Prefabricated drainage box culvert steel formwork construction technology

Abstract

The invention discloses a construction technology for a prefabricated drainage box culvert steel formwork, and is suitable for the technical field of box culvert formwork construction. The drainage box culvert steel formwork system comprises the construction steps of construction preparation, installation of a pedestal and an inner formwork support, installation of a box culvert foundation, installation of an inner formwork assembly, installation of a formwork assembly, one-time pouring forming, formwork removal after pouring and transferring. The construction site regionalization layout is adopted, a box culvert steel bar binding area and a formwork installation transverse moving area with an adjustable inner formwork support are arranged, the circulating operation of formwork erecting, pouring, demolding and transferring is achieved through a main beam suspension type inner formwork assembly, and a hydraulic formwork collecting device is innovatively adopted for driving a symmetrical hinged type inner formwork system; and in combination with the symmetry and multi-point uniform stress characteristics of a plurality of auxiliary supporting devices, the bending deformation of the inner template is effectively controlled through sequential control of a layered equal-height high-speed pouring process with preferential base angles.

Description

Technical Field

[0001] This invention relates to the field of formwork construction technology for box culverts in marine water intake and drainage engineering, and particularly to a construction process for prefabricated steel formwork for drainage box culverts. Background Technology

[0002] In the marine water intake and drainage projects of nuclear power plants, box culverts, as key hydraulic structures, bear the core functions of transporting cooling water and balancing the sea level. Traditional formwork technology mostly uses loose wooden molds or fixed steel molds, which have many defects in the construction process: the formwork installation relies on manual assembly piece by piece, and the construction cycle of a single section is as long as 5-7 days; demolding requires knocking to separate, which is time-consuming and labor-intensive; the joint tightness is poor, which easily leads to grout leakage and honeycomb surface; high-altitude demolding is prone to falls, and full-span scaffolding occupies a lot of space and has a high risk of overturning. While some improvements have been proposed to address the limitations of existing technologies, significant shortcomings remain. For example, Chinese patent CN112761187A, concerning a large-diameter well electric formwork system, uses an electric hoist to lift the entire formwork, supporting variable-diameter construction. However, it relies on multi-machine synchronous control, making operation complex and requiring 8-10 people to coordinate. Furthermore, the high manufacturing cost of the large truss makes it difficult to apply to standard box culvert projects. Chinese patent CN218965724U proposes a U-shaped aqueduct pull-out inner formwork assembly, innovatively employing a self-contained guide wheel design, allowing the inner formwork assembly to move on the concrete surface. However, this technology focuses on U-shaped aqueduct construction and is difficult to directly apply to precast drainage box culvert construction. It also requires a certain degree of flatness in the concrete surface to ensure smooth movement of the guide wheels. To address these limitations, a more efficient, safe, and reliable construction process for precast drainage box culvert steel formwork assemblies is urgently needed. By optimizing formwork design and construction procedures, the efficiency and quality of precast drainage box culvert construction can be further improved, while reducing construction costs. Summary of the Invention

[0003] The purpose of this invention is to provide a construction process for prefabricated drainage culvert steel formwork, which solves the core problems of low efficiency and poor adaptability of traditional processes.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A construction process for prefabricated drainage box culvert steel formwork includes the following steps:

[0006] S1. Construction Preparation: Divide the construction site into a box culvert reinforcement binding area and a formwork installation and lateral movement area; according to the drainage box culvert design requirements, prefabricate the platform, end formwork and outer formwork assembly;

[0007] S2. Installation of pedestals and inner formwork supports: The length of the pedestals is determined according to the design length of the precast drainage culvert. Multiple pedestals are placed at intervals in the template installation transverse movement area. An inner formwork support is installed between the two ends of each pedestal. The center line of each inner formwork support is consistent with the center line of each pedestal. The inner formwork support has a built-in jack. The jack adjusts the elevation of each inner formwork support to the design height.

[0008] S3. Installation of box culvert foundation: Hoist the box culvert foundation obtained from the box culvert reinforcement binding area to the first support;

[0009] S4. Installation of the inner mold assembly: First, hoist the main beam into place and set it on the inner mold supports on both sides of the second base. The top of the main beam is installed with the corresponding number of inner top molds in axial sequence according to the preset template number. The two ends of the inner top mold are hinged to two symmetrical inner side molds. Each inner side mold is hinged to a corner mold at its lower end. The whole structure is symmetrical. The inner side molds and corner molds are adjusted by the extension and retraction of the mold retraction device controlled by the hydraulic system.

[0010] S5. Installation of the formwork assembly: The inner formwork assembly is transferred to the first pedestal via the walking system set at both ends of the main beam. The two ends of the main beam are respectively mounted on the inner formwork supports on both sides of the first pedestal. The outer formwork assembly, inner formwork assembly and end formwork are installed in sequence to complete the installation of the formwork assembly.

[0011] S6. One-time casting and shaping: The concrete cavity to be poured is formed by the outer mold assembly, inner mold assembly and end mold and then poured and cured until the concrete strength is reached.

[0012] S7. Demolding and transfer after pouring: The second pedestal is used to pre-assemble the box culvert foundation. First, the outer formwork assembly and end formwork are removed. Then, the inner formwork assembly is demolded and transferred to the second pedestal for the installation of the next formwork assembly.

