Roadbed structure for preventing upward arching deformation of railway roadbed filler and construction method

Abstract

The invention discloses a subgrade structure for preventing upward arching deformation of railway subgrade filler and a construction method.The subgrade structure comprises a subgrade bed surface layer, a subgrade bed bottom layer, a subgrade body, a base flexible cushion layer and a foundation from top to bottom, and the subgrade bed bottom layer is divided into an improved filling area and a filler filling area; meanwhile, an isolating layer system composed of a surface isolating layer, a side slope isolating layer and a bottom isolating layer is arranged, all the isolating layers are connected through connectors to form a closed area, a filling area containing iron sulfide filler is wrapped, and contact between water and oxygen is blocked. During construction, site preparation and foundation treatment are firstly carried out, and then the steps of improved soil preparation, filling of all layers, isolation layer laying and the like are sequentially completed. The structure and the method can effectively prevent roadbed arching caused by oxidation expansion of the iron sulfide-containing filler, reasonably utilize the filler and save engineering investment, and are suitable for railway roadbed construction of the sulfur-containing mineral filler.

Description

Technical Field

[0001] This patent relates to the field of railway roadbed structure forms and construction methods, specifically to a roadbed structure and construction method for preventing railway roadbed filler from arching and deforming. Background Art

[0002] my country's railway system is developing rapidly. By the end of 2024, my country had built and operated over 160,000 kilometers of railway mileage, including over 48,000 kilometers of high-speed railways. High-speed operation places extremely high demands on the smoothness of ballastless track. Safety measures during railway survey, design, construction, and operation are primarily focused on preventing subsidence of the subgrade and track. However, in recent years, problems with ballastless track subgrade deformation have emerged during operation. These problems have occurred on long and large trunk lines in western China, intercity high-speed lines in central China, and high-speed trunk lines in mountainous areas of southern China, severely impacting track smoothness and operating safety. Subgrade arching has been observed on several railway lines, including the Lanzhou-Xinjiang Railway and the Shanghai-Kunming High-Speed ​​Railway. When the amount of arching reaches a certain level, remediation is required. Subgrade arching is a major technical challenge and pain point in my country's ballastless track high-speed railway technology. Arching mechanisms and prevention techniques have become a key constraint on the development of my country's high-speed railways, necessitating systematic research.

[0003] Research on the mechanisms of subgrade arching is primarily focused on foundation arching and subgrade filler arching. The concept of subgrade arching caused by foundation expansion is a long-standing topic, and most relevant findings are based on foundation rock and soil tests, water-soil or water-rock interactions, and unloading mechanics models. These findings reveal a clear expansion mechanism and distinct contributing factors. However, research on subgrade arching caused by fillers began relatively recently, and the physical and chemical processes involved are complex, involving numerous substances and environmental factors. While qualitative understanding of the filler expansion reaction has been achieved, and some progress has been made in understanding cement expansion caused by sulfate attack in transition sections, persistent arching has occurred on many high-speed rail lines currently under construction, even without expansive soils and due to chemical attack by sulfur-containing minerals on high-speed rail fillers. This phenomenon is also known to occur even in environments without added cement. The deformation is characterized by long periods, large arching, non-convergence, irreversibility, strong chemical expansion forces, and difficulty in remediation.

[0004] Preventing basal arching caused by oxidation and expansion of iron sulfide fillers is a major technical challenge facing high-speed railways. Conventionally, the most direct approach to circumventing this problem is to avoid using such fillers for roadbed construction. However, the measurement of iron sulfide content in roadbed fillers can have significant errors. Currently, the accuracy of commonly used XRD or XRF monitoring is typically 1%. Existing engineering examples show that pyrite content exceeding 1% in roadbed fillers can cause basal arching. On the other hand, in areas where fillers are scarce, finding a way to prevent basal arching caused by iron sulfide fillers and fully utilizing the available iron sulfide fillers can reduce the cost of purchasing fillers and save project investment. Therefore, engineering measures are necessary to prevent oxidation of iron sulfide fillers in roadbed fillers. Commonly used methods include improving expansive soil roadbeds and isolating saline soil roadbeds. Relevant literature indicates that the pyrite weathering process manifests as an interaction between the pyrite, water, and oxygen systems. When sulfide minerals such as pyrite are present in roadbed fillers, the pyrite oxidizes in the natural environment to generate large amounts of sulfate and iron ions. Excess sulfate in minerals such as ferroalloy and chlorophyllin, which contain large amounts of water of crystallization, reacts with other mineral components such as dolomite and calcite to form gypsum. When the sulfur in the iron ore is converted into gypsum with an equal molar amount of sulfur, its volume can expand by more than five times, causing roadbed arching. In this process, water and oxygen are key factors in the oxidation and expansion of pyrite. Therefore, the key to preventing arching in roadbeds containing sulfur-containing fillers lies in water and oxygen barrier treatment.

