due to traffic loads, environmental effects, and maintenance conditions. Furthermore, during milling, the degree of tool wear, milling depth, and milling drum speed also affect its surface texture state. By introducing texture depth to verify the initial determination result, it is possible to... This further reflects the true texture and effective contact conditions of the milled tread surface, making the roughness level more consistent with the actual site conditions. The threshold range is determined through on-site interlayer pull-out tests. The interlayer pull-out strength can directly reflect the actual bonding performance between the old and new structural layers. Therefore, the threshold parameter obtained by establishing a correspondence between pull-out strength and construction depth links the roughness state with the actual stress performance of the interface. The roughness state obtained in this way can not only reflect the texture characteristics of the tread surface, but also characterize the level of interface bonding ability, thus providing a reliable basis for determining the amount of adhesive to be applied, and improving the adaptability of the interface treatment measures of each step to the actual engineering requirements.

[0017] Furthermore, this invention corrects the standard adhesive coating amount by using both roughness correction coefficient and height correction coefficient, so that the actual adhesive coating amount can simultaneously take into account the tread texture characteristics and the stress characteristics of the step structure, achieving a match between the adhesive dosage and the actual interface requirements under different construction conditions, and improving the interlayer bonding performance, shear resistance and long-term service stability of the splicing interface between new and old pavements.

[0018] Furthermore, this invention differentiates the re-compaction method based on the actual amount of adhesive applied, the type of fill material, and the difference in fill thickness, enabling the re-compaction method to adapt to material properties, structural thickness, and interfacial bonding state simultaneously. It determines the appropriate re-compaction working mode based on the fill material type, ensuring that the compaction method matches the evolution law of the material's internal structure. It determines the baseline number of re-compaction compactions and the baseline single-compaction speed based on the fill material thickness, ensuring that the effective compaction energy per unit area is adapted to the fill layer thickness. Furthermore, it adjusts the initial re-compaction based on the actual amount of adhesive applied. The method is verified by adjusting the number of re-compaction times and the speed of each re-compaction when the amount of interfacial adhesive changes. This ensures that the effective compaction energy obtained at the interface matches the actual amount of adhesive applied, so that a more uniform compaction effect and stable interlayer bonding state can be obtained under different construction conditions. This improves the overall density and interlayer bonding performance of the interface between new and old pavements, reduces the risk of interlayer slippage, loosening and early cracking caused by insufficient compaction, excessive compaction or uneven interface bonding, and at the same time takes into account construction quality and efficiency, thereby improving the long-term service stability of the widened pavement. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the construction process of a method for widening and splicing old and new asphalt pavements based on stepped excavation, as an embodiment of the present invention. Figure 2 This is a cross-sectional view of the new and old road surface splicing structure according to an embodiment of the present invention; Figure 3 This is a flowchart illustrating the roughness level determination process according to an embodiment of the present invention. Figure 4 This is a flowchart illustrating the process of determining the compression method in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0021] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0022] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0023] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] Please see Figure 1 The diagram shown is a flowchart of the construction process for widening and splicing asphalt pavement based on stepped excavation according to an embodiment of the present invention. This embodiment provides a construction method for widening and splicing asphalt pavement based on stepped excavation, including: Step S1: Mill several steps from bottom to top along the widened side of the old roadbed to obtain the tread material type and measured structural depth of each step to determine the actual roughness level of each step's tread. Step S2: Determine the roughness correction coefficient and height correction coefficient based on the tread roughness grade and the corresponding step riser height, respectively, to determine the amount of adhesive to be applied; Step S3: Determine the re-pressing method based on the amount of adhesive applied, the type of filler material, and the thickness of the filler material.

[0025] Specifically, this invention obtains the tread material type corresponding to each level of step and comprehensively determines the tread roughness level by combining the measured structural depth. Based on the roughness level and step riser height, it determines the amount of adhesive to be applied. Based on the type of filling material, the thickness of the filling material, and the amount of adhesive applied, it adjusts the re-compaction method, establishing a scientific basis for controlling the amount of adhesive applied. This avoids problems such as insufficient local adhesive due to uniform application affecting the interlayer bonding strength, or slippage and water seepage caused by excessive adhesive, thus improving the bonding reliability of the splicing interface. At the same time, the re-compaction method is determined based on the type of filling material, the thickness of the filling material, and the amount of adhesive applied, so that each structural layer can obtain a compaction effect that matches its material characteristics and the amount of adhesive applied. This improves the compaction uniformity and overall stability of the splicing area between the new and old roadbeds, thereby enhancing the structural integrity, crack resistance, and durability of the splicing part between the new and old pavements.