[0013] As a preferred embodiment of the present invention, the process of installing and dismantling the auxiliary support device is also included. The auxiliary support device includes vertical struts, horizontal struts, and diagonal struts. The inner mold is composed of first and second inner molds that support each other. Both the first and second inner molds have obtuse sections and vertical sections that are obtuse to each other. The angle formed by the vertical section and the corner mold is equal to the obtuse angle. The corner mold is composed of first and second corner molds that are symmetrical to each other. The specific installation and dismantling process is as follows:

[0014] a) During formwork erection, after the inner top formwork is installed, vertical struts are installed on both sides of the main beam below the inner top formwork;

[0015] b) The first inner mold and the second inner mold are installed symmetrically, the inclined section is hinged to the inner top mold, and a transverse support rod is set between the first inner mold and the second inner mold.

[0016] c) The first and second corner molds, which are hinged to the vertical section, are installed symmetrically. Diagonal braces are set at the center of the bottom of the main beam and connected to the first and second corner molds respectively to complete the temporary support of the inner mold assembly in step S4.

[0017] d) Install the mold-collecting device sequentially according to the preset template numbers, and install and debug the hydraulic system;

[0018] e) When demolding after completing step S6 and casting, remove the diagonal bracing, horizontal bracing, and vertical bracing in reverse order according to steps a) to c).

[0019] Furthermore, after completing step c), the process also includes adjusting the inner mold assembly: controlling the jacks of the inner mold support to raise and lower according to the design requirements, adjusting the inner mold assembly to the design height, controlling the mold-collecting device through the hydraulic system to adjust the corner molds and inner side molds to their positions, adjusting the length of the transverse support rods between the first and second inner side molds, and adjusting the length of the diagonal support rods between the first and second corner molds and the main beam, thus completing the adjustment of the inner mold assembly.

[0020] As a preferred technical solution of the present invention, the one-time casting and molding in step S6 adopts a horizontal layered method to cast the concrete cavity at a constant speed. For the precast drainage box culvert with a double cavity structure, the casting is carried out in the following manner:

[0021] The horizontal layering involves dividing the concrete cavity to be poured into three layers: the bottom slab thickness layer (first pouring the bottom concrete of the box culvert); the middle and side wall height layer (after the concrete of the bottom slab thickness layer has been poured to near the bottom chamfer position, after the initial setting of the bottom slab thickness layer concrete is completed, then pouring the side wall and middle wall concrete); and the top slab thickness layer (after the concrete of the middle and side wall height layer has been poured to near the chamfer position, after the initial setting of the top slab concrete is completed, pouring the concrete above the inner top formwork up to the designed height of the box culvert). It is particularly important to note that layered pouring is performed before the initial setting of the concrete, and the new and old concrete layers must be vibrated before pouring the next layer to prevent "cold joints".

[0022] As a preferred technical solution of the present invention, in step S700, the inner mold assembly is demolded. The inner template serves as the main body of the inner mold assembly, i.e., the inner template is demolded. The inner template is formed by an inner top mold, an inner side mold, and a corner mold, creating a symmetrical structure with an open bottom. A pair of symmetrical demolding devices control the inner side mold and the corner mold through a hydraulic system. The demolding device includes a first demolding cylinder and a second demolding cylinder. The inner mold has an inclined section and a vertical section. The inclined section is opposite to the corner mold, and the first demolding cylinder is provided between them. The vertical section is connected to the side of the main beam through the second demolding cylinder. The demolding process is as follows:

[0023] 1) Removing the inner mold and corner mold: Start the hydraulic system, first control the first mold retraction cylinder to retract the corner mold, and then control the second mold retraction cylinder to retract the inner mold;

[0024] 2) Removal of the inner top mold: The top of the inner mold support is equipped with a drive roller, and the bottom of the main beam is equipped with a slide rail that matches the drive roller. Adjust the jack of the inner mold support to fall, the inner mold assembly descends, and the inner top mold separates from the top wall of the box culvert cavity.

[0025] 3) Overall lateral movement: The inner mold assembly enters the walking state from the demolding state through the walking system; the walking system includes a support frame, support legs and walking wheels. The support frame is located at both ends of the main beam and within the range between the two inner mold supports. Each support frame has support legs at both ends of the horizontal bottom, and each support leg is equipped with a walking wheel.

[0026] The main beam is driven forward by the drive rollers. The front end of the main beam moves to the second pedestal, the rear end inner formwork support descends and detaches from the main beam, and the traveling wheels located at the rear end of the main beam drive into the bottom plate surface of the box culvert cavity. The inner formwork assembly continues to move forward, and the front end inner formwork support is adjusted to make the main beam horizontal. Auxiliary supports are erected at the pre-embedded points on the second pedestal. The front end of the main beam passes through the auxiliary supports until it reaches its position, and the inner formwork assembly moves laterally to the second pedestal.

[0027] Furthermore, the lateral distance between the inner sides of the two support legs below each support frame is greater than the lateral distance between the outer sides of the two drive rollers on the inner mold support.

