Long wall concrete structure crack control method based on limited horizontal shrinkage strain
By monitoring and calculating the limited horizontal shrinkage strain of the long wall concrete structure, combined with the expanded concrete test, the expansion agent dosage of the gradient structure is determined, and vertical gradient concrete construction is carried out, which solves the problems of excessive expansion agent dosage and low crack control efficiency in the prior art, and achieves efficient concrete crack control effect.
Patent Information
- Application Number
- CN202510019354.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-07
- Publication Date
- 2025-06-06
AI Technical Summary
The prior art cannot accurately quantify the constraint stress of the long wall structure of concrete, resulting in excessive expansion agent usage, increasing project costs and affecting crack control efficiency.
By obtaining the size of the long wall concrete structure, making small model sections of the same proportion, regularly monitoring their horizontal shrinkage strain, calculating the limiting horizontal shrinkage strain, and combining the limited expansion rate test of the expanded concrete, the expanded concrete mix ratio of each gradient structure is determined, and vertical gradient concrete construction is carried out.
It effectively reduces the harmful tensile stress in the confined area of the poured concrete structure, ensures the concrete compensation and shrinkage effect while reducing the amount of expansion agent, reduces the crack resistance cost, and optimizes crack control work.
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Figure CN120105520A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of water transport and water conservancy engineering, and in particular to a crack control method for a long wall concrete structure based on limiting horizontal shrinkage strain. Background Art
[0002] The restraint stress of concrete refers to the internal stress that occurs when concrete is subjected to external loading due to the limitations of surrounding constraints. In concrete structures, the existence of restraint stress can improve the stress performance of concrete, reduce cracks and deformation of concrete, and improve the overall stability of the structure.
[0003] In the field of concrete engineering, especially long wall concrete structures, adding expansion agents has become an important technical means to improve concrete performance and inhibit concrete structure cracking. As an admixture, expansion agents can produce a small volume expansion during the hydration process of concrete. This expansion effect can effectively compensate for the self-shrinkage of concrete due to changes in temperature and humidity, thereby greatly reducing the restraining tensile stress of the external old structure on the newly poured concrete, and effectively avoiding the formation of concrete cracks.
[0004] At present, both domestic and foreign normative documents or works believe that the restraint stress of concrete will become smaller and smaller along the foundation height direction. However, factors such as concrete foundation mix ratio, concrete strength grade, source of concrete raw materials, climate characteristics, etc. will affect the stress distribution of concrete after hardening. For different concrete long wall structures, the restraint stress cannot be accurately quantified by relying solely on theoretical calculations. Therefore, the dosage of expansion agent calculated based on theoretical calculations will cause waste of materials, increase the overall cost of the project, and affect the economy of the project. Summary of the invention
[0005] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a crack control method for long wall concrete structure based on limiting horizontal shrinkage strain, which can ensure that the concrete has a shrinkage compensation effect while effectively reducing the overall dosage of the expansive agent, thereby improving the crack control efficiency of the long wall concrete.
[0006] According to an embodiment of the present invention, a crack control method for a long wall concrete structure based on limited horizontal shrinkage strain comprises: S1: obtaining the size of a long wall concrete structure, making a small concrete model segment of the same scale according to the size of the long wall concrete structure, and carrying out regular strain monitoring on the small concrete model segment of the same scale to obtain the horizontal shrinkage strain of each gradient structure at a predetermined elevation position in the small concrete model segment of the same scale; S2: calculating and obtaining the limited horizontal shrinkage strain of each gradient structure at a predetermined elevation position in the small concrete model segment of the same scale according to the horizontal shrinkage strain of each gradient structure at an elevation position in the small concrete model segment of the same scale; S3: carrying out a limited expansion rate test of expansive concrete; S4: determining the expansive concrete mix ratio of each gradient structure according to the result of the limited expansion rate test of expansive concrete and the limited horizontal shrinkage strain of each gradient structure at a predetermined elevation position in the small concrete model segment of the same scale; S5: carrying out vertical gradient concrete construction of the long wall concrete structure according to the mix ratio of each gradient expansive concrete.