[0026] Please see Figure 2 As shown, it is a cross-sectional view of the splicing structure of the old and new road surfaces according to an embodiment of the present invention; In this embodiment, in step S1, a milling machine is used to form a first step 1, a second step 2 and a third step 3 from bottom to top along the widening side of the old roadbed. After milling, the material type of each step tread is obtained, which includes granular materials, inorganic binder stabilized materials and asphalt mixtures. In this embodiment, the type of material can be determined based on the old road design data or in combination with the results of on-site core sampling and testing.

[0027] In this embodiment, when the tread material type is granular material, the initial roughness level is determined to be high roughness; when the tread material type is inorganic binder stabilized material, the initial roughness level is determined to be medium roughness; and when the tread material type is asphalt mixture, the initial roughness level is determined to be low roughness.

[0028] Different tread materials exhibit significantly different surface textures under the same milling process due to variations in their composition and bonding methods. Therefore, the surface roughness can be initially determined based on material type. For granular materials, the aggregates primarily rely on interlocking to form an integral structure. During milling, the bonding constraint is weak, resulting in a high degree of aggregate exposure and easily leading to significant surface undulations. Therefore, the initial roughness level is determined to be high roughness. In inorganic binder-stabilized materials, the aggregates are bound by cement and other binders. After milling, some aggregates are exposed, while others remain covered by the slurry. The resulting surface texture falls between that of granular materials and asphalt mixtures. Therefore, the initial roughness level is determined to be medium roughness. In asphalt mixtures, the aggregates are encased in asphalt binder. After milling, the surface is relatively smooth with minimal texture undulations. Therefore, the initial roughness level is determined to be low roughness.

[0029] It is understandable that, since the material categories of road structural layers fall within the conventional technical content of this field, those skilled in the art can determine the material type. Granular materials refer to materials that are not consolidated as a whole using cementing materials and whose strength is mainly formed by intergranular interlocking and friction, including graded crushed stone, natural sand and gravel, and graded gravel. Inorganic binder stabilized materials refer to materials formed by stabilizing aggregates using inorganic binders such as cement, lime, and fly ash, including cement-stabilized crushed stone, cement-stabilized sand and gravel, and lime-fly ash stabilized crushed stone. Asphalt mixtures refer to pavement materials formed by mixing asphalt as a binder with mineral aggregates, including AC type asphalt concrete, SMA asphalt mastic crushed stone mixture, and OGFC drainage asphalt mixture.

[0030] Please see Figure 3 As shown, it is a flowchart of the roughness level determination in an embodiment of the present invention; In this embodiment, after determining the initial roughness level in step S1, the construction depth of each step surface is measured, and the measured construction depth is compared with the threshold range corresponding to the initial roughness level to determine the actual roughness level of the tread surface. If the measured construction depth falls within the threshold range corresponding to the current level, the original level is maintained; If the measured construction depth is greater than the upper limit of the threshold interval, then adjust to one level in the direction of high roughness; If the measured construction depth is less than the lower limit of the threshold interval, then adjust to one level in the direction of lower roughness; If the current roughness level has reached the preset maximum roughness level or the preset minimum roughness level, then the current roughness level will remain unchanged. The texture depth threshold range is the target texture depth range corresponding to each initial roughness level, obtained through calibration and verification by interlayer pull-out tests. Specifically, for each initial roughness level, multiple milled tread specimens with gradient texture depths are prepared. A standardized amount of adhesive is applied to the surface of each specimen, and after a specified curing time, interlayer pull-out tests are conducted to obtain the interlayer pull-out strength corresponding to different texture depths. The texture depth corresponding to the first time the interlayer pull-out strength falls below the design minimum standard value is taken as the lower limit of the texture depth threshold range corresponding to the initial roughness level, and the texture depth corresponding to the first time the interlayer pull-out strength exceeds the design minimum standard value is taken as the upper limit of the texture depth threshold range corresponding to the initial roughness level. This determines the texture depth threshold range corresponding to each initial roughness level. The minimum design standard value is determined based on the minimum pull-out strength standard value of interlayer bonding specified in the project design documents, and the standard adhesive coating amount is determined based on the coating amount recommended by the construction specifications corresponding to the type of adhesive used in the project.

