CN116674052A - Concrete anti-cracking control method for ballastless track slab - Google Patents
Concrete anti-cracking control method for ballastless track slab Download PDFInfo
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- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 3
- 229910052925 anhydrite Inorganic materials 0.000 claims description 3
- 229910052791 calcium Inorganic materials 0.000 claims description 3
- 239000011575 calcium Substances 0.000 claims description 3
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims description 3
- 239000000292 calcium oxide Substances 0.000 claims description 3
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 3
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 claims description 3
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- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 3
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 3
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28B1/00—Producing shaped prefabricated articles from the material
- B28B1/04—Producing shaped prefabricated articles from the material by tamping or ramming
- B28B1/045—Producing shaped prefabricated articles from the material by tamping or ramming combined with vibrating or jolting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28B1/00—Producing shaped prefabricated articles from the material
- B28B1/08—Producing shaped prefabricated articles from the material by vibrating or jolting
- B28B1/093—Producing shaped prefabricated articles from the material by vibrating or jolting by means directly acting on the material, e.g. by cores wholly or partly immersed in the material or elements acting on the upper surface of the material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28B11/00—Apparatus or processes for treating or working the shaped or preshaped articles
- B28B11/24—Apparatus or processes for treating or working the shaped or preshaped articles for curing, setting or hardening
- B28B11/245—Curing concrete articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28B13/00—Feeding the unshaped material to moulds or apparatus for producing shaped articles; Discharging shaped articles from such moulds or apparatus
- B28B13/02—Feeding the unshaped material to moulds or apparatus for producing shaped articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28B17/00—Details of, or accessories for, apparatus for shaping the material; Auxiliary measures taken in connection with such shaping
- B28B17/0063—Control arrangements
- B28B17/0081—Process control
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Ceramic Engineering (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Structural Engineering (AREA)
- Automation & Control Theory (AREA)
- Machines For Laying And Maintaining Railways (AREA)
Abstract
The application relates to a track traffic technology, in particular to a ballastless track slab concrete crack prevention control method which can effectively control slab concrete cracks and comprises the following steps: calculating concrete cracking risk coefficients under different working conditions according to different concrete performance indexes by adopting a finite element analysis numerical simulation method:sigma (t) and f t (t) is the maximum tensile stress and tensile strength of the concrete at the moment t; if eta<0.7, executing the following steps; selection and eta<0.7 pair ofThe concrete comprises 5-10% of anticracking agent by weight of the concrete cementing material; pouring concrete into a mould at 5-28 ℃, pouring the concrete in a Z shape between prefabricated sleeper blocks, wherein the height of a discharge hole is not more than 0.5m; pouring, paving and leveling, and then spraying a water evaporation inhibitor for primary plastering; after the initial setting of the concrete surface, performing second plastering and then spraying a water evaporation inhibitor; covering a plastic film and curing the thermal insulation material for at least 14 days; the temperature and strain around the center, upper surface, side surfaces, prefabricated pillows of the ballast bed are monitored and maintenance measures are adjusted accordingly.
Description
Technical Field
The application relates to a track traffic technology, in particular to a concrete anti-cracking control method for a ballastless track bed plate.
Background
The railway is the backbone of the comprehensive transportation system, is an important support for constructing a modern economic system, and plays an important role in promoting the economic society of China and the good and rapid development. The ballastless track has the advantages of good stability, less line maintenance and repair workload, good durability, high comprehensive economic benefit and the like, and has become the development trend of high-speed railways in various countries in the world.
The double-block ballastless track consists of steel rails, fasteners, prefabricated double-block sleepers, a current runner bed board and a base board, wherein the concrete structure of the track bed board has the congenital defects of long and continuous strips, combination of cast-in-situ and prefabrication and the like, and is influenced by environmental conditions, structural forms, material properties, construction processes and the like, cracks can appear in a large number after concrete pouring, including transverse through cracks, splayed cracks around the sleepers and the like, so that the construction quality is seriously influenced, the operation and maintenance workload is increased, and the durability of the ballastless track structure is reduced.
