A concrete structure and construction method for preventing cracks in a cast-in-place tunnel main structure

Abstract

The present application is a kind of concrete structure for preventing cast-in-place tunnel main structure cracking and its construction method, the concrete structure is by targeted zoning of the tunnel main body concrete structure, and by regulating the formula of concrete to make the zoning of concrete has different expansion coefficient, so that the concrete structure of different zoning has different deformation performance and deformation timing, the constraint stress of concrete structure also decreases with the zoning interface gradient, to change the expansion performance of concrete, compensate shrinkage strain, so that the constraint stress of concrete in different zoning is significantly weakened, the anti-cracking property of concrete structure itself is significantly improved, and the shrinkage cracking problem of concrete is significantly improved; and the concrete structure for preventing cast-in-place tunnel main structure cracking is simple, low in cost, has significant improvement effect on the shrinkage cracking problem of concrete, and is suitable for large-scale application in immersed tube open section and open-cut tunnel main structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of concrete engineering, in particular to a concrete structure for preventing cracking of cast-in-place tunnel main structure and a construction method thereof. BACKGROUND

[0002] At present, in the concrete construction engineering of the open section of immersed tube and the main structure of open-cut tunnel, it is very difficult to control the cracking and leakage of the concrete structure due to the large size of the concrete structure, resulting in the problem of cracking and leakage of the concrete being very prominent. It is found through research that the cracking and leakage problem in the concrete construction process of the open section of immersed tube and the main structure of open-cut tunnel is mainly caused by the early shrinkage of the concrete. Therefore, how to effectively control the early shrinkage cracking of the concrete structure is the key to solving the cracking and leakage problem in the concrete construction process of the open section of immersed tube and the main structure of open-cut tunnel.

[0003] For the early shrinkage cracking problem of the concrete structure, the existing technology also provides a solution, such as: (1) adopting the method of adding cooling water pipes in the concrete to reduce the temperature of the concrete by using cooling water to improve the cracking risk of the concrete; (2) adopting the whole section one-time pouring process to form the whole concrete structure. According to many engineering practices, it is found that the above-mentioned methods can indeed effectively improve the early shrinkage cracking problem in the concrete construction process, and they are also commonly used in the concrete construction to avoid cracking of the concrete. However, when the above-mentioned process is used in the concrete structure construction of the open section of immersed tube and the main structure of open-cut tunnel, due to the actual problems such as high engineering support excavation conditions and formwork process requirements, poor site construction conditions, etc. of the open section of immersed tube and the main structure of open-cut tunnel, it leads to the defects of large construction difficulty, large resource investment and long construction period, and is not suitable for large-scale application in the concrete structure construction of the open section of immersed tube and the main structure of open-cut tunnel. Therefore, the early shrinkage cracking problem of the concrete structure of the open section of immersed tube and the main structure of open-cut tunnel has not been well solved. SUMMARY

[0004] The present application aims to: in view of the defects of high cost and complex structure of the existing concrete structure for improving the early shrinkage cracking problem of the concrete used in the open section of immersed tube and the main structure of open-cut tunnel, a concrete structure for preventing cracking of cast-in-place tunnel main structure and a construction method thereof are proposed. The concrete structure adjusts the formula of the concrete to make the partitioned concrete have different expansion coefficients, so that the restraint stress of the concrete in different partitions is significantly weakened, and the anti-cracking property of the concrete structure itself is significantly improved. The concrete structure for preventing cracking of cast-in-place tunnel main structure is simple, low in cost, has a significant improvement effect on the shrinkage cracking problem of the concrete, and is suitable for large-scale application in the open section of immersed tube and the main structure of open-cut tunnel.

