A construction method of self-compacting concrete for box culvert bottom

Abstract

The application provides a box culvert bottom self-compacting concrete construction method, relates to the shield construction technical field, and through the arrangement of multiple box culverts in a shield segment, the matched cover template with an observation hole is made according to a reserved hole, and the cover template is detachably connected through a connecting structure, the pouring area is divided and is soft-isolated through a partition, then the self-compacting concrete is symmetrically poured into each segmented area in sequence, the height of the poured self-compacting concrete is monitored through the observation hole, when the self-compacting concrete reaches a preset height, the pouring is stopped and the observation hole is blocked; the special structures such as the arc bottom surface of the box culvert and the air duct are effectively matched, the problem of backfilling the gap between the prefabricated box culvert and the segment is solved, the problems of insufficient compactness, bubble accumulation and template floating during concrete pouring are avoided, the backfilling quality and the structural safety are ensured, the overall structural integrity and the reasonable stress after the on-site assembly of the prefabricated box culvert are improved, and the construction demand of the scene needing to reduce ground disturbance such as underwater sea-crossing and dense urban areas is met.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of shield construction, in particular to a self-compacting concrete construction method for the bottom of a box culvert. BACKGROUND

[0002] As an arc-shaped prefabricated component constituting the main structure of a tunnel, the circular cross section of a segment cannot directly meet the requirements of vehicle traffic. By setting a box culvert inside the segment structure, a traffic passage with a horizontal bearing surface is constructed, thereby realizing the safe traffic function of personnel and vehicles in the tunnel.

[0003] In the field of tunnel shield construction, the traditional cast-in-place inverted arch construction has the defects of long cycle and large environmental impact, and the prefabricated box culvert technology improves the quality controllability through factory production, and significantly shortens the construction period through on-site assembly, and is especially suitable for underwater cross-sea and dense urban areas and other scenes that require reduced ground disturbance, and has become the preferred solution for underpass railway projects.

[0004] However, due to the cumulative error of prefabricated components and on-site assembly, it is difficult to achieve complete adhesion between the box culvert and the segment; to compensate for this error, a raised support structure is usually pre-set at the bottom of the box culvert, resulting in an inherent gap between the box culvert and the segment; to ensure the integrity of the structure and avoid uneven stress on the raised part at the bottom of the box culvert in the later stage, self-compacting concrete needs to be backfilled in the gap, but the arc-shaped bottom surface of the box culvert and the special structure of the distribution of the two side air ducts and the evacuation passage reserved hollows make it easy to have problems such as insufficient compactness, bubble accumulation and formwork floating during concrete pouring, directly affecting the backfill quality and structural safety. SUMMARY

[0005] The purpose of the present application is to solve the above problems, and provide a self-compacting concrete construction method for the bottom of a box culvert.

[0006] The present application provides a self-compacting concrete construction method for the bottom of a box culvert, comprising the following steps:

[0007] S100: arranging a plurality of box culverts in a shield segment; the box culvert comprises a top plate and an arc-shaped bottom plate, and the arc-shaped bottom plate is provided with a reserved hole;

[0008] S200: manufacturing a covering formwork matched with the reserved hole according to the reserved hole, the covering formwork being provided with at least one observation piece, and the observation piece being provided with an observation hole penetrating along the axis thereof;

[0009] S300: covering the reserved hole with the covering formwork, and detachably connecting the covering formwork and the top plate through a connecting structure;

[0010] S400: divide the area to be poured between the box culvert bottom and the shield segment into a plurality of segmented areas, and use a separator for soft isolation between adjacent segmented areas;

[0011] S500: sequentially symmetrically pour self-compacting concrete on each segmented area;

[0012] S600: monitor the height of the poured self-compacting concrete through the observation hole, and block the observation hole when the self-compacting concrete reaches the preset height.

[0013] According to the technical scheme provided in the application, the top of the covering template is knocked during the pouring of the self-compacting concrete to avoid the self-compacting concrete at the reserved hole being not densely filled.

[0014] According to the technical scheme provided in the application, the side of the covering template close to the shield segment is provided with a flexible isolation layer, which is used to eliminate the generation of air bubbles.

