Roadbed treatment methods

Abstract

This invention discloses a roadbed treatment method, comprising the following steps: compacting and leveling a soft soil foundation; laying a layer of crushed stone on the soft soil foundation; laying a first geotextile layer on the crushed stone layer; setting multiple reinforcing cages at the toe of the slopes on both sides of the roadbed; adding stones into the reinforcing cages; filling a first layer of fill material on top of the first geotextile layer; setting a first horizontal reinforcement on top of the first fill material layer; laying a permeable layer on top of the first horizontal reinforcement; laying a second layer of fill material on top of the permeable layer; setting a second horizontal reinforcement on top of the second fill material layer; and filling a surface layer on top of the second horizontal reinforcement. By setting the first horizontal reinforcement, the second horizontal reinforcement, and the reinforcing cages in synergy, the bearing capacity of the foundation is improved in multiple dimensions; by setting the permeable layer, a good drainage channel is formed in the roadbed, improving the permeability of the roadbed, thereby improving the problems of weak bearing capacity and poor permeability of soft soil foundations and effectively reducing roadbed defects.

Description

Technical Field

[0001] This invention relates to the field of civil engineering technology. More specifically, this invention relates to a method for roadbed treatment. Background Technology

[0002] With the rapid development of the national economy, the construction of highways and high-speed railways has been vigorously promoted. These projects inevitably encounter soft soil foundations. First, soft soil itself has weak bearing capacity, making it difficult to meet the basic construction requirements of roadbeds. Second, the moisture content of soft soil directly affects the performance of roadbed fill materials, thus causing settlement problems. To reduce the damage to soft soil roadbeds, many technologies and methods have been proposed for soft soil foundation treatment, and pile foundation treatment is an effective method to improve the bearing capacity of the foundation.

[0003] Sand and gravel pile foundations are a type of compaction pile foundation, a commonly used method for treating soft soil foundations. Sand piles and sand and gravel piles are collectively referred to as sand and gravel piles. Holes are drilled in the soft soil using methods such as vibration, impact, or water jetting, and sand, gravel, or crushed stone is forced into the holes to form a large-diameter, dense pile body composed of sand or gravel (crushed stone). The resulting pile body has good permeability, but its ability to improve the bearing capacity of the foundation is limited.

[0004] The article "A Review of Academic Research on Roadbed Engineering in China 2021" (Vol. 34, No. 3 of the *China Journal of Highway and Transport*) reviews a new pile foundation technology—cast-in-place X-shaped concrete piles. Based on the principle of peripheral expansion of anisotropic cross-sections, this technology fully utilizes the anisotropic characteristics of the pile cross-section, increasing the side friction of the pile and thus improving the bearing capacity of the foundation compared to traditional cylindrical piles. However, while this type of concrete pile foundation can significantly improve the bearing capacity of the foundation, its poor permeability means it cannot effectively improve the permeability of soft soil foundations.

[0005] Therefore, for soft soil foundations, a comprehensive treatment method needs to be designed that can both improve the bearing capacity of the foundation and improve its permeability. Summary of the Invention

[0006] One object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages that will be described later.

[0007] Another objective of this invention is to provide a roadbed treatment method that can effectively improve the bearing capacity and permeability of soft soil foundations, ensure the construction quality of soft soil roadbeds, and effectively reduce soft soil roadbed defects.

[0008] To achieve these objectives and other advantages according to the present invention, a roadbed treatment method is provided, comprising the following steps:

[0009] Step 1: Compact and level the soft soil foundation. Lay a layer of crushed stone on the soft soil foundation and compact it.

[0010] Step 2: Lay a first layer of geotextile on the gravel layer;

[0011] Step 3: Install multiple steel cages at the toe of the slopes on both sides of the roadbed. Each steel cage extends along the height of the roadbed and its bottom end passes through the first geotextile and crushed stone layer and extends into the soft soil foundation.

[0012] Step 4: Add stones into the steel cage and compact and level it.

[0013] Step 5: Fill the first layer of fill material on top of the first geotextile, and compact and level it.

[0014] Step 6: A first horizontal reinforcement is installed above the first layer of filler, and then compacted and leveled.

