Loading device for simulating dynamic action of bullet train bogie load on ballastless track roadbed

Abstract

The invention provides a loading device for simulating the dynamic action of a bullet train bogie load on a ballastless track roadbed, which relates to the technical field of railway roadbed dynamic performance evaluation and comprises a loading plate, a vibration platform, accessories and a servo vibration motor control system. The four cushion blocks corresponding to the positions of wheels of the double-shaft bogie transmit exciting force generated by rotation of the eccentric blocks to the loading plate with the cross section bending rigidity consistent with that of the ballastless track structure and the width identical to that of the base plate, and the distribution form of loads output to a roadbed surface is similar to that of a real vehicle and a real road. The maximum dead weight of the vibration platform is not lower than half of the dynamic load peak value of the bullet train bogie to be simulated, and the maximum dynamic load amplitude capable of being output by the servo vibration motor excitation vibration platform under the maximum balance weight condition is not smaller than the dead weight of the vibration platform. The invention solves the problems of abrasion, vibration, loud noise, high manufacturing and maintenance cost, complex cooling system and the like caused by the fact that the traditional vibration motor adopting mechanical connection realizes the same-phase synchronous rotation in the reverse direction.

Description

Technical Field

[0001] The invention relates to the technical field of railway roadbed dynamic performance evaluation, and in particular to a loading device for simulating the dynamic effect of a motor vehicle bogie load on a ballastless track roadbed. Background Art

[0002] Railway subgrade is a geotechnical structure that supports the track structure and upper train loads, and is mainly composed of bulk materials such as soil and rock. Due to the loose porosity of soil and rock, the subgrade structure has a relatively weak ability to resist deformation. In particular, the part of the subgrade that is in direct contact with the track structure is prone to cumulative deformation under the action of long-term train cyclic loads, showing failure and damage characteristics, affecting the safe operation of the line. The ballastless track structure has low adaptability to subgrade deformation, and it is particularly necessary to control the cumulative deformation of the subgrade soil during the operation stage. Therefore, after the subgrade is built and before the track is laid, it is crucial to carry out dynamic response and accelerated fatigue tests using a loading device that simulates the dynamic effects of a train, obtain the subgrade dynamic parameters, and evaluate the subgrade's ability to resist cumulative deformation, which is crucial for engineering construction.

[0003] The loading device used for on-site roadbed dynamic testing mainly uses an inertial exciter to generate harmonic force, excite a large mass counterweight to vibrate vertically, and output load to the ground. The valley value of the load is used to simulate the deadweight of the track structure, and the peak-valley value simulates the train load. Existing inertial loading devices install mechanical connectors such as gears between the rotating shafts of the eccentric blocks to ensure that the eccentric blocks in the exciter rotate synchronously in opposite directions and in the same phase, and stably output vertical exciting force. However, during the use of this device, the connecting components between the rotating shafts of the eccentric blocks are subject to large mechanical wear, and a cooling system is required for the connecting components, resulting in a complex exciter structure, large volume, high manufacturing, maintenance and repair costs, and large environmental vibration noise. In addition, existing inertial loading devices mostly use rigid foundations to transfer loads to the roadbed surface, so the distribution of vibration stress on the roadbed is quite different from that of the roadbed under actual track structure conditions, and the dynamic system response composed of the loading device and the roadbed structure is difficult to reflect the actual roadbed structure performance. Therefore, it is necessary to explore a new type of railway roadbed cyclic loading device to overcome the above-mentioned shortcomings. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a loading device for simulating the dynamic effect of a motor vehicle bogie load on a ballastless track subgrade. The present invention solves the problems of high wear, vibration, and noise, high manufacturing and maintenance costs, and complex cooling systems caused by the traditional mechanically connected vibration motors that realize synchronous rotation in the opposite directions. At the same time, by reasonably setting the key parameters of the loading device, the load amplitude and distribution form output to the subgrade surface are simulated to be close to those of a real vehicle and a real road.

[0005] In order to achieve the above objectives, the technical solution adopted by the present invention is: a loading device that simulates the dynamic effect of the EMU bogie load on the ballastless track subgrade, including a loading plate cast in situ on the flat subgrade surface, a vibration platform located on the loading plate, accessories connected to the vibration platform, and a servo vibration motor control system connected to the vibration platform.

