Ballastless track interlayer interface testing device and testing method

Abstract

The present invention provides a ballastless track interlayer interface testing device and testing method, which relate to the technical field of track performance evaluation. The ballastless track interlayer interface testing device includes a box and a test piece arranged in the box, a loading system, a deformation testing system and a temperature control system; the middle part of the test piece is the interlayer interface, the test piece is arranged at the lower part of the box, and an ammonium chloride solution covering the test piece is also arranged in the box; the temperature control system includes a heating structure arranged at the lower part of the box for heating the ammonium chloride solution; the loading system is arranged at the upper part of the test piece for applying a downward load force to the test piece; the deformation testing system includes a displacement sensor fixed on the test piece, and the displacement sensor is used to detect the downward displacement of the test piece while the loading system applies a downward load force to the test piece; through the setting of the ammonium chloride solution, the temperature control system and the loading system can realize the simulation of the degradation process of the interlayer interface of the ballastless track structure under the coupling action of water, heat and force in the laboratory.

Description

Technical Field

[0001] The present invention relates to the technical field of track performance evaluation, and in particular to a ballastless track interlayer interface testing device and a performance evaluation method. Background Art

[0002] Ballastless track structures use a monolithic foundation of concrete, asphalt mixtures, and other materials instead of a granular gravel roadbed. They provide a smooth and stable foundation for the rapid operation of high-speed rail tracks and are currently the predominant track structure used in high-speed rail. However, relevant domestic research data indicates that ballastless track structures inevitably suffer varying degrees of damage during operation due to the influence of train loads, temperature, moisture, and other factors. Deterioration of the interlayer interface of ballastless track, leading to crack separation and slurry bleeding, is a major ballastless track hazard and poses a serious threat to the safe operation of high-speed rail. However, standardized testing and assessment methods for interlayer interface degradation of ballastless track structures are currently lacking, both domestically and internationally.

[0003] For example, the Chinese invention patent document with application number 202010047479X discloses a method for testing the fracture toughness of the interlayer interface of ballastless track, the steps of which include (1) making a concrete test block of a double-layer concrete structure containing interlayer cracks; (2) installing the concrete test block on a testing machine, and installing at least one of a displacement sensor, a strain gauge, etc. to pre-tension the concrete test block, and the pre-tension load is a failure load with a value range of [0% to 20%]; (3) adjusting the measuring instrument and conducting a formal test, controlling the load speed at 0.1 to 1 mm / min until the specimen is destroyed, and recording the failure load and fracture position; (4) processing the test results to solve the fracture toughness.

[0004] However, the existing test method for the fracture toughness of the interlayer interface of ballastless track only tests the crack length of the interlayer interface under the action of load in air to further obtain the fracture toughness. In the actual working environment, temperature and moisture will also cause a certain degree of damage to the interlayer interface. This test method cannot measure the displacement change of the specimen under the influence of temperature and moisture when subjected to load. Summary of the Invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide a ballastless track interlayer interface testing device to solve the problem that the testing method in the prior art cannot test the displacement change of the specimen under the influence of temperature and moisture when it is subjected to load.

[0006] The technical solution of the ballastless track interlayer interface testing device of the present invention is:

[0007] The ballastless track interlayer interface testing device includes a box body and a loading system, a deformation testing system and a temperature control system arranged in the box body;

[0008] A test piece and an ammonium chloride solution covering the test piece are provided at the lower part of the box, and the middle part of the test piece is an interlayer interface extending in a vertical direction;

[0009] The temperature control system includes a heating structure provided at the lower portion of the box body for heating the ammonium chloride solution;

[0010] The loading system is arranged on the upper part of the specimen, and is used to apply a downward load force to the specimen;

[0011] The deformation testing system includes a displacement sensor fixed on the specimen, and the displacement sensor is used to detect the downward displacement of the specimen when the loading system applies a downward load force to the specimen.

[0012] Furthermore, two supporting rods are provided at the bottom of the specimen and are arranged symmetrically along the interlayer interface. The two supporting rods are used to support the specimen, and the distance between the two supporting rods is 1.