[0005] A Chinese invention patent (publication number CN115492174A) discloses an anti-freeze structure for roadbeds in seasonally frozen soil areas and its construction method. The structure comprises, from bottom to top, a gravel layer, a filler layer, a cement-stabilized crushed stone layer, a conductive base layer, and a pavement layer. Hard insulation panels, gravel slope protection layers, and one-way drainage pipes are installed on both side slopes. By combining active defense, passive insulation, and drainage principles, the structure can effectively prevent frost heave in seasonally frozen soil areas and improve the freeze-thaw stability of the roadbed structure. The patent (publication number CN106638200A) discloses a roadbed antifreeze and interception and drainage facility and construction method suitable for seasonally frozen soil areas. The method adopts the method of laying a crushed stone layer wrapped by a filter layer under the base layer, laying a filter layer and an interception and drainage layer around the grooves on both sides of the roadbed, laying a crushed stone layer wrapped by the filter layer on both sides of the road, laying a crushed stone layer and an anti-filter layer on the interception and drainage layer, and then laying an insulation layer, a plain soil layer and a surface vegetation layer. The drainage is collected through the crushed stone layer and the interception and drainage layer. The insulation layer is used to ensure that the water in the drainage layer will not freeze and be discharged outside the drainage field, ensuring that the roadbed will not be damaged by freeze-thaw during operation. Patent (publication number CN 202730544 U) discloses a frost-heaving-resistant roadbed structure for deep seasonal frozen soil. By sequentially laying an antifreeze layer, a barrier layer, another antifreeze layer, and a sealing layer above the subgrade from bottom to top, this structure eliminates the two essential conditions for frost heaving in the subgrade—water and frost-heaving-sensitive soil—and prevents frost heaving in deep seasonal frozen soil. Patent (publication number CNCN 211227880 U) discloses a foundation structure for limited deformation and anti-arching in expansive soil. The structure comprises a flexible cushion layer, a raft slab, and reinforced piles extending into the subgrade soil. This structure not only effectively ensures load-bearing and settlement control, but also prevents arching damage to the subgrade structure caused by soil expansion. These patents all address the prevention and control of seasonal frost heaving or arching deformation in expansive soil foundations, and do not address the prevention and control of arching deformation in subgrade fillers.

[0006] In summary, the existing technology has obvious deficiencies in solving the problem of basal arching of roadbed containing sulfide iron fillers. There is an urgent need for a roadbed structure and construction method that can effectively isolate water and oxygen and reasonably utilize sulfur-containing fillers. Summary of the Invention

[0007] The purpose of this patent is that, on the one hand, even if the roadbed filler contains a small amount of pyrite and other substances that are easy to cause the roadbed to arch, it can still be used as roadbed filling; on the other hand, when using roadbed fillers containing pyrite to fill the roadbed, it is necessary to prevent the oxidized and expansive minerals in the roadbed fillers such as iron sulfide from coming into contact with oxygen and water to undergo oxidation reactions, causing the roadbed filler to expand and arch. The key to preventing the arching of roadbed fillers such as iron sulfide is to isolate water and oxygen.

[0008] In order to achieve the above-mentioned object, the present invention provides a roadbed structure for preventing the deformation of railway roadbed filler, characterized in that it comprises, from top to bottom, a roadbed subgrade surface layer (1), a roadbed subgrade bottom layer (2), a roadbed body (3), a base flexible cushion layer (4) and a foundation (5); the roadbed subgrade bottom layer (2) comprises a subgrade bottom layer improved filling area (2.1) and a subgrade bottom layer filler filling area (2.2); the roadbed structure further comprises a roadbed isolation layer (6), the roadbed isolation layer (6) comprises a roadbed surface isolation layer (6.1), a roadbed side slope isolation layer (6.2) and a roadbed bottom isolation layer (6.3); the roadbed surface isolation layer (6.1) is arranged in the subgrade bottom layer improved filling area (2.1) At the bottom, the roadbed bottom isolation layer (6.3) is arranged on the upper part of the base flexible cushion layer (4), and the roadbed side slope isolation layer (6.2) is arranged on both sides of the slope of the roadbed body (3); the roadbed surface isolation layer (6.1) and the roadbed bottom isolation layer (6.3) are medium-coarse sand cushion layers with a layer of composite geomembrane sandwiched in the middle; the roadbed side slope isolation layer (6.2) can be laid directly or by digging steps according to the flexibility of its material; the geotextiles of the roadbed surface isolation layer (6.1), the roadbed side slope isolation layer (6.2) and the roadbed bottom isolation layer (6.3) are connected with a waterproof mesh mat or a waterproof geotextile joint to form a closed area, which wraps the base bed bottom filler filling area (2.2) and the roadbed body (3).