[0015] Step 7: Lay a permeable layer above the first horizontal reinforcement;

[0016] Step 8: Lay a second layer of filler material on top of the permeable layer, and compact and level it.

[0017] Step 9: A second horizontal reinforcement is provided above the second layer of filler, with its top flush with the top of the steel cage;

[0018] Step 10: Fill the surface layer above the second horizontal reinforcement.

[0019] Preferably, both the first horizontal reinforcement and the second horizontal reinforcement include two layers of second geotextile and a geogrid disposed between the two layers of second geotextile.

[0020] Preferably, the reinforcing cage includes multiple longitudinal reinforcing bars and multiple transverse reinforcing bars for binding the longitudinal reinforcing bars. The multiple longitudinal reinforcing bars are set vertically to the soft soil foundation. The cross-sectional shape of the reinforcing cage is X-shaped, and the four perimeters of the reinforcing cage are arc-shaped.

[0021] Preferably, the geogrid is a polypropylene biaxial geogrid.

[0022] Preferably, the permeable layer includes multiple permeable pipes and coarse sand filling the outer wall of the permeable pipes. The steps for laying the permeable layer are as follows:

[0023] Step 1: Fill a layer of coarse sand on top of the first horizontal reinforcement;

[0024] Step 2: Lay a permeable pipe assembly on top of the coarse sand. The permeable pipe assembly includes multiple first permeable pipes laid at intervals along the length of the roadbed and multiple second permeable pipes perpendicular to the length of the first permeable pipes. Multiple second permeable pipes are connected between adjacent first permeable pipes. The first permeable pipes extend along the width of the roadbed and their length is consistent with the width of the roadbed.

[0025] Step 3: Fill a layer of coarse sand on the permeable pipe assembly and compact it.

[0026] Preferably, after the steel reinforcement cage is laid, during the laying process in steps five to nine, a hydraulic rammer is used to compact the perimeter of the steel reinforcement cage every 2 meters.

[0027] Preferably, during the laying process in steps one through nine, compaction is carried out using a dynamic compaction device at 3-meter intervals.

[0028] Preferably, drainage ditches are set on both sides of the roadbed, and the first permeable pipe is connected to the drainage ditch.

[0029] Preferably, the surface layer is an asphalt layer.

[0030] Preferably, the surface layer is a permeable concrete layer.

[0031] The present invention has at least the following beneficial effects:

[0032] 1. This invention improves the bearing capacity of the foundation by setting up a vertical steel cage. The cross-sectional shape of the steel cage is set as X-shaped with four arc-shaped perimeters to increase its pile side friction resistance. It can improve the bearing capacity of the foundation more than the traditional cylindrical pile. At the same time, well-graded stone is placed inside the steel cage, which can improve the bearing capacity of the foundation on the one hand, and on the other hand, it is also a good drainage channel, thereby improving the stability of the roadbed and reducing post-construction settlement.

[0033] The bearing capacity of the foundation is further improved by setting up a first horizontal reinforcement and a second horizontal reinforcement. Both the first and second horizontal reinforcements include two layers of second geotextile and a geogrid between the two layers of second geotextile. The geogrid has a strong stress resistance, which effectively reduces roadbed settlement. At the same time, the geogrid can also improve the shear resistance of the roadbed, thereby increasing the bearing capacity of the foundation and reducing roadbed settlement. Due to the presence of the second geotextile, a good drainage channel is formed, which drains excess liquid and gas from the roadbed and effectively improves permeability.

[0034] In summary, by setting up horizontally laid first and second horizontal reinforcements in synergy with vertically set steel cages, the bearing capacity of the foundation is improved in multiple dimensions, while also ensuring good permeability.

[0035] 2. To further improve the permeability of the roadbed, this invention incorporates a permeable layer containing multiple permeable pipes. This permeable layer has a strong drainage and infiltration capacity, forming a good drainage channel. Water in the roadbed is drawn into the hollow permeable pipes and discharged outside the roadbed. This solves the problems of soft and wet roadbeds and frost heaves in summer, as well as the problem of groundwater exposure and ice formation in the roadbed area in winter. Furthermore, by improving the permeability of the roadbed, it effectively reduces roadbed settlement.