[0031] The initial roughness grade is a preliminary prediction of the roughness state of the tread surface after milling based on the tread material type. Under identical milling conditions, the initial roughness grade and its corresponding texture depth threshold range match. However, in actual construction, factors such as milling tool wear, milling depth, milling drum speed, aging of the old road, and local aggregate loss can affect the actual texture depth, which may deviate from the texture depth threshold range corresponding to the initial roughness grade. Therefore, it is necessary to further verify the initial roughness grade based on the measured texture depth. The pull-out strength generally increases with the texture depth. However, since the texture depth is sampled discretely according to a preset gradient, the actual test can only obtain a few sets of discrete texture depth-pull-out strength data, making it difficult to directly obtain the texture depth corresponding to the interlayer pull-out strength being exactly equal to the design minimum standard value. Therefore, the lower limit of the threshold interval is defined as the construction depth corresponding to the first time the interlayer pull-out strength is less than the minimum design standard value, and the upper limit of the threshold interval is defined as the construction depth corresponding to the first time the interlayer pull-out strength is greater than the minimum design standard value. The construction depth threshold interval corresponds to the range of construction depths where the interlayer pull-out strength reaches the minimum design standard value under the construction conditions of using the standard adhesive coating amount. This indicates that the interlayer pull-out strength can meet the design requirements without increasing or decreasing the amount of adhesive coating, and that the initial roughness level determined according to the tread material type can meet the subsequent construction requirements. Therefore, the original roughness level should be maintained without adjustment. When the measured construction depth is greater than the upper limit of the threshold interval, it indicates that the actual construction depth is greater than the critical construction depth required to meet the design requirements. Therefore, it should be adjusted one level towards higher roughness to reduce the subsequent amount of adhesive coating. When the measured construction depth is less than the lower limit of the threshold interval, it indicates that the interlayer pull-out strength is difficult to meet the design requirements under the standard adhesive coating amount. Therefore, it should be adjusted one level towards lower roughness to increase the subsequent amount of adhesive coating.

[0032] Specifically, when determining the surface roughness state, this invention first establishes an initial roughness level using the material type, and then verifies and adjusts the level based on the texture depth, so that the roughness state can establish a correspondence with the actual interfacial bonding ability. Since different structural layer materials have different surface characteristics and binder adsorption capabilities, granular materials typically have larger pores and stronger mechanical interlocking capabilities, inorganic binder stabilized materials have relatively dense surfaces, and asphalt mixtures typically have an asphalt film covering the surface. Therefore, the material type can reflect the basic bonding characteristics of the interface. Furthermore, the surface texture state of the same material will vary during long-term service due to traffic loads, environmental effects, and maintenance conditions. During milling, tool wear, milling depth, and milling drum speed also affect the surface texture state. By introducing texture depth to verify the initial determination result, this invention can... This further reflects the true texture and effective contact conditions of the milled tread surface, making the roughness level more consistent with the actual site conditions. The threshold range is determined through on-site interlayer pull-out tests. The interlayer pull-out strength can directly reflect the actual bonding performance between the old and new structural layers. Therefore, the threshold parameter obtained by establishing a correspondence between pull-out strength and construction depth links the roughness state with the actual stress performance of the interface. The roughness state obtained in this way can not only reflect the texture characteristics of the tread surface, but also characterize the level of interface bonding ability, thus providing a reliable basis for determining the amount of adhesive to be applied, and improving the adaptability of the interface treatment measures of each step to the actual engineering requirements.

[0033] In this embodiment, step S2 involves determining a roughness correction coefficient based on the actual roughness level of the tread surface and a height correction coefficient based on the riser height, which are used to correct the standard adhesive coating amount to determine the actual adhesive coating amount. The standard adhesive application amount is the standard application amount recommended by the construction specification corresponding to the type of adhesive used in the project. The higher the actual tread roughness grade, the larger the roughness correction factor; the greater the riser height, the larger the height correction factor. A higher actual tread roughness grade results in more pronounced surface undulations and larger texture depressions. To ensure the adhesive fully fills these depressions and forms a continuous, uniform adhesive layer, the roughness correction factor needs to be increased to increase the actual adhesive application amount. A larger riser height leads to a greater height difference between the new and old roadbeds. Under vehicle loads, shear stress concentration and interlayer relative displacement are more likely to occur at the edge of the step, placing higher demands on interlayer bonding performance. Therefore, it is necessary to increase the adhesive application amount.