[0007] The crack control method for a long wall concrete structure based on limited horizontal shrinkage strain according to an embodiment of the present invention has at least the following beneficial effects: by defining and calculating the limited horizontal shrinkage strain of the long wall concrete structure at different gradient positions, it is further ensured that the expansion rate of the vertical expansion gradient concrete is adapted to the limited horizontal shrinkage strain at each gradient position; during the hydration process of the concrete, the expansion performance of the concrete is controlled so that the concrete gradually adapts to the degree of external constraints, thereby forming a structure with different expansion performance gradients in the constraint area of the long wall concrete structure by pouring gradient expansion concrete, and thereby effectively reducing the harmful tensile stress in the constraint area of the poured concrete structure, ensuring that the concrete has the same compensation shrinkage effect while effectively reducing the overall dosage of the expansion agent, reducing the anti-cracking cost of the structure, and optimizing the crack control work of the long wall concrete from a technical and economic level.
[0008] According to some embodiments of the present invention, in S1, regular strain monitoring of the same-scale concrete small model segment includes: obtaining the vertical expansion gradient number according to the same-scale concrete small model segment; obtaining the vertical expansion interval according to the vertical expansion gradient number; arranging strain gauges at the top structure elevation of the same-scale concrete small model segment; and arranging strain gauges at the elevation of each gradient structure in the same-scale concrete small model segment according to the vertical expansion interval.
[0009] According to some embodiments of the present invention, the strain gauge is arranged at the geometric center of the top structure, and the strain gauge is arranged at the geometric center of each gradient structure.
[0010] According to some embodiments of the present invention, at least two gradient structures are provided.
[0011] According to some embodiments of the present invention, in S2, the calculation formula of the limited horizontal shrinkage strain at the predetermined elevation position of each gradient structure is:
[0012] M=ZX n ;
[0013] Among them, M is the horizontal shrinkage strain value of each gradient structure, Z is the horizontal shrinkage strain value at the top elevation, X n It is the horizontal shrinkage strain value of the nth level gradient structure starting from the structural base.
[0014] According to some embodiments of the present invention, in S3, carrying out a test on the limited expansion rate of expansive concrete includes: presetting multiple concrete expansive agent dosages; respectively preparing concrete according to different expansive agent dosages, and casting to form multiple concrete specimens with different expansive agent dosages; presetting multiple concrete curing days, and curing multiple concrete test blocks according to the preset concrete curing days; and obtaining the limited expansion rates of concrete specimens at different expansive agent dosages in the preset concrete curing days.
[0015] According to some embodiments of the present invention, the preset concrete curing days include at least the 7th day and the 28th day after pouring.
[0016] According to some embodiments of the present invention, the preset range of the concrete expansion agent dosage is 0 to 10%.
[0017] According to some embodiments of the present invention, in S4, determining the expansive concrete mix ratio of each gradient structure includes: obtaining the limited horizontal shrinkage strain value of each gradient structure; obtaining the limited expansion rate of concrete specimens at different concrete curing days under different expansive agent dosages; sorting the limited horizontal shrinkage strain values of each gradient structure and the limited expansion rate of concrete specimens at different concrete curing days under each expansive agent dosage; when the limited expansion rate of the concrete specimens at the same expansive agent dosage under all concrete curing days is greater than the limited horizontal shrinkage strain value of the gradient structure, determining the dosage of the expansive agent in the corresponding gradient structure.
[0018] According to some embodiments of the present invention, in S5, the vertical gradient concrete construction includes: S5.1: tying steel bars and setting up concrete formwork support; S5.2: roughening the base layer and cleaning the foundation bin surface; S5.3: pouring the first gradient compensating shrinkage concrete according to the thickness and mix ratio of the gradient structure; S5.4: vibrating the first gradient compensating shrinkage concrete; S5.5: repeating S5.3 and S5.4 until the Nth gradient compensating shrinkage concrete is poured and vibrated; S5.6: pouring ordinary concrete of the same grade to the designed elevation and vibrating the surface.