[0036] 3. This invention ensures the performance of the steel cage by rationally setting the installation steps. The steel cage is laid first, and then the first and second horizontal reinforcements are laid. This allows for timely correction of the steel cage's deviation during the installation process, ensuring that the steel cage is placed smoothly and is in a vertical position after installation, thus maximizing its effect of providing foundation bearing capacity.

[0037] 4. After the steel reinforcement cage is laid, during the process of laying the first layer of fill material to the second horizontal reinforcement, the soil around the steel reinforcement cage is compacted, which greatly increases the shear strength of the soil around the steel reinforcement cage and significantly increases the pile side friction resistance, thus exhibiting superior bearing and deformation properties.

[0038] 5. In the process of laying the roadbed, the present invention adopts a layered compaction or rolling method, and is combined with compaction reinforcement measures every 3m, so that the roadbed has a good reinforcement effect, high bearing capacity and uniform bearing capacity distribution, which can effectively ensure the construction quality of the roadbed.

[0039] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0040] Figure 1 This is a cross-sectional schematic diagram of the roadbed described in this invention;

[0041] Figure 2 This is a perspective view of the steel cage described in this invention; Attached image description:

[0043] 1- Crushed stone layer; 2- First geotextile; 3- Reinforcing cage; 4- First fill layer; 5- First horizontal reinforcement; 51- Second geotextile; 52- Geogrid; 53- Second geotextile; 6- Permeable layer; 7- Second horizontal reinforcement; 71- Second geotextile; 72- Geogrid; 73- Second geotextile; 8- Surface layer. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, so that those skilled in the art can implement it based on the description.

[0045] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0046] It should be noted that, unless otherwise specified, the experimental methods described in the following implementation plan are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified.

[0047] In the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0048] like Figure 1 As shown, the present invention provides a roadbed treatment method, comprising the following steps:

[0049] Step 1: Compact and level the soft soil foundation. Lay a layer of crushed stone 1 on the soft soil foundation and compact and level it.

[0050] Step 2: Lay a first layer of geotextile 2 on the crushed stone layer 1;

[0051] Step 3: Install multiple steel cages 3 at the toe of the slopes on both sides of the roadbed. Each steel cage 3 extends along the height of the roadbed and its bottom end passes through the first geotextile 2 and the crushed stone layer 1 and extends into the soft soil foundation.

[0052] Step 4: Add stones into the steel cage 3 and compact and level it;

[0053] Step 5: Fill the first layer of filler material 4 on top of the first geotextile 2, and compact and level it.

[0054] Step 6: A first horizontal reinforcement 5 is installed above the first layer of filler 4, and then compacted and leveled.

[0055] Step 7: Lay a permeable layer 6 above the first horizontal reinforcement 5;

[0056] Step 8: Lay the second layer of filler material on top of the permeable layer 6, and compact and level it.

[0057] Step 9: A second horizontal reinforcement 7 is provided above the second layer of filler, with its top flush with the top of the steel cage 3;

[0058] Step 10: Fill the surface layer 8 above the second horizontal reinforcement 7.

[0059] After the construction of this embodiment is completed, the cross-sectional diagram of the roadbed is as follows: Figure 1As shown, the soft soil subgrade includes, from bottom to top, the following: soft soil foundation, crushed stone layer 1, first geotextile 2, first filler layer 4, first horizontal reinforcement 5, permeable layer 6, second filler layer, second horizontal reinforcement 7, and surface layer 8. Multiple steel cages 3 are installed at the toe of the slopes on both sides of the subgrade. Each steel cage 3 extends along the height of the subgrade, and its bottom end passes through the first geotextile 2 and crushed stone layer 1 and extends into the soft soil foundation. Stone material is placed inside the steel cage 3.