[0009] Furthermore, the subgrade surface layer (1) is filled with graded crushed stone, with a filling thickness of ≥0.4m; the improved filling area (2.1) of the subgrade bottom layer is filled with fillers of Group A or B or improved fillers, and the total filling thickness of the improved filling area (2.1) of the subgrade bottom layer and the subgrade surface layer (1) is ≥1.0m; the subgrade bottom layer filler filling area (2.2) and the subgrade body (3) are filled with sulfide-containing fillers, and the total filling thickness of the improved filling area (2.1) of the subgrade bottom layer and the filler filling area (2.2) of the subgrade bottom layer is ≥2.3m. The total filling thickness of the subgrade surface layer and the improved filling area of ​​the subgrade bottom layer is not less than 1.0m, so as to ensure that there is no sulfide-containing subgrade filler within the atmospheric influence range, and effectively prevent the upper subgrade filler from coming into contact with water and air and causing oxidation reaction and arching. When using the improvement process, the improvement plan and mix ratio of the improved soil need to be determined through indoor tests. It is recommended to use inert oxygen agents or gelling agents as improvers to improve sulfide-containing roadbed fillers.

[0010] Furthermore, the improved filler in the improved fill area (2.1) of the subgrade bed is a sulfide-containing roadbed filler modified with an oxygen inert agent or gelling agent. The dosage of the oxygen inert agent or gelling agent is determined through laboratory testing. The oxygen inert agent consumes oxygen or forms a physical barrier, blocking the contact between the sulfide and oxygen, thereby inhibiting the oxidation expansion reaction at the source. The gelling agent can undergo a gelling and solidification reaction with the sulfide particles, encapsulating the sulfide and filling the pores, reducing water penetration and oxygen diffusion channels. The activity of the sulfide in the improved filler is passivated, significantly weakening its ability to form expansive minerals such as sulfate and gypsum when exposed to water and oxygen, thereby preventing volume expansion.

[0011] Furthermore, the base flexible cushion layer (4) has a thickness of ≥0.6 m and is composed of sand and gravel, graded crushed stone or a combination of waterproof geosynthetics.

[0012] Furthermore, a transverse drainage slope with a slope rate of 4% is provided at the contact surface between the roadbed surface layer (1) and the improved filling area (2.1) of the bottom layer of the roadbed.

[0013] Furthermore, the roadbed structure also includes a roadbed slope protection area (7), a bidirectional geogrid (8), a roadbed slope protection structure (9) and a drainage ditch (10); the roadbed slope protection area (7) is set on the slopes on both sides of the roadbed body (3), and is filled with qualified fillers or improved soil. A concrete water-cutting skeleton is set on the slope surface, and soil and shrubs are planted in the water-cutting skeleton; the bidirectional geogrid (8) is set in the roadbed slope protection area (7), with a width of ≥3m, and is laid in layers at a certain height at intervals, with the outer edge folded back; the roadbed slope protection structure (9) is set at the foot of the embankment, and is selected from mortar-laid stone, concrete foot wall or retaining wall; the drainage ditch (10) is set on the outer side of the embankment foot.

[0014] Furthermore, when the roadbed slope isolation layer (6.2) is laid by digging steps, the step height is 0.4-0.8m, and the step width meets the minimum requirement of the geogrid laying length; the drainage geotechnical structure is arranged under the bidirectional geogrid (8) and is in close contact with the bidirectional geogrid (8).