[0019] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The present invention is further described below in conjunction with the accompanying drawings and embodiments:
[0021] Figure 1 1 is a schematic diagram of a process of a long wall concrete structure crack control method based on limiting horizontal shrinkage strain according to an embodiment of the present invention;
[0022] Figure 2 It is a schematic diagram of the process of vertical gradient concrete construction in the crack control method of a long wall concrete structure based on limiting horizontal shrinkage strain in an embodiment of the present invention;
[0023] Figure 3 is a schematic diagram of a long wall concrete structure after pouring in a specific embodiment of the present invention;
[0024] Figure 4 It is a schematic diagram of the state of free deformation of the long wall concrete structure in the case of no foundation constraint in a specific embodiment of the present invention;
[0025] Figure 5 is a schematic diagram of the deformation state of the long wall concrete structure under the condition of foundation constraint in a specific embodiment of the present invention;
[0026] Figure 6 It is a schematic diagram of the external restraint stress of the long wall concrete structure under the condition of foundation restraint in a specific embodiment of the present invention;
[0027] Figure 7 It is a schematic diagram of the layered pouring of long wall concrete in a specific embodiment of the present invention. DETAILED DESCRIPTION
[0028] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.
[0029] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.
[0030] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.
[0031] refer to Figures 1 to 7 A crack control method for a long wall concrete structure based on limiting horizontal shrinkage strain according to an embodiment of the present invention is described.
[0032] like Figure 1 and Figure 2 As shown, according to an embodiment of the present invention, a method for controlling cracks in a long wall concrete structure based on limiting horizontal shrinkage strain comprises:
[0033] S1: Obtain the size of the long wall concrete structure, make a small concrete model segment of the same scale according to the size of the long wall concrete structure, and conduct regular strain monitoring on the small concrete model segment of the same scale to obtain the horizontal shrinkage strain at the predetermined elevation position of each gradient structure in the small concrete model segment of the same scale;
[0034] S2: according to the horizontal shrinkage strain at each elevation position of the gradient structure in the small concrete model segment of the same scale, the limited horizontal shrinkage strain at the predetermined elevation position of each gradient structure in the small concrete model segment of the same scale is calculated;
[0035] S3: Conduct a test on the limited expansion rate of expansive concrete;
[0036] S4: Determine the expansive concrete mix ratio of each gradient structure according to the results of the limited expansion rate test of expansive concrete and the limited horizontal shrinkage strain at the predetermined elevation position of each gradient structure in the small model section of the same proportion concrete;
[0037] S5: Carry out vertical gradient concrete construction of long wall concrete structure according to the mix ratio of each gradient expansion concrete.
[0038] Therefore, by defining and calculating the restricted horizontal shrinkage strain of the long wall concrete structure at different gradient positions, it is further ensured that the expansion rate of the vertical expansion gradient concrete is adapted to the restricted horizontal shrinkage strain at each gradient position. During the hydration process of the concrete, the expansion performance of the concrete is controlled to gradually adapt to the degree of external constraints, so that a structure with different expansion performance gradients is formed in the constraint area of the long wall concrete structure by pouring gradient expansion concrete, and thereby effectively reducing the harmful tensile stress in the constraint area of the poured concrete structure, ensuring that the concrete has the same compensating shrinkage effect while effectively reducing the overall dosage of the expansive agent, reducing the anti-cracking cost of the structure, and optimizing the crack control work of the long wall concrete from a technical and economic level.
[0039] In S1, regular strain monitoring is carried out on the small concrete model section of the same scale, including: obtaining the vertical expansion gradient number according to the small concrete model section of the same scale, obtaining the vertical expansion interval according to the vertical expansion gradient number, arranging strain gauges at the top structure elevation of the small concrete model section of the same scale, and arranging strain gauges at the elevation of each gradient structure in the small concrete model section of the same scale according to the vertical expansion interval.
[0040] The strain gauge is arranged at the geometric center of the top structure, and the strain gauge is arranged at the geometric center of each gradient structure.
[0041] Wherein, at least two gradient structures are provided.