[0006] The beneficial effects of the present invention are:

[0007] (1) The loading device provided by the present invention simulates the dynamic effect of the EMU bogie load on the ballastless track subgrade. The servo vibration motor controller forces the motor to drive the eccentric block to rotate synchronously in the opposite direction and the same phase within a wide frequency range, thereby generating a stable vertical exciting force. The vibration motor with the eccentric block installed does not need to be equipped with mechanical connecting parts between the shafts such as gears, chains, and belts, as well as a cooling system for cooling the mechanical connecting parts such as gears. The device has a simple and compact structure, low mechanical wear of components, low manufacturing, maintenance and repair costs, and low environmental vibration and noise. At the same time, compared with equipping the shafts with mechanical connecting parts such as gears on which the eccentric block is installed, the eccentric block controlled by the servo control system has better reliability in the opposite direction and the same phase synchronization under high-frequency rotation conditions, which is conducive to the output of stable high-frequency vertical exciting force, and the device is safer and more durable.

[0008] (2) The loading device provided by the present invention simulates the dynamic effect of the EMU bogie load on the ballastless track subgrade, and the load distribution form output to the subgrade surface is consistent with the load distribution form generated by the bogie of an actual operating train on the subgrade surface under the ballastless track structure, so that the dynamic response of the subgrade-loading device system can more realistically reflect the dynamic performance of the ballastless track subgrade structure.

[0009] Further, the loading plate is a rectangular reinforced concrete plate;

[0010] The width of the reinforced concrete slab is the same as the supporting layer or base plate of the ballastless track to be simulated, the cross-sectional bending stiffness of the reinforced concrete slab is consistent with the ballastless track structure, and the length of the reinforced concrete slab is not less than the longitudinal distribution range of the dynamic stress on the roadbed surface caused by the EMU bogie load.

[0011] The beneficial effect of the above further solution is that the contact relationship between the loading plate and the roadbed provided by the invention can achieve a technical effect similar to the interaction characteristics of the simulated ballastless track structure and the roadbed.

[0012] Further, the vibration platform includes a vibration platform bottom plate, a plurality of counterweights respectively located on the vibration platform bottom plate, two servo vibration motors with the same parameters, and a plurality of eccentric blocks installed at both ends of the servo vibration motor rotating shaft, and the servo vibration motor is connected to a servo vibration motor control system;

[0013] The vibration platform bottom plate is a reinforced concrete plate, a servo vibration motor mounting bolt is pre-buried in the middle of the vibration platform bottom plate, and first reserved holes are provided on both sides of the vibration platform bottom plate;

[0014] Each of the counterweight blocks is a reinforced concrete slab, and a plurality of counterweight blocks are symmetrically installed on both sides of the bottom plate of the vibration platform, and the second reserved hole set on each side of the counterweight block is vertically aligned with the first reserved hole;

[0015] Two servo vibration motors are symmetrically installed in the middle of the vibration platform bottom plate and fixedly connected by servo vibration motor mounting bolts pre-buried in the middle of the vibration platform bottom plate; four groups of eccentric blocks are evenly installed at the four ends of the rotating shafts of the two servo vibration motors, and the mass and eccentric radius of the eccentric blocks are adjustable.

[0016] The beneficial effect of the above further scheme is that the vibration platform mass, vibration motor eccentric block mass and eccentric radius adjustment provided by the present invention can achieve the technical effect that the load amplitude output by the vibration system is the same as the simulated EMU bogie load.

[0017] Furthermore, the mass of the vibration platform is adjusted by increasing or decreasing the number of counterweight blocks, and the maximum deadweight (M max ×g) shall not be less than 0.5 times of the peak value of the dynamic load of the EMU bogie, where M max represents the maximum mass of the vibration platform, and g represents the acceleration due to gravity.

[0018] The beneficial effect of the above further scheme is that the loading device provided by the present invention for simulating the dynamic effect of the EMU bogie load on the ballastless track subgrade requires that the maximum deadweight of the vibration platform is not less than half of the peak value of the dynamic load of the EMU bogie to be simulated, so as to avoid limiting the performance of the device due to insufficient mass of the vibration platform.