[0028] As a preferred technical solution of the present invention, step 3) of the overall lateral movement also includes a step of adjusting the center of gravity of the main beam. Specifically, when the front end of the main beam presses onto the auxiliary support, the center of gravity of the main beam is on the left side of the inner formwork support between the first and second platforms. During the transfer, the offset of the center of gravity of the main beam Δx≤0.2L, that is, the lateral offset of the center of gravity of the main beam shall not exceed 20% of the span L of the main beam. The span L of the main beam represents the horizontal projection length of the main beam from one end of the inner formwork support to the other end of the inner formwork support. After the main beam has moved into place, the auxiliary support is removed. Through the rapid positioning of the auxiliary support and the embedded parts, combined with the center of gravity offset control of Δx≤0.2L, the overturning moment of the main beam during the transfer across the platforms is automatically balanced. When the offset exceeds the limit, hydraulic compensation is activated immediately to ensure lateral stability (offset tolerance <5mm).

[0029] Furthermore, the total length of the main beam is 1.6 to 1.7 times the design length of the drainage box culvert.

[0030] In summary, compared with the prior art, the beneficial effects of the present invention are:

[0031] Firstly, the modular construction organization design significantly optimized the construction cycle. Through the coordinated operation of the formwork lateral movement system and the inner formwork support, combined with the standardized installation and dismantling process of the temporary support system, continuous multi-station flow operation was achieved. The "formwork support-pouring-demolding-transfer" cycle system of the inner formwork assembly, together with the pre-installation mechanism of the box culvert foundation, formed a spatial interleaving construction mode, which improved the formwork turnover efficiency by more than 40%. At the same time, through the mechatronics integration design of the hydraulic formwork retraction device and the walking system, the interval time between processes was shortened, and a highly efficient and collaborative prefabrication production cycle was established.

[0032] Secondly, multiple auxiliary support devices are evenly distributed axially within the inner formwork assembly, providing uniform support points within the box culvert cavity. This ensures uniform stress distribution during pouring and effectively controls the deformation of the inner formwork. Through transverse segmented and horizontal layered pouring processes, a bottom corner-priority and symmetrical synchronous pouring sequence is adopted, along with layer thickness control using uniform pouring at equal height and speed. This reduces the risk of concrete segregation and ensures structural compactness by prioritizing the filling of stress concentration areas. Furthermore, the symmetrical characteristics of the auxiliary support devices and the uniform stress distribution at multiple points prevent the inner formwork from shifting and deforming, significantly improving the integrity and durability of the box culvert structure.

[0033] Finally, the innovative design of the main beam based on the cantilever beam principle solved the deflection control problem. The cantilever section of the main beam is set at 1.6-1.7 times the length of the box culvert. The negative bending moment at the cantilever end is used to offset the positive bending moment at mid-span, reducing the mid-span deflection by up to 59%. Combined with a precise control system with a center of gravity offset Δx≤0.2L and a hydraulic compensation mechanism for the auxiliary supports, a dynamic balance system is constructed. This system not only ensures structural stability during formwork transfer but also achieves a dual improvement in safety and accuracy during construction through the rapid positioning technology of embedded parts. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the construction process of the prefabricated drainage box culvert steel formwork of the present invention.

[0035] Figure 2 This is a schematic diagram of the steel formwork structure for a drainage box culvert.

[0036] Figure 3 for Figure 2 CC cross-section;

[0037] Figure 4 for Figure 2 Cross-sectional view of DD;

[0038] Figure 5 This is a schematic diagram of the installation of the inner top mold and vertical support rods;

[0039] Figure 6 This diagram shows the installation steps for the inner mold and the transverse support rod.

[0040] Figure 7 The diagram shows the installation steps for the corner mold and diagonal brace.

[0041] Figure 8 The formwork support state after installing the mold retraction cylinder on the inner mold assembly;

[0042] Figure 9 The mold closing state after installing the mold closing cylinder on the inner mold assembly;

[0043] Figure 10 This is a schematic diagram of the installation of the platform and the inner mold support;

[0044] Figure 11 This is a schematic diagram showing the installation of the inner mold assembly from the second mounting base to the first mounting base;

[0045] Figure 12 This is a schematic diagram showing the template assembly transitioning from the casting state to the demolding state.

[0046] Figure 13 This is a schematic diagram of the lateral movement of the inner mold assembly;

[0047] Figure 14 This is a schematic diagram of the horizontal layered casting of the precast drainage box culvert of the present invention;

[0048] In the diagram: 100-Precast drainage box culvert, 1-Main beam, 2-Platform, 21-First platform, 22-Second platform, 3-Inner formwork support, 300-Jack, 4-Inner formwork assembly, 40-Inner top formwork, 400-Vertical strut, 41-Inner side formwork, 411-First inner side formwork, 412-Second inner side formwork, 410-Horizontal strut, 42-Corner formwork, 421-First corner formwork, 422-Second corner formwork, 420-Diagonal strut, 43-First formwork retraction cylinder, 44-Second formwork retraction cylinder, 5-Outer formwork assembly, 6-End formwork, 7-Ground, 8-Walking system, 81-Walking wheel, 82-Support leg, 83-Support frame, 9-Lowering height, 10-Auxiliary support, 11-Main beam center of gravity, 12-Embedded parts. Detailed Implementation

[0049] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0050] like Figure 1-14 As shown, a construction process for prefabricated drainage box culvert steel formwork includes the following steps:

[0051] S1. Construction Preparation: The construction site is divided into a box culvert reinforcement binding area and a formwork installation and lateral movement area; according to the design requirements of the 100mm precast drainage box culvert, precast platforms 2, end molds 6, and outer mold assemblies 5 are prepared; as follows... Figure 2-4 As shown, the precast drainage culvert steel formwork structure includes a platform 2, end molds 6, an outer mold assembly 5, and an inner mold assembly 4. The inner mold assembly 4 includes an inner mold support system, a walking system 8, and a hydraulic system. The walking system 8 includes a main beam 1 and a walking device. Inner mold supports 3 are provided on both sides of the platform 2. The main beam 1 is located directly above the platform 2, and its bottom ends are supported on the inner mold supports 3. The inner mold support system includes several support units and a mold closing device. Several inner molds are evenly distributed along the length of the main beam 1. The inner molds include an inner top mold 40, an inner side mold 41, and a corner mold 42.