At present, more engineering is to improve the cracking resistance of the concrete of the ballast bed plate by one or more measures of selecting raw materials, optimizing cooperation, improving construction process and the like, but the problem of cracking of the concrete of the ballast bed cannot be completely solved due to the lack of accurate evaluation of the cracking risk and influencing factors of the concrete of the ballast bed plate. CN110184864a discloses a method for reducing the crack rate of a track slab of a double-block ballastless track, which focuses on construction engineering, but does not relate to the risk assessment of the crack of the track slab, and is difficult to accurately control the crack resistance of concrete. CN108149526a and CN103603236a both disclose a method for controlling cracks of a slab of a double-block ballastless track, but only the process measures are controlled from the concrete pouring process, and no concrete cracks are analyzed and controlled from the source.
Therefore, for cast-in-place concrete of the ballast-free track bed slab, a method for controlling concrete cracks of the ballast-free track bed slab, which integrates crack resistance design, material selection, construction measure improvement and crack resistance effect monitoring, is needed, and is very important for improving engineering quality.
Disclosure of Invention
The embodiment of the application provides a ballastless track slab concrete anti-cracking control method, which can effectively control slab concrete cracks.
According to one aspect of the application, there is provided a ballastless track slab concrete crack control method comprising the steps of:
(1) According to a concrete cracking risk assessment model considering multi-factor interaction, calculating concrete cracking risk coefficients of the ballastless track bed board under different working conditions according to different concrete performance indexes by adopting a numerical simulation method based on finite element analysis:wherein sigma (t) is the maximum tensile stress of concrete at time t, f t (t) is the tensile strength of the concrete at the moment t; if eta<0.7, the cracking risk is low, and the subsequent steps are executed;
(2) Selecting concrete with performance index corresponding to eta <0.7, wherein the concrete contains an anticracking agent accounting for 5-10% of the weight of the concrete cementing material;
(3) Pouring concrete into a mould at 5-28 ℃, pouring the concrete between prefabricated sleeper blocks back and forth according to a Z-shaped route to uniformly distribute the concrete, wherein the height of a discharge hole is not more than 0.5m; vibrating by adopting an inserted vibrating rod;
(4) Pouring, paving and leveling, spraying a water evaporation inhibitor, and then performing first plastering; after the initial setting of the concrete surface, performing secondary plastering, and then spraying a water evaporation inhibitor again; covering a plastic film and a heat preservation material for maintenance for at least 14 days;
(5) The temperature and the strain of the center of the track bed plate, the periphery of the prefabricated sleeper block, the upper surface of the track bed plate and the side surface of the track bed plate are monitored in real time, and maintenance measures are adjusted according to the monitoring results.
Preferably, in any of the embodiments,
the anticracking agent comprises the following components in percentage by weight: 50-80% of expansion component, 20-40% of anhydrite and 5-10% of ground slag powder, wherein the expansion component comprises one or a combination of a plurality of calcium oxide expansion clinker, calcium sulfoaluminate expansion clinker and magnesium oxide expansion clinker.
Preferably, in any of the embodiments,
the mold entering temperature of the concrete is as follows: the temperature is not more than 28 ℃ in summer, 18-25 ℃ in spring and autumn and 5-18 ℃ in winter.
Preferably, in any of the embodiments,
the dosage of the water evaporation inhibitor is 100-300 g/m 2 And atomizing the diluent by using spraying equipment, and uniformly spraying the atomized diluent on the surface of the concrete.
Preferably, in any of the embodiments,
the heat dissipation coefficient of the concrete surface after the heat insulation material is covered is not more than 30 kJ/(m) 2 ·h·℃)。
Preferably, in any of the embodiments,
the temperature is monitored by a temperature sensor, the precision of the temperature sensor is 0.1 ℃, and the measuring points comprise the temperature of the height center of the track bed board along the length direction of the track, the surrounding temperature of the prefabricated sleeper blocks, the temperatures of the upper surface and the side surface of the track bed board and the ambient temperature.
Preferably, in any of the embodiments,
the strain is monitored by a strain sensor, such as a vibrating wire strain gauge with an accuracy of 0.01 mu epsilon, and the measuring points should include the strain of the height center of the track bed along the length direction of the track, the strain of the height center along the thickness direction, and the strain around the prefabricated sleeper.