[0015] According to the technical scheme provided in the application, the step S100 further includes the following steps:

[0016] S010: a discharge pipe is arranged between the shield well ground tank truck and the tunnel tank truck, and the self-compacting concrete is lowered into the tunnel tank truck through the discharge pipe;

[0017] S020: the self-compacting concrete is transported to the segmented area by a transport vehicle.

[0018] According to the technical scheme provided in the application, a plurality of buffers are arranged on the discharge pipe along the length direction thereof, the distance between adjacent buffers does not exceed a set distance, and the buffers are used to prevent the performance of the self-compacting concrete from being excessively lost during falling.

[0019] According to the technical scheme provided in the application, the connecting structure includes a plurality of fixing members arranged along the length direction of the covering template, and a connecting assembly, one end of the connecting assembly is clamped with the fixing members, and the other end of the connecting assembly abuts against the top plate.

[0020] According to the technical scheme provided in the application, the step S600 further includes the following steps:

[0021] S700: when the self-compacting concrete is initially set, the covering template is removed, and the concrete at the observation hole is leveled.

[0022] Compared with the prior art, the application has the following beneficial effects:

[0023] The application provides a self-compacting concrete construction method for a box culvert bottom, which is characterized in that: a plurality of box culverts are arranged in a shield segment, a matching cover template with an observation hole is made according to a reserved hole, and the cover template is detachably connected through a connecting structure, the pouring area is divided and is soft-separated through a separation piece, and then the self-compacting concrete is symmetrically poured into each segmented area in sequence, the height of the poured self-compacting concrete is monitored through the observation hole, and the observation hole is blocked when the self-compacting concrete reaches a preset height.

[0024] It should be understood that the description of technical features, technical solutions, beneficial effects or similar language in the present application does not imply that all features and advantages can be achieved in any single embodiment. On the contrary, it can be understood that the description of a feature or a beneficial effect means that the specific technical feature, technical solution or beneficial effect is included in at least one embodiment. Therefore, the description of technical features, technical solutions or beneficial effects in the specification does not necessarily refer to the same embodiment. Furthermore, the technical features, technical solutions and beneficial effects described in the embodiments can be combined in any appropriate manner. Those skilled in the art will understand that the embodiments can be implemented without one or more specific technical features, technical solutions or beneficial effects of a particular embodiment. In other embodiments, additional technical features and beneficial effects can be identified in specific embodiments that do not embody all embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creating any creative labor.

[0026] Figure 1 A flowchart of a self-compacting concrete construction method for a box culvert bottom provided by the embodiments of the present application;

[0027] Figure 2 A connection diagram of a cover template and a box culvert provided by the embodiments of the present application;

[0028] Figure 3 A schematic diagram of a discharging pipe provided by the embodiments of the present application;

[0029] Figure 4A schematic diagram illustrating the pouring of self-compacting concrete to the bottom of a box culvert, provided as an embodiment of this application;

[0030] Figure 5 This is a schematic diagram showing the area to be poured divided into several segmented areas according to an embodiment of this application.

[0031] In the diagram: 1. Feed pipe; 2. Buffer; 3. Pouring trolley; 4. Box culvert; 41. Top slab; 5. Shield tunnel segment; 6. Covering formwork; 7. Fixture; 8. Self-compacting concrete; 9. Steel pipe; 10. Observation piece; 11. Isolation piece; 12. U-shaped frame; 13. Screw; 14. Adjusting nut. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. The descriptions in this section are merely illustrative and explanatory, and should not be construed as limiting the scope of protection of this application. Specifically, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort should fall within the scope of protection of this application.

[0033] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or apparatus.

[0034] To make the technical solution of this application clearer and easier to understand, the following describes a construction method for self-compacting concrete at the bottom of a box culvert provided by an embodiment of this application.

