Geogrid for ballast bed reinforcement

Abstract

The present application relates to a kind of geogrids for ballast bed reinforcement, which is laid on ballast layer on subgrade bottom layer, the grid density of geogrid in different ballast bed transverse regions is different, adjacent two geogrid regions of different grid density are connected by connecting rod or integrally formed, and geogrid is also embedded by ballast layer and sleeper.According to the linkage relationship of ballast micro-motion and stress and the characteristics of ballast transverse migration, geogrid is divided into sleeper core area, under-rail area and ballast shoulder area.Compared with prior art, the present application fully considers the linkage relationship of ballast micro-motion and stress and the characteristics of ballast transverse migration, and proposes a geogrid reinforcement design method with three-level differentiated grid density, i.e.the grid density of sleeper core area and ballast shoulder area is higher, and the grid density of under-rail area is lower, which helps to improve the long-term dynamic stability and durability of ballast bed.

Description

Technical Field

[0001] This invention relates to the field of geogrid technology, and in particular to a geogrid for reinforcing crushed stone roadbeds. Background Technology

[0002] Traffic loads can cause lateral migration of ballast in ballasted tracks, leading to adverse conditions such as track bed deformation, increased stress on the subgrade surface, and reduced lateral resistance of the track bed. This can in turn induce a series of stability problems that endanger train operation safety, such as ballast sinking and track expansion.

[0003] With the rapid development of railways towards heavy-haul and high-speed rail, the impact of the aforementioned problems is becoming increasingly prominent. Existing research shows that geogrids can effectively reduce track settlement and constrain the lateral displacement of ballast. They also offer advantages such as low cost and ease of construction. Therefore, geogrids are currently used in the maintenance of existing lines to reduce lateral ballast flow and improve the lateral stability of the track bed. New lines are also beginning to use geogrids for pre-installation reinforcement. The geometry and density of the grid cells are two key design parameters for geogrids.

[0004] Traditional geogrids are generally composed of single square or triangular units, and both types use a uniform grid density. Numerous studies have analyzed the impact of geogrid design parameters on reinforcement effectiveness under the premise of uniform grid density. For example, triangular grids are more effective at controlling vertical settlement of the track bed, while square grids are more effective at constraining lateral ballast displacement. Compared to uniaxial geogrids, biaxial geogrids exhibit a more pronounced interlocking effect and better overall integrity. The grid density should take into account the ballast gradation; excessively large or small pore sizes will weaken the interlocking effect.

[0005] Because the vertical stress in the track bed is distributed in a saddle shape along the transverse direction (i.e., the vertical stress decreases from the rail position to the sleeper end position, the track center position, and the ballast shoulder position), the uniform grid density design results in different degrees of reinforcement effect of the grid in different areas. This to some extent exacerbates the uneven distribution of stress on the ballast and grid along the transverse direction, thus posing potential risks to the long-term stability of the track bed and the durability of the grid. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology, where traditional geogrids are generally composed of single square or triangular units, which pose potential risks to the long-term stability and durability of the track bed, and to provide a geogrid for the reinforcement of crushed stone track beds.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A geogrid for reinforcing crushed stone track bed, the geogrid is laid on the ballast layer on the subgrade layer, the geogrid has different mesh densities in different transverse areas of the track bed, and two adjacent geogrid areas with different mesh densities are connected to each other by connecting rods or integral one-time molding, the geogrid is also embedded by the ballast layer and sleepers.

[0009] Furthermore, based on the linkage between the microscopic motion and stress of the ballast and the lateral migration characteristics of the ballast, the geogrid is divided into a core area, a rail sub-area, and a ballast shoulder area. The core area, rail sub-area, and ballast shoulder area are distributed symmetrically from the centerline of the track to the ballast shoulder. The boundary of each area is determined by the dynamic stress distribution characteristics. The rail sub-area of ​​the core area has the largest dynamic stress, and the rail sub-area of ​​the ballast shoulder area has the smallest dynamic stress.

[0010] Furthermore, the area of ​​the pillow core region on one side of the line centerline is the boundary of the high stress influence area of ​​the line centerline, and the width of the pillow core region on one side of the line centerline is... w 1. It is related to the sleeper model.