Preferably, in any of the embodiments,
the data acquisition frequency of the real-time monitoring is 0.5-2 hours once.
The ballastless track slab concrete crack prevention control method provided by the embodiment of the application can effectively control the slab concrete crack.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following discussion will discuss the embodiments or the drawings required in the description of the prior art, and it is obvious that the technical solutions described in connection with the drawings are only some embodiments of the present application, and that other embodiments and drawings thereof can be obtained according to the embodiments shown in the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a flowchart of a ballastless track slab concrete anti-cracking control method according to an embodiment of the present application.
Figure 2 shows the cracking risk coefficient of the concrete of the road bed under different working conditions.
Fig. 3 shows the results of monitoring the strain in the thickness direction of the concrete center of the example and comparative example track bed boards.
Detailed Description
The following description of the embodiments of the present application will be made in detail with reference to the accompanying drawings, wherein it is apparent that the embodiments described are only some, but not all embodiments of the present application. All other embodiments, which can be made by a person of ordinary skill in the art without the need for inventive faculty, are within the scope of the application, based on the embodiments described in the present application.
The embodiment of the application provides a concrete crack control method for a ballastless track slab, which can effectively control concrete cracks.
According to one aspect of the application, there is provided a ballastless track slab concrete crack control method comprising the steps of:
(1) According to a concrete cracking risk assessment model considering multi-factor interaction, calculating concrete cracking risk coefficients of the ballastless track bed board under different working conditions according to different concrete performance indexes by adopting a numerical simulation method based on finite element analysis:wherein sigma (t) is the maximum tensile stress of concrete at time t, f t (t) is the tensile strength of the concrete at the moment t; if eta<0.7, the risk of cracking is low,executing the subsequent steps;
(2) Selecting concrete with performance index corresponding to eta <0.7, wherein the concrete contains an anticracking agent accounting for 5-10% of the weight of the concrete cementing material;
(3) Pouring concrete into a mould at 5-28 ℃, pouring the concrete between prefabricated sleeper blocks back and forth according to a Z-shaped route to uniformly distribute the concrete, wherein the height of a discharge hole is not more than 0.5m; vibrating by adopting an inserted vibrating rod;
(4) Pouring, paving and leveling, spraying a water evaporation inhibitor, and then performing first plastering; after the initial setting of the concrete surface, performing secondary plastering, and then spraying a water evaporation inhibitor again; covering a plastic film and a heat preservation material for maintenance for at least 14 days;
(5) The temperature and the strain of the center of the track bed plate, the periphery of the prefabricated sleeper block, the upper surface of the track bed plate and the side surface of the track bed plate are monitored in real time, and maintenance measures are adjusted according to the monitoring results.
In this way, in the concrete anti-cracking control method for the ballastless track slab of the embodiment of the application, a numerical simulation method based on finite element analysis is adopted to perform system simulation calculation on different concrete performance indexes according to a concrete cracking risk assessment model, and the cracking risk (corresponding to a concrete cracking coefficient eta) of the concrete in the system is assessed. If η <0.7, it is indicated that the risk of cracking of the concrete in the system is low in the simulated evaluation, so that the subsequent steps (2) - (5) can be continued; otherwise, the concrete cracking risk in the system is higher, and the concrete performance index may need to be adjusted (for example, different concrete material proportions may be selected) to simulate and calculate the concrete cracking risk in the adjusted system again.
The cracking resistance agent is added into the concrete to compensate the shrinkage of the concrete so as to reduce the cracking risk, and a series of measures are taken to reduce the cracking risk and ensure the construction quality. For example, by the action of the anti-cracking agent, the concrete can generate certain expansion deformation at the early stage of hardening, so that the shrinkage of the concrete is effectively compensated at the later temperature drop stage, the overall anti-cracking capacity of the concrete is improved, and the cracking risk is reduced.
Wherein, unlike the straight line pouring mode in the prior art, the embodiment of the application pours back and forth according to the Z-shaped route, so that the cloth can be more uniform.
In addition, the height of the discharge hole for concrete pouring is not more than 0.5m, so that the segregation of concrete can be effectively prevented, and the pouring uniformity is improved.
