An ultra-light composite roadbed structure and a construction method thereof

Abstract

The application discloses a kind of super-light composite roadbed structures and construction methods thereof, the roadbed structure, including foundation, sand cushion is equipped on foundation, sand cushion is uniformly distributed with EPS pile, EPS pile is equipped with bubble light soil between, EPS pile top end is equipped with pavement structure layer, the side of pavement structure layer is equipped with guardrail, using the super-light composite roadbed structure and construction methods thereof of the application, can improve the integrity and stability of roadbed structure, with the advantages of high safety and low construction cost.

Description

Technical Field

[0001] This invention belongs to the field of building construction technology. Specifically, this invention relates to an ultra-lightweight composite roadbed structure and its construction method. Background Technology

[0002] With the rapid development of my country's economy and society, traffic volume has continued to grow, and the capacity and service level of expressways in many regions are struggling to meet the increasing traffic volume and the needs of socio-economic development. In particular, a number of expressways built and put into operation around 2000 are located close to urban areas, with relatively unique road network corridors. With long-term traffic congestion becoming the norm, this poses a serious challenge to road safety and smooth traffic flow, and cannot provide sustained and efficient support for rapid socio-economic development. Therefore, reconstruction and expansion are imperative.

[0003] However, in the process of urbanization, after the operation of shallow-buried subways that pass under highways, control protection zones have been delineated along the subway route, and strict regulations have been imposed on the displacement of subway tunnels and the additional load on the outer wall of the tunnel structure. The highway reconstruction and expansion using ordinary fill or lightweight soil widening schemes cannot meet the relevant subway regulations, affecting the structural safety and operational safety of the subway. The bridge crossing scheme also has many shortcomings: large span, high cost, large construction disturbance, high safety risks, and uneven settlement of the roadbed caused by bridge splicing, which affects the operational safety of the highway.

[0004] How to effectively reduce the cost of highway reconstruction and expansion while ensuring the structural and operational safety of subways, and improve the safety of highway construction and operation, is a pressing technical challenge that needs to be addressed in similar projects within this industry. Therefore, there is an urgent need to find a fast and safe highway subgrade design structure.

[0005] Patent CN116516776A, published on August 1, 2023, discloses a construction method for a bubble-mixed lightweight soil embankment. This method includes the following steps: excavating the area to be constructed to form a horizontal construction surface; filling, leveling, and compacting the horizontal construction surface; excavating a stepped structure on the side of the horizontal construction surface near the slope bottom; compacting the surface of the stepped structure and constructing an embankment foundation on the top surface of the stepped structure; constructing a panel foundation on the embankment foundation; installing precast panels on the panel foundation to form a casting cavity; pouring bubble-mixed lightweight soil into the casting cavity to form a bubble-mixed lightweight soil layer; and laying a road surface on the top surface of the horizontal construction surface and the bubble-mixed lightweight soil layer to obtain the embankment. This bubble-mixed lightweight soil embankment construction method is not applicable to areas with severely limited additional loads and does not enhance the overall stability and safety of the roadbed structure. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing an ultra-lightweight composite roadbed structure and its construction method that improves the integrity and stability of the roadbed structure, enhances safety, and reduces construction costs.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The ultra-lightweight composite roadbed structure includes a foundation, a sand cushion layer on the foundation, EPS piles evenly distributed on the sand cushion layer, air-filled lightweight soil between the EPS piles, a pavement structure layer at the top of the EPS piles, and guardrails on the side of the pavement structure layer.

[0009] A reinforced concrete slab is provided between the bottom of the road structure layer and the top of the EPS pile.

[0010] The reinforced concrete slabs are laid in layers below the pavement structure layer.

[0011] The top of the sand cushion layer is provided with a reverse filter geotextile, and the sand cushion layer is provided with a rigid plastic permeable pipe, which is arranged horizontally.