[0015] Another aspect of the present invention provides a method for constructing a roadbed structure for preventing the upward arching deformation of railway roadbed filler as described above, characterized in that it comprises the following steps: S1, Work Preparation: Level the roadbed and fill the construction site, test the bearing capacity of the foundation, and if the foundation is weak, reinforce the foundation or excavate and replace it with filling; S2, making improved soil: determine the improvement scheme and mix ratio of improved soil based on experience or through indoor tests, and use an inert oxygen agent or gelling agent to improve the sulfide-containing roadbed filler; S3, constructing a base flexible cushion layer and a roadbed bottom isolation layer: laying a base flexible cushion layer (4) with a thickness of ≥0.6m on the roadbed base, laying a medium-coarse sand cushion layer on top of the base flexible cushion layer (4), and sandwiching a composite geomembrane between the medium-coarse sand cushion layer to form a roadbed bottom isolation layer (6.3); S4, road base body and isolation layer filling: construct the road base body (3) in layers on the flexible cushion layer (4) at the base, wherein the two sides of each layer of the road base body (3) are filled with improved soil or qualified A and B fillers, and the middle is filled with sulfide-containing road base fillers, which are spread separately and rolled uniformly to form a "sandwich" sandwich structure; the road base fillers are loaded, leveled, and rolled in layers, and the compacted thickness of each layer is ≤30cm. During the filling process, a drainage mesh mat or drainage geotextile is laid to form a road base slope isolation layer (6.2); and the road base slope protection structure (9), road base slope protection area (7) and bidirectional geogrid (8) are constructed in this way; S5, filling of the subgrade bed bottom filler: after the subgrade body (3) is filled to the designed height, the subgrade bed bottom filling area (2.2) is filled on the subgrade body (3); S6, Construction of roadbed surface isolation layer: Lay a medium-coarse sand cushion layer on top of the roadbed base filler, and sandwich a composite geomembrane between the cushion layers on the medium-coarse sand cushion layer to form the roadbed surface isolation layer (6.1); S7, filling of the subgrade base improvement area: fill the subgrade base improvement area (2.1) on the subgrade surface isolation layer (6.1); S8, roadbed surface filling: Use graded crushed stone to fill the roadbed surface (1).

[0016] Furthermore, the foundation reinforcement treatment adopts composite foundation reinforcement, and the pile length and pile diameter need to be checked to meet the settlement and stability control requirements, and the pile quality and composite foundation bearing capacity are tested after construction.

[0017] Furthermore, when the roadbed slope isolation layer (6.2) is laid by digging steps, steps of a certain height are reserved according to the design size, and drainage-proof mesh mats or drainage-proof geotextiles are laid on the steps in sequence; when the bidirectional geogrid (8) is laid, the outer edge folding length is ≥1m, and the roadbed slope protection structure (9) is filled and compacted by small machinery.

[0018] Beneficial effects of the present invention: 1. This invention utilizes a roadbed structure that combines an improved fill area with an iron sulfide filler area and an isolation layer. This avoids the significant increase in improvement or fill costs associated with using only improved soil or qualified filler, while also avoiding the risk of arching associated with using only iron sulfide filler. By rationally utilizing sulfur-containing filler, significant project costs can be saved while ensuring the safety and stability of the roadbed.

[0019] 2. By establishing a subgrade improved fill area and a subgrade surface isolation layer within the subgrade surface fill layer, the infiltration of surface water can be effectively blocked, reducing the seepage impact of surface water on the fill material. The subgrade surface isolation layer and the subgrade subgrade surface layer must be at least 1.0m thick to ensure that no iron sulfide-containing subgrade fill material is within the atmospheric influence range. This effectively protects the upper subgrade fill material from contact with water and air, preventing oxidation reactions that can cause arching.

[0020] 3. By installing an isolation layer on the roadbed surface, on both sides of the slope, and at the base, a closed isolation system is formed. This effectively blocks the infiltration of surface water and groundwater, reducing the impact of moisture on the filler. Furthermore, the isolation layer blocks the filler from oxygen in the air, fundamentally preventing oxidation reactions between the roadbed filler and water and oxygen, thereby effectively preventing roadbed deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of a roadbed structure for preventing the upward arching deformation of railway roadbed filler in one embodiment of the present invention.

[0022] Figure 2 It is a schematic diagram of a roadbed structure for preventing the upward arching deformation of railway roadbed filler in another embodiment of the present invention.