[0019] Furthermore, the accessories include 4 vibration platform pads, 8 connecting screws, nuts and washers;

[0020] Each of the vibration platform pads is placed above the loading plate, and the position of each of the vibration platform pads corresponds to the four wheel load action points of the motor vehicle bogie. The vibration platform bottom plate is placed flat on the vibration platform pads, and the center of the vibration platform bottom plate is vertically aligned with the intersection of the diagonal lines of the four vibration platform pads, and is in uniform contact with the four vibration platform pads. The central cross section of the counterweight block on each side is in the same vertical plane as the vibration platform pad on the corresponding side.

[0021] The eight connecting screws respectively pass through the first reserved hole of the vibration platform bottom plate and the second reserved hole of the counterweight block, and gaskets and nuts are installed at both ends of the connecting screws to connect the vibration platform bottom plate and the counterweight block.

[0022] The beneficial effect of the above further scheme is that the vibration platform pads and connecting bolts and other accessories provided by the present invention can achieve the technical effect that the position of the load action point output by the vibration platform is consistent with the simulated EMU bogie load, and at the same time, the vibration platform base plate and the counterweight block are connected as a whole to ensure the smooth and safe operation of the vibration platform.

[0023] Still further, the servo vibration motor control system includes a servo vibration motor controller and a connecting line;

[0024] The servo vibration motor controller is connected to the servo vibration motor through a connecting line to control the speed of the servo vibration motor, ensuring that the two servo vibration motors rotate synchronously in opposite directions and in the same phase to generate a stable vertical exciting force.

[0025] The beneficial effect of the above further scheme is that the servo vibration motor control system provided by the present invention can realize the technical effect of two vibration motors driving the eccentric blocks to rotate synchronously in opposite directions and in the same phase within a wide frequency range, thereby generating a stable vertical exciting force.

[0026] Furthermore, the selection of the servo vibration motor includes the following steps:

[0027] S1. Measure the maximum mass M of the vibration platform max , and the vertical stiffness coefficient K provided to the vibration platform by the roadbed, loading plate and vibration platform pad, determine the minimum natural frequency f of the vibration system n,min ;

[0028] S2. Obtain the maximum exciting force F and the maximum rotational angular frequency ω that the selected servo vibration motor can generate, and determine the eccentric block parameters for a single servo vibration motor, that is, the maximum value of the product of the eccentric block mass m and the eccentric radius r (m·r) max ;

[0029] S3, measure the vertical damping coefficient C provided to the vibration platform by the roadbed, loading plate and vibration platform pad, and determine the maximum value (m·r) of the servo vibration motor max and the minimum natural frequency f n,min Under the condition, the dynamic load amplitude F' output by the vibration platform;

[0030] S4. Determine whether the dynamic load amplitude F' output by the vibration platform under the excitation of the servo vibration motor is not less than the maximum deadweight (M max ×g), if yes, then the selection process is completed, otherwise, a servo vibration motor that can output a larger exciting force F is reselected, and the process returns to step S2 until the requirements are met.

[0031] The beneficial effect of the above further scheme is that the selection of the servo vibration motor provided by the present invention takes into account factors such as the mass of the vibration platform, support stiffness and damping, output load amplitude, etc., the comprehensive influence on the output load of the vibration platform and the power amplification effect, avoids insufficient output capacity of the exciting force of the selected vibration motor, and can achieve the technical effect of reasonable selection of the vibration motor under the load amplitude simulation of the EMU bogie.

[0032] Furthermore, the dynamic load amplitude F' output by the vibration platform is expressed as follows:

[0033]

[0034] (m·r) max =F / ω 2

[0035]

[0036] The beneficial effect of the above further scheme is that the output load amplitude expression of the vibration platform provided by the present invention clarifies the functional relationship between factors such as the mass of the vibration platform, support stiffness and damping, maximum exciting force of the vibration motor and rotation angular frequency, and can achieve the technical effect of fine control of key parameters of the loading device. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A loading device for simulating the dynamic effect of EMU bogie load on ballastless track subgrade.

[0038] Figure 2 This is a servo vibration motor selection flow chart.