[0012] The EPS piles have a diameter of 75cm, are evenly spaced, and have a center-to-center spacing of 110cm.

[0013] The bottom of the EPS pile is provided with a wire mesh, which includes individual wire mesh units. Each individual wire mesh unit has a regular hexagonal structure, and the spacing between the individual wire mesh units is adapted to the spacing of the EPS piles. The bottom of the EPS pile is connected to the wire mesh by wire.

[0014] The construction method for this ultra-lightweight composite roadbed structure includes the following steps:

[0015] S1. Clear, level, and compact the construction site, and backfill with a sand cushion layer;

[0016] S2. Lay a steel mesh on the sand cushion layer;

[0017] S3. Set up a wire mesh 10cm above the sand cushion layer or 10cm below the expected pouring height each time. Fix it with construction boundary templates. In the filling area, use anchor rods to drive deep into the foundation for fixation. Specific holes in the wire mesh are used to bury EPS piles.

[0018] S4. Bury and fix EPS piles. Adjacent EPS piles are bonded together by a thin layer of adhesive mortar. Install the support panel in the construction boundary area.

[0019] S5. Pour the aerated lightweight soil by pumping, ensuring that the outlet is buried in or close to the surface of the aerated lightweight soil.

[0020] S7. After the pouring is completed, the air-bubbly lightweight soil should be covered and protected after it has solidified.

[0021] S8. Set up reinforced concrete slabs according to the filling height, and repeat steps S3 to S7 to ensure that the overall horizontal layering is carried out during the pouring process.

[0022] S9. After the final pouring of the aerated lightweight soil is completed, a geomembrane is installed on top of the aerated lightweight soil.

[0023] S10, Construction pavement structure layer, drainage facilities and roadside guardrails, use crushed stone cushion layer or subbase material to adjust longitudinal and transverse slopes.

[0024] Step S1 includes the following steps: clearing the topsoil layer of the foundation to a thickness of 30cm, cutting the old roadside slope to a slope ratio of 1:1.0 and then excavating steps; leveling and compacting the site; laying a 0.3m thick sand cushion layer on the base; arranging rigid plastic permeable pipes on the slope and in the sand cushion layer, and laying reverse filter geotextile on the top surface of the sand cushion layer.

[0025] In step S4, settlement joints are set along the entire longitudinal section of the roadbed and filled.

[0026] In step S5, the maximum thickness of each layer of bubble-bubbled lightweight soil is 1m, and the time interval between each layer is at least 24 hours.

[0027] The technical advantages of this invention are as follows: The ultra-lightweight composite roadbed structure and its construction method fundamentally solve the problem of severely limited additional loads on shallowly buried subway tunnels and the resulting control of subway structural displacement and deformation. This structure has relatively low construction costs, simple and mature construction technology, easily controllable construction quality, good durability, and guaranteed operational safety. For construction areas crossing shallowly buried subway tunnels, the ultra-lightweight composite roadbed structure using aerated lightweight soil + EPS piles can minimize the impact of construction on subway structural displacement and additional loads, ensuring construction and subway operational safety, and has strong adaptability and application prospects. The reinforced concrete slabs installed inside the aerated lightweight soil or at the bottom of the road surface enhance the integrity and stability of the structure, ensuring the safety and stability of the roadbed structure. Furthermore, by installing permeable pipes to form a drainage cushion layer, the problem of roadbed uplift can be avoided.