[0013] Furthermore, the loading system includes two vertical columns fixedly arranged at intervals at the bottom of the box;

[0014] The loading system further includes a first pressing plate, a second pressing plate, and a third pressing plate slidably arranged on the two columns from bottom to top, an elastic member is installed on each of the columns between the second pressing plate and the third pressing plate, and a force measuring member is installed between the first pressing plate and the second pressing plate;

[0015] A contact piece for abutting the specimen is installed on the first pressure plate, and an adjusting piece is movably arranged on the column on the top of the third pressure plate. The adjusting piece is used to press the third pressure plate, the second pressure plate and the first pressure plate downward in sequence to apply a load force to the specimen.

[0016] Furthermore, two contact members are provided, and the two contact members are arranged symmetrically about the interlayer interface, and the horizontal distance between the contact members located on the same side of the interlayer interface as the support rod is a.

[0017] Furthermore, two displacement sensors are provided, and the two displacement sensors are symmetrically spaced on the test piece with respect to the interlayer interface;

[0018] Assume that the elastic modulus of the specimen is E, then E=[Fa(la-2a 2 -2ab)] / 4f ave I, where F is the reading of the force measuring piece, b is the horizontal distance between the contact piece and the nearest displacement sensor, and f ave is the average reading of the two displacement sensors, I is the section inertia moment of the specimen, and I = wh 3 / 12, w is the width of the specimen, h is the height of the specimen.

[0019] Furthermore, the tops of the two columns are provided with threads, and the adjusting member is a fastening nut matching the threads.

[0020] Furthermore, the deformation testing system further includes a fixing frame, both ends of which are fixed on the test piece, and the displacement sensor is installed on the fixing frame.

[0021] The testing method using the above-mentioned ballastless track interlayer interface testing device includes:

[0022] S1: Add the prepared ammonium chloride solution into the box and ensure that the liquid level of the ammonium chloride solution is higher than the top surface of the test piece;

[0023] S2: Turn on the heating structure and place it in the solution to heat the ammonium chloride solution so that the ammonium chloride solution is maintained at the required temperature for the test;

[0024] S3: operate the loading system to apply a load force F to the specimen to degrade the specimen, and operate the loading system to unload;

[0025] S4: Operate the loading system again to apply the load force F, and read the displacement sensor to show the displacement is f ave ;

[0026] S5: Calculate the elastic modulus of the specimen;

[0027] S6: Determine whether the elastic modulus of the specimen meets the test standard. If not, repeat steps S1 to S5. If yes, proceed to S7.

[0028] S7: The loading system is operated again to continue loading until the specimen breaks. Phenolphthalein is sprayed on the interlayer interface. The area that turns red after phenolphthalein staining is the non-degraded area. The degradation degree D of the interlayer interface is calculated based on the area of ​​the non-degraded area.

[0029] Furthermore, in step S6, the elastic modulus of the specimen (1) is E, E = [Fa(la-2a 2 -2ab)] / 4f ave I.

[0030] Furthermore, the degradation degree of the interlayer interface is D, D = (A total -A red ) / A total , A total is the total cross-sectional area of ​​the interface between layers, A red It is the area of ​​the interlayer interface without degradation, that is, the total area of ​​the area that turns red after phenolphthalein staining.

[0031] Beneficial effects: The ballastless track interlayer interface test device includes a box and a specimen arranged in the box, a loading system, a deformation testing system and a temperature control system; the middle part of the specimen is the interlayer interface, the specimen is arranged at the lower part of the box, and an ammonium chloride solution covering the specimen is also arranged in the box; the temperature control system includes a heating structure arranged at the lower part of the box for heating the ammonium chloride solution; the loading system is arranged at the upper part of the specimen for applying a downward load force to the specimen.

[0032] By setting up ammonium chloride solution, temperature control system and loading system, the degradation process of the interface between ballastless track structures under the coupling action of water, heat, force and other factors can be simulated in the laboratory, which can highly reflect the actual degradation of the interface between ballastless track layers.