It should be emphasized here that the secondary finishing process is an important measure for improving the construction quality, and that the corresponding spraying of the water evaporation inhibitor after each finishing can further maintain the stability of the concrete system and reduce the risk of cracking.
In addition, the concrete is covered with a plastic film and a heat insulation material for maintenance, and the concrete is also an important measure for reducing the cracking risk and ensuring the construction quality.
The ballastless track slab concrete crack prevention control method provided by the embodiment of the application can effectively control the slab concrete crack.
Preferably, in any embodiment, the anti-cracking agent comprises, in weight percent: 50-80% of expansion component, 20-40% of anhydrite and 5-10% of ground slag powder, wherein the expansion component comprises one or a combination of a plurality of calcium oxide expansion clinker, calcium sulfoaluminate expansion clinker and magnesium oxide expansion clinker.
Preferably, in any embodiment, the in-mold temperature of the concrete is: the temperature is not more than 28 ℃ in summer, 18-25 ℃ in spring and autumn and 5-18 ℃ in winter.
Alternatively, in one embodiment, the temperature control means may include cooling with low temperature water, mix water plus ice, concrete aggregate.
Preferably, in any embodiment, the moisture evaporation inhibitor is used in an amount of 100 to 300g/m 2 And atomizing the diluent by using spraying equipment, and uniformly spraying the atomized diluent on the surface of the concrete.
Preferably, in any embodiment, after the heat insulation material is covered, the surface heat dissipation coefficient of the concrete is not more than 30 kJ/(m) 2 ·h·℃)。
Preferably, in any embodiment, the temperature is monitored by a temperature sensor with an accuracy of 0.1 ℃, and the measuring points should include the temperature of the height center of the track bed along the length direction of the track (wherein the temperature sensor is located at the center position of the track bed along the height direction and can extend along the length direction of the track to monitor the temperature in that direction), the temperature around the prefabricated pillow, the temperature of the upper surface and the side surface of the track bed, and the ambient temperature.
Preferably, in any embodiment, the strain is monitored by a strain sensor, such as a vibrating wire strain gauge, with an accuracy of 0.01 μ, the measurement points should include strain in the track slab height center along the track length direction (where the strain sensor is located at the track slab center in the height direction and can extend along the track length direction to monitor strain/deformation in that direction), strain in the thickness direction in the height center (where the strain sensor is located at the track slab center in the height direction and can extend along the track thickness (vertical) direction to monitor strain/deformation in that direction), strain around the preformed sleeper.
Optionally, in one embodiment, if the temperature of the concrete is abnormal (for example, the temperature difference between the surface and the inner side of the concrete is excessively large) in the step (5), the heat preservation maintenance measure can be enhanced according to the monitoring result. For example, when the temperature difference between the inside and the outside of the concrete is found to be too large based on the monitoring results of the temperature and the strain, one or more layers of heat insulation materials can be added for covering and curing.
Preferably, in any embodiment, the data acquisition frequency of the real-time monitoring may be 0.5 to 2 hours.
Optionally, in one embodiment, the monitoring result in the step (5) is substituted into the concrete cracking risk assessment model in the step (1) to perform inversion calculation so as to evaluate the concrete cracking resistance effect in real time. In practice, by monitoring the temperature and strain of key parts of the track bed slab, the actual cracking value of the track bed slab concrete can be calculated in an inversion way, thereby determining the cracking risk (high, medium or low) of the concrete and evaluating the cracking effect of the concrete.
Optionally, in an embodiment, the maintenance measure is adjusted and the fracture control solution is perfected according to the result of the inversion calculation.
Optionally, in one embodiment, the result of the inversion calculation shows that the cracking risk of the concrete is low, and the inversion calculation result is consistent with the expected result because the concrete performance index is selected according to the low cracking risk condition of η <0.7 in the step (1), which indicates that the cracking effect of the concrete is better.
Optionally, in an embodiment, in displaying the concrete cracking risk according to the result of the inversion calculation, since the concrete performance index is selected according to the low cracking risk condition of η <0.7 in the step (1), the inversion calculation result is inconsistent with the expectation, which indicates that the cracking effect of the concrete is poor, and the process needs to be adjusted.