[0011] Furthermore, the geogrid unit in the core region is square or equilateral triangle in shape, with the side length of the square being 1.5 to 1.7 times the length of the core. D 50 The size of the equilateral triangle is 1.8 to 2.0 times its side length. D 50 Size, of which D 50 The median particle size of the ballast is given.

[0012] Furthermore, the area under the rail on one side of the track centerline is defined as the projection of the midpoint of the sleeper's inclined side onto the horizontal plane of the geogrid to the boundary of the high-stress-affected area, and the width of the area under the rail on one side is... w 2. Lateral distance between the outermost edge of the sleeper and the track bed L s The embedment depth of geogrids h and the spread angle of the train's dynamic load on the railbed θ Regarding the width of one side of the under-rail area w The expression for calculating 2 is:

[0013]

[0014] In the formula, The width of the pillow area on one side of the center line of the track.

[0015] Furthermore, the geogrid unit in the track sub-zone is shaped like an equilateral triangle, with a side length of 3.5 to 4.0 times the length of the track. D 50 Size, of which D50 The median particle size of the ballast is given.

[0016] Furthermore, the ballast shoulder area extends from the edge of the track underpass to the edge of the ballast, and the width of the ballast shoulder area on one side of the track bed is... w 3 depends on the half-length of the track bed in the plane of the geogrid. w The width of the pillow area on one side of the track centerline w 1 Width of one side of the lower section of the track w 2 The width of the ballast shoulder area on one side of the track bed. w The expression for calculating 3 is:

[0017]

[0018]

[0019] In the formula, w 0 represents the width of the top surface of the track bed. The depth at which sleepers are embedded in the ballast. h This refers to the embedment depth of the geogrid. This is the proportionality coefficient.

[0020] Furthermore, the geogrid unit in the ballast shoulder area is rectangular in shape, with the shorter side of the rectangle being 1.5 to 1.7 times the length of the ballast shoulder. D 50 The size should be 3.0 to 3.4 times the length of the longer side. D 50 Size, of which D 50 The median particle size of the ballast layer.

[0021] Furthermore, the geogrid is located within 15-20cm of the bottom of the sleeper.

[0022] Furthermore, the geogrid is made of high molecular polymer plastic.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) This invention combines the macroscopic dynamic response of the track bed and the multi-scale characteristics and dynamic correlation of the microscopic stress and motion of the ballast. From the perspective of ballast motion and stress, a geogrid for the reinforcement of crushed stone track bed is designed. The geogrid grid density is smaller in the area near the sleeper, which reduces the situation of ballast breakage due to restricted rotation. The geogrid grid density is larger in the area near the sleeper core, which improves the regional support stiffness. The geogrid grid density is larger in the longitudinal direction near the ballast shoulder, which restricts the geometric changes caused by the lateral migration of the ballast.

[0025] The three-level differentiated grid density design better matches the lateral stress distribution characteristics in the track bed, making the lateral stress distribution of the track bed and grid more uniform, improving the long-term operational stability of the track bed and the durability of the grid, while also helping to reduce the possibility and severity of track bed defects.

[0026] (2) A lower grid density is used in the high stress area under the track to reduce the constraint on particle rotation, thereby effectively leveraging the ability of the discrete particle system to diffuse and coordinate loads, reducing the contact force level between particles, and reducing crushing and pulverization.

[0027] The medium stress area in the sleeper uses a higher grid density to effectively constrain particle rotation, improve the regional support stiffness, and make the lateral distribution of stress in the track bed and sleeper more uniform.

[0028] The use of higher grid density in the low-stress area of ​​the ballast shoulder helps maintain the geometry of the ballast shoulder and improves the lateral restraint in the middle of the track bed. Because the stress level in the ballast shoulder is low, the strength requirement of the grid in this area can be lower than that in the sleeper core and under-rail areas. This invention helps improve the long-term dynamic stability and durability of crushed stone track. Attached Figure Description

[0029] Figure 1 This is a top view of a geogrid used for reinforcing crushed stone roadbed, provided in an embodiment of the present invention.