[0033] The deformation testing system includes a displacement sensor fixed on the specimen. The displacement sensor is used to detect the downward displacement of the specimen while the loading system applies a downward load force to the specimen. The elastic modulus of the specimen can be further calculated through the detected displacement. The service performance of the interlayer interface can be reflected by the change in the elastic modulus. It has the advantages of economical and reasonable cost, simple and stable testing, and reliable and accurate results. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the structure of the ballastless track interlayer interface testing device of the present invention;

[0035] Figure 2 Schematic diagram of the bending force of a test piece of the ballastless track interlayer interface testing device of the present invention;

[0036] Figure 3 A load-deflection curve diagram of a specimen of the ballastless track interlayer interface testing device of the present invention during a loading failure process after degradation;

[0037] Figure 4 This is a boundary contour diagram of the interlayer interface of the ballastless track interlayer interface testing device of the present invention after being phenolphthalein dyed.

[0038] In the figure: 1. test piece, 2. interface between layers, 3. bottom plate, 4. column, 5. support rod, 6. contact member, 7. first pressure plate, 8. second pressure plate, 9. third pressure plate, 10. elastic member, 11. fastening nut, 12. force measuring member, 13. displacement sensor, 14. fixing plate, 15. fixing bracket, 16. box, 17. ammonium chloride solution, 18. heating structure, 19. cover plate, 20. switch valve, 21. wires;

[0039] F. Force ring reading, a. Horizontal distance between the support rod and the contact piece on the same side of the interlayer interface, l. Distance between the two support rods, b. Horizontal distance between the contact piece and the nearest displacement sensor. DETAILED DESCRIPTION

[0040] The following is a detailed description of the specific embodiments of the ballastless track interlayer interface testing device of the present invention in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0041] A specific embodiment of a ballastless track interlayer interface 2 testing device of the present invention is as follows Figure 1 As shown, the ballastless track interlayer interface 2 test device of the present invention includes a box 16 and a specimen 1, a loading system, a deformation testing system and a temperature control system arranged in the box 16; the size of the specimen 1 is 400mm×100mm×100mm, and the middle part of the specimen 1 is the interlayer interface 2, and the specimens 1 on both sides of the interlayer interface 2 are cast with concrete materials of different structural layers; the outer side of the specimen 1 excluding the interlayer interface 2 is coated with sealant to ensure that other parts of the specimen 1 except the interlayer interface 2 will not be affected by degradation.

[0042] The bottom of the box 16 is provided with a bottom plate 3, and the specimen 1 is provided on the bottom plate 3. The loading system is provided on the upper part of the specimen 1 to apply a downward load force to the specimen 1. Two supporting rods 5 are provided between the bottom of the specimen 1 and the bottom plate 3, which are symmetrically supported about the interlayer interface 2. The loading system includes two columns 4 fixed at intervals at the bottom of the box 16, and a first pressing plate 7, a second pressing plate 8 and a third pressing plate 9 slidingly provided on the columns 4 from bottom to top. An elastic member 10 is installed between the second pressing plate 8 and the third pressing plate 9, and the elastic member 10 is an elastic compression spring. The first pressing plate 7 and the second pressing plate 9 are symmetrically supported about the interlayer interface 2. A force measuring piece 12 is installed at the position of the interlayer interface 2 between the pressure plates 8. The force measuring piece 12 can be a force ring or a dynamometer. The force ring or dynamometer is used to measure in real time the load force F applied by the loading system to the specimen. A contact piece 6 for contacting the specimen 1 is installed on the first pressure plate 7, and an adjusting piece is movably set on the column 4 at the top of the third pressure plate 9. The adjusting piece is used to squeeze the third pressure plate 9, the second pressure plate 8 and the first pressure plate 7 downward in sequence to apply a load force to the specimen 1. Specifically, the contact piece 6 is a pressure rod, and two pressure rods are provided. The two pressure rods are arranged symmetrically about the interlayer interface 2.