[0035] like Figure 1 As shown in the figure, this embodiment provides a method for constructing self-compacting concrete at the bottom of a box culvert, which includes the following steps:

[0036] S100: Multiple box culverts 4 are arranged inside the shield tunnel segment 5; the box culvert 4 includes a top plate 41 and an arc-shaped bottom plate, and the arc-shaped bottom plate is provided with reserved holes;

[0037] Specifically, the plurality of box culverts 4 are arranged along the length direction of the shield segment 5, and the adjacent two box culverts 4 are tightly fitted; the box culvert 4 is produced by factory prefabrication, and the box culvert 4 is integrated with the top plate 41 and the arc-shaped bottom plate structure in the prefabrication stage, and the bottom plate is provided with standardized holes to meet the functional requirements of the tunnel air duct and the evacuation passage. The modular assembly system ensures the geometric precision of the components through factory quality control, greatly improves the on-site assembly efficiency, and at the same time eliminates the disturbance risk of traditional cast-in-place construction to the surrounding soil.

[0038] Optionally, the step S100 comprises the following steps before the step S100:

[0039] S010: A feeding pipe 1 is arranged between the shield well ground tank truck and the tunnel tank truck, and the self-compacting concrete 8 is lowered into the tunnel tank truck through the feeding pipe 1;

[0040] S020: The self-compacting concrete 8 is transported to the segmented area by the transport vehicle.

[0041] Specifically, after the self-compacting concrete 8 is inspected and qualified, the following material conveying process is executed:

[0042] A feeding hopper is arranged at the discharge port of the self-compacting concrete mixing station, the concrete mixed in the self-compacting concrete mixing station is conveyed into the shield well ground tank truck through the feeding hopper, then the shield well ground tank truck travels to the vicinity of the shield well, a feeding pipe 1 is arranged between the shield well ground tank truck and the tunnel tank truck, and the concrete output by the mixing station is gravity-conveyed into the tunnel tank truck through the feeding pipe 1 by using the potential energy of the height difference; the tunnel tank truck is transported to the bottom segment pouring area of the box culvert 4, forming a three-level logistics system of “centralized mixing → vertical conveying → mobile transportation”; the system ensures the homogeneity of the concrete through factory mixing, vertically feeds into the tunnel tank truck in the tunnel, and finally accurately delivers the concrete to the pouring area by the tunnel tank truck, providing material performance guarantee for subsequent high-precision backfill construction.

[0043] Optionally, a plurality of buffers 2 are arranged along the length direction of the feeding pipe 1, and the distance between adjacent buffers 2 does not exceed a set distance, and the buffer 2 is used to prevent the self-compacting concrete 8 from losing too much performance during the falling process.

[0044] Specifically, because the height difference between the self-compacting concrete mixing station and the tunnel tank truck is too large, the concrete is prone to segregation phenomenon due to too much performance loss during the falling process; therefore, as shown in FIG. 2, a plurality of buffers 2 are arranged along the length direction of the feeding pipe 1, and the distance between adjacent buffers 2 does not exceed a set distance, and the buffer 2 is used to prevent the self-compacting concrete 8 from losing too much performance during the falling process. Figure 3As shown, a plurality of buffers 2 are arranged on the length direction of the feeding pipe 1, and in this embodiment, the buffers 2 are diamond-shaped buffers; the distance between adjacent buffers 2 does not exceed a set distance, forming a stepped kinetic energy reduction structure; the buffer 2 takes a diamond-shaped steel plate as a core component, and its flow-approaching surface is arranged at an angle with the concrete falling trajectory, and through the double mechanisms of collision diversion and vortex damping, the concrete falling kinetic energy is reduced, ensuring that the concrete flow state is smoothly transferred to the tunnel tank car at the bottom of the shaft, and completely eliminating the risk of aggregate segregation caused by height difference; in this embodiment, the set distance is 8 meters.

[0045] In this embodiment, the distance between the buffer 2 near the top of the feeding pipe 1 and the bottom surface, and the distance between the buffer near the bottom of the feeding pipe 1 and the shield bottom are also not more than the set distance.

