Humidified ballast bed modeling method considering liquid bridge force

Abstract

The invention discloses a humidifying ballast bed modeling method considering liquid bridge force, and belongs to the technical field of railway particle flow numerical simulation. The method comprises the following steps: constructing a ballast particle discrete element model to obtain a clump polymer; constructing a hydraulic bridge force calculation model; constructing a liquid bridge contact constitutive model according to the liquid bridge force calculation model; and according to the ballast particle discrete element model and the liquid bridge contact constitutive model, constructing a humidifying ballast bed discrete element model. By considering the cohesion effect of the liquid bridge force on the humidifying ballast bed, on one hand, the method is used for testing the repose angle under the humidifying condition, and on the other hand, the liquid bridge contact constitutive model is constructed according to the liquid bridge force calculation model, so that the simulation of the mechanical properties of the humidifying ballast bed is more accurate, and the method has certain significance for researching the humidifying ballast.

Description

Technical Field

[0001] This invention relates to a method for modeling wetted track bed considering liquid bridge forces, belonging to the field of numerical simulation technology of railway granular flow. Background Technology

[0002] Railways are the backbone of the comprehensive transportation system, playing a crucial role in economic and social development. Ballast, as a vital component of railway track structure, primarily serves to bear loads, drain water, and reduce vibrations. Its mechanical properties directly affect track smoothness, stability, and train operation safety. Traditionally, research on ballast mechanical behavior has largely been based on the assumption of dry conditions. However, railways inevitably operate in various humidity environments, such as rainy days, high-humidity areas, or waterlogged conditions due to poor drainage. The presence of moisture significantly alters the interaction forces between ballast particles, thus affecting the macroscopic mechanical response of the entire ballast layer, such as strength, deformation, and stability.

[0003] The Discrete Element Method (DEM) has become a powerful tool for studying the mechanical behavior of ballast particles due to its ability to accurately simulate the discontinuities and large deformation characteristics of granular materials. Currently, DEM simulation technology for dry ballast beds is relatively mature, and the Hertz-Mindlin contact model is usually used to simulate the elastic contact and friction between particles.

[0004] Existing discrete element models for wetted ballast have a significant limitation: they generally do not adequately consider the influence of humidity or oversimplify the characterization of liquid bridging forces. Specifically, current models mostly simulate the contact behavior of wetted ballast based on JKR contact theory, but this method struggles to accurately reflect its contact mechanical properties under different moisture contents. In reality, the mechanical properties of wetted ballast are significantly dependent on moisture content, and existing models lack sufficient characterization ability in this crucial aspect. Therefore, establishing a model that can more comprehensively and accurately simulate the mechanical properties of wetted ballast has become a problem that needs to be solved. Summary of the Invention

[0005] This invention provides a modeling method for wetted track bed that considers liquid bridging forces. By taking into account the cohesive effect of liquid bridging forces on the wetted track bed, it can be used for angle of repose testing under wetted conditions. On the other hand, based on the liquid bridging force calculation model, a liquid bridging contact constitutive model is constructed to make the simulation of the mechanical properties of the wetted track bed more accurate, which is of certain significance for the study of wetted ballast.

[0006] The technical solution of this invention is:

[0007] A method for modeling a wetted track bed considering liquid bridging forces includes:

[0008] S1. Construct a discrete element model of ballast particles to obtain clump aggregates;

[0009] S2. Construct a liquid bridge force calculation model;

[0010] S3. Based on the liquid bridge force calculation model, construct the liquid bridge contact constitutive model;

[0011] S4. Based on the discrete element model of ballast particles and the constitutive model of liquid bridge contact, construct the discrete element model of wetted track bed.

[0012] Furthermore, S1 specifically refers to:

[0013] Various ballast particles of different shapes are placed on a scanning stage at different angles. The outer contours of the ballast particles of different shapes are obtained by scanning with a laser. Then, the extracted outer contours are filled with ball units to obtain clump aggregates.

[0014] Further, S2 includes:

[0015] S201. Take the outer surface of the liquid bridge between any two adjacent wetted ballast particles as the cylindrical side surface of a frustum, and construct the expression for the volume of the liquid bridge.

[0016] S202. The condition for the existence of liquid bridging force is defined as follows: the distance between two adjacent wetted ballast particles is less than or equal to the critical fracture distance. When the liquid bridge is in place, it exists; conversely, when the liquid bridge breaks, the liquid bridge force disappears.

