Rapid evaluation method for repairing effect of gap between plate-type ballastless track layers

Abstract

The invention discloses a method for rapidly evaluating the repairing effect of an inter-layer gap of a plate-type ballastless track, and belongs to the technical field of testing of building materials, and the method comprises the following steps: preparing a ballastless track concrete gap component according to the gap characteristics of the ballastless track; performing high-frequency fatigue loading on the ballastless track concrete gap component according to the ultimate strength to obtain fatigue displacement and fatigue life; and comprehensively evaluating the crack repairing effect according to the fatigue displacement and the fatigue life. According to the method, the ballastless track concrete open joint component conforming to structural characteristics and open joint characteristics is prepared, a fatigue test system better matched with the actual service condition is formulated, and a rapid evaluation method is provided for the ballastless track concrete open joint repairing effect; and a method is provided for determining a slab ballastless track clothing gap repairing system and selecting a repairing material.

Description

Technical Field

[0001] This invention relates to the field of building material testing technology, specifically to a rapid evaluation method for the repair effect of interlayer gaps in slab track, which is applicable to the concrete performance test of layered slab track structures, and is particularly suitable for evaluating the repair effect of fatigue performance after gaps. Background Technology

[0002] Slab track, primarily constructed with concrete, is widely used in high-speed railways, with CRTS I, CRTS II, and CRTS III types being the most common. The ballastless track structure mainly consists of rail fasteners, precast track slabs, a filling layer, and a base plate. The track slab directly bears the load of the high-speed train, while the cast-in-place filling layer, located between the base plate and the track slab, primarily serves to limit track slab displacement and transfer loads. However, during service, the layered structure of the ballastless track can develop gaps, affecting the stability and safety of train operation. Furthermore, the high-frequency fatigue loads of the train can cause these gaps to develop rapidly.

[0003] Depending on their location within the ballastless track, joints can be categorized into end joints (located at the four corners of the track slab), center joints (located in the middle of the track slab), and whole-slab joints. Since train fatigue loads primarily act on the track slab, joints mostly occur between the infill layer and the track slab. Once a joint forms, the fatigue load from the train will generate more significant vertical displacement and acceleration, exacerbating the joint's development. Therefore, timely repair of joints is necessary to ensure the stability and safety of the ballastless track during service. To clarify the impact of fatigue loads on ballastless track structures, existing standards such as "Fatigue Test Method for Prestressed Concrete Sleepers" (TB / T 1878-2002), "CRTSⅡ Type Double-Block Ballastless Track Concrete Slab" (TB / T3399-2015), and "Bending Fatigue Test Method for Prestressed Concrete Simply Supported Beams" (TB / T 2326-1992) have specified fatigue test methods for different structures. The standard "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete" (GB / T 50082-2009) also specifies the fatigue performance of concrete materials. However, the loading frequency in the relevant standards is only 4Hz~8Hz, which is significantly different from the fatigue load of high-speed rail (above 200 km / h, loading frequency ≥ 20Hz, bending fatigue load).

[0004] The main repair method after the formation of gaps is grouting repair. Currently, a relatively comprehensive study has been conducted on repair technology and repair materials. Patent inventions such as the repair technology and device for self-compacting concrete of high-speed railway ballastless track (CN202210242762.7), the repair structure for gaps between layers of ballastless track structure (CN201820434992.2), a rapid repair method for gaps in unit slab ballastless track using cement emulsified asphalt mortar (CN201410654892.7), and a repair material and method for filling layer of longitudinally connected slab ballastless track (CN202310124585.7) have provided repair methods, equipment, and materials for gap damage in slab ballastless track. However, due to the large size of ballastless track structures, the analysis of the repair effect, especially the repair effect under train fatigue load, is insufficient. Standards such as "A Test Method for Dynamic Performance of Concrete Embedded Structure of Ballastless Track throughout its Life Cycle" (CN202310117325.7) and "A Test Method for Dynamic Performance of Concrete in Layered Composite Structure of Ballastless Track throughout its Life Cycle" (CN202310117359.6) have developed concrete specimens that conform to the structure of ballastless track by proportionally scaling down the ballastless track, thus enabling rapid evaluation of the fatigue performance of concrete in layered and embedded ballastless track. However, there is currently no method for evaluating the repair effect of ballastless track.