[0023] In the figure: 1—subgrade surface layer, 2—subgrade bottom layer, 3—subgrade body, 2.1—subgrade bottom layer improved filling area, 2.2—subgrade bottom layer filler filling area, 4—base flexible cushion layer, 5—foundation, 6—subgrade isolation layer, 6.1—subgrade surface isolation layer, 6.2—subgrade slope isolation layer, 6.3—subgrade bottom isolation layer, 7—subgrade slope protection area, 8—bidirectional geogrid, 9—subgrade slope protection structure, 10—drainage ditch, 11 filling steps. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. The following embodiments are not intended to limit the present invention but are merely intended to illustrate the present invention.

[0025] In the specific embodiments, steps, material selections, and numerical parameters that are not described in detail are all conventional choices in the prior art or any currently disclosed prior art.

[0026] See also Figure 1 and Figure 2 , Figure 1 and Figure 2This is the subgrade structure for preventing the arching deformation of railway subgrade fillers in this embodiment. The subgrade structure comprises a subgrade surface layer 1, a subgrade bottom layer 2, a subgrade body 3, a base flexible cushion layer 4, a foundation 5, a subgrade isolation layer 6, a subgrade slope protection area 7, a bidirectional geogrid 8, a subgrade slope protection structure 9, and a drainage ditch 10. From top to bottom, the subgrade structure comprises the subgrade surface layer 1, the subgrade bottom layer 2, the subgrade body 3, the base flexible cushion layer 4, and the foundation 5. The subgrade bottom layer 2 comprises an improved subgrade filling area 2.1 and a subgrade filler filling area 2.2. The subgrade isolation layer 6 comprises a subgrade surface isolation layer 6.1, a subgrade slope isolation layer 6.2, and a subgrade bottom isolation layer 6.3.

[0027] The surface layer 1 of the roadbed is filled with graded crushed stone in accordance with railway standards, with a filling thickness of ≥0.4m; the improved filling area 2.1 of the bottom layer of the roadbed is filled with normal A and B group fillers or improved fillers. The filling thickness of the surface layer 1 of the roadbed and the improved filling area 2.1 of the bottom layer of the roadbed is required to be ≥1.0m, which can avoid the roadbed fillers without sulfide within the range of atmospheric influence, thereby effectively preventing the upper roadbed fillers from contacting with water and air to avoid oxidation reactions causing arching; the fillers of the improved filling area 2.1 of the bottom layer of the roadbed can be qualified A and B group fillers or improved roadbed fillers containing sulfides. When using the improvement process, the improvement plan and mix ratio of the improved soil need to be determined through indoor tests. It is recommended to use inert oxygen agents or gelling agents as improvers to improve the roadbed fillers containing sulfides. The subgrade bottom filler filling area 2.2 and the roadbed body 3 can be filled with iron sulfide filler with a low content. The filling thickness of the subgrade bottom improved filling area 2.1 and the subgrade bottom filler filling area 2.2 is required to be ≥2.3m.

[0028] A 4% transverse drainage slope is established at the interface between the subgrade surface layer 1 and the improved fill area 2.1 of the subgrade bottom layer to ensure that moisture in the subgrade surface layer drains out of the subgrade along the drainage slope. A base flexible cushion layer 4 with a thickness of ≥0.6m is provided beneath the subgrade body 3. This cushion layer 4 is composed of a combination of sand, gravel, graded crushed stone, or waterproof geosynthetics. This cushion layer 4 not only isolates water, drains water, and improves the water stability of the base and subgrade, but also strengthens the isolation between the subgrade isolation layer 6.3 and the subgrade body 3 and the foundation 5, enhancing the isolation function of the isolation layer. Below the base flexible cushion layer 4 is the foundation 5. If the foundation is weak, it will require foundation reinforcement or excavation and replacement according to the subgrade foundation treatment requirements.

[0029] The roadbed isolation layer 6 includes a roadbed surface isolation layer 6.1, a roadbed side slope isolation layer 6.2, and a roadbed bottom isolation layer 6.3. The roadbed surface isolation layer 6.1 is set at the bottom of the improved filling area 2.1 of the subgrade bottom layer, the roadbed bottom isolation layer 6.3 is set on the upper part of the base flexible cushion layer 4, and the roadbed side slope isolation layer 6.2 is set on both sides of the slope of the roadbed body 3. The roadbed surface isolation layer 6.1 and the roadbed bottom isolation layer 6.3 are 0.1m thick medium-coarse sand cushion layers, and a layer of composite geomembrane is sandwiched in the middle of the medium-coarse sand cushion layer. The roadbed side slope isolation layer 6.2 can be made of PCF composite drainage mesh mats or drainage geotextiles. Depending on the flexibility of the material, it can be directly laid (attached Figure 1 ) or dig steps and pave (with Figure 2 ). When the roadbed slope isolation layer 6.2 is laid in the form of filling steps 11, the step height is consistent with the geogrid laying height, which is 0.6m, and the step width should be able to meet the minimum requirement for the geogrid laying length. During the laying process, the geotextile is adjacent to the geogrid at the bottom of the geogrid. It should be noted that the geotextile should not be damaged during the geogrid laying process. The geotextiles of the roadbed surface isolation layer 6.1 and the roadbed bottom isolation layer 6.3 are connected to the drainage mesh mat and drainage geotextile of the roadbed slope isolation layer 6.2 to form a closed area, which wraps the base bed bottom filler filling area 2.2 and the roadbed body 3, thereby isolating oxygen and water.

