Carrying and assembling construction process of three-opening type prefabricated box culvert adaptive to limited space

Abstract

The invention discloses a carrying and splicing construction process of a three-opening type prefabricated box culvert adaptive to a limited space. The carrying and splicing construction process comprises the following steps: S1, prefabricating and forming the box culvert; s2, transporting the box culvert; and S3, hoisting and splicing the box culvert. On the one hand, the pre-buried assembly with the hoisting holes is formed based on pre-burying and exterior combination, hoisting stress point positions are increased, multi-point-position hoisting of the box culvert is facilitated, hoisting forward movement and hoisting overturning of the box culvert are facilitated, and potential safety hazards caused by stress concentration during hoisting of the three-opening type prefabricated box culvert are reduced; on the other hand, on the basis of horizontal transportation and transfer unloading of the box culvert, centering adjustment of the connection vehicle and down-regulation of the gravity center of the box culvert, the box culvert can be reversed and hoisted to move forwards in the hole, meanwhile, the space to be installed is utilized to implement in-situ overturning and alignment adjustment of the box culvert, and therefore the box culvert is suitable for carrying and assembling of the three-opening type prefabricated box culvert in the limited space.

Description

Technical Field

[0001] This invention relates to the field of large shield tunnel construction technology, specifically to a safe unloading and assembly technology for large-size precast box culverts in confined spaces, which is particularly applicable to the unloading and assembly operations of fully precast box culverts with three-section and other large cross-sections in large-diameter shield tunnel projects. Background Technology

[0002] In recent years, with the rapid development of transportation infrastructure, large-diameter shield tunnel projects have been widely used in projects such as river crossings, sea crossings, and urban underground utility tunnels, driving the upgrading of tunnel internal structure construction towards industrialization and prefabrication. Among these, box culverts, as the core load-bearing and functional components inside the tunnel, have gradually shifted from traditional single-arch cast-in-place structures to three-arch and various types of fully prefabricated structures. Increasing the prefabrication rate has become a key technical path to reduce on-site work intensity, shorten construction cycles, and ensure project quality. To further reduce the amount of cast-in-place work inside the tunnel and improve construction efficiency, the design dimensions of prefabricated box culverts are showing a gradual increasing trend to match the cross-sectional characteristics and multi-functional integration requirements of large-diameter shield tunnels. However, the internal space of shield tunnels is limited by structural constraints such as the clearance of the shield machine trolley and the inner diameter of the tunnel segments, and the unloading of box culverts requires reliance on temporary transportation and hoisting equipment within the tunnel. This makes the unloading and assembly of large-size prefabricated box culverts within the tunnel a prominent technical challenge during construction.

[0003] In existing technologies, the unloading methods for precast box culverts in tunnels are mainly divided into two categories: vertical transportation unloading and horizontal transportation unloading. For box culverts with smaller height dimensions, vertical transportation is usually adopted, where the box culvert is placed vertically on a transport vehicle, and transportation and unloading are achieved by utilizing the clearance height of the shield tunneling trolley to meet the condition of "box culvert height + transport vehicle height < trolley clearance height". For box culverts with larger dimensions, horizontal transportation is often adopted, where the box culvert is placed horizontally on a transport vehicle, and the operation is completed with the adaptation standard of "box culvert single section width (2m) + transport vehicle height < trolley clearance height". However, when the size of the precast box culvert exceeds a certain proportional relationship with the inner diameter of the tunnel segment, the above conventional unloading methods have obvious limitations: if the horizontal transportation mode is adopted, when the sum of "box culvert single section width + transport vehicle height" exceeds the effective working height of the hoisting equipment (crane) in the tunnel, or when the "box culvert horizontal width" exceeds the safe working range corresponding to the hoisting range of the crane, the box culvert cannot be lifted and unloaded smoothly by the crane; thus, the conditions for construction in the tunnel cannot be met.