[0017] S203. Based on the liquid bridge volume and the existence conditions of the liquid bridge force, a liquid bridge force calculation model is constructed; the expression of the liquid bridge force calculation model is:

[0018] ;

[0019] in, Indicates the liquid bridge force. The surface tension coefficient, The solid-liquid contact angle, The distance between two wetted ballast particles. For equivalent particle radius, Let be the volume of the liquid bridge.

[0020] Furthermore, the volume expression of the liquid bridge is as follows:

[0021] ;

[0022] in, It is a half-filled corner. and These represent the radii of two adjacent wetted ballast particles.

[0023] Furthermore, the critical fracture distance The expression is:

[0024] ;

[0025] in, This is the solid-liquid contact angle.

[0026] Furthermore, the constitutive model expression for the liquid bridge contact is:

[0027] ;

[0028] in, For the total contact force, For the equivalent elastic modulus, The normal overlap is... For equivalent particle radius, This is the force of the liquid bridge.

[0029] Furthermore, the construction of the discrete element model of the wetted track bed is specifically as follows: First, a ballast track bed outline model is established, and sleepers are arranged at the corresponding positions; then, model parameters are set, and the track bed is filled with discrete elements in combination with the clump aggregate and liquid bridge contact constitutive model established in step S1; after filling is completed, the initial stable state is achieved through gravity deposition and compaction to obtain the discrete element model of the wetted track bed.

[0030] Furthermore, model parameters were set, and based on the liquid bridge contact constitutive model, a ballast particle repose angle test was conducted under humidification conditions: a cylindrical wall was established, and ballast particle parameters, liquid parameters, and particle-cylinder contact parameters were set. The ballast-ballast contact model was then set as a liquid bridge contact constitutive model. Ballast particles were generated in the cylinder, and the cylinder was filled with ballast particles using a rain method. After filling, the particles were allowed to settle naturally in the container under gravity until they reached stability. After the ballast particles were completely stable, the upper cylinder wall was slowly raised at a preset speed, allowing the ballast particles in the cylinder to slide down naturally under gravity and slowly change into an aggregated state. Under humidification conditions, the surface tension coefficient in the ballast particle parameters ranged from 0.065 to 0.072 N / m.

[0031] Furthermore, the model parameters include ballast particle parameters and liquid parameters; the ballast particle parameters include ballast particle material, density, shear modulus, Poisson's ratio, and coefficient of friction; the liquid parameters include surface tension coefficient. Solid-liquid contact angle between two wetted ballast particles .

[0032] The beneficial effects of this invention are as follows: The discrete element model of the wetted track bed uses liquid bridging force as its core mechanism. By constructing liquid bridging forces between ballast particles, it achieves the bonding effect of the wetted ballast. Furthermore, relying on the bonding and constraint effects of the liquid bridges, it reproduces the real physical effects of moisture acting on the ballast from a mechanical transmission perspective. Simultaneously, the discrete element model of the wetted track bed innovatively incorporates a liquid bridge volume distribution strategy, providing scientific and systematic quantitative support for the analysis of the mechanical properties and structural behavior of the wetted track bed under different moisture content conditions (constructing a moisture-free wetted track bed with different liquid bridge volumes, surface tension coefficients, and solid-liquid contact angles). Attached Figure Description

[0033] Figure 1-4 This is a partial discrete element model diagram of ballast particles provided by the present invention.

[0034] Figure 5 This is a simplified schematic diagram of the liquid bridge provided by the present invention.

[0035] Figure 6 This is a portion of the code for adding liquid bridge property parameters provided by the present invention.

[0036] Figure 7 This is a flowchart illustrating the process of the discrete element method experiment for the rest angle provided by the present invention.

[0037] Figure 8 This is a schematic diagram showing the results of the discrete element method experiment on the rest angle under two states provided by the present invention.

[0038] Figure 9 This invention provides a discrete element model for wetted track beds.

[0039] Figure 10 The flowchart provides a method for modeling a wetted track bed that takes into account liquid bridge forces. Detailed Implementation

[0040] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0041] Example 1: As Figures 1-10 As shown, a method for modeling a wetted track bed considering liquid bridging forces includes:

[0042] S1. Construct a discrete element model of ballast particles to obtain clump aggregates;

[0043] S2. Construct a liquid bridge force calculation model;

[0044] S3. Based on the liquid bridge force calculation model, construct the liquid bridge contact constitutive model;

[0045] S4. Based on the discrete element model of ballast particles and the constitutive model of liquid bridge contact, construct the discrete element model of wetted track bed.