[0043] In this embodiment, the tops of the two columns 4 are threaded, and the adjusting member is a tightening nut 11 that matches the threads. During use, tightening the tightening nut 11 causes the third pressure plate 9, the second pressure plate 8, and the first pressure plate 7 to press downward in sequence to apply a load to the specimen 1. This can reduce the reliance on large loading equipment and continuous power supply during the test, while also facilitating supplementary loading operations at any time during the test. When the required load is applied to the specimen 1 by tightening the nut 11 with the wrench knob, the interlayer interface 2 of the specimen 1 is subjected to bending, and the specimen 1 is subjected to linearly varying stress along the height direction. This more closely resembles the stress characteristics of a ballastless track structure under the influence of daily temperature gradients and more accurately reflects the degradation effect of temperature on the interlayer interface 2 of the ballastless track.

[0044] The deformation test system includes a displacement sensor 13, which is fixed at the flexibility measuring point on the vertical surface of the specimen 1. In this embodiment, the deformation test system also includes a fixing frame 15, both ends of which are fixedly connected to the specimen 1. Two displacement sensors 13 are provided, and the two displacement sensors 13 are installed on the fixing frame 15 symmetrically about the interlayer interface 2. A fixing plate 14 is also attached and fixed at the deflection measuring point of the specimen 1. The displacement sensor 13 is arranged directly above the fixing plate 14, as shown in FIG. Figure 3 As shown, during the test, the displacement sensor 13 can measure the displacement f of the specimen 1 after experiencing different degrees of degradation. ave , and according to the load force displayed in real time by the force measuring piece and the displacement displayed in real time by the displacement sensor, a load-deflection curve of the specimen in the loading failure process after deterioration can be drawn.

[0045] like Figure 2 As shown in FIG. 1 , when the force measuring piece shows F, the force distributed to each pressure rod is F / 2. The horizontal spacing between the support rod 5 and the pressure rod on the same side of the interlayer interface 2 is a. The spacing between the two support rods 5 is l, and l = 300 mm. The horizontal spacing between the two pressure rods is 100 mm, that is, a = 100 mm. The displacement sensor 13 is set at the deflection measuring point. The horizontal distance between the pressure rod and the nearest displacement sensor 13 is b. The elastic modulus of the specimen 1 is E, E = [Fa(la-2a 2 -2ab)] / 4f ave I, where I is the section moment of inertia of the specimen, and I = wh 3 / 12, w is the width of specimen 1, h is the height of specimen 1, and the data are substituted into the calculation to obtain the elastic modulus of specimen 1, thereby testing the service performance of the interlayer interface 2.

[0046] The box 16 also contains an ammonium chloride solution 17. Specifically, the ammonium chloride solution 17 can accelerate the decomposition of hydration products at the interlayer interface 2, increase the interface porosity, and accurately accelerate the degradation process of the simulated interlayer interface 2 under the action of moisture. The higher the concentration of the ammonium chloride solution 17, the faster the degradation rate of the interlayer interface 2 by moisture, which can accelerate the degradation effect of moisture on the interlayer interface 2 of the ballastless track.

[0047] Phenolphthalein turns red when it comes into contact with alkali, and the ammonium chloride solution 17 reacts with the calcium hydroxide inside the concrete, which consumes the calcium hydroxide in the deteriorated part. Therefore, the deteriorated area is neutral or acidic and will not show color after spraying phenolphthalein. Based on this principle, the deterioration degree D of the interlayer interface 2 after deterioration can be calculated, as follows: Figure 4 As shown, Figure 4 A is a schematic cross-sectional view of the interlayer interface 2 after spraying phenolphthalein. total is the total cross-sectional area of ​​the interlayer interface 2, A red is the total area of ​​the reddened region after phenolphthalein dyeing, that is, the area of ​​the interlayer interface 2 that has not been degraded. The remaining non-reddened region is the degraded region. Then D=(A total -A red ) / A total .