[0004] Therefore, based on the above, the following technical challenges exist for large-section, fully prefabricated box culverts with three openings: 1) In tunnel engineering with large-diameter shields, the carrying capacity of transportation equipment and the scope of hoisting equipment operation, as the diameter of the shields increases, the size of the box culverts also increases. Due to multiple factors such as the constraints of the internal space of the tunnel, it is obvious that ordinary transportation modes can hardly meet the spatial needs. 2) Since the product is a three-section prefabricated box culvert (weighing about 30 tons, also called an arc-shaped component), the hoisting position can only be the top of the box culvert. Therefore, when the crane is hoisting, it not only needs to lift the entire box culvert vertically to detach it from the transport trolley, but also the stress point is concentrated on the top of the box culvert, causing stress concentration. That is, it cannot meet the space requirements for unloading the box culvert, and at the same time, it cannot eliminate the assembly safety hazards caused by stress concentration. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an improved transportation and assembly construction process for a three-section prefabricated box culvert that is adapted to confined spaces.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A transportation and assembly construction process for a three-section precast box culvert adapted to confined spaces, wherein the box culvert forms an assembly side and a hoisting side from both sides along its thickness direction, and the box culvert includes a horizontal section, an arc-shaped bottom, and a vertical support section, wherein an evacuation hole is formed on the vertical support section. The process includes the following steps: S1, Prefabrication of box culverts Using the bottom corner of the evacuation hole near the hoisting side as a reference, pre-embedded and assembled pre-embedded components are formed at the bottom corners of the two vertical support parts respectively. Each pre-embedded component includes a first part pre-embedded and formed integrally with the vertical support part, and a second part that is detached from the first part and has a hoisting hole. S2, Box Culvert Transportation First, the box culvert is placed horizontally on a transport vehicle with its self-assembly side facing down and its hoisting side facing up. The transport vehicle then moves the flat-lying box culvert forward into the transfer area. Second, the transfer equipment in the transfer area unloads the box culvert from the transport vehicle and moves it to the bottom of the box culvert using a shuttle vehicle. At the same time, the center alignment of the shuttle vehicle's carrying platform and the box culvert is adjusted. Finally, the transfer equipment lowers the box culvert onto the carrying platform below, with the box culvert's center of gravity close to the center of the tunnel. The carrying platform rotates around its own axis to ensure that the horizontal section of the box culvert extends in the same direction as the horizontal section of the already installed box culvert, while keeping the box culvert on the shuttle vehicle lying flat with its horizontal section facing backward, its curved bottom facing forward, and its hoisting side facing upward. S3, hoisting and assembly of box culverts First, align the lifting tools with the corresponding lifting holes on the horizontal and vertical support sections, then lift the culvert horizontally and move it forward to the front of the box culvert to be installed. Second, using the rear edge of the assembly side as a reference, flip the front end of the box culvert downwards so that the horizontal part of the box culvert faces upwards, the curved bottom faces downwards, and the assembly side faces backwards. Then align the box culvert vertically with the already installed box culvert. Finally, using the lifting side of the frontmost installed box culvert as the reference side, connect and splice the box culvert from the assembly side to the reference side.

[0007] According to a specific embodiment and preferred aspect of the present invention, in step S1, the first component includes an L-shaped steel plate forming the bottom corner of the evacuation hole, pre-embedded ribs and sleeves respectively penetrating the horizontal and vertical portions of the L-shaped steel plate into the interior of the vertical support portion; the second component includes an external module having a horizontal base and a vertical base, and an external connector for detaching and assembling the horizontal base and the vertical base with the aligned sleeve, wherein a lifting hole is formed on the external module. By aligning and assembling the two components, the two lifting holes are kept relatively aligned, thereby facilitating the control of the center of gravity during the lifting process. This not only ensures safety but also guarantees that the load-bearing capacity formed by the pre-embedded components meets the lifting requirements regardless of the angle.

[0008] Furthermore, steel plate rings are welded to both ends of the lifting hole. The core purpose of these steel plate rings is to enhance, protect, and improve reliability. For example, they disperse stress concentration, as the edge of the lifting hole is the area of ​​highest stress concentration. By increasing the stress-bearing area, the steel plate rings more evenly transmit the enormous concentrated force to the main structure, effectively preventing the steel at the hole edge from tearing or undergoing plastic deformation due to excessive stress. They also protect the slings and prevent accidents; the steel plate rings form a smooth and robust guide surface, reducing the risk of direct friction and cutting between the slings (wire ropes, lifting slings) and the edge of the lifting hole, thus extending the service life of the slings. The thickened edges also greatly improve the resistance to deformation, ensuring that the slings are always in the designed position during hoisting, preventing them from coming off or getting stuck, and improving operational safety. Maintaining the stability of the aperture and controlling the center of gravity, the steel plate ring can effectively resist external forces during hoisting, maintaining the designed shape and size of the hoisting hole. At the same time, based on the alignment and disassembly and control of the center of gravity, it ensures that the hoisting force is always transmitted in the predetermined direction, making the box culvert more stable during hoisting and preventing the center of gravity from shifting due to the deformation of the aperture.

[0009] In some specific implementations, the embedded ribs are shaped into straight rods, I-shaped, L-shaped, T-shaped, and hook-shaped types. The rated load of the embedded components, which are composed of embedded ribs, sleeves, external modules, and external connectors with different shapes, is greater than the bearing stress at any angle during actual hoisting. This not only relatively evenly distributes the stress concentration caused by hoisting, but also makes it more conducive to flipping within confined spaces.