[0039] Figure 3 Schematic diagram of the relationship between the output load amplitude and deadweight of the vibration platform under different excitation frequencies.

[0040] Among them, 1-loading plate, 101-reinforced concrete plate, 2-vibration platform, 201-vibration platform bottom plate, 202-counterweight block, 203-servo vibration motor, 204-eccentric block, 205-first reserved hole, 206-servo vibration motor mounting bolt, 3-accessories, 301-vibration platform pad, 302-connecting screw, 303-nut, 304-gasket, 4-servo vibration motor control system, 401-servo vibration motor controller, 402-connecting wire. DETAILED DESCRIPTION

[0041] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0042] Example 1

[0043] like Figure 1 As shown, the present invention provides a loading device for simulating the dynamic effect of a motor vehicle bogie load on a ballastless track subgrade, comprising a loading plate 1 cast on a flat subgrade surface, a vibration platform 2 located on the loading plate 1, an accessory 3 connected to the vibration platform 2, and a servo vibration motor control system 4 connected to the vibration platform 2.

[0044] In this embodiment, the loading plate 1 is a rectangular reinforced concrete plate 101; the width of the reinforced concrete plate 101 is the same as the supporting layer or base plate of the ballastless track to be simulated, the cross-sectional bending stiffness of the reinforced concrete plate 101 is consistent with the ballastless track structure, and the length of the reinforced concrete plate 101 is not less than the longitudinal distribution range of the dynamic stress on the roadbed surface caused by the EMU bogie load.

[0045] In this embodiment, the vibration platform 2 includes a vibration platform base plate 201, a plurality of counterweights 202 (8 counterweights 202) respectively located on the vibration platform base plate 201, two servo vibration motors 203 with the same parameters (2 servo vibration motors 203), and multiple eccentric blocks 204 (4 groups of eccentric blocks 204) installed at both ends of the rotating shaft of the servo vibration motor 203, and the servo vibration motor 203 is connected to the servo vibration motor control system 4; the vibration platform base plate 201 is a reinforced concrete plate, and a servo vibration motor mounting bolt 206 is pre-buried in the middle of the vibration platform base plate 201, and first reserved holes 205 are provided on both sides of the vibration platform base plate 201; each counterweight The weight blocks 202 are all reinforced concrete slabs. Multiple counterweight blocks 202 are symmetrically installed on both sides of the vibration platform base plate 201. The central cross-section of the counterweight block 202 on each side is in the same vertical plane as the vibration platform pad 301 on the corresponding side. The second reserved hole set on each side of the counterweight block 202 is vertically aligned with the first reserved hole 205; two servo vibration motors 203 are symmetrically installed in the middle of the vibration platform base plate 201, and are fixedly connected by the servo vibration motor mounting bolts 206 embedded in the middle of the vibration platform base plate 201; four groups of eccentric blocks 204 are evenly installed at the four ends of the rotating shafts of the two servo vibration motors 203, and the mass and eccentric radius of the eccentric blocks 204 are adjustable.

[0046] In this embodiment, the mass of the vibration platform 2 is adjusted by increasing or decreasing the number of counterweight blocks 202, and the maximum deadweight (Mmax ×g) shall not be less than 0.5 times of the peak value of the dynamic load of the EMU bogie, where M max represents the maximum mass of the vibration platform 2, and g represents the acceleration due to gravity.

[0047] In this embodiment, the accessory 3 includes 4 vibration platform pads 301, 8 connecting screws 302, nuts 303 and gaskets 304; each vibration platform pad 301 is placed above the loading plate 1, and the position of each vibration platform pad 301 corresponds to the 4 wheel load action points of the EMU bogie. The vibration platform base plate 201 is placed flat on the vibration platform pad 301, and the center of the vibration platform base plate 201 is vertically aligned with the intersection of the diagonals of the 4 vibration platform pads 301, and is in uniform contact with the 4 vibration platform pads 301; the 8 connecting screws 302 respectively pass through the first reserved hole 205 of the vibration platform base plate 201 and the second reserved hole of the counterweight block 202, and gaskets 304 and nuts 303 are installed at both ends of the connecting screws 302 to connect the vibration platform base plate 201 and the counterweight block 202.