[0030] Figure 2 This is a top view of a geogrid used for reinforcing crushed stone roadbed, provided in an embodiment of the present invention.

[0031] Figure 3 A schematic diagram of the cross-sectional structure of a geogrid for reinforcing a crushed stone track bed, provided as an embodiment of the present invention, when used in a crushed stone track bed;

[0032] In the diagram, 1 is geogrid, 2 is connecting rod, 3 is ballast layer, and 4 is sleeper. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed during use. They are 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.

[0037] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0038] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0039] Example 1

[0040] like Figure 1-3 As shown, this embodiment provides a geogrid for reinforcing crushed stone track beds. The geogrid is laid on the ballast layer on the subgrade layer. The geogrid has different mesh densities in different transverse areas of the track bed. Two adjacent geogrid areas with different mesh densities are connected to each other by connecting rods or integral one-time molding. The geogrid is also buried by the ballast layer and sleepers.

[0041] In other words, the installation of geogrids includes both geometry and location. Geometry includes the geogrid mesh density at different transverse positions of the track bed and the locations where the geogrid mesh density changes along the transverse direction of the track bed. Installation location includes the embedment depth of the geogrid.

[0042] This invention analyzes the macroscopic and microscopic multi-scale response of the ballast bed under variable frequency and variable amplitude dynamic loads, and finds the correlation characteristics between particle motion and force: (1) Under traffic load, the rotation (cumulative rotation angle) of ballast particles in the horizontal plane and the rolling (recoverable rotation angle) in the vertical plane are the main forms of their lateral migration, while the lateral translation of ballast particles is not obvious; therefore, restricting particle rotation can effectively control ballast particle migration; (2) The permanent rotation and recoverable rotation of ballast particles can effectively dissipate kinetic energy, which not only helps to reduce the contact force level between particles, but also reduces the probability of single-point fatigue failure; therefore, excessive restriction of particle rotation will increase the contact force between particles and aggravate the crushing and pulverization of ballast particles. Further research found that using Figure 1 The geogrid reinforcement design method with three-level differentiated geogrid density shown can better match the saddle-shaped stress distribution in the track bed, which helps to reduce the unevenness of the stress distribution in the track bed and geogrid along the lateral direction, thereby improving the long-term dynamic stability of the crushed stone track bed and the durability of the geogrid.

[0043] Preferred, such as Figure 1-3 As shown, based on the linkage between the microscopic motion and stress of the ballast and the lateral migration characteristics of the ballast, the geogrid is divided into three regions, which are symmetrically distributed with the centerline of the track as the axis. From the centerline of the track to the ballast shoulder, they are successively the core area, the under-rail area, and the ballast shoulder area. The boundary of each region is determined by the dynamic stress distribution characteristics. The under-rail area has the largest dynamic stress, followed by the core area, and the ballast shoulder area has the smallest dynamic stress.

[0044] For the pillow core area, the range of the pillow core area on one side of the track centerline is the boundary of the high stress influence area of ​​the track centerline. Preferably, the distribution range on one side of the track centerline is from the track center to the midpoint of the pillow's inclined edge. The width of the pillow core area on one side of the track centerline is... w 1. As can be seen from the basis for defining the scope, w 1 This is related to the specifications used for the sleepers. The stress level in the sleeper core area is moderate, therefore a higher grid density is used; simultaneously, because the stress distribution in this area is relatively uniform, square or equilateral triangular units can be used, with the side length of the square selected to be 1.5 to 1.7 times the [specific value missing]. D 50 For the size, the side length of the equilateral triangle should be 1.8 to 2.0 times its normal length. D 50 size, D 50 The median particle size of the ballast layer effectively constrains particle rotation and improves regional support stiffness.