[0042] Among them, the maximum thickness of the gradient structure is 0.1l, where l is the longest side dimension of the small concrete model segment of the same scale. It should be noted that, mapped to the long wall concrete structure, the maximum thickness of the gradient structure is 0.1L, where L is the longest side dimension of the long wall concrete structure. Since the thickness of the strong constraint zone of the long wall concrete structure is at 0.2 times the height of the maximum dimension of the structure, but there is still constraint stress below 0.45L, the total thickness of the gradient layer can be further extended to 0.45L, or even larger, but cannot be less than 0.2L, that is, the thickness range of the gradient structure is greater than 0.2L.
[0043] In S2, the calculation formula of the limiting horizontal contraction strain is:
[0044] M=ZX n ;
[0045] Among them, M is the horizontal shrinkage strain value of each gradient structure, Z is the horizontal shrinkage strain value at the top elevation, X n is the horizontal shrinkage strain value of the nth gradient structure from the base of the structure. It should be noted that the strain at the elevation of the top gradient structure is regarded as the free horizontal shrinkage strain of the structure, X n The horizontal shrinkage strain values of the top gradient structure are not included.
[0046] In S3, conducting a test on the limited expansion rate of expansive concrete includes: presetting multiple concrete expansive agent dosages, mixing concrete according to different expansive agent dosages, and casting to form multiple concrete specimens with different expansive agent dosages, presetting multiple concrete curing days, curing multiple concrete test blocks according to the preset concrete curing days, and obtaining the limited expansion rates of concrete specimens at different expansive agent dosages during the preset concrete curing days.
[0047] It should be noted that the concrete curing days at least include the 7th day and the 28th day after pouring, and the preset multiple concrete expansion agent dosages are all in the range of 0 to 10%.
[0048] In S4, determining the expansive concrete mix ratio of each gradient structure includes: obtaining the limited horizontal shrinkage strain value of each gradient structure, obtaining the limited expansion rate of concrete specimens at different concrete curing days under different expansive agent dosages, sorting the limited horizontal shrinkage strain value of each gradient structure and the limited expansion rate of concrete specimens at different concrete curing days under each expansive agent dosage, and when the limited expansion rate of the concrete specimens at the same expansive agent dosage at all concrete curing days is greater than the limited horizontal shrinkage strain value of the gradient structure, determining the dosage of the expansive agent in the corresponding gradient structure.
[0049] In S5, the vertical gradient concrete construction includes tying steel bars, setting up concrete formwork support, roughening the base, cleaning the foundation silo, pouring the first gradient shrinkage compensating concrete according to the thickness and mix ratio of the gradient structure, vibrating the first gradient shrinkage compensating concrete, repeating the pouring and vibrating until the Nth gradient shrinkage compensating concrete is poured and vibrated, pouring the same grade of ordinary concrete to the design elevation and vibrating the surface. Among them, after pouring the same grade of ordinary concrete to the design elevation, this part of the structure is the top structure, and the strain at the top structure elevation is regarded as the free horizontal shrinkage strain of the structure.
[0050] It should be noted that the British standard CI RIA C766 believes that the long wall constraint on the rigid foundation can be calculated according to the formula. The domestic standard "Technical Specification for Temperature Crack Control of Mass Concrete in Water Transport Engineering" (JTS / T 202-1-2022) believes that the thickness of the strong constraint zone is within 0.2 times the height of the maximum dimension L of the structure (that is, within the range of ≤0.2L). In Chapter 6 of Wang Tiemeng's domestic book "Crack Control of Engineering Structures", it is believed that the height range of the concrete constraint zone is within 0.45 times the maximum dimension L, that is, within the height range of 0.45L. The external constraint stress in the concrete structure manifests as tensile stress, and decreases nonlinearly with the increase of the structure height. The concrete structure in the remaining area can be considered to be almost free of constraint stress.
[0051] Therefore, both domestic and foreign normative documents or works believe that the restraint stress of concrete will decrease along the foundation height direction. However, for different concrete long wall structures, the restraint stress cannot be accurately quantified by relying solely on theoretical calculations, because factors such as the concrete foundation mix ratio, concrete strength grade, concrete raw material source, and climate characteristics will affect the stress distribution of concrete after hardening. If an overly conservative approach is taken for this purpose, such as uniformly increasing the amount of expansion agent, it will cause a waste of data and is not conducive to saving materials and energy.