[0052] S2. Installation of pedestals and inner formwork supports: The length of pedestal 2 is determined according to the design length of the precast drainage culvert 100. Multiple pedestals 2 are placed at intervals on the ground 7 of the template installation transverse movement area. An inner formwork support 3 is installed between the two ends of each pedestal 2. The center line of each inner formwork support 3 is consistent with the center line of each pedestal 2. The inner formwork support 3 has a built-in jack 300. The jack 300 adjusts the elevation of each inner formwork support 3 to the design height.

[0053] S3. Installation of box culvert foundation: Hoist the box culvert foundation obtained from the box culvert reinforcement binding area to the first support 21;

[0054] S4. Installation of the inner mold assembly: (e.g.) Figure 10 As shown, the main beam 1 is first hoisted into place and erected on the inner formwork supports 3 on both sides of the second pedestal 22, as follows. Figures 5-9 As shown, the top of the main beam 1 is installed with a corresponding number of inner top molds 40 in axial sequence according to the preset template number. The two ends of the inner top mold 40 are hinged to two symmetrical inner side molds 41. Each inner side mold 41 is hinged to a corner mold 42 at its lower end. The whole structure is symmetrical. The inner side molds 41 and corner molds 42 are adjusted by the extension and retraction of the mold-collecting device controlled by the hydraulic system.

[0055] S5. Installation of the template assembly: such as Figure 11 As shown, the inner mold assembly 4 is transferred to the first pedestal 21 via the walking system 8 set at both ends of the main beam 1. The two ends of the main beam 1 are respectively mounted on the inner mold supports 3 on both sides of the first pedestal 21. The outer mold assembly 5, the inner mold assembly 4, and the end mold 6 are installed in sequence, as shown. Figure 2 As shown, the installation of the template assembly is complete;

[0056] S6. One-time casting and shaping: such as Figure 14 As shown, the concrete cavity to be poured is formed by the outer mold assembly 5, the inner mold assembly 4 and the end mold 6 and then poured and cured until the concrete reaches the required strength.

[0057] S7. Demolding and transfer after pouring: such as Figure 11-13 As shown, the second base 22 is used to pre-assemble the box culvert foundation. First, the outer mold assembly 5 and the end mold 6 are removed, and then the inner mold assembly 4 is demolded. The demolded inner mold assembly 4 is then transferred to the second base 22 for the installation of the next template assembly.

[0058] In a preferred embodiment of this invention, the installation and removal process of the auxiliary support device is also included. The auxiliary support device includes a vertical strut 400, a horizontal strut 410, and an oblique strut. The inner mold 41 is composed of two symmetrical inner molds, each having an oblique section and a vertical section at an obtuse angle to each other. The angle formed by the vertical section and the corner mold 42 is equal to the obtuse angle. The corner mold 42 is composed of two symmetrical corner molds 42. Figure 7 As shown, the specific installation and dismantling process is as follows:

[0059] a) During formwork erection, after the inner top formwork 40 is installed, vertical struts 400 are set on both sides of the main beam 1 below the inner top formwork 40.

[0060] b) The first inner mold 411 and the second inner mold 412 are symmetrically installed, and the inclined section is hinged to the inner top mold 40. A transverse support rod 410 is provided between the first inner mold 411 and the second inner mold 412.

[0061] c) The first corner mold 421 and the second corner mold 422, which are hinged to the vertical section, are installed symmetrically. A diagonal brace 420 is set at the bottom center of the main beam 1 and connected to the first corner mold 421 and the second corner mold 422 respectively, to complete the temporary support of the inner mold assembly 4 in step S4.

[0062] d) Install the mold-collecting device sequentially according to the preset template numbers, and install and debug the hydraulic system;

[0063] like Figure 9 As shown, the auxiliary support device and the mold-collecting device are not in the same cross-section. The mold-collecting device includes a first mold-collecting cylinder and a second mold-collecting cylinder, and is equipped with a hydraulic system. The hydraulic system includes an oil pump, a control valve group, an oil tank, and oil pipes. The oil pump is connected to the oil inlet of the control valve group through oil pipes. The oil outlet of the control valve group is connected to the oil inlet and outlet of the first mold-collecting cylinder and the second mold-collecting cylinder through oil pipes. The extension and retraction movements of the first mold-collecting cylinder and the second mold-collecting cylinder are adjusted by the control valve group to ensure that the sealing rings at each oil pipe joint are intact and there is no oil leakage. The hydraulic system is tested to ensure that each cylinder and oil circuit works smoothly.