[0034] Specifically, this invention corrects the standard adhesive coating amount by using both roughness correction coefficient and height correction coefficient, so that the actual adhesive coating amount can simultaneously take into account the tread texture characteristics and the stress characteristics of the step structure, achieving a match between the adhesive dosage and the actual interface requirements under different construction conditions, and improving the interlayer bonding performance, shear resistance and long-term service stability of the splicing interface between new and old pavements.

[0035] Please see Figure 4 The diagram shown is a flowchart for determining the compression method according to an embodiment of the present invention. In this embodiment, step S3 determines the re-compaction method based on the actual adhesive coating amount, filler material type, and filler material thickness. The re-compaction method includes determining the re-compaction working mode, the number of re-compaction compaction cycles, and the single re-compaction speed. Specifically, it includes... The secondary compaction mode is determined based on the type of filling material. Specifically, when the filling material is granular, the secondary compaction mode is vibratory compaction; when the filling material is an inorganic binder stabilized material, the secondary compaction mode is a combination of vibration and rubbing compaction, performed in the order of vibration compaction and rubbing compaction; and when the filling material is asphalt mixture, the secondary compaction mode is rubbing compaction. Granular materials are unconsolidated granular materials. Their compaction goal is to form a stable interlocking skeleton during particle rearrangement. Since there is no continuous cementing medium between particles, the compaction effect mainly depends on whether the particles can overcome contact friction to complete rearrangement and gradually eliminate internal porosity. Vibratory compaction continuously inputs alternating power into the granular system, causing the particle contact state to constantly change, promoting particle rolling, sliding, and re-interlocking, gradually forming a dense skeleton. This directly meets the compaction requirements of granular materials. If kneading compaction is used, the kneading action mainly manifests as surface shearing and localized kneading, lacking sufficient internal dynamic excitation. The particle rearrangement depth is limited, making it difficult to effectively eliminate internal porosity in the fill layer, resulting in a weak improvement in overall density. If a combination of vibratory compaction and kneading compaction is used, continuing to apply kneading action after vibration has formed a stable particle skeleton can easily disturb the established particle contact relationship, causing some particles to shift again, thus reducing particle interlocking stability. Inorganic binder stabilized materials... The material is a composite system supported by both aggregate skeleton and cementitious structure. Its compaction process requires both increasing the density of the aggregate skeleton and improving the distribution of cementitious material within the skeleton. Vibration compaction or kneading compaction alone cannot achieve the desired compaction effect. First, vibration compaction is used to establish a stable aggregate skeleton, followed by kneading compaction. This allows the cementitious material to further fill the particle contact area and remaining micropores under the combined action of normal pressure and tangential shear, while also improving surface uniformity. The two methods work together to simultaneously meet the compaction requirements for both skeleton formation and cementitious structure perfection. Asphalt mixtures belong to a viscoelastic cementitious system. Its compaction process includes not only the rearrangement of aggregates but also the redistribution and coating of asphalt cement between aggregates. During kneading compaction, normal pressure and tangential shear act on the mixture, enabling the aggregates to adjust their posture within a small range. At the same time, it promotes the uniform spread of asphalt cement and fills the voids between aggregates, forming a continuous and uniform asphalt film while maintaining the stability of the aggregate interlocking structure.

[0036] The number of re-compaction cycles and the single re-compaction speed are determined based on the thickness of the filling material. The greater the thickness of the filling material, the more benchmark re-compaction cycles are required, and the lower the benchmark single re-compaction speed is. The smaller the thickness of the filling material, the fewer benchmark re-compaction cycles are required, and the higher the benchmark single re-compaction speed is. The thickness of the fill material determines the transmission path and attenuation degree of compaction energy within the fill layer. After the compaction load acts on the surface of the fill layer, the compaction energy is gradually transmitted into the interior of the fill layer and attenuates continuously with increasing transmission depth. The number of re-compaction cycles determines the cumulative number of compaction load applications, and the speed of each re-compaction cycle determines the duration of the compaction load per unit area. Both factors together determine the effective compaction energy obtained per unit area.