[0028] This ultra-lightweight composite roadbed structure employs a design where EPS piles are completely encased in aerated lightweight soil. This avoids ultraviolet radiation, significantly extending the service life of the EPS material and prolonging the durability of the EPS pile composite material. The EPS piles are mass-producible and standardized chemical products, facilitating convenient transportation and storage, and offering simple fixing methods. The aerated lightweight soil construction process is mature, safe, reliable, and quality-controllable, accelerating construction progress and greatly reducing construction costs. Attached Figure Description

[0029] This manual includes the following figures, which illustrate the following:

[0030] Figure 1 This is a schematic diagram of the ultralight composite roadbed structure of the present invention;

[0031] Figure 2-1 and Figure 2-2 This is a schematic diagram of the arrangement of the reinforced concrete slab of the present invention;

[0032] Figure 3-1 and Figure 3-2 This is a schematic diagram of the roadbed cross section after the application of this invention;

[0033] Figure 4 This is a schematic diagram of the cross-sectional arrangement of the bubble-filled lightweight soil and EPS piles in this invention.

[0034] Figure 5 This is a cross-sectional view of the wire mesh of the present invention. Detailed Implementation

[0035] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention, and to facilitate its implementation.

[0036] like Figures 1 to 5 As shown, the ultra-lightweight composite roadbed structure includes a foundation, a sand cushion layer on the foundation, EPS piles evenly distributed on the sand cushion layer, air-filled lightweight soil between the EPS piles, a road structure layer at the top of the EPS piles, and guardrails on the side of the road structure layer.

[0037] EPS (polystyrene foam) piles, as a component of ultra-lightweight composite roadbed structures, possess advantages such as self-support, compressibility, and ease of construction, and are widely used in road engineering both domestically and internationally. The scheme of completely encasing EPS piles with aerated lightweight soil not only replaces part of the aerated lightweight soil to reduce the weight of the roadbed structure but also effectively prevents the EPS material from gradually yellowing and its compressibility from decreasing due to long-term exposure to ultraviolet (UV) radiation, thereby improving the durability and service life of the EPS material. Therefore, the durability of the aerated lightweight soil + EPS pile composite material is essentially equivalent to that of the aerated lightweight soil itself. To reduce the weight of the roadbed structure by replacing part of the aerated lightweight soil with EPS, the composition of 1 cubic meter of aerated lightweight soil is as follows: 180 kg cement, 234 kg water, 646 L of aerated air, and 180 kg mineral admixture, with a wet density of approximately 4.0–6.0 kN / m³. 3 The EPS pile has a forming diameter of 75cm and a density of 0.2kN / m³. 3The overall unit weight of the composite roadbed structure is approximately 2.4 kN / m³. 3 It has a density of 40% to 60% that of ordinary aerated lightweight soil and 13% that of ordinary fill roadbed.

[0038] Bubble-foamed lightweight soil is a roadbed structure made from a highly fluid mixture of cement, water, air bubbles, and mineral admixtures in a specific ratio, which is then foamed and solidified. Its unconfined compressive strength, resilient modulus, shear strength, and other mechanical properties meet the requirements for road applications. Furthermore, it maintains mechanical stability and exhibits good durability under long-term exposure to external factors such as alternating wet and dry conditions, cyclic loading, freeze-thaw cycles, and corrosive substances, meeting the design service life requirements for highway engineering. EPS piles are polystyrene plastic cylindrical piles with a closed-cell structure, formed by pre-foaming expandable polystyrene beads in a mold, with a service temperature not exceeding 75℃. They possess strong water and chemical stability. EPS piles are evenly distributed at certain intervals on the foundation cushion layer, fixed at the lower end, and filled between the piles with prepared bubble-foamed lightweight soil. This creates a composite roadbed structure system where the bubble-foamed lightweight soil and EPS piles jointly bear the loads generated by the road surface and passing vehicles.

[0039] like Figure 2-2 As shown, a reinforced concrete slab is installed between the bottom of the pavement structure layer and the top of the EPS piles. Depending on the height of the subgrade structure, the reinforced concrete slab is installed in different ways. When the height is less than or equal to 6.5m, an additional reinforced concrete slab with a thickness of about 15cm is installed between the top of the ultra-lightweight composite subgrade structure and the pavement structure layer.