[0064] e) When demolding after completing step S6 and casting, remove the diagonal brace 420, horizontal brace 410 and vertical brace 400 in reverse order according to steps a) to c).

[0065] It should be noted that, for example Figure 3 and Figure 4 As shown, in this embodiment, the auxiliary support device and the formwork closing device are arranged at intervals along the direction 100 of the precast drainage box culvert. In the double-cavity precast drainage box culvert, each cavity contains the same device within the same cross-sectional plane; that is, a formwork closing device is installed on each inner template. Figure 3 Or auxiliary support devices such as Figure 4 In this embodiment, a combination of a mold-collecting device and an auxiliary support device is used for intermittent placement. The above method of installing and removing temporary supports can provide necessary support at critical stages without affecting the overall mold-building and mold-collecting process, effectively improving the reliability and safety of mold operation and ensuring the efficient and stable operation of the production process.

[0066] Furthermore, after completing step c), the process also includes adjusting the inner mold assembly 4: According to design requirements, the jacks 300 of the inner mold support 3 are raised and lowered to adjust the inner mold assembly 4 to the designed height. The hydraulic system is used to control the mold-collecting device to adjust the corner molds 42 and inner molds 41 outwards into position. The length of the transverse support rods 410 between the first and second inner molds is adjusted, as are the lengths of the diagonal support rods 420 between the first and second corner molds and the main beam 1, thus completing the adjustment of the inner mold assembly 4. After the inner mold assembly 4 is transferred, it is poured and cured at the original installation location, improving both the utilization rate of the inner mold assembly 4 and construction efficiency.

[0067] In a preferred embodiment of this invention, the one-time casting process in step S6 employs a horizontal, layered approach to pour the concrete cavities at a constant rate. For precast drainage box culverts with a double-cavity structure, the pouring is carried out in the following manner:

[0068] like Figure 14 As shown, the horizontal layering divides the concrete cavity to be poured into three layers: bottom slab thickness layer A: the bottom concrete of the box culvert is poured first; middle side wall height layer B: after the concrete of the bottom slab thickness layer has been poured close to the bottom chamfer position, the side wall and middle wall concrete is poured after the initial setting of the bottom slab thickness layer concrete. In this embodiment, the side wall height layer B is relatively high, so it is divided into B1 layer and B2 layer; top slab thickness layer C: after the B2 layer of the middle side wall height layer has been poured close to the chamfer position, the concrete is poured from the inner top formwork to the designed height of the box culvert after the initial setting of the concrete.

[0069] Special attention should be paid to pouring the concrete in layers before it sets. When pouring new and old concrete, the previous layer of concrete should be vibrated before pouring the next layer to prevent "cold joints". This embodiment adopts a design of horizontal segmentation and horizontal layering for one-time casting. The casting is carried out in segments along the length of the box culvert to reduce the amount of concrete poured at one time. The bottom formwork is poured first, and the upper part is poured after initial setting. When pouring the upper part, both sides must be poured simultaneously. If it is a double-cavity structure, the left and right side walls and the middle wall of the same cross section, such as the DD cross section, must be poured at the same height to ensure balanced stress on the formwork and avoid displacement or deformation due to unilateral stress, thus ensuring the quality of the box culvert. Uniform layered casting is used to prevent segregation of concrete due to its own weight and to ensure sufficient vibration. The upper layer is poured before the lower layer of concrete initially sets, utilizing the plastic state of the concrete to promote interlayer bonding and avoid cold joints. The interval time is set according to the initial setting time of the cement to ensure interlayer bond strength. The bottom-to-top casting sequence of bottom → middle side wall → top slab conforms to the structural stress transmission logic. Following the principle of left-right symmetry, the bottom foundation is cured first to provide stable support for the upper layer and prevent formwork deformation.

[0070] The symmetrical characteristics of the above auxiliary support devices, combined with the uniform stress distribution at multiple points and the equal-height, equal-speed casting process, form a synergistic mechanism that effectively controls the deformation of the inner formwork. Specifically, this is manifested in:

[0071] Firstly, the symmetrical installation of the inner formwork structure, including the first and second inner side molds and the corner molds 42, creates geometric stability with obtuse angles between them. In this embodiment, the 135° angle between the vertical sections of the corner molds and the inner side molds, along with the symmetrical arrangement of the transverse struts 410 and diagonal struts 420, allows the lateral pressure during concrete pouring on both sides to cancel each other out, preventing tilting or displacement of the formwork due to unilateral pressure. The diagonal struts 420 between the corner molds 42 on both sides and the bottom of the main beam 1 form a triangular support system, enhancing the bending stiffness of the formwork system and resisting the asymmetric load generated by concrete flow. Multiple auxiliary support devices are evenly arranged along the axial direction of the precast drainage culvert 100, with each support point sharing the local pressure to avoid stress concentration. This distribution method decomposes the overall load into multiple small-scale force units, reducing the risk of single-point deformation. The hydraulic system adjusts the length of the struts and the height of the jacks 300, compensating for minor displacements of the formwork during pouring in real time, ensuring that the support points are always evenly stressed.

[0072] Secondly, pouring at the same height and speed ensures that the concrete pressure increases evenly in time and space, avoiding local sudden loads that could lead to support instability. The layering sequence is optimized, with the first layer prioritizing the pouring of the chamfered area, taking advantage of the high stability of the bottom support structure. Subsequent layers gradually utilize the rigid auxiliary support of the cured concrete from bottom to top, forming a progressive force transfer path.