[0046] Furthermore, S1 specifically refers to:

[0047] Various ballast particles of different shapes are placed on a scanning stage at different angles. The outer contours of the ballast particles of different shapes are obtained by scanning with a laser. Then, the extracted outer contours are filled with ball units to obtain clump aggregates.

[0048] Further, S2 includes:

[0049] S201. Take the outer surface of the liquid bridge between any two adjacent wetted ballast particles as the cylindrical side surface of a frustum, and construct the expression for the volume of the liquid bridge.

[0050] S202. The condition for the existence of liquid bridging force is defined as follows: the distance between two adjacent wetted ballast particles is less than or equal to the critical fracture distance. When the liquid bridge is in place, it exists; conversely, when the liquid bridge breaks, the liquid bridge force disappears.

[0051] S203. Based on the liquid bridge volume and the existence conditions of the liquid bridge force, a liquid bridge force calculation model is constructed; the expression of the liquid bridge force calculation model is:

[0052] ;

[0053] in, Indicates the liquid bridge force. The surface tension coefficient, The solid-liquid contact angle, The distance between two wetted ballast particles. For equivalent particle radius, Let be the volume of the liquid bridge.

[0054] Furthermore, the volume expression of the liquid bridge is as follows:

[0055] ;

[0056] in, It is a half-filled corner. and These represent the radii of two adjacent wetted ballast particles.

[0057] Furthermore, the critical fracture distance The expression is:

[0058] ;

[0059] in, This is the solid-liquid contact angle.

[0060] Furthermore, the constitutive model expression for the liquid bridge contact is:

[0061] ;

[0062] in, For the total contact force, For the equivalent elastic modulus, The normal overlap is... For equivalent particle radius, This is the force of the liquid bridge.

[0063] Furthermore, the construction of the discrete element model of the wetted track bed is specifically as follows: First, a ballast track bed outline model is established, and sleepers are arranged at the corresponding positions; then, model parameters are set, and the track bed is filled with discrete elements in combination with the clump aggregate and liquid bridge contact constitutive model established in step S1; after filling is completed, the initial stable state is achieved through gravity deposition and compaction to obtain the discrete element model of the wetted track bed.

[0064] Furthermore, model parameters were set, and based on the liquid bridge contact constitutive model, a ballast particle repose angle test was conducted under humidification conditions: a cylindrical wall was established, and ballast particle parameters, liquid parameters, and particle-cylinder contact parameters were set. The ballast-ballast contact model was then set as a liquid bridge contact constitutive model. Ballast particles were generated in the cylinder, and the cylinder was filled with ballast particles using a rain method. After filling, the particles were allowed to settle naturally in the container under gravity until they reached stability. After the ballast particles were completely stable, the upper cylinder wall was slowly raised at a preset speed, allowing the ballast particles in the cylinder to slide down naturally under gravity and slowly change into an aggregated state. Under humidification conditions, the surface tension coefficient in the ballast particle parameters ranged from 0.065 to 0.072 N / m.

[0065] For example, to verify the applicability of the liquid-bridge contact constitutive model in discrete element simulation, a comparative experiment on the angle of repose of ballast under dry and wet conditions was conducted using PFC software. Premium grade ballast was used in the experiment. Particles were generated in a cylinder using a "rainfall method" and allowed to settle naturally under gravity. Subsequently, the cylinder wall was slowly raised at a speed of 0.01 m / s, allowing the ballast particles to slide naturally under gravity and form an accumulation. Under wet conditions, the angle of repose of ballast particles was tested according to the liquid-bridge contact constitutive model; under dry conditions, it was tested according to the Hertz-Mindlin contact model. Under both conditions, except for the contact model and liquid parameters, the other ballast particle parameters remained consistent with the particle-cylinder contact parameters. Specifically, under wet conditions, the surface tension coefficient of the ballast particles ranged from 0.065 to 0.072 N / m, and the solid-liquid contact angle... Take 30°.

[0066] Furthermore, the model parameters include ballast particle parameters and liquid parameters; the ballast particle parameters include ballast particle material, density, shear modulus, Poisson's ratio, and coefficient of friction; the liquid parameters include surface tension coefficient. Solid-liquid contact angle between two wetted ballast particles .