[0037] When the fill material is thick, the attenuation of compaction energy during its transfer to the bottom of the fill layer is more pronounced, resulting in relatively insufficient effective compaction energy in the bottom area. If fewer re-compaction cycles or higher single-cycle compaction speeds are used, uneven compaction within the fill layer and insufficient density in the lower areas can easily occur. Therefore, it is necessary to increase the number of re-compaction cycles and reduce the single-cycle compaction speed to allow the compaction load to act on the same area multiple times, thereby increasing the effective compaction energy per unit area. When the fill material is thin, compaction energy can be more easily transferred to the entire fill layer. If more re-compaction cycles or lower single-cycle compaction speeds are used, excessively high effective compaction energy per unit area will not only reduce construction efficiency but may also lead to over-compaction, localized displacement, or particle breakage of the surface material. Therefore, reducing the number of re-compaction cycles and increasing the single-cycle compaction speed can improve construction efficiency while ensuring compaction quality.

[0038] The initial re-compaction method is obtained based on the determined re-compaction working mode, the benchmark re-compaction number of times, and the benchmark single re-compaction speed. The initial re-compaction method is verified based on the actual adhesive coating amount to determine the actual re-compaction method. When the actual adhesive coating amount is less than or equal to a preset threshold, the initial re-compaction method remains unchanged; when the actual adhesive coating amount is greater than the preset threshold, the re-compaction number of times is increased and the single re-compaction speed is decreased. The actual amount of adhesive applied determines the thickness of the bonding layer formed at the splicing interface and the distribution of the adhesive at the interface. During the re-compaction process, the adhesive needs to be fully spread under the compaction load and penetrate into the surface texture of the tread to form a continuous and uniform interfacial bonding layer. When the actual amount of adhesive applied is less than or equal to the preset threshold, the thickness of the interfacial bonding layer is within the design control range. The current compaction load can promote the adhesive to fully fill the surface texture and form a continuous bonding layer that meets the interlayer bonding requirements. Therefore, maintaining the initial re-compaction method is sufficient to meet the construction requirements. When the actual amount of adhesive applied is greater than the preset threshold, the thickness of the bonding layer formed at the interface increases, and the amount of adhesive filling in the surface texture and the excess amount at the interface increase accordingly. If the initial re-compaction method is still used, the effective compaction energy obtained per unit area is insufficient, the adhesive is difficult to fully spread into the texture, and may form enriched areas locally at the interface, affecting the effective contact and mechanical interlocking effect between aggregates. Therefore, it is necessary to increase the number of compaction cycles and reduce the speed of each compaction cycle, so that the compaction load is applied to the same area multiple times, thereby increasing the effective compaction energy obtained per unit area, promoting the further spreading of the adhesive, its penetration into the texture, and the removal of local excess adhesive material, so that a uniform, continuous, and stable adhesive layer is formed at the interface.

[0039] The preset threshold is obtained through experimental calibration. Specifically, under the condition that the type of filling material, the thickness of the filling material and the re-compression working mode are kept consistent, multiple sets of different actual adhesive coating amounts are set for testing, and the corresponding initial re-compression methods are used to complete the re-compression. Then, the interface state after re-compression is detected, and the maximum actual adhesive coating amount that can form a continuous and uniform interface bonding layer and meet the interlayer bonding performance requirements in the initial re-compression method is taken as the preset threshold.