[0060] In the above technical solution, step one: The soft soil foundation is compacted and leveled using dynamic compaction. Before treatment, a test compaction is conducted to determine the compaction parameters. Then, the compaction point locations are set. These locations can be arranged in, but are not limited to, equilateral triangles, isosceles triangles, or squares, with a square being preferred. The spacing between each compaction point is controlled at 4-5 meters. Dynamic compaction is performed in multiple passes, preferably three passes, with a certain interval between each pass to allow for the dissipation of excess pore water pressure in the soft soil. After dynamic compaction, the strength of the soft soil foundation can be effectively improved, and the compressibility of the soft soil can be reduced. Then, on the soft soil… A layer of crushed stone 1 is laid on the base and compacted. To ensure a high degree of compaction, a layered and multiple compaction method is adopted, with each layer being 200-300mm thick. At the edge of the crushed stone layer 1, a rammer is used for additional compaction. The compacted crushed stone cushion layer has high strength and good density, which can effectively transfer the road load on the roadbed to the soft soil foundation and the strata below the soft soil foundation, ensuring the stability of the roadbed. Since the crushed stone cushion layer is flexible, it can adjust the stress on the foundation and make it uniform. At the same time, the crushed stone layer 1 also has a drainage function, which can enhance the drainage of the roadbed.

[0061] Step 2: Lay a first geotextile 2 on the crushed stone layer 1. When laying the geotextile, use sandbags at 1-2m intervals to load the geotextile, so that the geotextile is tightly attached to the crushed stone layer 1 to ensure the quality of the geotextile laying. The geotextile should be laid smoothly and loosely, not taut, and a certain amount of leeway should be left to accommodate deformation. The geotextile can form drainage channels to drain excess liquid and gas in the subgrade. At the same time, the geotextile can isolate the crushed stone layer 1 and the first filler layer 4 with different physical properties, forming a stable interface and maintaining the overall structure and function of the materials of the crushed stone layer 1 and the first filler layer 4.

[0062] Step 3: Install multiple steel cages 3 at the toe of the slopes on both sides of the roadbed. Each steel cage 3 extends along the height of the roadbed, and its bottom end passes through the first geotextile 2 and the crushed stone layer 1 and extends into the soft soil foundation. By setting up vertical steel cages 3, the bearing capacity of the foundation can be enhanced. Laying up the steel cages 3 first, and then carrying out the layered laying work in steps 6 to 9, can correct the deviation in time during the process of laying the lower steel cages 3, ensuring that the steel cages 3 are placed smoothly and in a vertical state after installation, so as to maximize the effect of providing the bearing capacity of the foundation.

[0063] Step 4: Add well-graded aggregate into the steel cage 3, compact and level it to ensure that the compaction degree meets the requirements; the aggregate can improve the bearing capacity of the foundation on the one hand, and on the other hand, it is also a good drainage channel, thereby improving the stability of the roadbed and reducing post-construction settlement.

[0064] Step 5: Fill the first layer of fill material 4 on top of the first geotextile 2, and compact and level it; select fill material that is easy to compact, has high strength and good water stability to improve compaction performance and strength, so that the water in the subgrade can be better absorbed, thereby improving the stability of the subgrade; the fill material can be, but is not limited to, well-graded gravel, crushed stone soil, sandy gravel and crushed stone sand, coarse and fine sandy silt in coarse soil, light and heavy silty clay in fine soil, foamed lightweight soil, preferably foamed lightweight soil, which is a lightweight material with low density, and can reduce the settlement of the foundation by reducing the additional stress in the foundation.

[0065] Step Six: A first horizontal reinforcement 5 is installed above the first layer of filler 4 and compacted and leveled; by setting the first horizontal reinforcement 5, the bearing capacity of the foundation is further improved, which can effectively make up for the deficiency of the limited horizontal range of the steel cage 3; by setting the horizontal first horizontal reinforcement 5 and the vertical steel cage 3, the bearing capacity of the foundation is improved in a coordinated and multi-dimensional manner.

[0066] Step 7: Lay a permeable layer 6 on top of the first horizontal reinforcement 5; by setting the permeable layer 6, the permeability of the roadbed is further enhanced, and a good drainage channel is formed, which improves the stability of the soft soil roadbed and reduces post-construction settlement.