[0010] Furthermore, the outer surface of the L-shaped steel plate is flush with the inner wall of the evacuation hole, and the two end faces of the evacuation hole are flush with the opposite end faces of the L-shaped steel plate; both the horizontal and vertical bases are aligned and fitted with the opposite end faces of the L-shaped steel plate. Because the outer surface is flush with the inner wall of the evacuation hole, the L-shaped steel plate and the embedded reinforcement are part of the box culvert, and the assembled box culvert does not need to extend beyond the L-shaped steel plate and embedded reinforcement, nor does it affect the performance of the evacuation hole itself. Then, the alignment and fitting of the bases maximizes the contact area with the L-shaped steel plate, which is more conducive to uniform stress distribution.

[0011] According to another specific embodiment and preferred aspect of the present invention, the transportation process in step S2 includes a forward movement process, a transfer process, and a reversing process. During the transfer process, multiple shifting unloading outriggers are simultaneously lifted to unload the box culvert from the transport vehicle; and during the reversing process, multiple shifting unloading outriggers are simultaneously lowered to place the box culvert onto the carrying platform. The purpose of the transfer is not only to facilitate the transfer between the transport vehicle and the connecting vehicle, but also to more effectively lower the center of gravity of the box culvert so that it lies flat inside the tunnel, with its center of gravity relatively close to the center of the tunnel. This provides maximum space for the reversing of the box culvert and the forward movement of the crane, avoiding collisions between the box culvert and the tunnel walls during transfer and forward movement.

[0012] Preferably, during the forward movement, the transport vehicle moves along the middle of the horizontal section of the installed box culvert, and in straight-line travel, the length direction of the box culvert is consistent with the forward direction. This alignment along the middle section avoids excessive differences in distance between the box culvert and the left and right walls, minimizes the range of motion for center-of-gravity alignment adjustments, and facilitates easier reversal and forward movement of the box culvert.

[0013] In some specific implementations, the reversing process includes a centering connection process and a rotational alignment process. The centering connection process includes an initialization phase, a sensing phase, a calculation phase, a control phase, and an execution phase. The initialization phase involves presetting the box culvert design parameters and a reference coordinate system, with the box culvert thickness direction as the X-axis, the box culvert width direction as the Y-axis, and the box culvert height direction as the Z-axis. The parameters include length, width, height, material density, and segment weight. The sensing phase involves synchronously collecting real-time distance data between the shuttle vehicle and the left side wall, right side wall, and top of the box culvert using distance measuring sensors. The calculation phase involves obtaining the three-dimensional coordinates of the shuttle vehicle relative to the box culvert and the coordinates of the box culvert's center of gravity. The control phase generates a center of gravity adjustment command for the shuttle vehicle based on the coordinate deviation and dynamically adjusts the centering position. The execution phase, after center of gravity alignment, triggers a mechanical lock to stably lock the shuttle vehicle and the box culvert together. In short, the reversing process is broken down into five distinct stages: initialization, perception, calculation, control, and execution. This division embodies a complete perception-decision-execution closed-loop control concept. Its advantages are: the entire connection process is clearly defined, making it easy to understand, implement, and debug; each stage has independent functions, reducing system complexity and improving maintainability and reliability; from data acquisition and coordinate calculation to dynamic adjustment and final locking, the entire process requires no manual intervention, achieving a high degree of automation; in addition, based on the mechanical locking device, it prevents the shuttle vehicle from tilting or overturning due to inaccurate positioning at the bottom of the box culvert, causing the center of gravity to shift.

[0014] Furthermore, the ranging sensor includes a left-side sensor, a right-side sensor, and a top sensor. The left-side sensor is installed in the middle of the left side of the shuttle vehicle, with the detection direction perpendicular to the left side wall of the box culvert, and collects the lateral distance L1. The right-side sensor is installed in the middle of the right side of the shuttle vehicle, with the detection direction perpendicular to the right side wall of the box culvert, and collects the lateral distance L2. The top sensor is installed at the center of the top of the shuttle vehicle, with the detection direction perpendicular to the top of the box culvert, and collects the vertical distance H. Based on the preset reference coordinate system, the distance data is converted into the three-dimensional coordinates of the shuttle vehicle through trigonometric function calculations. Y = Y0 + ΔY = Y0 + (L1 - L2) ÷ 2, where Y is the current lateral coordinate of the shuttle vehicle; Y0 is the lateral reference coordinate of the box culvert centerline; and ΔY is the lateral offset of the shuttle vehicle relative to the centerline. Z = Z0 + ΔZ = Z0 + (H0 - H), where Z is the current vertical coordinate of the shuttle vehicle; Z0 is the reference coordinate of the top of the box culvert; ΔZ is the vertical offset of the shuttle vehicle relative to the top of the box culvert; H0 is the design height of the box culvert; and H is the distance from the top surface of the support platform to the top of the box culvert. First, the symmetrical layout of the three sensors (left, right, and top) enables comprehensive perception of the shuttle vehicle's position and orientation within the culvert cross-section at minimal cost (using only three data points). Second, the coordinate transformation formula is based on simple geometric relationships, has low computational complexity, fast response, and clear physical meaning, and can convert raw distance data into spatially meaningful coordinates in real time.