[0005] In order to achieve the above-mentioned purpose, the present application provides a kind of concrete structure for preventing cast-in-place tunnel main structure cracking, including several segments of tunnel length direction sequentially connected concrete section;The concrete section includes the bottom plate, side wall and top plate sequentially connected in the direction of section perpendicular to tunnel length;The bottom plate includes the first bottom plate, second bottom plate and third bottom plate of the same length sequentially connected in the direction of tunnel length, the concrete expansion coefficient of the first bottom plate and third bottom plate is same, and greater than the concrete expansion coefficient of the second bottom plate;The side wall includes the first side wall and second side wall sequentially connected from top to bottom in the direction of section perpendicular to tunnel length, the height of the first side wall is 2 times of the second side wall, and the concrete expansion coefficient of the first side wall is greater than the concrete expansion coefficient of the second side wall;The top plate includes the first top plate, second top plate and third top plate of the same length sequentially connected in the direction of tunnel length, the concrete expansion coefficient of the first top plate and third top plate is same, and greater than the concrete expansion coefficient of the second top plate.

[0006] The concrete structure for preventing cast-in-place tunnel main structure cracking of the present application is divided into different zones by targetedly dividing the concrete structure of tunnel main body, and the concrete of different zones has different expansion coefficients by regulating the formula of concrete, so that the concrete structures of different zones have different deformation performance and deformation timing, the constraint stress of concrete structure also decreases gradually along the interface of different zones, the expansion performance of concrete is changed, the shrinkage strain is compensated, so that the constraint stress of concrete in different zones is significantly weakened, the anti-cracking property of concrete structure itself is significantly improved, and the shrinkage cracking problem of concrete is significantly improved.The concrete structure for preventing cast-in-place tunnel main structure cracking is simple, low in cost, has remarkable effect on improving the shrinkage cracking problem of concrete, and is suitable for large-scale application in immersed tube open section and open-cut tunnel main structure.

[0007] Preferably, the length (in the direction of tunnel length) of the concrete section is not more than 35 m, and more preferably, the length of the concrete section is 10-35 m.The length of the preferred concrete section is suitable for on-site pouring of concrete, and the construction period and difficulty can be controlled, and the shrinkage cracking of concrete can be easily controlled.

[0008] Preferably, the difference between the concrete expansion coefficients of the first bottom plate and the second bottom plate is not less than 15%, and more preferably, the first bottom plate is formed by pouring conventional concrete, and the second bottom plate is formed by pouring anti-cracking concrete.The preferred concrete pouring type can improve the shrinkage cracking problem of the concrete in the bottom plate area at a lower concrete cost, and is more suitable for large-scale application and promotion.

[0009] Preferably, the difference between the concrete expansion coefficients of the first side wall and the second side wall is not less than 15%; more preferably, the first side wall is formed by pouring of conventional concrete, and the second side wall is formed by pouring of anti-cracking concrete; the preferred concrete pouring type can improve the concrete shrinkage and cracking problem in the side wall area at a lower concrete cost, and is more suitable for large-scale application and promotion.

[0010] Preferably, the difference between the concrete expansion coefficients of the first top plate and the second top plate is not less than 15%; more preferably, the first top plate is formed by pouring of conventional concrete, and the second bottom plate is formed by pouring of anti-cracking concrete; the preferred concrete pouring type can improve the concrete shrinkage and cracking problem in the top plate area at a lower concrete cost, and is more suitable for large-scale application and promotion.

[0011] To achieve the above-mentioned purpose, the application further provides a construction method of a concrete structure for preventing cracking of a cast-in-place tunnel main structure, comprising the following steps:

[0012] S1: According to the design requirements of the tunnel main body, the pre-constructed tunnel main structure is divided into a plurality of to-be-poured segments connected in sequence along the length direction of the tunnel;

[0013] S2: According to the construction requirements and sequence of the tunnel main structure, a to-be-poured segment is selected, and the to-be-poured segment is divided into a to-be-poured bottom plate area, a to-be-poured side wall area and a to-be-poured top plate area according to the cross-section direction perpendicular to the length of the tunnel;

[0014] S3: The to-be-poured bottom plate area is first divided into to-be-poured bottom plate 1 area, to-be-poured bottom plate 2 area and to-be-poured bottom plate 3 area with the same length along the length direction of the tunnel; different expansion coefficient concrete is used to pour the to-be-poured bottom plate 1 area, the to-be-poured bottom plate 2 area and the to-be-poured bottom plate 3 area to form a first bottom plate, a second bottom plate and a third bottom plate, thereby completing the pouring of the bottom plate;