[0052] like Figures 3 to 7 As shown, the crack control method of long wall concrete structure based on limiting horizontal shrinkage strain is specifically described below with a specific implementation.
[0053] The method for confirming the limited expansion rate is measured after curing in 40°C water for 28 days according to the technical specification for the application of magnesium oxide expansion agent for concrete (T / CECS540-2018). Specifically, taking the vertical gradient expansion concrete with 8% magnesium oxide expansion agent as an example, its components are cement, fly ash, sand, stone, water, water reducer and magnesium oxide expansion agent. Excluding magnesium oxide expansion agent, the total mass of the remaining components is 100%, then, cement is 11.9wt.%, fly ash is 5.3wt.%, stone is 47.3%wt.%, sand is 28.3wt.%, water is 6.9wt.%, water reducer is 0.3wt.%, and magnesium oxide expansion agent is 1.50wt.%.
[0054] Furthermore, the only difference between the components of the vertical gradient expansive concrete added with 6% and 4% magnesium oxide expansive agent and the components of the vertical gradient expansive concrete added with 8% magnesium oxide expansive agent is that the components of the vertical gradient expansive concrete added with 6% magnesium oxide expansive agent contain 1.10wt.% of magnesium oxide expansive agent, the components of the vertical gradient expansive concrete added with 4% magnesium oxide expansive agent contain 0.72wt.% of magnesium oxide expansive agent, and the remaining materials are adjusted proportionally.
[0055] It needs to be explained that the basic mix ratio is selected based on actual engineering applications. Different engineering projects will have different basic mix ratios, depending on the concrete design strength, concrete durability index and on-site trial mixing conditions.
[0056] Furthermore, the cement strength grade used in this specific embodiment is P.O42.5, the sand is machine-made sand produced by an ordinary sand and gravel plant, the fineness modulus of the machine-made sand is 2.79, and the component is mostly limestone. The gravel is crushed limestone, and is composed of 5mm to 20mm graded gravel and 16mm to 31.5mm graded gravel in a ratio of 6:4. The water is local tap water for the project, the water reducer is a high-performance polycarboxylate water reducer, and the MgO content of the magnesium oxide expansion agent is 86.2%.
[0057] Furthermore, strain gauges were placed at the geometric center of the small concrete model section of the same scale, 0.1L, 0.2L and the top elevation from the bottom of the long wall concrete structure. The observation results are as follows:
[0058] The horizontal shrinkage strain at the 0.1L elevation after 7 days of pouring is X 1 =36με;
[0059] The horizontal shrinkage strain at the 0.2L elevation after 7 days of pouring is X 2 =82με;
[0060] The horizontal shrinkage strain at the top elevation after 7 days of pouring is Z = 125με;
[0061] The horizontal shrinkage strain at the 0.1L elevation after 28 days of pouring is X 1 =97με;
[0062] The horizontal shrinkage strain at the 0.2L elevation after 28 days of pouring is X 2 =255με;
[0063] The horizontal shrinkage strain at the top elevation 28 days after pouring is Z = 374με.