[0046] Specifically, in order to ensure the high fluidity and self-compacting ability of the self-compacting concrete 8, reduce the concrete production and transportation time, and ensure that the concrete is poured with the best performance, a self-compacting concrete mixing station is arranged beside the construction shield shaft; in order to ensure the performance of the self-compacting concrete 8, the self-compacting concrete 8 is pre-mixed, and the mix proportion of the self-compacting concrete 8 is finally determined to generate qualified self-compacting concrete 8; in this embodiment, the mix proportion of self-compacting concrete 8 is shown in Table 1.

[0047] Table 1: Mix proportion of self-compacting concrete per cubic meter, kg / m³

[0048]

[0049] Specifically, the pouring operation should be completed within 2 hours after the production of the self-compacting concrete 8.

[0050] S200: According to the reserved hole, a matching cover template 6 is made, and the cover template 6 is provided with at least one observation piece 10, and the observation piece 10 is provided with an observation hole penetrating along its axis;

[0051] Specifically, based on the contour of the reserved hole of the arc-shaped bottom plate of the box culvert 4, the cover template 6 is customized and prefabricated; the cover template 6 is arc-shaped, and the cover template 6 takes a high-strength PP plastic steel plate as the main body, and the thickness is 8 mm; in this embodiment, the surface of the cover template 6 is integrated with four observation pieces 10, and the four observation pieces 10 are distributed and arranged at the four corners of the cover template 6; the observation piece 10 penetrates to open an observation hole along the vertical axis and extends upward to form a monitoring channel, the inner wall of the observation hole is polished and provided with a scale mark, so that the operator can directly observe the change of the concrete liquid level in the hole, and simultaneously realize the double monitoring functions of pouring, exhaust and filling state.

[0052] Optionally, the side of the cover template 6 close to the shield segment 5 is provided with a flexible isolation layer, which is used to eliminate the generation of bubbles.

[0053] Specifically, a flexible isolation layer is set on the side of the covering template 6 facing the shield segment 5. This isolation layer is made of a water-permeable and lightweight non-woven geotextile material, which has a rough surface and a smooth surface. The rough surface is fixed to the covering template 6 by direct spraying of sponge adhesive, and the smooth surface faces the shield segment 5. The smooth surface is in direct contact with the self-compacting concrete 8. The adsorption effect of the flexible structure eliminates the surface laitance and air bubbles, thereby achieving the essential optimization of the appearance quality of the cast body.

[0054] S300: The pre-reserved holes are covered by a cover template 6, and the cover template 6 and the top plate 41 are detachably connected by a connecting structure;

[0055] Optionally, the connection structure includes: a fastener 7 and a connecting assembly. Multiple fasteners 7 are provided and arranged along the length of the covering template 6. Each fastener 7 is detachably connected to the top plate 41 through three connecting assemblies. One end of the connecting assembly is snapped into the fastener 7, and the other end of the connecting assembly abuts against the top plate 41.

[0056] Specifically, the covering template 6 is precisely positioned and installed on the pre-reserved holes in the arc-shaped bottom plate of the box culvert 4, and a rigid connection structure is used to achieve a detachable connection with the top plate 41 of the box culvert; such as Figure 2 As shown, the connecting structure includes multiple fasteners 7 arranged along the length of the covering template 6. In this embodiment, the fasteners 7 are square timbers. A vertically bearing connecting assembly is also provided, comprising a steel pipe 9, a U-shaped frame 12, a screw rod 13, and an adjusting nut 14. The steel pipe 9 is arranged vertically, with one end abutting against the top plate 41. The U-shaped frame 12 is snapped onto the square timber, and a screw rod 13 is provided at the end of the U-shaped frame 12 away from the square timber. An adjusting nut 14 is threaded onto the screw rod 13. The screw rod 13 is inserted into the end of the steel pipe 9 away from the top plate 41. The length of the connecting assembly is adjusted by rotating the adjusting nut 14, thereby adapting to changes in the distance between the top plate 41 and the covering template 6 under different construction conditions.

[0057] Specifically, the square timber, acting as a load transfer medium, transforms the concentrated force applied by the steel pipe 9 into a uniform load, which is then evenly transferred to the surface of the covering template 6.

[0058] S400: The area to be poured between the bottom of the box culvert 4 and the shield tunnel segment 5 is divided into several segments, and adjacent segments are softly isolated by the isolation component 11.