Optionally, in one embodiment, the concrete cracking risk assessment model considering multi-factor interactions is a concrete cracking risk assessment model under multi-field coupling.
Optionally, in one embodiment, the concrete cracking risk assessment model comprises the following influencing factors or combinations thereof: hydration, temperature, humidity, concrete deformation/restraint.
Optionally, in one embodiment, the concrete cracking risk assessment model described in step (1) is implemented by:
establishing a finite element model of the ballastless track structure,
determining the thermal parameter boundary condition of the concrete according to the actual required working condition,
a hydration-temperature-humidity coupling (composite) model control equation is established,
the temperature field distribution and history (i.e., temperature dynamics) of the structure are solved using a finite element method.
In the prior art, only end point parameter results (such as mold entering temperature) are usually considered when considering the concrete cracking risk, but the detailed influence of temperature change on concrete cracking in the whole thermodynamic process is not fully considered, so that the concrete cracking risk actually occurring in the construction process is often higher than expected. In contrast, in the technical scheme of the application, the dynamic detailed information such as the temperature condition, the temperature distribution condition and the like of each time period which are mutually separated is considered, and the (local) refining treatment can be carried out according to the needs, so that the simulation evaluation of the concrete cracking risk is more accurate and reliable.
Optionally, in one embodiment, the concrete cracking risk assessment model is established by a hydration-temperature-humidity coupled model control equation, an energy conservation equation, and a temperature deformation calculation.
Optionally, in one embodiment, calculating the concrete cracking risk coefficient in step (1) may include the steps of:
the temperature deformation (e.g. low temperature shrinkage) and chemical deformation (e.g. shrinkage due to chemical reaction) of the concrete are calculated,
calculating shrinkage stress generated by the concrete structure by using the calculation results of temperature and shrinkage deformation, structural constraint conditions (such as the cast-in-situ track slab is constrained by the poured concrete) and creep functions,
and calculating a concrete cracking risk coefficient according to the shrinkage stress of the concrete structure.
In this way, considering various factors which can influence structural deformation (such as expansion and shrinkage deformation caused by chemical or temperature factors), the peripheral stress condition of the concrete is comprehensively evaluated so as to obtain an accurate and reliable concrete cracking risk coefficient.
Optionally, in one embodiment, the ballastless track is a dual block ballastless track.
From the actual on-site observation results, after the concrete pouring is completed for 3 months, the track bed plate adopting the method has no cracks, and the model inversion calculation results show that: the cracking risk coefficients of the center point and the surface of the ballast bed plate are smaller than 0.7, the ballast bed plate is basically free from cracking, and the cracking effect is good.
Comparative example
The comparative example and the example belong to the same engineering project, and one section of track slab can be selected as the application of the comparative example. The concrete mix ratios (kg/m) of the comparative examples and examples 3 ) The following table shows that the raw materials of the concrete are the same in specification and performance, and the steps and construction process measures are basically the same, except that the concrete is mixed in proportion, i.e. the comparative example is not doped with anti-cracking agent.
| Cement and its preparation method | Fly ash | Sand and sand | Broken stone | Anticracking agent | Water and its preparation method | Water reducing agent | Air entraining agent | |
| Examples | 300 | 68 | 710 | 1110 | 32 | 143 | 4 | 1.18 |
| Comparative example | 300 | 100 | 710 | 1110 | 0 | 143 | 4 | 1.18 |
The comparative example carries out real-time online monitoring of temperature and strain, carries out inversion calculation of cracking risk according to the monitoring result, and the calculation result shows that the cracking analysis of the central point is 1.05 and the cracking risk is higher. Fig. 2 shows the evaluation calculation results of the cracking risk coefficients of the concrete of the road bed board under different working conditions, and the concrete in-mold temperature of 32 ℃, the in-mold temperature of 28 ℃ and the center point cracking risk coefficient of the cracking agent under the three working conditions of 28 ℃ are evaluated and calculated by adopting a road bed board concrete cracking risk evaluation model, and according to the graph, when the concrete in-mold temperature is 32 ℃, the maximum cracking risk coefficient of the center of the road bed board is 1.26, and the cracking is inevitable; when the temperature of the die is reduced to 28 ℃ by adopting a temperature control measure, the cracking risk is reduced to a certain extent, but the maximum cracking risk coefficient is 1.07 and is still greater than 1.0, so that the problem of cracking of the road bed board cannot be completely solved; when the mold temperature is 28 ℃, adopting measures of adding an anticracking agent into concrete to compensate shrinkage, wherein the maximum cracking risk coefficient is 0.65 and is smaller than the critical value of 0.7, and basically no cracking occurs. The cracking risk assessment result shows that under the current working condition, the problem of the cracking of the track bed board cannot be completely solved by only reducing the mold-entering temperature of the concrete, and the track bed board concrete cannot crack basically by adopting the methods of controlling the mold-entering temperature and doping the cracking inhibitor.