[0030] Roadbed slope protection zones 7 are set on the slopes on both sides of the roadbed body 3. The roadbed slope protection zones 7 are filled with qualified fillers or improved soil. A concrete water-cutting frame is set on the slope surface for planting soil and shrubs for protection. Several bidirectional geogrids 8 are set in the roadbed slope protection zone 7. The bidirectional geogrids 8 are used to reinforce the embankment slopes. The width should be no less than 3m. The geogrids are laid in layers at intervals of 0.6m. The outer edge is folded back. The folding length meets the requirements of the "Technical Specifications for the Application of Geosynthetics for Railway Roadbed".

[0031] A roadbed slope protection structure 9 is installed at the toe of the embankment. Depending on the embankment's height, a mortared stone / concrete foot wall or retaining wall can be used to enhance the stability of the roadbed slope against sliding along the toe. A drainage ditch 10 is designed outside the embankment's toe to collect runoff from the roadbed surface and facilitate its drainage outside the roadbed.

[0032] This roadbed structure adopts the roadbed structure form of improved filling area + iron sulfide filler filling area + isolation layer. Improved soil or qualified filler is used to form a wrapping area, which is wrapped with the isolation layer to form the filling area containing iron sulfide filler, thereby isolating the filler in the filling area containing iron sulfide filler from contact with air and moisture, and avoiding oxidation reaction of iron sulfide filler to cause arching of the roadbed.

[0033] This embodiment also provides a roadbed structure implementation process for preventing the railway roadbed filler from arching and deforming: (1) Work preparation Prepare the roadbed construction site and level the base to ensure that the base surface is flat, solid, and free of debris and weeds.

[0034] (2) Testing the bearing capacity of the foundation If the foundation is soft, it is necessary to reinforce the foundation or excavate and replace it in accordance with the foundation treatment requirements of high-speed railway subgrades.

[0035] (3) Making improved soil Combined with the specific conditions of the construction area, the improvement plan and mix ratio of the improved soil are determined based on experience or through indoor tests. Generally, inert oxygen agents or gelling agents are used as improvers to improve sulfide-containing roadbed fillers.

[0036] (4) Construction of flexible cushion layer at the base and isolation layer at the bottom of the roadbed A flexible cushion layer is laid on the base of the roadbed, and a 0.1m thick medium-coarse sand cushion layer is laid on the upper part of the flexible cushion layer. A layer of composite geomembrane is sandwiched in the middle of the cushion layer to form a base isolation layer. During the laying process, it is necessary to ensure that the composite geomembrane is not damaged and the joints are well sealed to prevent water and oxygen penetration.

[0037] (5) Road foundation and isolation layer filling Starting from the base flexible cushion layer 4, improved soil or qualified A and B fillers are used on both sides of the road base body 3, and sulfide-containing roadbed filler is spread separately in the middle and rolled uniformly to form an improved soil (qualified filler) filling area wrapping the sulfide-containing iron filler filling area.

[0038] The prepared roadbed fill is loaded, leveled, and compacted layer by layer. After each layer is completed, the roadbed fill quality is inspected for compaction, smoothness, and other factors to ensure it meets design requirements. During the construction of the roadbed fill, the compacted thickness of each layer should not exceed 30 cm.

[0039] During the filling process of the roadbed body 3, waterproof mesh mats and waterproof geotextiles are laid to form the roadbed slope isolation layer 6.2. Figure 2 When digging steps, steps 11 should be reserved according to the designed dimensions, and drainage mesh mats and drainage geotextiles should be laid on the steps in sequence to form the roadbed slope isolation layer 6.2.