[0048] A temperature control system is also provided in the box 16. The temperature control system includes a heating structure 18. Specifically, the heating structure 18 is a heating tube, which is electrically connected to an external power supply through an electric wire. The heating tube is used to control the temperature of the ammonium chloride solution. The heating tube can be set to different temperature values ​​according to demand to control the temperature of the ammonium chloride solution, thereby simulating the acceleration effect of temperature on the interlayer interface 2 of the moisture-degraded specimen 1, and more reasonably reflecting the degradation process of the interlayer interface 2 of the ballastless track structure under the action of water-thermal coupling.

[0049] In addition, in order to ensure that the device will not be affected by degradation during use, the first pressure plate 7, the second pressure plate 8, the third pressure plate 9, the bottom plate 3, the column 4, the support rod 5 and the contact member 6 of the device are all made of stainless steel. The box body 16 adopts a heat-insulating box to achieve a heat-insulating effect. An opening is opened above the box body 16, and a cover plate 19 matching the opening is provided above the box body 16 to ensure that the ammonium chloride solution will not evaporate and decrease during the heating process. The bottom of the box body 16 is connected to a water outlet, and a switch valve 20 is installed on the water outlet. When the degradation is completed, the switch valve 20 on the water outlet is opened to allow the ammonium chloride solution to flow to the outside of the box body 16, and the test piece 1 can be removed.

[0050] The present invention also provides a testing method using the above-mentioned ballastless track interlayer interface testing device:

[0051] S1: Prepare specimens according to the material mix ratio of concrete for different structural layers of ballastless track, add the prepared solution into the box, and ensure that the liquid level of the solution is higher than the top surface of the specimen;

[0052] S2: Turn on the heating tube and place it in the ammonium chloride solution to heat the ammonium chloride solution, so that the ammonium chloride solution is maintained at the required temperature for the test to degrade the specimen;

[0053] S3: Operate the wrench to tighten the fastening nut to apply a load force F to the specimen, causing the specimen to deteriorate, and then rotate the fastening nut in the opposite direction to unload;

[0054] S4: Tighten the fastening nut again and read the displacement sensor to show the displacement is f ave ;

[0055] S5: Calculate the elastic modulus of the specimen;

[0056] S6: Determine whether the elastic modulus of the specimen meets the test standard. If not, repeat steps S1-S5.

[0057] S7: Tighten the fastening nut again and continue loading until the specimen breaks. Phenolphthalein is sprayed on the interlayer interface and the degree of deterioration D of the interlayer interface is calculated.

[0058] In step S6, the elastic modulus of the specimen (1) is E, E = [Fa(la-2a 2 -2ab)] / 4f ave I.

[0059] In step S7, the degradation degree of the interlayer interface is D, D = (A total -A red ) / A total , A total is the total cross-sectional area of ​​the interface between layers, A red It is the area of ​​the interlayer interface without degradation, that is, the total area of ​​the area that turns red after phenolphthalein staining.