[0045] For the track subgrade area, the range of the track subgrade area on one side of the track centerline is the projection of the midpoint of the sleeper's inclined side onto the horizontal plane of the geogrid to the boundary of the high-stress-affected area, preferably the projection of the midpoint of the sleeper's inclined side onto the horizontal plane of the geogrid to the boundary of the high-stress-affected area. The width of the track subgrade area on one side is... w 2. Lateral distance between the outermost edge of the sleeper and the track bed L s The embedment depth of geogrids h and the spread angle of the train's dynamic load on the railbed θ Regarding the width of one side of the track sub-area. w The expression for calculating 2 is:

[0046]

[0047] In the formula, The width of one side of the track under section. The width of the pillow area on one side of the center line of the track.

[0048] In the high-stress region under the track, a lower grid density is used to reduce the constraint on particle rotation. The grid is selected as an equilateral triangle, with a side length of 3.5 to 4.0 times the [missing information - likely a specific unit of measurement]. D 50 The size of the particles is adjusted to effectively utilize the diffusion and load coordination capabilities of the discrete particle system, reduce the contact force level between particles, and minimize breakage and pulverization.

[0049] For the ballast shoulder area, the width of the ballast shoulder area on one side of the track centerline is determined by the dynamic stress distribution characteristics. The range of the ballast shoulder area on one side is from the edge of the under-rail zone to the edge of the ballast. The width of the ballast shoulder area on one side of the track bed... w 3 depends on the half-length of the track bed in the plane of the geogrid. w The width of the pillow area on one side of the track centerline w 1 Width of one side of the lower section of the track w 2 The width of the ballast shoulder area on one side of the track bed. w The expression for calculating 3 is:

[0050]

[0051]

[0052] In the formula, w 0 represents the width of the top surface of the track bed. The depth at which sleepers are embedded in the ballast. h This refers to the embedment depth of the geogrid. This is the proportionality coefficient.

[0053] In the low-stress area of ​​the ballast shoulder, a higher grid density is used, with rectangular grids selected, and the shorter side length chosen to be 1.5 to 1.7 times the length of the ballast.D 50 The size should be 3.0 to 3.4 times the length of the longer side. D 50 The size helps maintain the geometric shape of the ballast shoulder and enhances the lateral restraint in the middle of the track bed.

[0054] Furthermore, preferably, since square or triangular geogrids can be used in the core area, the side length of the square geogrid is taken as the side length of the equilateral triangular geogrid in the track sub-area. The side length of the triangle is taken as the side length of the equilateral triangular geogrid in the track sub-area. The ballast shoulder area primarily serves to constrain the lateral displacement of the ballast; therefore, a rectangular geogrid is used, with its shorter side length being the same as the side length of an equilateral triangular geogrid. The longer side length is taken as the side length of the equilateral triangular geogrid. times.

[0055] Optionally, the geogrid is positioned 15-20 cm away from the top of the ballast layer covering it.

[0056] As a preferred technical solution, the geogrid material is a high-molecular polymer plastic.

[0057] Furthermore, geogrids with different mesh densities can be connected in the transverse direction of the track bed using the following two methods:

[0058] (1) Determine w1~w3 and grid size according to the structure size and laying depth of the crushed stone track bed, and process geogrid with three levels of differentiated grid density in one step;

[0059] (2) Considering the difficulty and cost of one-time molding, connecting rods can be used for connection.

[0060] The following is a specific implementation process for the aforementioned geogrid:

[0061] The geogrid designed in this invention is planned to be used in a railway line construction project. The site parameters involved in the project are shown in the table below:

[0062] Table 1 Field Parameters

[0063]

[0064] According to the design method of the novel geogrid proposed in this invention, the geogrid parameters are obtained based on the field parameters.

[0065] Table 2 Geogrid Parameters

[0066]

[0067] In actual construction, geogrids are made of high-molecular polymer plastic. When geogrids with different mesh densities need to be connected in the longitudinal direction of the track bed or in the transverse direction, connecting rods are used. Figure 2 As shown, ballast layer 3 is laid on the surface of the roadbed layer. D 50 Fill the gap to 4cm and compact it to the specified height (e.g., 100mm), ensuring it is flat.

[0068] Geogrid 1 is laid with a total width of 4847.6 mm. The half-length of the core area is 347.5 mm, the half-length of the rail under area is 1092.5 mm, and the half-length of the ballast shoulder area is 983.8 mm. The geometry of the core area grid is square. Geogrid 1 is connected according to the calculation requirements. The connection is made with connecting rod 2 to ensure overall stability and left-right symmetry.