[0040] The construction of the roadbed slope protection structure 9, the roadbed slope protection area 7 and the bidirectional geogrid 8 is completed in sequence. In order to avoid damage to the drainage mat and the drainage geotextile, the roadbed slope protection structure 9 should be filled and compacted with small machinery as much as possible.

[0041] (6) Filling of subgrade base bed After the roadbed body is filled to the designed height, the same filling method is used to fill the bottom filler area of ​​the roadbed to ensure that the filling quality of the bottom filler area of ​​the roadbed meets the design requirements.

[0042] (7) Construction of roadbed surface isolation layer A 0.1m thick medium-coarse sand cushion layer is laid on top of the subgrade filler layer, with a composite geomembrane layer sandwiched between the cushion layers to form the subgrade surface isolation layer 6.1. During the laying process, ensure that the isolation layer is laid flat and firmly, and is closely connected to the surrounding structures.

[0043] (8) Filling of the improved area of ​​the roadbed bottom layer The improved subgrade layer is constructed on top of the subgrade surface isolation layer. The filler for the improved area can be improved soil or qualified Group A or B filler that does not contain iron sulfide. During the filling process, the quality of the filler and the filling process must be carefully controlled to ensure that the fill thickness and compaction degree of the improved area meet the design requirements.

[0044] (9) Surface filling of roadbed The surface layer of the roadbed is filled with graded crushed stone, with a laying thickness of not less than 0.4m, to ensure that the flatness and compaction of the surface layer of the roadbed meet the railway design standards, and ultimately form a complete roadbed structure that prevents the railway roadbed filler from arching and deformation.

[0045] The above detailed description is a specific description of one feasible embodiment of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A roadbed structure for preventing the deformation of railway roadbed filler, characterized in that: From top to bottom, it includes a roadbed surface layer (1), a roadbed bottom layer (2), a roadbed body (3), a base flexible cushion layer (4) and a foundation (5); the roadbed bottom layer (2) includes a basebed bottom improved filling area (2.1) and a basebed bottom filler filling area (2.2); the roadbed structure also includes a roadbed isolation layer (6), and the roadbed isolation layer (6) includes a roadbed surface isolation layer (6.1), a roadbed slope isolation layer (6.2) and a roadbed bottom layer. Isolation layer (6.3); the roadbed surface isolation layer (6.1) is arranged at the bottom of the improved filling area (2.1) of the subgrade bottom layer, the roadbed bottom isolation layer (6.3) is arranged on the upper part of the base flexible cushion layer (4), and the roadbed slope isolation layer (6.2) is arranged on both sides of the slope of the subgrade body (3); the roadbed surface isolation layer (6.1) and the roadbed bottom isolation layer (6.3) are medium-coarse sand cushion layers with a composite geomembrane layer in the middle; the roadbed slope isolation layer ( 6.2) Depending on the flexibility of the material, the geotextiles of the roadbed surface isolation layer (6.1), the roadbed slope isolation layer (6.2) and the roadbed bottom isolation layer (6.3) are connected with the anti-drainage mesh mat or the anti-drainage geotextile joint to form a closed area, which wraps the base bed bottom filler area (2.2) and the roadbed body (3).

2. The roadbed structure for preventing the camber deformation of railway roadbed filler according to claim 1, characterized in that: The surface layer (1) of the roadbed is filled with graded crushed stone, with a filling thickness of ≥0.4m; the improved filling area (2.1) of the bottom subgrade is filled with group A or B fillers or improved fillers, and the sum of the filling thicknesses of the improved filling area (2.1) of the bottom subgrade and the surface layer (1) of the roadbed is ≥1.0m; the filler filling area (2.2) of the bottom subgrade and the roadbed body (3) are filled with iron sulfide-containing fillers, and the sum of the filling thicknesses of the improved filling area (2.1) of the bottom subgrade and the filler filling area (2.2) of the bottom subgrade is ≥2.3m.

3. The roadbed structure for preventing the upturn deformation of railway roadbed filler according to claim 2 is characterized in that: The improved filler of the subgrade improved filling area (2.1) is a sulfide-containing roadbed filler improved by an inert oxygen agent or a gelling agent, and the dosage of the inert oxygen agent or the gelling agent is determined based on experience or through indoor tests.

4. The roadbed structure for preventing the upturn deformation of railway roadbed filler according to claim 1 is characterized in that: The base flexible cushion layer (4) has a thickness of ≥0.6 m and is composed of sand and gravel, graded crushed stone or a combination of waterproof geosynthetics.