[0060] By setting up an ammonium chloride solution 17, a temperature control system, and a loading system, the degradation process of the interlayer interface of the ballastless track structure under the coupling action of water, heat, and force can be simulated in the laboratory. The simulated degradation can highly reflect the actual degradation of the interlayer interface of the ballastless track, and a corresponding performance analysis method for the degraded interlayer interface is proposed based on the test device. It has the advantages of reasonable cost, simple and stable testing, and reliable and accurate results.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A testing method using a ballastless track interlayer interface testing device, characterized in that: The ballastless track interlayer interface testing device comprises a box (16) and a loading system, a deformation testing system and a temperature control system arranged in the box (16); A test piece (1) and an ammonium chloride solution (17) covering the test piece (1) are provided at the lower portion of the box (16); the middle portion of the test piece (1) is an interlayer interface (2) extending in a vertical direction; The temperature control system includes a heating structure (18) disposed at the lower portion of the box (16) for heating the ammonium chloride solution (17); The loading system is arranged on the upper part of the specimen (1), and the loading system is used to apply a downward load force to the specimen (1); The deformation testing system comprises a displacement sensor (13) fixed on the specimen (1), wherein the displacement sensor (13) is used to detect the downward displacement of the specimen (1) when the loading system applies a downward load force to the specimen (1); Two supporting rods (5) are provided at the bottom of the test piece (1) and are arranged symmetrically along the interlayer interface (2). The two supporting rods (5) are used to support the test piece (1). The distance between the two supporting rods (5) is l. The loading system comprises a contact member (6) for abutting against the test piece (1); Two contact members (6) are provided, and the two contact members (6) are arranged symmetrically with respect to the interlayer interface (2), and the horizontal distance between the support rod (5) and the contact member (6) located on the same side of the interlayer interface (2) is a; Test methods include: S1: Add the prepared ammonium chloride solution (17) into the box (16), and ensure that the liquid level of the ammonium chloride solution (17) is higher than the top surface of the test piece (1); S2: Turn on the heating structure (18) and place it in the ammonium chloride solution (17) to heat the ammonium chloride solution (17) so that the ammonium chloride solution (17) is maintained at the temperature required for the test; S3: operating the loading system to apply a load force F to the specimen (1) to degrade the specimen (1), and operating the loading system to unload; S4: Operate the loading system again to apply the load force F, and read the displacement sensor (13) to show the displacement is ; S5: Calculate the elastic modulus of specimen (1); S6: Determine whether the elastic modulus of the specimen (1) meets the test standard. If not, continue to repeat steps S1-S5. If yes, proceed to S7. S7: The loading system is operated again to continue loading until the specimen (1) breaks. Phenolphthalein is sprayed on the interlayer interface (2). The area that turns red after phenolphthalein staining is the non-degraded area. The degree of degradation D of the interlayer interface (2) is calculated based on the area of ​​the non-degraded area.

2. The testing method using the ballastless track interlayer interface testing device according to claim 1 is characterized in that: The loading system comprises two columns (4) fixedly arranged vertically at an interval at the bottom of the box (16); The loading system further comprises a first pressing plate (7), a second pressing plate (8) and a third pressing plate (9) which are slidably arranged on the two upright posts (4) from bottom to top, an elastic member (10) is installed on each upright post (4) between the second pressing plate (8) and the third pressing plate (9), and a force measuring member (12) is installed between the first pressing plate (7) and the second pressing plate (8); The contact member (6) is mounted on the first pressing plate (7); An adjusting member is movably provided on the column (4) at the top of the third pressing plate (9), and the adjusting member is used to sequentially press the third pressing plate (9), the second pressing plate (8) and the first pressing plate (7) downward to apply a load force to the specimen (1).

3. The testing method using the ballastless track interlayer interface testing device according to claim 2 is characterized in that: Two displacement sensors (13) are provided, and the two displacement sensors (13) are symmetrically spaced and arranged on the test piece (1) with respect to the interlayer interface (2). Assuming the elastic modulus of the specimen (1) is E, then ， Wherein F is the reading of the force measuring piece (12), b is the horizontal distance between the contact piece (6) and the nearest displacement sensor (13), is the average reading of the two displacement sensors (13), I is the section inertia moment of the specimen (1), and , w is the width of the specimen (1), and h is the height of the specimen (1).

4. The testing method using the ballastless track interlayer interface testing device according to claim 2 is characterized in that: The tops of the two upright posts (4) are provided with threads, and the adjusting member is a fastening nut (11) matching the threads.

5. The testing method using the ballastless track interlayer interface testing device according to claim 1 is characterized in that: The deformation testing system further comprises a fixing frame (15), both ends of the fixing frame (15) are fixed on the test piece (1), and the displacement sensor (13) is mounted on the fixing frame (15).

6. The testing method using the ballastless track interlayer interface testing device according to claim 1 is characterized in that In step S7, the degradation degree of the interlayer interface (2) is D, , is the total cross-sectional area of ​​the interlayer interface (2), and Ared is the area of ​​the non-degraded region of the interlayer interface (2), that is, the total area of ​​the region that turns red after phenolphthalein staining.

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