[0059] Specifically, such as Figure 5 As shown, to prevent voids in the self-compacting concrete 8 at the bottom of box culvert 4, the length of each pour should be controlled to be minimal. Based on the volume of the tunnel concrete mixer truck and the volume of self-compacting concrete 8 required for backfilling the bottom of each box culvert 4 segment, the area to be poured between the bottom of box culvert 4 and the shield tunnel segment 5 is divided into several sub-segments, for example... Figure 5The diagram shows segmented areas one, two, three, and four. In this embodiment, the volume of the tunnel concrete tanker is 8 cubic meters, and the volume of self-compacting concrete 8 required for backfilling the bottom of each box culvert 4 is 2.3 cubic meters. Therefore, three box culverts 4 are set up in each area to be poured. The width of a single box culvert 4 is 2m, so the length of each segment is 6m. Each segment is softly isolated by an isolation component 11. In this embodiment, the isolation component 11 is an inflatable rubber tube.

[0060] S500: Pour self-compacting concrete symmetrically into each segment area in sequence;

[0061] Specifically, each time self-compacting concrete is poured, construction should proceed from low to high according to the slope of the tunnel.

[0062] Specifically, such as Figure 4 As shown, during the pouring process, the self-compacting concrete 8 is unloaded from the tunnel truck onto the pouring trolley 3. The pouring trolley 3 is equipped with chutes on both sides. The lower end of the chutes precisely connects to the arc-shaped gap between the box culvert 4 and the shield tunnel segment 5. The concrete is injected into the gap cavity along the chutes, realizing directional fluid transport and precise filling under space-constrained conditions.

[0063] Optionally, after step S500 and before step S600, the following steps may also be included:

[0064] S501: During the pouring process, the top of the covering formwork 6 is tapped to prevent the self-compacting concrete 8 at the reserved holes from not being filled densely.

[0065] Specifically, during the pouring process, a high-frequency vibrator is used to regularly tap along the top of the covering template 6. The vibration energy is transmitted to the concrete fluid medium through the covering template 6, causing the internal microbubbles to migrate directionally along the arc-shaped bottom plate towards the observation hole and dissipate, so as to avoid the self-compacting concrete 8 at the reserved hole being not filled densely, thus achieving the synergistic enhancement of the structure's self-compacting performance and human intervention.

[0066] S600: The height of the poured self-compacting concrete 8 is monitored through the observation hole. When the self-compacting concrete 8 reaches the preset height, the observation hole is sealed.

[0067] Specifically, the operator monitors the level of the self-compacting concrete 8 in real time through the observation hole covering the template 6. When the concrete rises to the preset overflow mark of the observation hole, the observation hole is sealed with a rubber sealing plug. If the concrete height does not reach the preset overflow mark of the observation hole, the template is tapped to make the concrete around the template flow, effectively avoiding structural defects at the reserved holes of the box culvert 4 caused by under-pouring.

[0068] Optionally, the following steps may be included after step S600:

[0069] S700: When the self-compacting concrete 8 is initial setting, the covering formwork 6 is removed, and the concrete at the observation hole is leveled.

[0070] Specifically, after the self-compacting concrete 8 completes the initial setting process, the covering formwork 6 is removed in accordance with the principle of symmetry and gradual force, so as to avoid disturbing the surrounding poured concrete structure; after the covering formwork 6 is removed, the exposed concrete at the observation hole is finely leveled by using a high-precision leveling tool according to the overall flatness standard of the box culvert 4 bottom concrete surface, so as to ensure the smooth connection between the concrete surface at the observation hole and the surrounding concrete surface, and guarantee the continuity of the appearance and stress of the box culvert 4 bottom structure.