[0067] Step 8: Lay the second layer of filler material on top of the permeable layer 6, and compact and level it; the material of the second layer of filler material is the same as that of the first layer of filler material 4, and the function is the same, so it will not be described again here;

[0068] Step 9: A second horizontal reinforcement 7 is provided above the second layer of filler, with its top flush with the top of the steel cage 3; the second horizontal reinforcement 7 and the first horizontal reinforcement 5 are made of the same material and have the same function, which will not be described again here;

[0069] Step 10: Fill the surface layer 8 above the second horizontal reinforcement 7.

[0070] Another technical solution is that both the first horizontal reinforcement 5 and the second horizontal reinforcement 7 include two layers of second geotextile and a geogrid between the two layers of second geotextile. The geogrid has strong stress resistance, effectively reducing roadbed settlement. At the same time, the geogrid can also improve the shear resistance of the roadbed and increase the bearing capacity of the foundation, thereby reducing roadbed settlement. The horizontally laid geogrid and the vertically set steel cage 3 work together to improve the bearing capacity of the foundation in multiple dimensions. A second geotextile is provided above and below the geogrid. The second geotextile has the same material and function as the first geotextile 2 and can form a drainage channel to isolate materials with different physical properties and maintain the overall structure and function of the materials.

[0071] Another technical solution is that the reinforcing cage 3 includes multiple longitudinal reinforcing bars and multiple transverse reinforcing bars for binding the longitudinal reinforcing bars. The multiple longitudinal reinforcing bars are set vertically to the soft soil foundation, such as... Figure 2 The figure shown is a three-dimensional view of the steel cage 3 (the transverse steel bars are not shown in the figure). The cross-sectional shape of the steel cage 3 is X-shaped, and the four perimeters of the steel cage 3 are arc-shaped. According to the principle of peripheral expansion of the anisotropic cross-section, the characteristics of the anisotropic cross-section are fully utilized, which increases the side friction of the pile and can improve the bearing capacity of the foundation more than the traditional cylindrical pile.

[0072] Another technical solution is to use polypropylene bidirectional geogrid. Bidirectional geogrid has excellent properties such as high strength, good dimensional stability, light weight, good toughness, fatigue resistance, aging resistance, corrosion resistance and creep resistance. Polypropylene bidirectional geogrid has strong strength, which can effectively improve the performance of the subgrade and effectively reduce subgrade diseases.

[0073] Another technical solution involves a permeable layer 6 comprising multiple permeable pipes and coarse sand filling the outer walls of the permeable pipes. The permeable pipes have strong drainage and infiltration capabilities, drawing water from the roadbed into the hollow pipe body while trapping silt and impurities outside. Simultaneously, the permeable pipes possess sufficient resistance to flattening, are robust and durable, and prevent pipe collapse. They also have high tensile strength, capable of withstanding soil pressure and sliding. Specifically, the steps for laying the permeable layer 6 are as follows:

[0074] Step 1: Fill a layer of coarse sand on top of the first horizontal reinforcement 5. The coarse sand has good water permeability.

[0075] Step 2: Lay a permeable pipe assembly on top of the coarse sand. The permeable pipe assembly includes multiple first permeable pipes laid at intervals along the length of the roadbed and multiple second permeable pipes perpendicular to the length of the first permeable pipes. Multiple second permeable pipes are connected between adjacent first permeable pipes. The first permeable pipes extend along the width of the roadbed and have the same length as the width of the roadbed. Since their length extends to the edge of the roadbed, the water they absorb can be discharged outside the roadbed. By setting up the first and second permeable pipes, water in the soil can be absorbed in multiple dimensions. Since the second permeable pipes are connected to the first permeable pipes, the water absorbed by the second permeable pipes can be discharged outside the roadbed through the first permeable pipes.

[0076] Step 3: Fill a layer of coarse sand on the permeable pipe assembly and compact it.

[0077] By setting up a permeable layer 6, groundwater can be effectively diverted to the outside of the roadbed, thus playing a role in drainage. This solves the problems of soft and wet roadbeds and frost heaves in summer, as well as the problem of groundwater exposure and ice formation in the roadbed area in winter. Furthermore, by improving the permeability of the roadbed, it effectively reduces the settlement of the roadbed.