[0048] In this embodiment, the servo vibration motor control system 4 includes a servo vibration motor controller 401 and a connecting line 402; the servo vibration motor controller 401 is connected to the servo vibration motor 203 via the connecting line 402 to control the rotation speed of the servo vibration motor 203, thereby ensuring that the two servo vibration motors 203 rotate synchronously in opposite directions and in the same phase to generate a stable vertical exciting force, and achieving synchronous rotation in the same phase and in opposite directions under different rotation speed conditions to generate a stable vertical exciting force.

[0049] In this embodiment, Figure 2 As shown, the selection of the servo vibration motor 203 includes the following steps:

[0050] S1, measure the maximum mass M of vibration platform 2 max , and the vertical stiffness coefficient K provided to the vibration platform 2 by the roadbed, loading plate 1 and vibration platform pad 301, determine the minimum natural frequency f of the vibration system n,min :

[0051]

[0052] S2. Obtain the maximum exciting force F and the maximum rotational angular frequency ω that the selected servo vibration motor 203 can generate, and determine the parameters of the eccentric block 204 matched with a single servo vibration motor 203, that is, the maximum value (m·r) of the product of the mass m of the eccentric block 204 and the eccentric radius r. max :

[0053] (m·r) max =F / ω 2

[0054] S3, measure the vertical damping coefficient C provided to the vibration platform 2 by the roadbed, the loading plate 1 and the vibration platform pad 301, and determine the maximum value (m·r) of the servo vibration motor 203 max and the minimum natural frequency f n,min Under the following conditions, the dynamic load amplitude F' output by the vibration platform 2 is:

[0055]

[0056] S4, determine whether the dynamic load amplitude F' output by the vibration platform 2 under the excitation of the servo vibration motor 203 is not less than the maximum deadweight (M max ×g), if yes, the selection process is completed, otherwise, a servo vibration motor 203 that can output a larger exciting force F is reselected, and the process returns to step S2 until the requirements are met.

[0057] In summary, the loading device provided by the present invention has a simple structure, compact size, low manufacturing and operation costs, low environmental vibration and noise, and the system vibration formed with the roadbed can truly reflect the dynamic characteristics of the ballastless track roadbed structure, which is of great significance to improving the evaluation of the dynamic performance of the railway roadbed.

[0058] Example 2

[0059] A solution for the loading plate 1 is determined as follows: the reinforced concrete loading plate 101 is 10.0 m long, 3.1 m wide, and 0.35 m high. When conducting a subgrade structure dynamic performance test at a continuous position of the ballastless track structure base plate, the vibration platform pad 301 can be placed in the middle of the loading plate 1, with a horizontal spacing of 1.5 mm and a vertical spacing of 2.5 m.

[0060] A vibration platform base plate 201 is determined as: 4.2m long, 1.8m wide, and 0.5m high. A counterweight block 202 is determined as: 1.5m long, 2.0m wide, and 0.2m high. The weight of reinforced concrete is 24kN / m 3 The vibration platform base plate 201 has a deadweight of 90.72 kN, and each counterweight has a deadweight of 14.4 kN.

[0061] 0, 2, 4, 6, and 8 counterweights are symmetrically installed on both sides of the servo vibration motor 203 on the vibration platform bottom plate 201. Ignoring the dead weight of the servo vibration motor 203, the dead weight G of the vibration platform 2 is 90.72 kN, 119.52 kN, 148.32 kN, 177.12 kN, and 205.92 kN respectively.

[0062] Vibration platform 2 maximum deadweight G max (i.e. M max ×g) is about 205.92kN, and the maximum peak value of the bogie dynamic load that can be used for simulation is 411.84kN.

[0063] The following Figure 2 Follow the steps below to select a servo vibration motor:

[0064] Step S1: Take the stiffness coefficient K=850MN / m provided by the roadbed, loading plate 1 and vibration platform pad 301 to the vertical constraint of the vibration platform 2, and estimate the minimum natural frequency f of the vibration system n,min =32.34Hz.

[0065] Step S2: The maximum exciting force F=50 kN that the servo vibration motor 203 can generate, the maximum rotation speed is about 3000 rpm, the corresponding maximum rotation angular frequency ω=314.16 rad / s, and the maximum value of the product of the eccentric mass m and the eccentric radius r (m·r) max =0.51kg·m.