[0067] Example 2: As Figures 1-10 As shown, a method for modeling a wetted track bed considering liquid bridging forces includes the following steps:

[0068] 1. Place four different shaped ballast particles on the scanning stage at different angles, and use a laser to scan and obtain the outer contours of the four different shaped ballast particles (e.g., ...). Figures 1-4 The image shows the features of one face of the outer contour of four different shaped ballast particles; then, the extracted outer contour is filled using the ball element built into PFC to obtain a clump aggregate. The shear modulus, Poisson's ratio, and density of the ballast particle discrete element model are 20~25 GPA, 0.18~0.24, and 2600, respectively. .

[0069] II. To simplify the derivation of the liquid bridge volume and liquid bridge force, the outer surface of the liquid bridge between adjacent wetted ballast particles is approximated as a cylindrical frustum side surface, such as... Figure 5 As shown. At this point, the volume of the liquid bridge between adjacent wetted ballast particles can be considered as the volume of a frustum minus the volumes of the two spherical caps. Finally, the original volume of the liquid bridge can be calculated. for:

[0070]

[0071] in, Let f be the volume of the frustum. and The volumes of the two spherical caps and the frustum are respectively. for:

[0072]

[0073] In the formula, Indicates the height of the frustum ; and These are the radii of the bottom surfaces of the two ballast particle spheres (the two ballast particle spheres are considered as spheres). and These represent the heights of the two ball crowns.

[0074] The volume of the two spherical crowns and The solution can be approximated by a double integral. For the projection plane shown in the figure above, establish a Cartesian coordinate system with the t-direction and the n-direction as the principal directions, where the projection line of the bottom of the spherical cap is the t-axis and the projection plane of the center line of the liquid bridge is the n-axis. This yields the following approximation regarding... The analytical expression:

[0075]

[0076] in, Represents a rotation curve, i.e. Figure 5 The curve function (O1 and O2 represent the centers of the two particles); The radial coordinate represents the distance from any point on the rotation curve to the n-axis.

[0077] right Simplifying by Taylor expansion, we get ,Will Substitution And on Performing double integrals yields Therefore, the volumes of the two spherical caps can be obtained as:

[0078]

[0079] The volume of the frustum and the volume of the spherical crown Substitution The original liquid bridge volume can be obtained. for:

[0080] ;

[0081] In the formula, ,when and When the magnitudes are similar, we can obtain It is very small compared to the other two items, so it can be discarded.

[0082] Due to the radius of the base of the two spherical crowns and The volume of the liquid bridge has a geometric relationship with the particle radius. After simplification, we can obtain the expression for the volume of the liquid bridge as follows:

[0083] ;

[0084] in, The distance between the two ballast particles. It is a half-filled corner. and These are the radii of the two ballast particles, respectively.

[0085] Furthermore, to account for the existence condition of liquid bridging force, it is now defined that when the distance S between the two spheres of two adjacent wetted ballast particles is less than the critical fracture distance... When the liquid bridge exists, it is intact; conversely, when it is not intact, the liquid bridge breaks and the liquid bridge force disappears. Its critical breaking distance is... express:

[0086] ;

[0087] in, The solid-liquid contact angle, Let be the volume of the liquid bridge.

[0088] Furthermore, to greatly simplify the calculation of the liquid bridge force between two wetted ballast particles, it is assumed that the liquid bridge volume between each adjacent wetted ballast particle is maintained throughout the simulation process. The formula remains unchanged; when calculating the liquid bridge force between two wetted ballast particles, the analytical formula for the static liquid bridge force between two wet-bulb particles of different diameters is used. This formula is highly efficient while ensuring accuracy. The analytical formula for the liquid bridge force is as follows:

[0089]

[0090] in, The surface tension coefficient, The solid-liquid contact angle, The distance between the two ballast particles. Equivalent particle radius ( ), Let be the volume of the liquid bridge.

[0091] III. To achieve the coupling of the wetted ballast calculation model considering the liquid bridge force with the discrete element method, it is first necessary to define the parameters of the wetted ballast particle model, including ballast particle parameters, liquid parameters, and liquid bridge parameters; among which, the liquid parameters include the surface tension coefficient and the solid-liquid contact angle with the ballast. Liquid bridge parameters include liquid bridge volume. Critical fracture distance These liquid parameters need to be calculated and determined based on the different ballast particle radii used in the actual simulation process. Ballast particle parameters include their material, density, shear modulus, Poisson's ratio, and coefficient of friction. The ballast particles used meet the standards for premium-grade ballast, and the ballast parameters obtained after discrete element method calibration are shown in Table 1.