[0040] Specifically, this invention differentiates the re-compaction method based on the actual amount of adhesive applied, the type of fill material, and the difference in fill thickness, enabling the re-compaction method to adapt to material properties, structural thickness, and interfacial bonding state simultaneously. It determines the appropriate re-compaction working mode based on the fill material type, ensuring that the compaction method matches the evolution law of the material's internal structure. It determines the baseline number of re-compaction passes and the baseline single-pass re-compaction speed based on the fill material thickness, ensuring that the effective compaction energy per unit area is adapted to the fill layer thickness. Furthermore, it adjusts the initial re-compaction based on the actual amount of adhesive applied. The method is verified by adjusting the number of re-compaction times and the speed of each re-compaction when the amount of interfacial adhesive changes. This ensures that the effective compaction energy obtained at the interface matches the actual amount of adhesive applied, so that a more uniform compaction effect and stable interlayer bonding state can be obtained under different construction conditions. This improves the overall density and interlayer bonding performance of the interface between new and old pavements, reduces the risk of interlayer slippage, loosening and early cracking caused by insufficient compaction, excessive compaction or uneven interface bonding, and at the same time takes into account construction quality and efficiency, thereby improving the long-term service stability of the widened pavement.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A construction method for widening and splicing asphalt pavements by step-excavation, characterized in that, include, Several steps were milled from bottom to top along the widened side of the old roadbed to obtain the tread material type and measured structural depth of each step to determine the actual roughness level of each step's tread. Based on the actual roughness grade of the tread surface and the corresponding step riser height, roughness correction coefficients and height correction coefficients are determined respectively to determine the amount of adhesive coating; The method of re-compression is determined based on the amount of adhesive applied, the type of filler material, and the thickness of the filler material.

2. The construction method for widening and splicing asphalt pavement based on stepped excavation according to claim 1, characterized in that, The method for determining the actual grade of the tread surface roughness is as follows: The initial roughness level is determined based on the tread material type; The initial roughness grade is checked and adjusted based on the measured construction depth to obtain the actual surface roughness grade. The initial roughness level includes high roughness, medium roughness, and low roughness.

3. The construction method for widening and splicing asphalt pavement based on stepped excavation according to claim 2, characterized in that, When the tread material is a granular material, the initial roughness level is determined to be high roughness; When the tread material is an inorganic binder stabilized material, the initial roughness level is determined to be medium roughness. When the tread material type is asphalt mixture, the initial roughness level is determined to be low roughness.

4. The construction method for widening and splicing asphalt pavement based on stepped excavation according to claim 2, characterized in that, The aforementioned verification and adjustment include, The measured construction depth is compared with the threshold range corresponding to the initial roughness level; If the measured construction depth falls within the threshold range corresponding to the current level, the original level is maintained; If the measured construction depth is greater than the maximum value of the threshold interval, then adjust to one level in the direction of high roughness; If the measured construction depth is less than the minimum value of the threshold range, then adjust to one level in the direction of lower roughness.

5. The construction method for widening and splicing asphalt pavement based on stepped excavation according to claim 4, characterized in that, The method for determining the threshold range include, The interlaminar pull-out strength of multiple specimens with different construction depths under standard adhesive coating conditions was obtained; The construction depth corresponding to the first time the pull-out strength falls below the minimum design standard value is determined as the minimum value of the threshold interval. The construction depth corresponding to the first time the pull-out strength exceeds the minimum design standard value is determined as the maximum value of the threshold interval.

6. The construction method for widening and splicing asphalt pavement based on stepped excavation according to claim 1, characterized in that, The roughness coefficient increases with the increase of the actual roughness grade of the tread surface; The height correction factor increases as the riser height of the step increases.

7. The construction method for widening and splicing asphalt pavement based on stepped excavation according to claim 1, characterized in that, The re-compression method is determined based on the amount of adhesive applied, the type of filler material, and the thickness of the filler material, including: The initial compaction method is determined based on the type and thickness of the filling material; The initial re-pressing method is verified based on the amount of adhesive applied in order to determine the actual re-pressing method. The determination of the re-compaction method includes determining the re-compaction working mode, the number of re-compaction times and the speed of each re-compaction. The re-compaction working mode includes vibration compaction, rubbing compaction, and vibration-rubbing combined compaction.

8. The construction method for widening and splicing asphalt pavement based on stepped excavation according to claim 7, characterized in that, The process of determining the initial compaction method based on the type and thickness of the filling material includes, The working mode of secondary compaction is determined based on the type of filling material, and the number of secondary compaction cycles and the speed of each secondary compaction cycle are determined based on the thickness of the filling material.

9. The construction method for widening and splicing asphalt pavement based on stepped excavation according to claim 7, characterized in that, The process of verifying the initial re-pressing method based on the amount of adhesive applied to determine the actual re-pressing method includes the following steps: Based on the determined number of re-compaction times and the single re-compaction speed, it is determined whether the re-compaction effect on the adhesive is satisfied. If the re-compaction effect on the adhesive is not satisfied, the number of re-compaction times and the single re-compaction speed are adjusted.

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