[0015] Then on the bottom plate, the to-be-poured side wall area is divided into to-be-poured side wall 1 area and to-be-poured side wall 2 area from top to bottom according to the cross-section direction perpendicular to the length of the tunnel; different expansion coefficient concrete is used to sequentially pour the to-be-poured side wall 2 area and the to-be-poured side wall 1 area to form a first side wall and a second side wall, thereby completing the pouring of the side wall;

[0016] Finally, on the side wall, the to-be-poured top plate area is divided into to-be-poured top plate 1 area, to-be-poured top plate 2 area and to-be-poured top plate 3 area along the length direction of the tunnel; different expansion coefficient concrete is used to pour the to-be-poured top plate 1 area, the to-be-poured top plate 2 area and the to-be-poured top plate 3 area to form a first top plate, a second top plate and a third top plate, thereby completing the pouring of the top plate;

[0017] Pouring the selected concrete segment is completed by pouring the bottom plate, the side wall and the top plate respectively;

[0018] S4: repeating steps S2 and S3 to complete pouring of other concrete segments in the tunnel main body structure in sequence, thereby completing the construction of the concrete structure for preventing cracking of the cast-in-place tunnel main body structure.

[0019] Preferably, in step S3, the pouring of the bottom plate or the top plate is performed simultaneously in the zones. The simultaneous pouring is shorter in construction period, and the force between the zones is more uniform, which is beneficial to reducing deformation or cracks caused by uneven stress.

[0020] Preferably, in step S3, the pouring of the bottom plate, the side wall or the top plate is blocked by a blocking device between the zones to avoid mixing of the concrete in the zones during pouring. Most preferably, the blocking device is a closing net. The blocking device is good in blocking effect, low in cost and convenient to operate.

[0021] Compared with the prior art, the concrete structure for preventing cracking of the cast-in-place tunnel main body structure has the following advantages:

[0022] (1) The concrete structure for preventing cracking of the cast-in-place tunnel main body structure adjusts the formula of the concrete to make the partitioned concrete have different expansion coefficients, so that the restraint stress of the concrete in different partitions is significantly weakened, and the anti-cracking property of the concrete structure is significantly improved.

[0023] (2) The concrete structure for preventing cracking of the cast-in-place tunnel main body structure is simple and low in cost, has a remarkable improvement effect on the shrinkage and cracking of the concrete, and is suitable for large-scale application in the immersed tube open section and the open-cut tunnel main body structure.

[0024] (3) The construction method of the concrete structure for preventing cracking of the cast-in-place tunnel main body structure is small in construction difficulty and short in construction period, and is suitable for large-scale construction of the concrete structure for preventing cracking of the cast-in-place tunnel main body structure. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a schematic view of the tunnel main body concrete structure of embodiment 1 of the present application;

[0026] Figure 2 is a schematic view of the bottom plate of embodiment 1 of the present application;

[0027] Figure 3 is a schematic view of the side wall of embodiment 1 of the present application;

[0028] Figure 4 is a schematic view of the top plate of embodiment 1 of the present application.

[0029] Marked in the figure: 1-concrete segment; 2-floor; 201-first floor; 202-second floor; 203-third floor; 3-side wall; 301-first side wall; 302-second side wall; 4-top plate; 401-first top plate; 402-second top plate; 403-third top plate. DETAILED DESCRIPTION

[0030] The application will be described in further detail below with reference to the drawings.

[0031] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0032] Example 1

[0033] Project name: immersed tunnel buried section of a project

[0034] Tunnel main structure construction requirements:

[0035] Prevent cracking of the tunnel main concrete structure: the total length of the tunnel in the length direction is about 203m, divided into 8 segments, each segment length is 24~26m, each segment is connected in turn; randomly select any concrete segment 1 (length 25m, width 12.7m, height 9.2m) (see Figure 1 );