[0064] According to the calculation formula:
[0065] The limited horizontal shrinkage strain at the 0.1L elevation after 7 days of pouring is:
[0066] m 7 =ZX 1 =125με-36με=89με;
[0067] The limited horizontal shrinkage strain at the 0.2L elevation after 7 days of pouring is:
[0068] n 7 =ZX 2 =125με-82με=43με;
[0069] The limited horizontal shrinkage strain at the 0.1L elevation after 28 days of pouring is:
[0070] m 28 =ZX 1 =374με-97με=277με;
[0071] The limited horizontal shrinkage strain at the 0.2L elevation after 28 days of pouring is:
[0072] n 28 =ZX 2 =374με-255με=119με;
[0073] Furthermore, the expansion rate test of expansive concrete shows that:
[0074] The limiting expansion rate of the gradient expansion concrete with 4% magnesium oxide expansion agent added 7 days after pouring is a 7 =50με;
[0075] The limiting expansion rate of the gradient expansion concrete with 6% magnesium oxide expansion agent added 7 days after pouring is b 7 =90με;
[0076] The limiting expansion rate of the gradient expansion concrete with 8% magnesium oxide expansion agent added 7 days after pouring is c 7=140με;
[0077] The limiting expansion rate of the gradient expansion concrete with 4% magnesium oxide expansion agent added after pouring for 28 days is a 28 =170με;
[0078] The limiting expansion rate of the gradient expansion concrete with 6% magnesium oxide expansion agent added after pouring for 28 days is b 28 =230με;
[0079] The limiting expansion rate of the gradient expansion concrete with 8% magnesium oxide expansion agent added after pouring for 28 days is c 28 =280με;
[0080] The limiting horizontal shrinkage strain values of each gradient structure and the limiting expansion rates of concrete specimens at different concrete curing days under each expansive agent dosage are ranked, and the results are as follows:
[0081] n 7 <a 7 <m 7 <b 7 <c 7 ;
[0082] n 28 <a 28 <b 28 <m 28 <c 28 ;
[0083] It can be seen that when the expansive agent dosage is 8%, the corresponding restricted expansion rate is greater than the restricted horizontal shrinkage strain value of the first gradient structure after 7d and 28d of pouring; when the expansive agent dosage is 4%, the corresponding restricted expansion rate is greater than the restricted horizontal shrinkage strain value of the second gradient structure after 7d and 28d of pouring, thus confirming that the magnesium oxide expansive agent dosage of the first gradient concrete is 8%, and the magnesium oxide expansive agent dosage of the second gradient concrete is 4%.
[0084] like Figure 7 As shown in the figure, in order to verify the anti-cracking performance of gradient concrete, four scaled model sections of long wall concrete structure with the same size were formed outdoors:
[0085] (1) No magnesium oxide expansion agent is added to the long wall concrete;
[0086] (2) 8% magnesium oxide expansion agent is added to the entire long wall concrete;
[0087] (3) For long wall concrete below 0.2L height, concrete with 8% magnesium oxide expansion agent shall be used;
[0088] (4) Vertical gradient expansive concrete is used for long wall concrete below a height of 0.2L. The height of each layer of gradient concrete is 0.1L, and the total number of gradients is 2. The first layer is mixed with 8% magnesium oxide expansive agent, and the second layer is mixed with 4% magnesium oxide expansive agent.
[0089] The cracking of each small model was observed 28 days after concrete pouring, and the number of cracks was as follows:
[0090] (1) Four cracks appeared;
[0091] (2) No cracks;
[0092] (3) No cracks;
[0093] (4) No cracks.
[0094] From the perspective of economic cost, the amount of magnesium oxide expansion agent added in (1) to (4) accounts for 0%, 8%, 1.6% and 1.2% of the total cementitious material consumed in the structure casting, respectively. The market unit price of magnesium oxide expansion agent is about RMB 3,000 per ton. 3 Calculated based on the mass of cementitious materials consumed by concrete being 400 kg, the unit cost of (4) vertical gradient concrete is approximately RMB 90 and RMB 5 lower than that of (2) full expansive concrete and (3) strongly constrained expansive concrete, respectively. The crack control effects of the three are similar, but the economic benefits of (4) vertical gradient concrete are very considerable.
[0095] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.
Claims
1. A method for controlling cracks in long wall concrete structures based on limiting horizontal shrinkage strain, characterized in that: include: S1: Obtain the size of the long wall concrete structure, make a small concrete model segment of the same scale according to the size of the long wall concrete structure, and conduct regular strain monitoring on the small concrete model segment of the same scale to obtain the horizontal shrinkage strain at the predetermined elevation position of each gradient structure in the small concrete model segment of the same scale; S2: according to the horizontal shrinkage strain at each elevation position of the gradient structure in the small concrete model segment of the same scale, the limited horizontal shrinkage strain at the predetermined elevation position of each gradient structure in the small concrete model segment of the same scale is calculated; S3: Conduct a test on the limited expansion rate of expansive concrete; S4: Determine the expansive concrete mix ratio of each gradient structure according to the results of the limited expansion rate test of expansive concrete and the limited horizontal shrinkage strain at the predetermined elevation position of each gradient structure in the small model section of the same proportion concrete; S5: Carry out vertical gradient concrete construction of long wall concrete structure according to the mix ratio of each gradient expansion concrete.