FIG. 3 shows the results of monitoring strain in the center thickness direction of the concrete of the track bed slabs of the examples and the comparative examples, and it is clear from the graph that the maximum deformation generated by the expansion of the concrete of the examples is 423.9 [ mu ] epsilon, and the expansion per unit temperature generated in the temperature raising stage is 25.6 [ mu ] epsilon/DEGC; whereas the maximum expansion deformation of the concrete of the comparative example was 208.8. Mu.. Epsilon., the unit temperature rise at the temperature rise stage resulted in an expansion of 12.7. Mu.. Epsilon./DEG C. Compared with the comparative example, the monitoring result shows that the track bed concrete in the embodiment generates larger expansion deformation at the early stage of hardening, and can effectively compensate the shrinkage generated by the concrete at the later temperature drop stage, thereby improving the crack resistance of the track bed concrete.
From the field application effects of the examples and the comparative examples, the track bed plate in the examples has no cracks after 3 months of concrete pouring, while the comparative examples have a plurality of transverse cracks and splay cracks, which shows that: the method can effectively control the generation of concrete cracks of the road bed board, and improves the engineering quality.
Fig. 1 is a flowchart of a ballastless track slab concrete anti-cracking control method according to an embodiment of the present application. The embodiment shown in fig. 1 shows a concrete anti-cracking control method for a ballastless track bed board, which comprises the following steps:
110: according to a concrete cracking risk assessment model considering multi-factor interaction, calculating concrete cracking risk coefficients of the ballastless track bed board under different working conditions according to different concrete performance indexes by adopting a numerical simulation method based on finite element analysis:wherein sigma (t) is the maximum tensile stress of concrete at time t, f t (t) is the tensile strength of the concrete at the moment t; if eta<0.7, the cracking risk is low, and the subsequent steps are executed;
120: selecting concrete with performance index corresponding to eta <0.7, wherein the concrete contains an anticracking agent accounting for 5-10% of the weight of the concrete cementing material;
130: pouring concrete into a mould at 5-28 ℃, pouring the concrete between prefabricated sleeper blocks back and forth according to a Z-shaped route to uniformly distribute the concrete, wherein the height of a discharge hole is not more than 0.5m; vibrating by adopting an inserted vibrating rod;
140: pouring, paving and leveling, spraying a water evaporation inhibitor, and then performing first plastering; after the initial setting of the concrete surface, performing secondary plastering, and then spraying a water evaporation inhibitor again; covering a plastic film and a heat preservation material for maintenance for at least 14 days;
150: the temperature and the strain of the center of the track bed plate, the periphery of the prefabricated sleeper block, the upper surface of the track bed plate and the side surface of the track bed plate are monitored in real time, and maintenance measures are adjusted according to the monitoring results.
The ballastless track slab concrete crack prevention control method provided by the embodiment of the application can effectively control the slab concrete crack.
It is noted that relational terms such as first and second, and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the statement "comprises one" does not exclude that an additional identical element is present in a process, method, article or apparatus that comprises the element.
In the description of multiple elements herein, a plurality of juxtaposed features connected by "and/or" is meant to encompass one or more (or one or more) of these juxtaposed features. For example, the meaning of "a first element and/or a second element" is: one or more of the first element and the second element, i.e., only the first element, or only the second element, or both the first element and the second element (both present).