[0092] Table 1. Ballast Particle Parameters

[0093]

[0094] In a Visual Studio 2017 and Qt 5.12.0 environment, a secondary development and compilation environment for the contact model was built based on PFC. The source code of the built-in model in the PFC help documentation was imported into the header and source files of Visual Studio (since the discrete element contact model for wetted ballast requires the use of the Hertz Model built into PFC, the source code of this model was selected for secondary development in Visual Studio). The specific process is as follows: Figure 6 As shown: Based on the liquid bridge volume and the existence conditions of the liquid bridge force, a liquid bridge force calculation model is constructed, thereby completing the writing of secondary development code. The expression for the liquid bridge force calculation model is as follows:

[0095] ;

[0096] ;

[0097] in, For the total contact force, For the equivalent elastic modulus, The normal overlap is... For equivalent particle radius, The radius of the contact surface; This is the force of the liquid bridge.

[0098] IV. Reference Figures 7-8 To verify whether the above liquid bridge force calculation model can be successfully used for numerical simulation in discrete element method, a ballast repose angle test is generated using PFC. The specific steps are as follows:

[0099] Under humidification conditions, a discrete element model was performed using the particle size distribution of premium ballast. A cylindrical wall was established in the PFC (Polymerized Component Array), and parameters for ballast particles, liquid, and particle-cylinder contact were set. The contact model between ballast particles was then set as a liquid bridge contact constitutive model. Ballast particles were generated within the cylinder, and the cylinder was filled using a rain method. After filling, the particles were allowed to settle naturally under gravity until stabilization. Once the ballast particles were fully stabilized, the upper cylinder wall was slowly raised at a speed of 0.01 meters per second, causing all the ballast particles in the cylinder to slide down naturally under gravity, slowly changing into an aggregated state (e.g., ...). Figure 8 (b) Under humidification conditions, the surface tension coefficient of the ballast particles ranges from 0.065 to 0.072 N / m, and the solid-liquid contact angle is 30°. The parameters for the ballast particles are shown in Table 1, and the parameters for the particle-cylinder contact are shown in Table 2. Under humidification conditions, water molecules form liquid bridges at the contact points with the ballast particles, generating a liquid bridge force. This force manifests as an additional tensile force in the normal direction, hindering particle separation and thus introducing a cohesive component on top of the original friction angle, enhancing slope stability. Therefore, the angle of repose measured under humidification conditions is expected to be greater than that under dry conditions.

[0100] Table 2 Particle-Cylinder Contact Parameters

[0101]

[0102] Under dry conditions, a discrete element model was performed using the particle size distribution of premium ballast. A cylindrical wall was created in the PFC (Polarization Component Analysis) system, and ballast particle parameters and particle-cylinder contact parameters were set. The Hertz-Mindlin contact model was then used to set the ballast-to-ballast contact model. Ballast particles were then generated in the cylinder, and the cylinder was filled using a rain method. After filling, the particles were allowed to settle naturally under gravity until they stabilized. Once the ballast particles were completely stabilized, the upper cylinder wall was slowly raised at a speed of 0.01 meters per second, allowing all the ballast particles in the cylinder to slide down naturally under gravity and slowly change into a packed state (e.g., ...). Figure 8 (a) The values ​​of ballast particle parameters are shown in Table 1, and the values ​​of particle-cylinder contact parameters are shown in Table 2.

[0103] The angle of repose of ballast under dry and wet conditions, for example Figure 8 As shown. Measurements showed that the angle of repose for dry ballast was 34.8°, while that for wetted ballast was 35.6°. Simulation results indicate that the angle of repose under wetted conditions is significantly higher than that under dry conditions, which is consistent with theoretical expectations. This difference confirms the presence of additional cohesive forces generated by liquid bridging in the wetted ballast, thus verifying the rationality and feasibility of the discrete element model for the wetted ballast bed established in this invention.

[0104] It should be noted that in the above angle of repose test: the radius of the cylinder is 0.2m and the height is 1m. Ballast particles are generated inside the cylinder. The cylinder is filled using the rain method, and filling is stopped when the filling height reaches 0.5m. At this point, the initial stacking state of the cylinder is reached (e.g., Figure 7 (a) represents the initial stacking state. Figure 7 (b) is a diagram of the intermediate state of the cylindrical wall during lifting.