[0036] The concrete segment is composed of floor 2 (length 25m, width 12.7m, height 2.5m), side wall 3 (length 25m, width 1m, height 4.2m) and top plate 4 (segments at the exit or entrance have no top plate; length 25m, width 12.7m, height 2.5m) which are connected in turn in the direction perpendicular to the length of the tunnel (see Figure 1 );The floor 2 is divided into the same length (length 25m) (see Figure 2 );The side wall 3 is divided into first side wall 301 and second side wall 302 which are connected in turn in the direction perpendicular to the length of the tunnel from top to bottom, the height of the first side wall 301 is 4.2m; the height of the second side wall 302 is 4.2m (see Figure 3 );The top plate 4 is divided into the same length (length 25m) (see Figure 4). The first bottom plate 2 and the first top plate 4 are made of common concrete without expansion coefficient; the first side wall 301 and the second side wall 302 are made of micro-expansion concrete with expansion agent, and the concrete expansion rate is 0.18%; the second bottom plate 2 and the second top plate 4 are made of common concrete without expansion coefficient; the second side wall 301 and the second side wall 302 are made of micro-expansion concrete with expansion agent, and the concrete expansion rate is 0.18%; the concrete configuration mode of the subsequent segments is the same.

[0037] Specific pouring method:

[0038] S1: According to the design requirements of the tunnel main body, the pre-constructed tunnel main body structure is divided into a plurality of sequentially connected to-be-poured segments in the length direction of the tunnel;

[0039] S2: According to the construction requirements and sequence of the tunnel main body structure, a to-be-poured segment is selected, and the to-be-poured segment is divided into a to-be-poured bottom plate area, a to-be-poured side wall area and a to-be-poured top plate area in the direction perpendicular to the length of the tunnel;

[0040] S3: The to-be-poured bottom plate area is first divided into to-be-poured bottom plate 1 area, to-be-poured bottom plate 2 area and to-be-poured bottom plate 3 area with the same length in the length direction of the tunnel; different expansion coefficient concrete is used to pour the to-be-poured bottom plate 1 area, the to-be-poured bottom plate 2 area and the to-be-poured bottom plate 3 area, to form the first bottom plate, the second bottom plate and the third bottom plate, and then the pouring of the bottom plate 2 is completed;

[0041] Then on the bottom plate 2, the to-be-poured side wall area is divided into to-be-poured side wall 1 area and to-be-poured side wall 2 area from top to bottom in the direction perpendicular to the length of the tunnel; different expansion coefficient concrete is used to sequentially pour the to-be-poured side wall 2 area and the to-be-poured side wall 1 area, to form the first side wall 301 and the second side wall 302, and then the pouring of the side wall 3 is completed;

[0042] Finally, on the side wall 3, the to-be-poured top plate area is divided into to-be-poured top plate 1 area, to-be-poured top plate 2 area and to-be-poured top plate 3 area in the length direction of the tunnel; different expansion coefficient concrete is used to pour the to-be-poured top plate 1 area, the to-be-poured top plate 2 area and the to-be-poured top plate 3 area, to form the first top plate 401, the second top plate 402 and the third top plate 403, and then the pouring of the top plate 4 is completed;

[0043] Through the pouring of the bottom plate 2, the side wall 3 and the top plate 4 respectively, the pouring of the selected concrete segment 1 is completed;

[0044] S4: Repeat steps S2 and S3 to sequentially complete the pouring of other concrete segments 1 in the tunnel main body structure, thereby completing the construction of the concrete structure for preventing cracks in the cast-in-place tunnel main body structure.

[0045] Performance test results:

[0046] Through observation and testing at the junctions of the bottom plate 2 and the side walls 301 and 302, and the side walls 301 and 302 and the top plate 4, no obvious cracks are found, and the concrete expansion coefficients at the side walls 301 and 302 are monitored by using convergence instruments, and the concrete expansion coefficients are all more than 0.20%, reaching the design effect.