[0005] The evaluation of the repair effect of interlayer gaps in ballastless track still has the following problems: 1) The fatigue test loading frequency is too low, which is significantly different from the high-frequency fatigue load on ballastless track concrete and cannot accurately reflect the actual situation of the development of joints in ballastless track. 2) Existing research mainly focuses on repair techniques and materials, but lacks research on the evaluation of repair effects; 3) The size of the ballastless track structure is too large, and there is a lack of rapid evaluation methods for the repair effect of gaps in ballastless tracks.

[0006] Therefore, providing a rapid evaluation method for the repair effect of interlayer gaps in slab track is a problem that urgently needs to be solved by those skilled in the art, thus providing a standard method for determining the on-site repair system and selecting repair materials. Summary of the Invention

[0007] In view of this, the present invention addresses the current lack of a test method for evaluating the repair effect of interlayer gaps in slab track, and proposes a rapid evaluation method for the repair effect of interlayer gaps in slab track, so as to achieve a rapid and accurate evaluation of the repair effect of slab track.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A rapid evaluation method for repairing interlayer gaps in slab track includes the following steps: (1) Prepare concrete joint components for ballastless track according to the location of the joint. (2) Static loading was applied to the concrete specimens of the ballastless track joint, and their ultimate strength was measured; (3) Based on the ultimate strength, fatigue tests were conducted on the concrete joint components of ballastless track to obtain fatigue displacement and fatigue life; (4) Evaluate the joint repair effect based on fatigue displacement and fatigue life: ① The displacement data mainly includes the maximum vertical displacement of the track slab and the filling concrete. Under fatigue load, the maximum vertical displacement of the track slab concrete is... e 1. The maximum vertical displacement of the filling layer concrete is e 2. Calculate the seam propagation rate No: (1); when No Repair failure is defined as a failure rate of ≥20%. ② Collect the number of fatigue loading cycles at the point of failure due to seam separation. N 1 and fatigue life N 2. Calculate the effective coefficient of the seam gap. C e : (2); ③When C e If the percentage is ≤60%, the repair is considered unqualified; if it is <60%, the repair is considered unqualified. C e The repair effect is considered acceptable when the percentage is ≤80%; otherwise, it is considered acceptable. C e A repair rate of ≤100% is considered a good result. ④ When fatigue life N 2 reaches 2×10 6 When it is not broken N 2 takes the value 2 × 10 6 Second-rate.

[0009] Existing ballastless track gaps lead to decreased track structure stability, most commonly occurring between the track slab and the infill layer. As a typical characteristic of train operation, the slapping effect of fatigue loads causes the gaps to develop rapidly. When the gap widens, there is a significant difference in vertical displacement between the track slab and the infill layer, macroscopically manifested as a continuous opening between the upper and lower layers. Currently, grouting repair is the main method used to control gaps between ballastless track layers. After repair, the opening trend of the gap is significantly improved, while avoiding the displacement difference between the upper and lower layers caused by fatigue loads. However, if the repair effect is poor, the repaired gap area may still be damaged due to stress concentration and poor bonding.

[0010] Furthermore, the preparation method of the ballastless track concrete joint component in step (1) is as follows: 1) Based on the joint characteristics of ballastless track, the track slab concrete was mixed and poured into steel molds. After pouring for 1 day, the molds were removed and the samples were placed in a standard curing room for curing for no less than 14 days to obtain track slab concrete specimens. 2) After the track slab concrete has reached the curing time, put it back into the steel mold, and then fix the organic foam board in the given position of the track slab concrete. Among them, the plate joint specimen is fixed in the middle, and the plate corner joint specimen is fixed at both ends; 3) Fill the mold with filling layer concrete, remove the mold after 1 day and place it in a standard curing room for curing. The overall curing time of the specimen shall not be less than 28 days. 4) After the specimen is formed, the foam board is cleaned to form a gap. Then, the repair material is pressed into the gap by pressure grouting and left for no less than 1 day. 5) Use sandpaper to smooth out any uneven areas on the surface of the specimen, and observe the specimen to ensure that there are no holes with a diameter exceeding 5 mm and a depth exceeding 2 mm near the loading area.