[0071] Working principle: By arranging multiple box culverts 4 in the shield segment 5, a matching covering formwork 6 with an observation hole is made according to the reserved hole, and is detachably connected by a connecting structure, so as to divide the pouring area and isolate it by a spacer 11, then the segmented areas are poured with self-compacting concrete 8 in a symmetrical manner, the height of the poured self-compacting concrete 8 is monitored through the observation hole, and when the self-compacting concrete 8 reaches the preset height, the observation hole is blocked; the construction method provided by the application effectively adapts to the arc-shaped bottom surface of the box culvert 4 and other special structures, solves the problem of backfilling the gap between the prefabricated box culvert 4 and the shield segment 5, avoids the problems of insufficient compactness, bubble accumulation and formwork floating during concrete pouring, guarantees the backfilling quality and structural safety, improves the overall structural integrity and rationality of stress after the prefabricated box culvert 4 is assembled on site, and meets the construction needs of reducing ground disturbance in underwater sea-crossing, dense urban areas and other scenes.

[0072] In this paper, specific examples are used to illustrate the principles and embodiments of the application. The above examples are only used to help understand the method and its core idea. The above is only a preferred embodiment of the application. It should be noted that due to the limitation of language expression, there are infinite specific structures, and for ordinary skilled persons in the technical field, some improvements, refinements or changes can be made without departing from the principles of the application, or the above technical features can be combined in a proper way; these improvements, refinements, changes or combinations, or the application of the inventive concept and technical solution to other occasions without improvement, shall be regarded as the protection scope of the application.

Claims

1. A method for constructing self-compacting concrete at the bottom of a box culvert, characterized in that, Includes the following steps: S100: Multiple box culverts are arranged inside the shield tunnel segments; each box culvert includes a top plate and an arc-shaped bottom plate, and the arc-shaped bottom plate is provided with reserved holes; S200: A matching cover template is made according to the reserved holes. The cover template is provided with at least one observation piece. An observation hole is provided through the observation piece along its axis. The inner wall of the observation hole is polished and has scale markings. A flexible isolation layer is provided on the side of the cover template close to the shield tunnel segment. The flexible isolation layer is made of water-permeable and lightweight non-woven geotextile material. It has a rough surface and a smooth surface. The rough surface is fixed to the cover template by direct spray sponge adhesive. The smooth surface faces the shield tunnel segment and is in direct contact with the self-compacting concrete to eliminate surface laitance and air bubbles through its adsorption effect. S300: The pre-reserved hole is covered by the covering template, and the covering template and the top plate are detachably connected by a connecting structure; the connecting structure includes: a fastener and a connecting assembly, wherein multiple fasteners are provided and arranged along the length direction of the covering template, one end of the connecting assembly is engaged with the fastener, and the other end of the connecting assembly abuts against the top plate; the fastener is a square timber, which is used to convert the concentrated force applied by the connecting assembly into a uniform load and uniformly transmit it to the surface of the covering template; S400: The area to be poured between the bottom of the box culvert and the shield tunnel segment is divided into several segmented areas, and adjacent segmented areas are softly isolated by isolation components; S500: Symmetrically pour self-compacting concrete into each segment area in sequence; S600: The height of the poured self-compacting concrete is monitored through an observation hole. When the self-compacting concrete reaches a preset height, the observation hole is sealed.

2. The method for constructing self-compacting concrete at the bottom of a box culvert according to claim 1, characterized in that, During the pouring of the self-compacting concrete, the top of the covering template is tapped to prevent the self-compacting concrete from not filling the reserved holes densely.

3. The method for constructing self-compacting concrete at the bottom of a box culvert according to claim 1, characterized in that, The following steps are included before step S100: S010: A discharge pipe is installed between the surface tanker truck and the tunnel tanker truck in the shield shaft, and the self-compacting concrete is discharged into the tunnel tanker truck through the discharge pipe; S020: The self-compacting concrete is transported to the segmented area using a transport vehicle.

4. The method for constructing self-compacting concrete at the bottom of a box culvert according to claim 3, characterized in that, Multiple buffers are arranged along the length of the feed pipe, and the distance between adjacent buffers does not exceed a set distance. The buffers are used to prevent excessive performance loss of the self-compacting concrete during the falling process.

5. The method for constructing self-compacting concrete at the bottom of a box culvert according to claim 1, characterized in that, Step S600 is followed by the following steps: S700: After the self-compacting concrete has initially set, remove the covering template and level the concrete at the observation hole.

Images