[0015] In addition, the horizontal coordinate of the centroid G Y G Y =Y0+[(L1-L2)×α]÷2, where α is the mass distribution coefficient, which can be calibrated; the vertical coordinate of the centroid is G. Z G Z =Z0+(H0-H)×k, where the center of gravity height is estimated using the top distance and calibration coefficient k. That is, the formulas for the lateral coordinates of the center of gravity (introducing an empirical coefficient α) and the vertical coordinates (introducing a calibration coefficient k) avoid complex theoretical calculations and are more practical and operable through engineering calibration, thus approximating reality.

[0016] Furthermore, the control phase is based on a dynamic closed-loop control strategy, and the formula is as follows: u(t)=K p e(t)+K i +K d Where u(t) is the control output; e(t) is the deviation between the current coordinate and the centroid coordinate, e = target coordinate - current coordinate; K p ,K i ,K dHere, K represents the proportional, integral, and derivative gain coefficients; t is the time variable; and τ is the integral time variable. The classic PID control algorithm is used to achieve dynamic adjustment. Its advantages are: PID control can immediately generate adjustment commands based on the real-time deviation e(t), ensuring a fast system response; the integral term K... i It can accumulate and eliminate persistent deviations, enabling the shuttle bus to ultimately align precisely with the center of gravity coordinates; the differential term K d t can predict the trend of deviation changes and apply reverse control in advance, making the adjustment process smoother and avoiding oscillations around the target position.

[0017] Due to the implementation of the above technical solutions, the present invention has the following advantages compared with the prior art: In existing large-diameter shield tunneling projects, with increasing shield diameters and box culvert sizes, the space constraints within the tunnel and other factors make conventional transportation methods insufficient to meet spatial requirements. Furthermore, because the product is a three-section, large-section, fully prefabricated box culvert (weighing approximately 30 tons, also known as an arc-shaped component), its lifting position can only be the top of the culvert. Therefore, during lifting, the crane not only needs to vertically lift the entire box culvert to detach it from the transport trolley, but also concentrates stress at the top of the culvert, resulting in stress concentration. This not only fails to meet the space requirements for unloading the box culvert but also fails to eliminate the assembly safety hazards caused by stress concentration. This invention is based on... A comprehensive design was developed for the transportation and assembly construction process of a three-opening precast box culvert adapted to confined spaces, cleverly addressing the shortcomings and defects of existing technologies. Adopting this process, firstly, using the bottom corner of the evacuation opening near the hoisting side as a reference, pre-embedded components are pre-embedded and assembled at the bottom corners of the two vertical supports. Each pre-embedded component includes a first part integrally embedded with the vertical support and a second part detachable from the first part and forming a hoisting hole. Secondly, the box culvert is horizontally supported on a transport vehicle with the assembly side facing down and the hoisting side facing up, and the transport vehicle moves the horizontally laid box culvert forward into a transfer area. Then, based on the transfer equipment in the transfer area, the box culvert is unloaded from the transport vehicle, and... A shuttle bus is moved to the area beneath the box culvert, and the center alignment of the shuttle bus's carrying platform and the box culvert is adjusted. Then, a transfer device lowers the box culvert onto the carrying platform below, and the carrying platform rotates around its own axis to align the horizontal section of the box culvert with the horizontal section of the already installed box culvert, while maintaining the box culvert on the shuttle bus lying flat with its horizontal section facing backward, its curved bottom facing forward, and its lifting side facing upward. Finally, the lifting equipment is aligned with the corresponding lifting holes on the horizontal and vertical supports, and the crane is then lifted horizontally and moved forward to the front of the box culvert to be installed. Next, using the rear edge of the assembly side as a reference, the front end of the box culvert is flipped downward, so that the horizontal section of the box culvert faces upward, its curved bottom faces downward, and its assembly side faces backward. Finally, the box culvert is aligned with the already installed box culvert in a vertical alignment. Alignment is performed, and then the hoisting side of the frontmost installed box culvert is used as the reference side. The self-assembly side of the box culvert is then connected and spliced ​​with the reference side. Therefore, on the one hand, the present invention increases the number of stress points for hoisting by forming a pre-embedded component with hoisting holes based on the combination of pre-embedded and external assembly. This not only facilitates the multi-point hoisting of the box culvert, but also makes it easier to move the box culvert forward and rotate it during hoisting, reducing the safety hazards caused by the concentration of stress during the hoisting of the three-opening prefabricated box culvert. On the other hand, based on the flat transportation of the box culvert, transfer and unloading, centering adjustment of the connecting vehicle, and lowering of the center of gravity of the box culvert, the box culvert can be reversed and moved forward during hoisting within the tunnel. At the same time, the space to be installed is used to implement the in-situ rotation and alignment adjustment of the box culvert, thereby adapting to the transportation and assembly of the three-opening prefabricated box culvert in the confined space. Attached Figure Description