[0073] Finally, the vertical strut 400 resists vertical sinking, the horizontal strut 410 restricts horizontal expansion, and the diagonal strut suppresses torsional tendencies, forming a three-dimensional constraint system. Combined with the symmetry and multi-point support of the auxiliary support device, the deformation of the template is limited to the millimeter level. The symmetrical support system balances the load through geometric stability, and the stress is dispersed by multiple points. The equal height and equal speed of pouring ensures the spatiotemporal uniformity of the load application.

[0074] These three elements work together to form a closed-loop control mechanism of "spatial load equalization - dynamic equilibrium - real-time regulation," which fundamentally suppresses template deformation. Compared to traditional processes that rely on dense support or empirical reinforcement, this embodiment achieves a leap from passive bearing to active regulation.

[0075] In a preferred embodiment of this example, in step S700, the inner mold assembly 4 is demolded. The inner template serves as the main body of the inner mold assembly 4, i.e., the inner template is demolded. The inner template is formed by the inner top mold 40, the inner side mold 41, and the corner mold 42, creating a symmetrical structure with an open bottom. A pair of symmetrical demolding devices control the inner side mold 41 and the corner mold 42 via a hydraulic system. The demolding devices include a first demolding cylinder 43 and a second demolding cylinder 44. The inner side mold 41 has an inclined section and a vertical section. The inclined section is opposite to the corner mold 42, and the first demolding cylinder 43 is provided between them. The vertical section is connected to the side of the main beam 1 via the second demolding cylinder 44. The demolding process is as follows:

[0076] 1) Remove the inner mold 41 and corner mold 42: Start the hydraulic system, such as... Figure 9 As shown, first control the first mold retraction cylinder 43 to retract the corner mold 42, and then control the second mold retraction cylinder 44 to retract the inner mold 41.

[0077] 2) Remove the inner ejector mold 40: as shown Figure 12 As shown, the top of the inner mold support 3 is provided with a drive roller, and the bottom of the main beam 1 is provided with a slide rail that matches the drive roller. When the jack 300 of the inner mold support 3 is adjusted to a drop height 9 of 100cm, the inner mold assembly 4 drops and the inner top mold 40 separates from the top wall of the box culvert cavity.

[0078] 3) Overall lateral movement: such as Figure 13 As shown, the inner mold assembly 4 enters the walking state from the demolding state through the walking system 8; the walking system 8 includes a support frame 83, support legs 82 and walking wheels 81. The support frame 83 is located at both ends of the main beam 1 and within the range between the two inner mold supports 3. Each support frame 83 has support legs 82 at both ends of its horizontal bottom, and each support leg 82 is equipped with a walking wheel 81.

[0079] The main beam 1 is driven forward by the drive rollers. The front end of the main beam 1 moves to the second pedestal 22. The rear inner formwork support 3 descends and detaches from the main beam 1. The traveling wheel 81 located at the rear end of the main beam 1 drives into the bottom plate surface of the box culvert cavity. The inner formwork assembly 4 continues to move forward. The front inner formwork support 3 is adjusted so that the main beam 1 is in a horizontal state. The auxiliary support 10 is erected at the pre-embedded point on the second pedestal 22. The front end of the main beam 1 passes through the auxiliary support 10 until it moves into place. The inner formwork assembly 4 moves laterally to the second pedestal 22.

[0080] The above demolding steps are performed in stages using a hydraulic system: corner mold 42 → inner mold 41 → inner top mold 40, avoiding concrete damage caused by stress concentration; the traveling wheels 81 and the inner mold support 3 work together to achieve a seamless connection of "demolding and walking". The traveling wheels 81 drive into the bottom plate of the box culvert cavity as a temporary track, utilizing the existing structure for support, avoiding the need to lay additional tracks, and saving space and time; the demolding action and walking preparation are carried out simultaneously. Through the linkage control of the hydraulic system and the jack 300, the traditional discrete processes of demolding, hoisting and transportation are integrated into continuous actions, shortening the process interval to within 30 minutes, forming a rapid cycle of "demolding-transfer-support".

[0081] Furthermore, the lateral distance between the inner sides of the two support legs 82 below each support frame 83 is greater than the lateral distance between the outer sides of the two drive rollers on the inner mold support 3.

[0082] In a preferred embodiment of this invention, step 3) of the overall lateral movement further includes an adjustment step for the center of gravity 11 of the main beam. Specifically, when the front end of the main beam 1 presses onto the auxiliary support 10, the center of gravity of the main beam 1 is on the left side of the inner mold support 3 between the first platform 21 and the second platform 22. During the transfer, the offset of the center of gravity of the main beam 1 is Δx≤0.2L, that is, the lateral offset of the center of gravity 11 of the main beam must not exceed 20% of the span L of the main beam. The span L of the main beam represents the horizontal projection length of the main beam 1 from one end of the inner mold support 3 to the other end of the inner mold support 3. After the main beam 1 has moved into place, the auxiliary support 10 is removed. Through the rapid positioning of the auxiliary support 10 and the embedded part 12, combined with the center of gravity offset control of Δx≤0.2L, the overturning moment of the main beam during the transfer across the platform is automatically balanced. When the offset exceeds the limit, hydraulic compensation is activated immediately to ensure lateral stability (offset tolerance <5mm).