[0105] V. The specific steps for constructing the discrete element model of the wetted track bed are as follows: First, establish the outline model of the ballasted track bed according to railway design specifications, and arrange sleepers at the corresponding positions. Next, set the model parameters according to Table 1, and then set the contact model between ballasts as a liquid bridge contact constitutive model. Combined with the four types of irregular ballast particle clump aggregates established in step one, perform discrete element filling of the track bed according to the required gradation. After filling, gravity deposition and compaction are used to bring the track bed to an initial stable state, ultimately obtaining the following... Figure 9 The discrete element model of the wetted track bed is shown.

[0106] As can be seen from the above technical solution, the present invention can effectively simulate the physical effects of moisture on ballast.

[0107] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for modeling a wetted track bed considering liquid bridging forces, characterized in that, include: S1. Construct a discrete element model of ballast particles to obtain clump aggregates; S2. Construct a liquid bridge force calculation model; S3. Based on the liquid bridge force calculation model, construct the liquid bridge contact constitutive model; S4. Based on the discrete element model of ballast particles and the constitutive model of liquid bridge contact, construct the discrete element model of wetted track bed.

2. The wetted track bed modeling method considering liquid bridge force according to claim 1, characterized in that, Specifically, S1 is: Various ballast particles of different shapes are placed on a scanning stage at different angles. The outer contours of the ballast particles of different shapes are obtained by scanning with a laser. Then, the extracted outer contours are filled with ball units to obtain clump aggregates.

3. The wetted track bed modeling method considering liquid bridge force according to claim 1, characterized in that, S2 includes: S201. Take the outer surface of the liquid bridge between any two adjacent wetted ballast particles as the cylindrical side surface of a frustum, and construct the expression for the volume of the liquid bridge. S202. The condition for the existence of liquid bridge force is defined as follows: when the distance between two adjacent wetted ballast particles is less than or equal to the critical fracture distance, the liquid bridge exists; otherwise, the liquid bridge breaks and the liquid bridge force disappears. S203. Based on the liquid bridge volume and the existence conditions of the liquid bridge force, a liquid bridge force calculation model is constructed; the expression of the liquid bridge force calculation model is: ； in, Indicates the liquid bridge force. The surface tension coefficient, The solid-liquid contact angle, The distance between two wetted ballast particles. For equivalent particle radius, Let be the volume of the liquid bridge.

4. The wetted track bed modeling method considering liquid bridge force according to claim 3, characterized in that, The expression for the volume of the liquid bridge is as follows: ； in, It is a half-filled corner. and These represent the radii of two adjacent wetted ballast particles.

5. The wetted track bed modeling method considering liquid bridge forces according to claim 3, characterized in that, The critical fracture distance The expression is: .

6. The wetted track bed modeling method considering liquid bridge force according to claim 1, characterized in that, The constitutive model expression for the liquid bridge contact is: ； in, For the total contact force, For the equivalent elastic modulus, The normal overlap is... For equivalent particle radius, This is the force of the liquid bridge.

7. The wetted track bed modeling method considering liquid bridge forces according to claim 1, characterized in that, The construction of the discrete element model of the wetted track bed is as follows: First, a ballast track bed outline model is established, and sleepers are arranged at the corresponding positions; then, the model parameters are set, and the track bed is filled with discrete elements in combination with the clump aggregate and liquid bridge contact constitutive model established in step S1; after filling, the initial stable state is achieved through gravity deposition and compaction to obtain the discrete element model of the wetted track bed.

8. The wetted track bed modeling method considering liquid bridge force according to claim 1, characterized in that, Model parameters were set, and a ballast particle repose angle test was conducted under humidification conditions based on the liquid bridge contact constitutive model. A cylindrical wall was established, and ballast particle parameters, liquid parameters, and particle-cylinder contact parameters were set. The ballast-to-ballast contact model was then set as a liquid bridge contact constitutive model. Ballast particles were generated in the cylinder, and the cylinder was filled using a rain method. After filling, the particles were allowed to settle naturally under gravity until they stabilized. Once the ballast particles were completely stabilized, the upper cylinder wall was slowly raised at a preset speed, allowing the ballast particles in the cylinder to slide down naturally under gravity and slowly change into an aggregated state. Under humidification conditions, the surface tension coefficient in the ballast particle parameters ranged from 0.065 to 0.072 N / m.

9. The wetted track bed modeling method considering liquid bridge force according to claim 7 or 8, characterized in that, The model parameters include ballast particle parameters and liquid parameters; the ballast particle parameters include ballast particle material, density, shear modulus, Poisson's ratio, and coefficient of friction; the liquid parameters include surface tension coefficient and solid-liquid contact angle between two wetted ballast particles.

Images