[0078] Another technical solution involves compacting the perimeter of the reinforcing cage 3 with a hydraulic rammer every 2 meters during the laying process from steps five to nine after the reinforcing cage 3 has been laid. This compacts the soil around the reinforcing cage 3, increasing the soil's mechanical properties (including the internal friction angle and internal friction coefficient). Consequently, the shear strength of the soil around the reinforcing cage 3 is significantly improved, and the contact between the reinforcing cage 3 and the soil (including the first layer of filler 4, the second layer of filler, and coarse sand) becomes closer. This significantly increases the pile side friction resistance and provides superior bearing and deformation properties.

[0079] Another technical solution involves compacting the roadbed with a dynamic compaction device every 3 meters during the paving process from step one to step nine; and reinforcing the roadbed in layers during the paving process from step one to step nine, so that the roadbed has a good reinforcement effect, high bearing capacity and uniform bearing capacity distribution, which can effectively ensure the construction quality of the roadbed.

[0080] Another technical solution involves setting up drainage ditches on both sides of the roadbed, with a first permeable pipe connected to the drainage ditch. The first permeable pipe drains water from the roadbed into the drainage ditch to provide good foundation construction facilities.

[0081] Another technical solution is that the surface layer 8 is an asphalt layer.

[0082] Another technical solution is that the surface layer 8 is a permeable concrete layer.

[0083] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0084] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method of treating a subgrade, characterized by, The method comprises the following steps: Step 1: compacting and leveling the soft soil foundation, laying a layer of gravel on the soft soil foundation, and rolling and compacting; Step 2: laying a layer of first geotextile on the gravel layer; Step 3: arranging a plurality of steel cages at the slope toes of the side slopes of the roadbed, each steel cage extending along the height direction of the roadbed, and the bottom end extending into the soft soil foundation through the first geotextile and the gravel layer, the steel cage comprising a plurality of longitudinal steel bars and a plurality of transverse steel bars for binding the longitudinal steel bars, the longitudinal steel bars being arranged perpendicularly to the soft soil foundation, the cross-sectional shape of the steel cage being X-shaped, and the four perimeters of the steel cage being arc-shaped; Step 4: adding stones into the steel cage and compacting and leveling; Step 5: filling and compacting and leveling a first layer of filler on the first geotextile; Step 6: arranging a first horizontal reinforcing body on the first layer of filler and compacting and leveling; Step 7: laying a water-permeable layer on the first horizontal reinforcing body: (a) filling a layer of coarse sand on the first horizontal reinforcing body; (b) laying a water-permeable pipe group on the coarse sand, the water-permeable pipe group comprising a plurality of first water-permeable pipes arranged at intervals along the length direction of the roadbed and a plurality of second water-permeable pipes perpendicular to the length direction of the first water-permeable pipes, a plurality of second water-permeable pipes being connected between adjacent first water-permeable pipes, wherein the first water-permeable pipes extend along the width direction of the roadbed and have a length consistent with the width of the roadbed; (c) filling a layer of coarse sand on the water-permeable pipe group and compacting; Step 8: laying a second layer of filler on the water-permeable layer and compacting and leveling; Step 9: arranging a second horizontal reinforcing body on the second layer of filler, the top of the second horizontal reinforcing body being flush with the top of the steel cage, and the first horizontal reinforcing body and the second horizontal reinforcing body each comprising two layers of second geotextile and a geogrid arranged between the two layers of second geotextile; Step 10: filling a surface layer on the second horizontal reinforcing body, the surface layer being a water-permeable concrete layer.

2. The method of subgrade treatment according to claim 1, wherein The geogrid is a polypropylene bidirectional geogrid.

3. The method of subgrade treatment according to claim 1, wherein After the steel cage is laid, the perimeters of the steel cage are compacted every 2m during the laying process of steps 5-9 by using a hydraulic tamper.

4. The method for treating subgrade according to claim 1 or 3, wherein The compaction is performed every 3m during the laying process of steps 1-9 by using a dynamic compactor.

5. The method of subgrade treatment according to claim 1, wherein Drainage ditches are arranged at the two sides of the roadbed, and the first water-permeable pipes are in communication with the drainage ditches.

6. The method of subgrade treatment according to claim 1, wherein The surface layer is an asphalt layer.

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