[0069] Continue filling the ballast layer 3, and continue filling and compacting to the specified height (e.g., 100mm) twice to make the geogrid 1 buried at a depth of 20cm. During this process, compaction should be light at first and then heavy to prevent the geogrid 1 from being damaged.

[0070] Place concrete sleepers 4 at the designated locations. Sleepers 4 are 260cm long. After installation, fill the area around sleepers 4 with ballast to increase horizontal resistance.

[0071] Maintain a top surface width of 3.5m and a side slope gradient of 1:1.75.

[0072] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A geogrid for reinforcing crushed stone roadbeds, the geogrid being laid on a ballast layer above the subgrade layer, characterized in that, The geogrid has different mesh densities in different transverse areas of the track bed. Two adjacent geogrid areas with different mesh densities are connected to each other by connecting rods or integral one-time molding. The geogrid is also subject to the ballast layer and sleeper embedment. Based on the linkage between the microscopic motion and stress of the ballast and the lateral migration characteristics of the ballast, the geogrid is divided into a core area, a rail sub-area, and a ballast shoulder area. The core area, rail sub-area, and ballast shoulder area are distributed symmetrically from the centerline of the track to the ballast shoulder. The boundary of each area is determined by the dynamic stress distribution characteristics. The rail sub-area has the largest dynamic stress, and the ballast shoulder area has the smallest dynamic stress. The geogrid unit in the core area is square or equilateral triangle in shape, with the side length of the square being 1.5 to 1.7 times the length of the core. D 50 The size of the equilateral triangle is 1.8 to 2.0 times its side length. D 50 Size, of which D 50 The median particle size of the ballast; The geogrid unit in the track sub-zone is equilateral triangular in shape, with a side length of 3.5 to 4.0 times the length of the track. D 50 Size, of which D 50 The median particle size of the ballast; The geogrid unit in the ballast shoulder area is rectangular, with the shorter side length selected to be 1.5 to 1.7 times the length of the ballast shoulder. D 50 The size should be 3.0 to 3.4 times the length of the longer side. D 50 Size, of which D 50 The median particle size of the ballast is given.

2. A geogrid for reinforcing crushed stone roadbeds according to claim 1, characterized in that, The area of ​​the pillow core region on one side of the line centerline is the boundary of the high stress influence area of ​​the line centerline, and the width of the pillow core region on one side of the line centerline is... w 1. It is related to the sleeper model.

3. A geogrid for reinforcing crushed stone roadbeds according to claim 1, characterized in that, The area under the rail, on one side of the track centerline, extends from the projection of the midpoint of the sleeper's inclined side onto the horizontal plane of the geogrid to the boundary of the high-stress-affected area. The width of this area on one side is... w 2. Lateral distance between the outermost edge of the sleeper and the track bed L s The embedment depth of geogrids h and the spread angle of the train's dynamic load on the railbed θ Regarding the width of one side of the under-rail area w The expression for calculating 2 is: In the formula, The width of the pillow area on one side of the center line of the track.

4. A geogrid for reinforcing crushed stone roadbeds according to claim 1, characterized in that, The ballast shoulder area extends from the edge of the track underpass to the edge of the ballast, and the width of the ballast shoulder area on one side of the track bed is... w 3 depends on the half-length of the track bed in the plane of the geogrid. w The width of the pillow area on one side of the track centerline w 1 Width of one side of the lower section of the track w 2 The width of the ballast shoulder area on one side of the track bed. w The expression for calculating 3 is: In the formula, w 0 represents the width of the top surface of the track bed. The depth at which sleepers are embedded in the ballast. h This refers to the embedment depth of the geogrid. This is the proportionality coefficient.

5. A geogrid for reinforcing crushed stone roadbeds according to claim 1, characterized in that, The geogrid is located within 15-20cm of the bottom of the sleeper.

6. A geogrid for reinforcing crushed stone roadbeds according to claim 1, characterized in that, The geogrid is made of high molecular polymer plastic.

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