[0040] like Figure 2-1 As shown, the reinforced concrete slabs are layered below the pavement structure layer. When the height is greater than 6.5m, an additional 15cm thick reinforced concrete slab is added at the bottom of the pavement structure layer and at 5m intervals to ensure the safety and stability of the ultra-lightweight composite subgrade structure during construction and operation. This targeted design based on the height of the subgrade structure enhances its overall stability, forming a cohesive whole. This allows for the even distribution of traffic loads and the load from the superstructure, preventing stress concentration that could damage the aerated lightweight soil and EPS piles, and preventing harmful substances from penetrating the EPS pile material.

[0041] A reverse-filter geotextile is installed on top of the sand cushion layer, and rigid plastic permeable pipes are installed inside the sand cushion layer, arranged horizontally. The reverse-filter geotextile allows water to flow through while preventing soil loss under the action of osmotic pressure. The roadbed structure is placed on a 30cm thick sand cushion layer, and the horizontal 7.5cm diameter PVC rigid plastic permeable pipes are installed in the sand cushion layer to promptly discharge the upward-permeating groundwater outside the roadbed structure, achieving anti-buoyancy function and avoiding the risk of the roadbed structure floating during subsequent operation.

[0042] like Figure 1 As shown, the EPS piles have a diameter of 75cm, are evenly spaced, and have a center-to-center spacing of 110cm. Testing showed that when the center-to-center spacing of the EPS piles is 110cm and the EPS pile volume replacement rate reaches 42%, the overall unit weight of the ultra-light composite roadbed structure is approximately 2.4kN / m³. 3 Compared to a completely lightweight earthen subgrade structure, the weight reduction is over 40%, meeting the requirements for additional displacement and load generated by the shallow-buried subway. Numerical calculations show that the maximum horizontal displacement of the subway structure after construction is 0.40 mm, and the maximum vertical displacement is 0.92 mm, both less than the standard control value of 15 mm. The additional load generated by the subway shield tunnel structure after construction is only 16.18 kPa, compared to 31.1 kPa for the lightweight foamed concrete scheme, representing a 48% reduction in additional load. This ensures that the additional load on the outer wall of the subway shield tunnel structure meets the standard requirement of less than 20 kPa.

[0043] like Figure 5 As shown, the bottom of the EPS pile is equipped with a wire mesh. The wire mesh consists of individual wire mesh units, each with a regular hexagonal structure. The spacing of the individual wire mesh units matches the spacing of the EPS piles. The bottom of the EPS pile is connected to the wire mesh via wire. The wire mesh provides positioning for the EPS piles and also secures the bottom of the piles. The EPS piles are fixed to the foundation cushion layer by the wire mesh, ensuring they do not move, deform, or remain vertical during the pouring of the lightweight aerated soil. After the lightweight aerated soil is poured and hardened, during the upward pouring process, adjacent EPS pile sections are bonded together using a thin layer of high-quality bonding mortar until construction is complete.

[0044] like Figure 3-1 As shown, the foundation has a slope with steps. After the slope is cut, the part of the roadbed that connects with the road surface is a sloping structure, which helps to improve the bearing capacity of the roadbed. At the same time, the steps on the slope can facilitate the installation of EPS piles at the connection between the roadbed and the road surface.

[0045] The construction method for this ultra-lightweight composite roadbed structure includes the following steps:

[0046] S1. Clear, level, and compact the construction site, and backfill with a sand cushion layer;

[0047] S2. Lay a steel mesh on the sand cushion layer;

[0048] S3. Set up a wire mesh 10cm above the sand cushion layer or 10cm below the expected pouring height each time. Fix it with construction boundary templates. In the filling area, use anchor rods to drive deep into the foundation for fixation. Specific holes in the wire mesh are used to bury EPS piles.

[0049] S4. Bury and fix EPS piles. Adjacent EPS piles are bonded together by a thin layer of adhesive mortar. Install the support panel in the construction boundary area.