[0011] Furthermore, the foam board mentioned in step 2) is an organic material such as polystyrene or polyethylene foam that has poor adhesion to concrete. Its length ranges from 50 mm to 100 mm and its thickness ranges from 0.5 mm to 3 mm. To ensure the cleaning effect, toluene or other organic solvents can be used to clean the cracks. Then, the cracks can be rinsed with alcohol and water and thoroughly dried before grouting.

[0012] Furthermore, the track slab concrete is C60 concrete, and the filling layer concrete is C40 self-compacting concrete.

[0013] Furthermore, the pressure grouting method described in step 4) is as follows: Ⅰ. Preparation before joint grouting: Use a wire brush to clean the dust and slag from the joint surface; II. Setting up grouting ports: Set up grouting ports on one side of the joint, with the direction of the grouting ports parallel to the joint. Insert the grouting pipe into the grouting port to seal the gaps on the other sides. III. Grouting: When grouting begins, the grouting pressure must be maintained at ≤0.3 MPa to ensure that the joint is completely filled with grout and there are no large pores. The joint grouting is complete when the grouting material leaks out from the opposite side of the grouting area. IV. Complete the joint repair: After the repair material has fully cured, grind the joint surface smooth.

[0014] Furthermore, the method for measuring the ultimate strength under static loading in step (2) is as follows: the loading is performed on a press, and the loading speed is set to 0.05 MPa / s to 0.20 MPa / s to test the ultimate strength.

[0015] Furthermore, in step (3), to ensure that the fatigue load accurately reflects the train's operational characteristics, the fatigue test is conducted as follows: the upper limit of the fatigue loading stress is 0.3 to 0.7 times the ultimate strength, the stress ratio is 0.1, the loading method is bending fatigue, the loading waveform is a sine wave, and the loading frequency is... f ≥20 Hz, maximum load count is 2×10 6 Each test group shall contain no fewer than 5 test specimens.

[0016] Furthermore, in step (3), fatigue displacement is measured using displacement strain gauges, sensors, or DIC during the fatigue test.

[0017] Furthermore, in step (3), fatigue displacement is measured by means of displacement strain gauges, sensors or DIC during fatigue testing.

[0018] The beneficial effects of this invention are as follows: 1) This invention innovatively proposes a concrete joint component for ballastless track that conforms to the structural characteristics of ballastless track, while accurately reflecting different types of joint conditions; 2) A dynamic testing system that is closer to the actual service conditions of high-speed railways has been established, which can better reflect the development characteristics of interlayer gaps under fatigue loads; 3) It has enriched the experimental analysis technology for the repair effect of ballastless track, and the test results provide a standard method for determining the on-site repair system and selecting repair materials. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the joint-separated ballastless track joint component in the plate described in this invention; Figure 2 This is a schematic diagram of the joint-separation component of the ballastless track with corner separation as described in this invention; In the attached diagram, the structures indicated by each number are as follows: 1 - Concrete for sleeper with gap in slab; 2 - Self-compacting concrete for gap in slab; 3 - Repair location for gap in slab; 4 - Concrete for sleeper with gap at slab corner; 5 - Self-compacting concrete for gap at slab corner; 6 - Repair location for gap at slab corner. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0021] Example 1 Based on the characteristics of the joints in the slabs of ballastless track, joint components for concrete slabs of ballastless track that conform to the actual joint characteristics are prepared.