2. The method for controlling cracks in long wall concrete structures based on limiting horizontal shrinkage strain according to claim 1 is characterized in that: In S1, regular strain monitoring of small concrete model sections of the same scale includes: Obtain the vertical expansion gradient number based on the small concrete model segment of the same scale; Obtaining the vertical expansion interval according to the vertical expansion gradient number; Arrange strain gauges at the top structural elevation of the small concrete model section of the same scale; Strain gauges are arranged at the elevation of each gradient structure in the small concrete model section of the same scale according to the vertical expansion interval.
3. The method for controlling cracks in long wall concrete structures based on limiting horizontal shrinkage strain according to claim 2 is characterized in that: The strain gauge is arranged at the geometric center of the top structure, and the strain gauge is arranged at the geometric center of each gradient structure.
4. The method for controlling cracks in long wall concrete structures based on limiting horizontal shrinkage strain according to claim 2 is characterized in that: At least two gradient structures are provided.
5. The method for controlling cracks in long wall concrete structures based on limiting horizontal shrinkage strain according to claim 1 is characterized in that: In S2, the calculation formula for the limited horizontal shrinkage strain at the predetermined elevation position of each gradient structure is: M=Z-X n ; Among them, M is the horizontal shrinkage strain value of each gradient structure, Z is the horizontal shrinkage strain value at the top elevation, X n It is the horizontal shrinkage strain value of the nth level gradient structure starting from the structural base.
6. The method for controlling cracks in long wall concrete structures based on limiting horizontal shrinkage strain according to claim 1 is characterized in that: In S3, the expansion rate limit test of expansive concrete includes: Preset multiple concrete expansion agent dosages; Concrete is prepared according to different expansion agent dosages, and multiple concrete specimens with different expansion agent dosages are cast; Preset multiple concrete curing days, and perform curing on multiple concrete test blocks according to the preset concrete curing days; The limiting expansion rate of concrete specimens under different expansive agent dosages is obtained during the preset concrete curing days.
7. The method for controlling cracks in long wall concrete structures based on limiting horizontal shrinkage strain according to claim 6 is characterized in that: The preset concrete curing days include at least the 7th and 28th days after pouring.
8. The method for controlling cracks in long wall concrete structures based on limiting horizontal shrinkage strain according to claim 6 is characterized in that: The preset concrete expansion agent dosage ranges from 0 to 10%.
9. The method for controlling cracks in long wall concrete structures based on limiting horizontal shrinkage strain according to claim 1, characterized in that: In S4, determining the expansive concrete mix ratio of each gradient structure includes: Obtain the limit horizontal shrinkage strain value of each gradient structure; Obtain the limiting expansion rate of concrete specimens with different expansive agent dosages and different concrete curing days; The limiting horizontal shrinkage strain values of each gradient structure and the limiting expansion rates of concrete specimens at different concrete curing days under each expansive agent dosage are ranked; When the limited expansion rate of concrete specimens with the same expansive agent dosage is greater than the limited horizontal shrinkage strain value of the gradient structure under all concrete curing days, the dosage of the expansive agent in the corresponding gradient structure is determined.
10. The method for controlling cracks in long wall concrete structures based on limiting horizontal shrinkage strain according to claim 1, characterized in that: In S5, vertical gradient concrete construction includes: S5.1: Tie steel bars and set up concrete formwork support; S5.2: Roughen the base layer and clean the base surface; S5.3: pouring a first gradient shrinkage compensating concrete according to the thickness and mix ratio of the gradient structure; S5.4: vibrate the first gradient shrinkage compensating concrete; S5.5: Repeat S5.3 and S5.4 until the Nth gradient shrinkage compensating concrete is poured and vibrated; S5.6: Pour ordinary concrete of the same grade to the designed elevation and vibrate to finish.