[0050] S5. Pour the aerated lightweight soil by pumping, ensuring that the outlet is buried in or close to the surface of the aerated lightweight soil.

[0051] S7. After the pouring is completed, the air-bubbly lightweight soil should be covered and protected after it has solidified.

[0052] S8. Set up reinforced concrete slabs according to the filling height, and repeat steps S3 to S7 to ensure that the overall horizontal layering is carried out during the pouring process.

[0053] S9. After the final pouring of the aerated lightweight soil is completed, a geomembrane is installed on top of the aerated lightweight soil.

[0054] S10, Construction pavement structure layer, drainage facilities and roadside guardrails, use crushed stone cushion layer or subbase material to adjust longitudinal and transverse slopes.

[0055] In step 1 above, before construction, prepare the site for waterproofing and drainage. Then, clear the foundation surface to a depth of 30cm, and after the old roadside slope is reduced to a 1:1.0 slope, excavate a 1.0×1.0m step. φ7.5cm rigid plastic permeable pipes are laid transversely along the slope. Before filling, level and compact the site to a compaction degree of not less than 90%. Then, lay a 0.3m thick sand cushion layer at the base, embedding the φ7.5cm rigid plastic permeable pipes within the sand cushion layer. Finally, lay a layer of reverse filter geotextile on top of the sand cushion layer.

[0056] In step 5 above, the mix proportion of the aerated lightweight soil needs to be selected through testing. The testing should be conducted in advance to ensure that the required mix proportion is available during construction. If necessary, the relationship between 28-day and 7-day strength should be established so that the 7-day compressive strength can be used to judge the 28-day compressive strength during construction quality management. The foaming agent is crucial to the aerated lightweight soil technology. Regardless of whether a surface-active, protein-based, or resin-based agent is used, the foaming quality must be guaranteed. This means that the bubbles must be evenly distributed and stable in the aerated lightweight soil, ensuring its lightweight and flowability. Quality management during mixing of aerated lightweight soil is most demanding because ensuring its flowability and lightweight nature requires accurate material addition, controlled according to standards for wet density, air volume, and flowability.

[0057] In step 4 above, the sides of the aerated lightweight soil are protected with cement panels. The panels are precast and reinforced with angle steel. Strict dimensional control is required during panel fabrication to avoid installation difficulties. For irregularly shaped panels at the edges and top, adjustments to dimensions must be made according to the actual situation during construction. Joints between panels and between panels and the foundation must be tightly filled to prevent grout leakage; columns and panels must be secure to prevent collapse.

[0058] In the above-mentioned process of pouring aerated lightweight soil, the prepared and mixed aerated lightweight soil is generally pumped to the construction site. Under the premise of ensuring no material segregation and stable bubbles, the maximum distance for primary pumping is 500m. If the transportation distance exceeds this range, a relay pumping device should be installed or the mixing of bubbles should be moved to near the outlet of the pumping pipe. To ensure that the bubbles in the aerated lightweight soil are independently and uniformly distributed, and to minimize the defoaming of bubbles and material segregation, excessive vibration should be avoided during construction. Strict control of foam quality is required during pouring. To prevent settlement cracking or subgrade instability after pouring, the pouring process should be carried out directly from the front end of the hose, and the outlet should be buried in the aerated lightweight soil or as close as possible to its surface to avoid compromising the stability of the lightweight soil embankment after construction.

[0059] In step 7 above, after the aerated lightweight soil is poured, it needs to be cured. To prevent cracks from forming due to rapid drying, it needs to be covered with burlap sacks or similar protective coverings after curing. For protection during rainy weather, all work surfaces and areas susceptible to water damage must be covered with impermeable tarpaulins or tarpaulins before curing to prevent rain damage. For large volumes of aerated lightweight soil, the curing process should be strengthened to ensure that insufficient curing does not lead to cracks.