[0083] By adjusting the center of gravity 11 of the main beam and utilizing the auxiliary supports 10 and embedded parts 12 to achieve overall lateral movement, the aim is to ensure that the center of gravity offset of the main beam 1 does not exceed 20% of the span during transfer, thereby guaranteeing the stability and safety of the main beam 1. When Δx > 0.15L, eccentricity correction is performed on the main beam 1, and hydraulic compensation of the auxiliary supports 10 is automatically activated. Simultaneously, the design for the installation and removal of the auxiliary supports 10 provides temporary support during the lateral movement process while avoiding interference with subsequent operations, improving the stability and reliability of the entire demolding process, effectively preventing safety hazards caused by excessive center of gravity offset of the main beam 1, and ensuring the smooth progress of the production process and the normal operation of the equipment.

[0084] Furthermore, in this embodiment, the total length of the main beam 1 is 1.6-1.7 times the design length L0 of the precast drainage box culvert 100. This arrangement is equivalent to having cantilever sections at both ends of the main beam 1, with a cantilever length a = 0.3-0.35L0. The load on the cantilever section generates a negative bending moment at the support, partially offsetting the positive bending moment at mid-span, thus reducing the mid-span deflection. The mid-span deflection consists of two parts:

[0085]

[0086] Where: L0 is the design length of the drainage box culvert, in meters; q is the uniformly distributed load, in kN / m; E is the elastic modulus, in gigabytes of pressure (GPa); and I is the moment of inertia of the cross section, in meters. 4 ; 'a' represents the cantilever length, in meters (m).

[0087] When a = 0.3L0, the mid-span deflection is reduced by about 43% compared to a simply supported beam; when a = 0.35L0, it is reduced by about 59%.

[0088] Cantilever end deflection: When a = 0.3L0, the deflection at the cantilever end is usually much smaller than the deflection at mid-span, so the deflection of the cantilever segment itself is controllable.

[0089] This invention achieves continuous multi-station operation through modular construction organization design and the coordinated operation of the template lateral movement system and the inner formwork support 3. Multiple auxiliary support devices are evenly distributed axially within the inner formwork assembly 4 to effectively control the deformation of the inner formwork. The demolding process uses a hydraulic system to collect the formwork in stages, avoiding concrete damage caused by stress concentration and improving the safety and precision of the construction process. This invention not only improves construction efficiency but also further enhances the construction quality of the precast drainage box culvert 100 by optimizing the template design and construction process, and reduces construction costs. It is suitable for projects with high requirements for construction quality and efficiency, such as nuclear power plant marine water intake and drainage projects.

[0090] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A prefabricated drainage box culvert steel form construction process, characterized in that, The method comprises the following steps: S1, construction preparation: the construction site is divided into a box culvert steel bar binding area and a formwork installation and transverse area; a pedestal, an end form and an outer form assembly are prefabricated according to the design requirements of the drainage box culvert; S2, installation of the pedestal and the inner form support: the length of the pedestal is determined according to the design length of the prefabricated drainage box culvert, a plurality of pedestals are placed at intervals in the formwork installation and transverse area, an inner form support is installed between the two ends of each pedestal, a jack is built in the inner form support, and the elevation of each inner form support is adjusted to the design height by the jack; S3, installation of the box culvert foundation: the box culvert foundation obtained in the box culvert steel bar binding area is hoisted to the first pedestal; S4, installation of the inner form assembly: a main beam is hoisted in place and erected on the inner form supports on the two sides of the second pedestal, a corresponding number of inner top forms are installed on the main beam in the axial direction according to the preset formwork number, two inner side forms that are mutually symmetrical are hinged at the two ends of each inner top form, one corner form is hinged at the lower end of each inner side form, the whole is a mutually symmetrical structure, and the inner side forms and the corner forms are adjusted by the extension and retraction actions of the hydraulic system controlled retracting device; S5, installation of the formwork assembly: the inner form assembly is transferred to the first pedestal by the walking system arranged at the two ends of the main beam, the two ends of the main beam are erected on the inner form supports on the two sides of the first pedestal, the outer form assembly, the inner form assembly and the end form are installed in sequence, and the installation of the formwork assembly is completed; S6, one-time pouring and shaping: the pouring and curing of the to-be-poured concrete cavity enclosed by the outer form assembly, the inner form assembly and the end form are performed until the concrete strength is reached; S7, demolding and transfer after pouring: the second pedestal is pre-installed with the box culvert foundation, the outer form assembly and the end form are removed first, then the inner form assembly is demolded, and the demolded inner form assembly is transferred to the second pedestal for installation of the next formwork assembly.