The various embodiments provided in this application may be combined with each other as desired, e.g., features of any two, three or more embodiments may be combined with each other to form new embodiments of the application, which are also within the scope of the application unless stated otherwise or contradicted by skill.
The foregoing description of the exemplary embodiments of the application is not intended to limit the application to the precise form disclosed, and any modifications, equivalents, and variations which fall within the spirit and scope of the application are intended to be included in the scope of the application.
Claims (8)
1. The ballastless track slab concrete anti-cracking control method is characterized by comprising the following steps of:
(1) According to a concrete cracking risk assessment model considering multi-factor interaction, calculating concrete cracking risk coefficients of the ballastless track bed board under different working conditions according to different concrete performance indexes by adopting a numerical simulation method based on finite element analysis:wherein sigma (t) is the maximum tensile stress of concrete at time t, f t (t) is the tensile strength of the concrete at the moment t; if eta<0.7, the cracking risk is low, and the subsequent steps are executed;
(2) Selecting concrete with performance index corresponding to eta <0.7, wherein the concrete contains an anticracking agent accounting for 5-10% of the weight of the concrete cementing material;
(3) Pouring concrete into a mould at 5-28 ℃, pouring the concrete between prefabricated sleeper blocks back and forth according to a Z-shaped route to uniformly distribute the concrete, wherein the height of a discharge hole is not more than 0.5m; vibrating by adopting an inserted vibrating rod;
(4) Pouring, paving and leveling, spraying a water evaporation inhibitor, and then performing first plastering; after the initial setting of the concrete surface, performing secondary plastering, and then spraying a water evaporation inhibitor again; covering a plastic film and a heat preservation material for maintenance for at least 14 days;
(5) The temperature and the strain of the center of the track bed plate, the periphery of the prefabricated sleeper block, the upper surface of the track bed plate and the side surface of the track bed plate are monitored in real time, and maintenance measures are adjusted according to the monitoring results.
2. The ballastless track bed concrete anti-cracking control method of claim 1, wherein,
the anticracking agent comprises the following components in percentage by weight: 50-80% of expansion component, 20-40% of anhydrite and 5-10% of ground slag powder, wherein the expansion component comprises one or a combination of a plurality of calcium oxide expansion clinker, calcium sulfoaluminate expansion clinker and magnesium oxide expansion clinker.
3. The ballastless track bed concrete anti-cracking control method of claim 1, wherein,
the mold entering temperature of the concrete is as follows: the temperature is not more than 28 ℃ in summer, 18-25 ℃ in spring and autumn and 5-18 ℃ in winter.
4. The ballastless track bed concrete anti-cracking control method of claim 1, wherein,
the dosage of the water evaporation inhibitor is 100-300 g/m 2 And atomizing the diluent by using spraying equipment, and uniformly spraying the atomized diluent on the surface of the concrete.
5. The ballastless track bed concrete anti-cracking control method of claim 1, wherein,
the heat dissipation coefficient of the concrete surface after the heat insulation material is covered is not more than 30 kJ/(m) 2 ·h·℃)。
6. The ballastless track bed concrete anti-cracking control method of claim 1, wherein,
the temperature is monitored by a temperature sensor, the precision of the temperature sensor is 0.1 ℃, and the measuring points comprise the temperature of the height center of the track bed board along the length direction of the track, the surrounding temperature of the prefabricated sleeper blocks, the temperatures of the upper surface and the side surface of the track bed board and the ambient temperature.
7. The ballastless track bed concrete anti-cracking control method of claim 1, wherein,
the strain is monitored by a strain sensor, such as a vibrating wire strain gauge with an accuracy of 0.01 mu epsilon, and the measuring points should include the strain of the height center of the track bed along the length direction of the track, the strain of the height center along the thickness direction, and the strain around the prefabricated sleeper.
8. The ballastless track bed concrete anti-cracking control method of claim 1, wherein,
the data acquisition frequency of the real-time monitoring is 0.5-2 hours once.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117556521A (en) * | 2024-01-09 | 2024-02-13 | 深圳大学 | Digital twinning-based high-altitude tunnel lining cracking risk monitoring method and system |
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