5. The roadbed structure for preventing the upward arching deformation of railway roadbed filler according to claim 1, characterized in that: The contact surface between the roadbed surface layer (1) and the improved filling area (2.1) of the subgrade bottom layer is provided with a transverse drainage slope with an inclination rate of 4%.

6. The roadbed structure for preventing the upward arching deformation of railway roadbed filler according to claim 1 is characterized in that: The roadbed structure further comprises a roadbed slope protection zone (7), a bidirectional geogrid (8), a roadbed slope protection structure (9) and a drainage ditch (10); the roadbed slope protection zone (7) is arranged on the slopes on both sides of the roadbed body (3), and is filled with qualified fillers or improved soil, and a concrete water-cutting skeleton is arranged on the slope surface, and soil and shrubs are planted in the water-cutting skeleton; the bidirectional geogrid (8) is arranged in the roadbed slope protection zone (7), has a width of ≥3m, and is laid in layers at a certain height at intervals, with the outer edge folded back; the roadbed slope protection structure (9) is arranged at the foot of the embankment, and is selected from mortar-laid stone, concrete foot wall or retaining wall; the drainage ditch (10) is arranged on the outer side of the embankment foot.

7. The roadbed structure for preventing the upward arching deformation of railway roadbed filler according to claim 6, characterized in that: When the roadbed slope isolation layer (6.2) is laid by digging steps, the step height is 0.4-0.8m, and the step width meets the minimum requirement of the geogrid laying length; the drainage geotextile is arranged under the bidirectional geogrid (8) and is in close contact with the bidirectional geogrid (8).

8. A method for constructing a roadbed structure for preventing the upward arching deformation of railway roadbed filler according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, Work Preparation: Level the roadbed and fill the construction site, test the bearing capacity of the foundation, and if the foundation is weak, reinforce the foundation or excavate and replace it with filling; S2, making improved soil: determine the improvement scheme and mix ratio of improved soil based on experience or through indoor tests, and use an inert oxygen agent or gelling agent to improve the sulfide-containing roadbed filler; S3, constructing a base flexible cushion layer and a roadbed bottom isolation layer: laying a base flexible cushion layer (4) with a thickness of ≥0.6m on the roadbed base, laying a medium-coarse sand cushion layer on top of the base flexible cushion layer (4), and sandwiching a composite geomembrane between the medium-coarse sand cushion layer to form a roadbed bottom isolation layer (6.3); S4, road base body and isolation layer filling: construct the road base body (3) in layers on the flexible cushion layer (4) at the base, wherein the two sides of each layer of the road base body (3) are filled with improved soil or qualified A and B fillers, and the middle is filled with sulfide-containing road base fillers, which are spread separately and rolled uniformly to form a "sandwich" sandwich structure; the road base fillers are loaded, leveled, and rolled in layers, and the compacted thickness of each layer is ≤30cm. During the filling process, a drainage mesh mat or drainage geotextile is laid to form a road base slope isolation layer (6.2); and the road base slope protection structure (9), road base slope protection area (7) and bidirectional geogrid (8) are constructed in this way; S5, filling of the subgrade bed bottom filler: after the subgrade body (3) is filled to the designed height, the subgrade bed bottom filling area (2.2) is filled on the subgrade body (3); S6, Construction of roadbed surface isolation layer: Lay a medium-coarse sand cushion layer on top of the roadbed base filler, and sandwich a composite geomembrane between the cushion layers on the medium-coarse sand cushion layer to form the roadbed surface isolation layer (6.1); S7, filling of the subgrade base improvement area: fill the subgrade base improvement area (2.1) on the subgrade surface isolation layer (6.1); S8, roadbed surface filling: Use graded crushed stone to fill the roadbed surface (1).

9. The construction method according to claim 8, characterized in that: The foundation reinforcement treatment adopts composite foundation reinforcement, and the pile length and pile diameter need to be checked and calculated to meet the settlement and stability control requirements. After construction, the pile quality and composite foundation bearing capacity are tested.

10. The construction method according to claim 8, characterized in that: When the roadbed slope isolation layer (6.2) is laid by digging steps, steps of a certain height are reserved according to the design size, and drainage-proof mesh mats or drainage-proof geotextiles are laid on the steps in sequence; when the bidirectional geogrid (8) is laid, the outer edge fold length is ≥1m, and the roadbed slope protection structure (9) is filled and compacted by small machinery.

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