[0022] (1) The preparation process of the joint component is as follows: 1) First, prepare the track slab concrete (C60 concrete). Mix the concrete and pour it into steel molds. Remove the molds one day after pouring and place it in a standard curing room for 14 days. 2) Fix an organic polystyrene board with a length of 50 mm and a thickness of 2 mm to the middle of the C60 concrete forming surface, and then fix it in the steel mold with the forming surface facing up. 3) Continue pouring filling layer concrete (C40 self-compacting concrete) to fill the mold and cure for 14 days; 4) Use organic solvents to remove the organic polystyrene board, then rinse it with alcohol and water and dry it thoroughly; 5) Then, the repair material is pressed into the gap by pressure grouting. The repair material selected is TK-A type joint repair material. After hardening for 1 day, the surface is sanded to make it smooth. 6) Before the test, use sandpaper to smooth out any uneven areas on the surface of the specimen, ensuring that there are no holes with a diameter greater than 5 mm and a depth greater than 2 mm near the loading area.

[0023] (2) The experimental procedure is as follows: 1) A static loading test was conducted on 3 specimens at a loading rate of 0.10 MPa / s. The average flexural strength was measured to be 5.8 MPa. 2) Conduct fatigue tests and collect displacement data. The fatigue test regime is as follows: the upper limit of fatigue loading stress is 0.6 times the ultimate strength, the stress ratio is 0.1, the loading method is bending fatigue, and the loading waveform is a sine wave. 3) The displacement of the jointed components was collected using DIC technology. When Δε reached 20%, the number of fatigue loading cycles N1 was 610,000 and the fatigue life N2 was 780,000. 4) The calculated Ce value is 78.2%, which is considered a satisfactory repair result.

[0024] Example 2 Based on the characteristics of corner joints in ballastless track, corner joint components for concrete slabs of ballastless track that conform to the actual joint characteristics are prepared.

[0025] (1) The preparation process of the joint component is as follows: 1) First, prepare the track slab concrete (C60 concrete). Mix the concrete and pour it into steel molds. Remove the molds one day after pouring and place it in a standard curing room for 14 days. 2) Fix an organic polystyrene board with a length of 50 mm and a thickness of 2 mm to both ends of the C60 concrete forming surface, and then fix it in the steel mold with the forming surface facing up. 3) Prepare the filling layer concrete (C40 self-compacting concrete) and continue pouring it into the mold, then cure for 14 days; 4) Use organic solvents to remove organic polystyrene boards, rinse them thoroughly with alcohol and water, and dry them completely; 5) Then, the repair material is pressed into the gap by pressure grouting. The repair material selected is TK-A type joint repair material. After hardening for 1 day, the surface is sanded to make it smooth. 6) Before the test, use sandpaper to smooth out any uneven areas on the surface of the specimen, ensuring that there are no holes with a diameter greater than 5 mm and a depth greater than 2 mm near the loading area.

[0026] (2) The experimental procedure is as follows: 1) A static loading test was conducted on 3 specimens at a loading rate of 0.10 MPa / s. The average flexural strength was measured to be 6.4 MPa. 2) Conduct fatigue tests and collect displacement data. The fatigue test regime is as follows: the upper limit of fatigue loading stress is 0.6 times the ultimate strength, the stress ratio is 0.1, the loading method is bending fatigue, and the loading waveform is a sine wave. 3) The displacement of the jointed components was collected using DIC technology. The maximum Δε was found to be 11.2%, which was determined to be a case of no repair failure and a fatigue life N2 of 810,000 cycles. 4) If Ce is calculated to be 100%, the repair effect is considered to be good.

[0027] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for rapid evaluation of the repair effect of interlayer gaps in slab track, characterized in that, Includes the following steps: (1) Prepare concrete joint components for ballastless track according to the location of the joint. (2) Static loading was applied to the concrete specimens of the ballastless track joint, and their ultimate strength was measured; (3) Based on the ultimate strength, fatigue tests were conducted on the concrete joint components of ballastless track to obtain fatigue displacement and fatigue life; (4) Evaluate the joint repair effect based on fatigue displacement and fatigue life: ① The displacement data mainly includes the maximum vertical displacement of the track slab and the filling concrete. Under fatigue load, the maximum vertical displacement of the track slab concrete is... ε 1. The maximum vertical displacement of the filling layer concrete is ε 2. Calculate the seam propagation rate Δε: （1）； when Δε Repair failure is defined as a failure rate of ≥20%. ② Collect the number of fatigue loading cycles at the point of failure due to seam separation. N 1 and fatigue life N 2. Calculate the effective coefficient of the seam gap. C e : （2）； ③When C e If the percentage is ≤60%, the repair is considered unqualified; if it is <60%, the repair is considered unqualified. C e The repair effect is considered acceptable when the percentage is ≤80%; otherwise, it is considered acceptable. C e A repair rate of ≤100% is considered a good result. ④ When fatigue life N 2 reaches 2×10 6 When it is not broken N 2 takes the value 2 × 10 6 Second-rate.