[0060] In step 9 above, after the aerated lightweight soil is completed, a geomembrane should be promptly installed on top of the aerated lightweight soil to seal it and achieve waterproofing and seepage prevention. The geomembrane installation should minimize joints; any existing joints should be sealed.

[0061] In step 10 above, the roadside guardrail adopts SAm grade reinforced concrete wall-type guardrail, which is connected by pre-embedded steel bars in the top of the guardrail foundation; the longitudinal and transverse slopes are adjusted by crushed stone cushion layer or base course material.

[0062] Step S1 includes the following steps: clearing the topsoil layer of the foundation to a thickness of 30cm; cutting the old roadside slope to a 1:1.0 gradient and then excavating steps; leveling and compacting the site; laying a 0.3m thick sand cushion layer at the base; arranging rigid plastic permeable pipes on the slope and in the sand cushion layer; and laying a reverse filter geotextile on the top surface of the sand cushion layer. Cutting the old roadside slope to a 1:1.0 gradient creates a trapezoidal cross-section structure to prevent uneven pressure distribution in the foundation from causing localized soil settlement. The reverse filter geotextile prevents soil loss, and the rigid plastic permeable pipes drain groundwater that seeps upwards into the slope and sand cushion layer. The sand cushion layer material requirements are: a maximum particle size not exceeding 37.5mm, a fine particle content of less than 4.75mm not exceeding 10%, a fine particle content of less than 2.36mm not exceeding 6%, and virtually no fine particles smaller than 1.18mm. The PE drainage pipes used in rigid permeable pipes must meet the requirements of standard GB / T13663.2-2018 "Polyethylene (PE) Piping Systems for Water Supply - Part 2: Pipes". The geomembrane used for the filter should be M2 / PE type, 2mm thick, with an elongation greater than 50%, longitudinal and transverse tensile strength not less than 18kN / m, longitudinal and transverse right-angle tear strength not less than 100N / mm, CBR puncture strength not less than 6000N, and vertical permeability coefficient not exceeding 5x10⁻⁶. -11 cm / s.

[0063] In step S4, settlement joints are set and filled along the entire longitudinal section of the roadbed. The settlement joints are filled with asphalt-impregnated wood planks or plywood, and their locations correspond one-to-one with the settlement joints of the panels and their foundations. Settlement joints between panels are filled with asphalt-impregnated wood planks, and the surface of the joints is finished with a grooved finish for aesthetic purposes. Construction joints are set every 10 to 15 meters along the panels, with a width of 1 cm. These joints are filled with asphalt-impregnated hemp fiber across the entire cross-section, and their locations must correspond to the existing construction joints in the cross-sections of the aerated lightweight soil, panels, and their foundations.

[0064] In step S5, the maximum thickness of each layer of aerated lightweight soil poured is 1m, and the time interval between each layer is at least 24 hours. The aerated lightweight soil pouring process is carried out in layers simultaneously, with the entire filling body poured in horizontal layers. The maximum thickness of a single construction is no more than 1m, and the curing time is at least 24 hours. The next layer can only be constructed after each layer of aerated lightweight soil has cured to the design strength.

[0065] This ultra-lightweight composite roadbed structure and its construction method fundamentally solve the problem of severely limited additional loads on shallow-buried subway tunnels and the resulting challenges in controlling subway structural displacement and deformation. The structure boasts relatively low construction costs, simple and mature construction technology, easily controllable construction quality, good durability, and guaranteed operational safety. For construction areas crossing shallow-buried subway tunnels, the ultra-lightweight composite roadbed structure using aerated lightweight soil + EPS piles can minimize the impact of construction on subway structural displacement and additional loads, ensuring construction and subway operational safety, and demonstrating strong adaptability and application prospects. Reinforced concrete slabs installed inside the aerated lightweight soil or at the bottom of the road surface enhance the overall integrity and stability of the structure, ensuring the safety and stability of the roadbed structure. Furthermore, the installation of permeable pipes to form a drainage cushion layer prevents the roadbed from floating.