2. The construction process of the prefabricated drainage box culvert steel form according to claim 1, characterized in that: The method further comprises the installation and removal process of an auxiliary support device, the auxiliary support device comprises vertical struts, horizontal struts and diagonal struts, the inner side forms are composed of first and second inner side forms that are mutually opposed, the first and second inner side forms each have a diagonal segment and a vertical segment that are mutually obtuse, the included angle formed by the vertical segment and the corner form is equal to the obtuse angle, the corner form is composed of first and second corner forms that are mutually symmetrical, and the specific installation and removal process is as follows: a) when the form is supported, the vertical struts are arranged on the two sides of the main beam below the inner top form after the inner top form is installed; b) the first inner side form and the second inner side form are symmetrically installed, the diagonal segment is hinged to the inner top form, and the horizontal struts are arranged between the first inner side form and the second inner side form; c) the first corner form and the second corner form that are hinged to the vertical segment are symmetrically installed, the diagonal struts are arranged at the center of the bottom of the main beam and connected to the first corner form and the second corner form, and the temporary support of the inner form assembly in step S4 is completed; d) the retracting devices are installed in sequence according to the preset formwork number, and the hydraulic system is installed and debugged; e) when the demolding is completed after the one-time pouring and shaping in step S6, the diagonal struts, the horizontal struts and the vertical struts are removed in reverse according to steps a) to c).

3. The construction process of a prefabricated drainage box culvert steel form according to claim 2, characterized in that: After completing step c), the process also includes adjusting the inner mold assembly: according to the design requirements, control the jacks of the inner mold support to raise and lower, adjust the inner mold assembly to the design height, control the mold-collecting device through the hydraulic system to adjust the corner mold and inner mold to the position, adjust the length of the transverse support rod between the first and second inner molds, and adjust the length of the diagonal support rod between the first and second corner molds and the main beam respectively, and complete the adjustment of the inner mold assembly.

4. The construction process of a prefabricated drainage box culvert steel form according to claim 2, characterized in that: In step S6, the one-time casting process employs a horizontal, layered method for uniformly pouring the concrete into the cavity to be cast. For precast drainage box culverts with a double-cavity structure, the pouring is carried out in the following manner: The horizontal layering involves dividing the concrete cavity to be poured into three layers: the bottom slab thickness layer (first pouring the bottom concrete of the box culvert); the middle and side wall height layer (after the concrete of the bottom slab thickness layer has been poured to near the bottom chamfer position, after the initial setting of the concrete of the bottom slab thickness layer, pouring the side wall and middle wall concrete); and the top slab thickness layer (after the concrete of the middle and side wall height layer has been poured to near the chamfer position, after the initial setting of the concrete of the middle and side wall height layer, pouring the concrete above the inner top formwork up to the designed height of the box culvert).

5. The construction process of prefabricated drainage box culvert steel formwork according to claim 1, characterized in that: In step S700, the inner mold assembly is demolded. The inner template serves as the main body of the inner mold assembly, i.e., the inner template is demolded. The inner template is formed by the inner top mold, inner side mold, and corner mold, creating a symmetrical structure with an open bottom. A pair of symmetrical demolding devices control the inner side mold and corner mold through a hydraulic system. The demolding device includes a first demolding cylinder and a second demolding cylinder. The inner mold has an inclined section and a vertical section. The inclined section is opposite to the corner mold, and the first demolding cylinder is located between them. The vertical section is connected to the side of the main beam through the second demolding cylinder. The demolding process is as follows: 1) Removing the inner mold and corner mold: Start the hydraulic system, first control the first mold retraction cylinder to retract the corner mold, and then control the second mold retraction cylinder to retract the inner mold; 2) Removal of the inner top mold: The top of the inner mold support is equipped with a drive roller, and the bottom of the main beam is equipped with a slide rail that matches the drive roller. Adjust the jack of the inner mold support to fall, the inner mold assembly descends, and the inner top mold separates from the top wall of the box culvert cavity. 3) Overall lateral movement: The inner mold assembly enters the walking state from the demolding state through the walking system; the walking system includes a support frame, support legs and walking wheels. The support frame is located at both ends of the main beam and within the range between the two inner mold supports. Each support frame has support legs at both ends of the horizontal bottom, and each support leg is equipped with a walking wheel. The main beam is driven forward by the drive rollers. The front end of the main beam moves to the second pedestal, the rear end inner formwork support descends and detaches from the main beam, and the traveling wheels located at the rear end of the main beam drive into the bottom plate surface of the box culvert cavity. The inner formwork assembly continues to move forward, and the front end inner formwork support is adjusted to make the main beam horizontal. Auxiliary supports are erected at the pre-embedded points on the second pedestal. The front end of the main beam passes through the auxiliary supports until it reaches its position, and the inner formwork assembly moves laterally to the second pedestal.

6. The construction process of a prefabricated drainage box culvert steel form according to claim 5, characterized in that: The lateral distance between the inner sides of the two support legs below each support frame is greater than the lateral distance between the outer sides of the two drive rollers on the inner mold support.

7. The construction process of a prefabricated drainage box culvert steel form according to claim 5, characterized in that, The step of adjusting the center of gravity of the main beam is further included in the step 3) of overall transverse movement, specifically: when the front end of the main beam is pressed on the auxiliary support, the center of gravity of the main beam is on the left side of the inner mold support between the first pedestal and the second pedestal, and the offset amount Δx of the center of gravity of the main beam is ≤0.2L during the transverse movement, that is, the transverse offset of the center of gravity of the main beam cannot exceed 20% of the main beam span L, and the main beam span L represents the horizontal projection length of the main beam from one end of the inner mold support to the other end of the inner mold support, and the auxiliary support is removed after the main beam is moved to the position.

8. The construction process of a prefabricated drainage box culvert steel form according to claim 7, characterized in that: The total length of the main beam is 1.6-1.7 times the design length of the drainage box culvert.

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