[0066] Step S3: Take the damping coefficient C=830kN·s·m provided by the roadbed, loading plate 1 and vibration platform pad 301 to the vertical constraint of the vibration platform 2 -1 , the eccentric mass (202) is at a frequency f n,min When rotating, the vibration platform 2 outputs a dynamic load with an amplitude of F'=212.26 kN.

[0067] Step S4: The amplitude F' of the dynamic load is greater than the maximum deadweight G of the vibration platform 2. max (i.e. M max ×g) is 3.08% larger, F N =50kN servo vibration motor 203 meets the selection requirements.

[0068] The deadweight G of the vibration platform 2 is 90.72 kN, 119.52 kN, 148.32 kN, 177.12 kN, and 205.92 kN, and m·r=(m·r) max =0.51kg·m, the servo vibration motor 203 drives the eccentric block 204 to rotate at different frequencies f. The load amplitude F' output by the vibration platform 2 is compared with the deadweight G. Figure 3 As shown. When the frequency f is less than the natural frequency of the system, the load amplitude F' output by the vibration platform 2 increases with the increase of the frequency f; when the frequency f is greater than the natural frequency of the system, the load amplitude F' gradually decays with the increase of the frequency f; when the frequency f is the resonance frequency that is basically consistent with the natural frequency, the F' value is the largest.

[0069] In addition, Figure 3 It can be seen that when the self-weight of vibration platform 2 is the largest, the natural frequency of the system is the minimum value f n,min=32.34Hz, the corresponding maximum value of F' is smaller than other cases where the deadweight G is smaller. Therefore, the configuration with the largest deadweight of the vibration platform 2 is selected for the selection of the servo vibration motor 203, and the motor is matched with the counterweight of the loading device as much as possible to avoid the selected vibration motor's insufficient excitation force output capacity and thus limiting the performance of the loading device. During the use of the loading device, attention should be paid to adjusting the m·r value and rotation speed of the eccentric block 204 to ensure that the load amplitude F output by the vibration platform 2 is not greater than the deadweight G, so as to avoid the vibration platform 2 and the cushion block 301 from being separated, causing accidents such as the overturning of the loading device.

[0070] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A loading device for simulating the dynamic effect of a motor vehicle bogie load on a ballastless track subgrade, characterized in that: It comprises a loading plate (1) cast in situ on a flat roadbed surface, a vibration platform (2) located on the loading plate (1), an accessory (3) connected to the vibration platform (2), and a servo vibration motor control system (4) connected to the vibration platform (2).

2. The loading device for simulating the dynamic effect of a motor vehicle bogie load on a ballastless track subgrade according to claim 1, characterized in that: The loading plate (1) is a rectangular reinforced concrete plate (101); The width of the reinforced concrete slab (101) is the same as that of the ballastless track support layer or base plate to be simulated, the cross-sectional bending stiffness of the reinforced concrete slab (101) is consistent with that of the ballastless track structure, and the length of the reinforced concrete slab (101) is not less than the longitudinal distribution range of the dynamic stress on the roadbed surface caused by the load of the motor vehicle bogie.

3. The loading device for simulating the dynamic effect of a motor vehicle bogie load on a ballastless track subgrade according to claim 1, characterized in that: The vibration platform (2) comprises a vibration platform bottom plate (201), a plurality of counterweights (202) respectively located on the vibration platform bottom plate (201), two servo vibration motors (203) with the same parameters, and a plurality of eccentric blocks (204) installed at both ends of the rotating shaft of the servo vibration motor (203); the servo vibration motor (203) is connected to a servo vibration motor control system (4); The vibration platform bottom plate (201) is a reinforced concrete plate, a servo vibration motor mounting bolt (206) is pre-buried in the middle of the vibration platform bottom plate (201), and first reserved holes (205) are provided on both sides of the vibration platform bottom plate (201); Each of the counterweight blocks (202) is a reinforced concrete slab, and the multiple counterweight blocks (202) are symmetrically installed on both sides of the vibration platform bottom plate (201), and the second reserved hole arranged on each side of the counterweight block (202) is vertically aligned with the first reserved hole (205); Two servo vibration motors (203) are symmetrically mounted in the middle of a vibration platform bottom plate (201) and fixedly connected by servo vibration motor mounting bolts (206) pre-buried in the middle of the vibration platform bottom plate (201); four groups of eccentric blocks (204) are evenly mounted on four ends of the rotating shafts of the two servo vibration motors (203), and the mass and eccentric radius of the eccentric blocks (204) are adjustable.