2. The method for rapid evaluation of the repair effect of interlayer gaps in slab track according to claim 1, characterized in that, The preparation method of the ballastless track concrete joint component in step (1) is as follows: 1) Based on the joint characteristics of ballastless track, the track slab concrete was mixed and poured into steel molds. After pouring for 1 day, the molds were removed and the samples were placed in a standard curing room for curing for no less than 14 days to obtain track slab concrete specimens. 2) After the track slab concrete has reached the curing time, put it back into the steel mold, and then fix the organic foam board in the given position of the track slab concrete. Among them, the plate joint specimen is fixed in the middle, and the plate corner joint specimen is fixed at both ends; 3) Fill the mold with filling layer concrete, remove the mold after 1 day and place it in a standard curing room for curing. The overall curing time of the specimen shall not be less than 28 days. 4) After the specimen is formed, the foam board is cleaned to form a gap. Then, the repair material is pressed into the gap by pressure grouting and left for no less than 1 day. 5) Use sandpaper to smooth out any uneven areas on the surface of the specimen, and observe the specimen to ensure that there are no holes with a diameter exceeding 5 mm and a depth exceeding 2 mm near the loading area.

3. The method for rapid evaluation of the repair effect of interlayer gaps in slab track according to claim 2, characterized in that, The organic foam board mentioned in step 2) is an organic material that has poor adhesion to concrete. Its length ranges from 50 mm to 100 mm and its thickness ranges from 0.5 mm to 3 mm. To ensure the cleaning effect, toluene or other organic solvents can be used to clean the cracks. Then, it should be rinsed with alcohol and water and dried thoroughly before grouting.

4. The method for rapid evaluation of the repair effect of interlayer gaps in slab track according to claim 2, characterized in that, The track slab concrete is C60 concrete, and the filling layer concrete is C40 self-compacting concrete.

5. The method for rapid evaluation of the repair effect of interlayer gaps in slab track according to claim 2, characterized in that, The pressure grouting method described in step 4) is as follows: Ⅰ. Preparation before joint grouting: Use a wire brush to clean the dust and slag from the joint surface; II. Setting up grouting ports: Set up grouting ports on one side of the joint, with the direction of the grouting ports parallel to the joint. Insert the grouting pipe into the grouting port to seal the gaps on the other sides. III. Grouting: When grouting begins, the grouting pressure must be maintained at ≤0.3 MPa to ensure that the joint is completely filled with grout and there are no large pores. The joint grouting is complete when the grouting material leaks out from the opposite side of the grouting site. IV. Complete the joint repair: After the repair material has fully cured, grind the joint surface smooth.

6. The method for rapid evaluation of the repair effect of interlayer gaps in slab track according to claim 1, characterized in that, The method for measuring the ultimate strength under static loading in step (2) is as follows: it is carried out on a press, and the loading speed is set to 0.05 MPa / s to 0.20 MPa / s to test the ultimate strength.

7. The method for rapid evaluation of the repair effect of interlayer gaps in slab track according to claim 6, characterized in that, The fatigue test in step (3) is as follows: the upper limit of the fatigue loading stress is 0.3 to 0.7 times the ultimate strength, the stress ratio is 0.1, the loading method is bending fatigue, the loading waveform is a sine wave, and the loading frequency is... f ≥20 Hz, maximum load count is 2×10 6 Each test group shall contain no fewer than 5 test specimens.

8. The method for rapid evaluation of the repair effect of interlayer gaps in slab track according to claim 7, characterized in that, In step (3), fatigue displacement is measured by means of displacement strain gauges, sensors or DIC during fatigue testing.

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