[0066] This ultra-lightweight composite roadbed structure employs a design where EPS piles are completely encased in aerated lightweight soil. This enhances the service life of the EPS material and extends the durability of the EPS pile composite material. The EPS piles are mass-producible and standardized chemical products, facilitating convenient transportation and storage, and offering simple fixing methods. The aerated lightweight soil construction process is mature, safe, reliable, and quality-controllable, accelerating construction progress and significantly reducing construction costs.

[0067] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. An ultralight composite roadbed structure, characterized in that: The system includes a foundation, on which a sand cushion layer is provided. EPS piles are evenly distributed on the sand cushion layer, and air-filled lightweight soil is placed between the EPS piles. A pavement structure layer is provided at the top of each EPS pile, and a guardrail is provided on the side of the pavement structure layer. A reinforced concrete slab is provided between the bottom of the pavement structure layer and the top of the EPS piles. The reinforced concrete slab is arranged in layers below the pavement structure layer. A reverse filter geotextile is provided on top of the sand cushion layer, and a rigid plastic permeable pipe is provided inside the sand cushion layer, with the rigid plastic permeable pipe arranged horizontally. The EPS piles have a diameter of 75 cm and are evenly spaced, with a center-to-center spacing of 110 cm.

2. The ultralight composite roadbed structure according to claim 1, characterized in that: The bottom of the EPS pile is provided with a wire mesh, which includes individual wire mesh units. Each individual wire mesh unit has a regular hexagonal structure, and the spacing between the individual wire mesh units is adapted to the spacing of the EPS piles. The bottom of the EPS pile is connected to the wire mesh by wire.

3. A construction method for an ultralight composite roadbed structure as described in claim 2, characterized in that, Includes the following steps: S1. Clear, level, and compact the construction site, and backfill with a sand cushion layer; S2. Lay a steel mesh on the sand cushion layer; S3. Set up a wire mesh 10cm above the sand cushion layer or 10cm below the expected pouring height each time. Fix it with construction boundary templates. In the filling area, use anchor rods to drive deep into the foundation for fixation. The regular hexagonal structure holes of the wire mesh unit are used to bury EPS piles. S4. Bury and fix EPS piles. Adjacent EPS piles are bonded together by a thin layer of adhesive mortar. Install the support panel in the construction boundary area. S5. Pour the aerated lightweight soil by pumping, ensuring that the outlet is buried in or close to the surface of the aerated lightweight soil. S7. After the pouring is completed, the air-bubbly lightweight soil should be covered and protected after it has solidified. S8. Set up reinforced concrete slabs according to the filling height, and repeat steps S3 to S7 to ensure that the overall horizontal layering is carried out during the pouring process. S9. After the final pouring of the aerated lightweight soil is completed, a geomembrane is installed on top of the aerated lightweight soil. S10, Construction pavement structure layer, drainage facilities and roadside guardrails, use crushed stone cushion layer or subbase material to adjust longitudinal and transverse slopes.

4. The construction method of the ultra-lightweight composite roadbed structure according to claim 3, characterized in that, Step S1 includes the following steps: clearing the topsoil layer of the foundation to a thickness of 30cm, cutting the old roadside slope to a slope ratio of 1:1.0 and then excavating steps; leveling and compacting the site; laying a 0.3m thick sand cushion layer on the base; arranging rigid plastic permeable pipes on the slope and in the sand cushion layer, and laying reverse filter geotextile on the top surface of the sand cushion layer.

5. The construction method of the ultra-lightweight composite roadbed structure according to claim 3, characterized in that: In step S4, settlement joints are set along the entire longitudinal section of the roadbed and filled.

6. The construction method of the ultra-lightweight composite roadbed structure according to claim 3, characterized in that: In step S5, the maximum thickness of each layer of bubble-bubbled lightweight soil is 1m, and the time interval between each layer is at least 24 hours.

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