4. The loading device for simulating the dynamic effect of a motor vehicle bogie load on a ballastless track subgrade according to claim 3, characterized in that: The mass of the vibration platform (2) is adjusted by increasing or decreasing the number of counterweight blocks (202), and the maximum deadweight (M max ×g) shall not be less than 0.5 times of the peak value of the dynamic load of the EMU bogie, where M max represents the maximum mass of the vibration platform (2), and g represents the acceleration due to gravity.

5. The loading device for simulating the dynamic effect of a motor vehicle bogie load on a ballastless track subgrade according to claim 3, characterized in that: The accessory (3) includes four vibration platform pads (301), eight connecting screws (302), nuts (303) and washers (304); Each of the vibration platform pads (301) is placed above the loading plate (1), and the position of each of the vibration platform pads (301) corresponds to the four wheel load action points of the motor vehicle bogie. The vibration platform base plate (201) is placed flat on the vibration platform pads (301), and the center of the vibration platform base plate (201) is vertically aligned with the intersection of the diagonals of the four vibration platform pads (301) and is in uniform contact with the four vibration platform pads (301). The central cross section of the counterweight block (202) on each side is in the same vertical plane as the vibration platform pad (301) on the corresponding side. The eight connecting screws (302) respectively pass through the first reserved hole (205) of the vibration platform base plate (201) and the second reserved hole of the counterweight block (202), and gaskets (304) and nuts (303) are installed at both ends of the connecting screws (302) to connect the vibration platform base plate (201) and the counterweight block (202).

6. The loading device for simulating the dynamic effect of a motor vehicle bogie load on a ballastless track subgrade according to claim 3, characterized in that: The servo vibration motor control system (4) comprises a servo vibration motor controller (401) and a connecting line (402); The servo vibration motor controller (401) is connected to the servo vibration motor (203) via a connecting line (402) to control the rotation speed of the servo vibration motor (203) to ensure that the two servo vibration motors (203) rotate synchronously in opposite directions and in the same phase to generate a stable vertical exciting force.

7. The loading device for simulating the dynamic effect of a motor vehicle bogie load on a ballastless track subgrade according to claim 6, characterized in that: The selection of the servo vibration motor (203) comprises the following steps: S1. Maximum mass M of the measuring vibration platform (2) max , and the vertical stiffness coefficient K provided to the vibration platform (2) by the roadbed, the loading plate (1) and the vibration platform pad (301), determine the minimum natural frequency f of the vibration system n,min ; S2, obtaining the maximum exciting force F and the maximum rotational angular frequency ω that can be generated by the proposed servo vibration motor (203), and determining the parameters of the eccentric block (204) matched with the single servo vibration motor (203), that is, the maximum value (m·r) of the product of the mass m and the eccentric radius r of the eccentric block (204) max ; S3, measuring the vertical damping coefficient C provided to the vibration platform (2) by the roadbed, the loading plate (1) and the vibration platform pad (301), and determining the maximum value (m·r) of the servo vibration motor (203) max and the minimum natural frequency f n,min Under the condition, the dynamic load amplitude F' output by the vibration platform (2); S4, judging whether the dynamic load amplitude F' output by the vibration platform (2) under the excitation of the servo vibration motor (203) is not less than the maximum deadweight (M) of the vibration platform (2) max ×g), if yes, then the selection process is completed, otherwise, a servo vibration motor (203) that can output a larger exciting force F is reselected, and the process returns to step S2 until the requirements are met.

8. The loading device for simulating the dynamic effect of a motor vehicle bogie load on a ballastless track subgrade according to claim 7, characterized in that: The dynamic load amplitude F' output by the vibration platform (2) is expressed as follows: (m·r) max =F / ω 2

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