[0047] The above description is merely preferred embodiments of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for constructing a concrete structure to prevent cracking of a cast-in-situ tunnel main structure, characterized in that: The concrete structure comprises a plurality of concrete segments (1) connected in sequence along the length direction of the tunnel; the concrete segment (1) comprises a bottom plate (2), a side wall (3) and a top plate (4) connected in sequence in a section direction perpendicular to the length of the tunnel; the bottom plate (2) comprises a first bottom plate (201), a second bottom plate (202) and a third bottom plate (203) of the same length connected in sequence in the length direction of the tunnel, the concrete expansion coefficients of the first bottom plate (201) and the third bottom plate (203) being the same and greater than the concrete expansion coefficient of the second bottom plate (202); the side wall (3) comprises a section direction perpendicular to the length of the tunnel A first side wall (301) and a second side wall (302) are sequentially connected and arranged in a direction from top to bottom, the height of the first side wall (301) is twice that of the second side wall (302), and the concrete expansion coefficient of the first side wall (301) is greater than the concrete expansion coefficient of the second side wall (302); the top plate (4) comprises a first top plate (401), a second top plate (402), and a third top plate (403) of the same length, which are sequentially connected and arranged in a tunnel length direction, and the concrete expansion coefficients of the first top plate (401) and the third top plate (403) are the same and greater than the concrete expansion coefficient of the second top plate (402); The construction method comprises the following steps: S1: According to the design requirements of the tunnel main body, the pre-constructed tunnel main structure is divided into a number of sequentially connected sections to be cast along the tunnel length direction; S2: According to the construction requirements and sequence of the main structure of the tunnel, a section to be cast is selected, and the section to be cast is divided into a bottom plate area to be cast, a side wall area to be cast, and a top plate area to be cast according to a cross-section perpendicular to the length of the tunnel; S3: first, the bottom plate area to be cast is divided into a bottom plate area 1 to be cast, a bottom plate area 2 to be cast, and a bottom plate area 3 to be cast, each of the same length, along the length direction of the tunnel; concrete with different expansion coefficients is used to cast the bottom plate area 1 to be cast, the bottom plate area 2 to be cast, and the bottom plate area 3 to be cast, to form a first bottom plate (201), a second bottom plate (202), and a third bottom plate (203), thereby completing the casting of the bottom plate (2); Then, on the bottom plate (2), the side wall area to be cast is divided from top to bottom into a side wall area 1 to be cast and a side wall area 2 to be cast according to a cross-section direction perpendicular to the tunnel length; concrete with different expansion coefficients is used to cast the side wall area 2 and the side wall area 1 to be cast in sequence to form a first side wall (301) and a second side wall (302), thereby completing the casting of the side wall (3); Finally, on the side wall (3), the top plate area to be cast is divided into a top plate area 1 to be cast, a top plate area 2 to be cast, and a top plate area 3 to be cast along the tunnel length direction; concrete with different expansion coefficients is used to cast the top plate area 1 to be cast, the top plate area 2 to be cast, and the top plate area 3 to be cast to form a first top plate (401), a second top plate (402), and a third top plate (403), thereby completing the casting of the top plate (4); The casting of the selected concrete segment (1) is completed by casting the bottom plate (2), the side wall (3) and the top plate (4) respectively; S4: Repeat steps S2 and S3 to sequentially complete the pouring of other concrete segments (1) in the tunnel main structure, thereby completing the construction of a concrete structure that prevents cracking of the cast-in-place tunnel main structure.

2. The construction method according to claim 1, characterized in that: The length of the concrete segment (1) is not greater than 35m.

3. The construction method according to claim 2, characterized in that: The length of the concrete segment (1) is 10-35m.

4. The construction method according to claim 1, characterized in that: The difference between the concrete expansion coefficients of the first base plate (201) and the second base plate (202) is not less than 15%.

5. The construction method according to claim 1, characterized in that: The difference between the concrete expansion coefficients of the first side wall (301) and the second side wall (302) is not less than 15%.

6. The construction method according to claim 1, characterized in that: The difference between the concrete expansion coefficients of the first top plate (401) and the second top plate (402) is not less than 15%.

7. The construction method according to claim 1, characterized in that: In step S3, during the pouring of the bottom plate (2) or the top plate (4), each zone is poured simultaneously.

8. The construction method according to claim 1, characterized in that: In step S3, during the pouring process of the bottom plate (2), the side wall (3) or the top plate (4), a barrier device is used between the zones for blocking.

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