[0018] Figure 1 This is a structural schematic diagram of the three-section prefabricated box culvert (arc-shaped component) in this embodiment; Figure 2 This is a schematic diagram illustrating the implementation principle of this embodiment; Figure 3 This is a schematic diagram of the pre-embedded component in this embodiment; Figure 4 This is a schematic diagram of another structural distribution of the embedded components in this embodiment; Figure 5 for Figure 2 A front view diagram of the middle box culvert moving horizontally forward; Figure 6 for Figure 2 Front view diagram of the transfer and unloading process in the middle box culvert; Figure 7 for Figure 2 A schematic diagram of the connection and transfer structure of the middle box culvert; Figure 8 for Figure 7 A top view diagram (after reversal) Figure 9 for Figure 2 Main view diagram of the connection and transfer of the middle box culvert; Figure 10 for Figure 2 Schematic diagram of the horizontal hoisting of the middle box culvert; Figure 11 for Figure 2 A structural diagram of the intermediate box culvert during hoisting and tilting; Figure 12 for Figure 2 Structural diagram of the intermediate box culvert during hoisting and alignment; Wherein: H, Box culvert (three-way precast box culvert or arc-shaped component); h1, Horizontal section; h2, Arc-shaped bottom; h3, Vertical support section; h30, Evacuation hole; a, Assembly side; b, Lifting side; M, Embedded component; m1, First component; 10, L-shaped steel plate; 11, Embedded reinforcement; 12, Sleeve; m2, Second component; 20, External module; 200, Horizontal foot; 201, Vertical foot; 21, External connector; K, Lifting hole; 22, Steel plate ring; 1, Transport vehicle; 2, Transfer equipment (shifting unloading outrigger); 3, Shuttle vehicle; 30, Bearing platform; 4, Lifting tool; 5, Crane; T, Installed box culvert. Detailed Implementation

[0019] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0020] like Figure 1 and Figure 3 As shown, the three-hole prefabricated box culvert (hereinafter referred to as box culvert) of this embodiment has an assembly side a and a hoisting side b formed on both sides of the box culvert H in the thickness direction, and the box culvert includes a horizontal part h1, an arc-shaped bottom h2, and a vertical support part h3, wherein an evacuation hole h30 is formed on the vertical support part h3.

[0021] Combination Figure 2 , 4 As shown in Figure 12, the transportation and assembly construction process of the three-section prefabricated box culvert adapted to confined spaces in this embodiment includes the following steps: S1, Prefabrication of box culverts Taking the bottom corner of the evacuation hole h30 near the hoisting side b as a reference, pre-embedded and assembled pre-embedded components M are formed at the bottom corners of the two vertical support parts h3 respectively. Each pre-embedded component M includes a first part m1 that is pre-embedded integrally with the vertical support part h3 and a second part m2 that is detached from the first part m1 and has a hoisting hole K. S2, Box Culvert Transportation First, the box culvert H is horizontally supported on the transport vehicle 1 with its self-assembly side facing down (a) and its hoisting side facing up (b). The transport vehicle 1 then moves the flat-lying box culvert H forward into the transfer area. Second, the transfer device 2 in the transfer area unloads the box culvert H from the transport vehicle 1 and moves it to the underside of the box culvert H using a shuttle vehicle 3. At the same time, the center alignment adjustment of the support platform 30 of the shuttle vehicle 3 and the box culvert H is performed. Finally, the transfer device 2 aligns the box culvert H with the support platform 30 below, with the center of gravity of the box culvert H close to the center of the tunnel (the distance between the center of gravity and the center is ±20mm). The support platform 30 rotates around its own axis so that the horizontal part h1 of the box culvert H is aligned with the horizontal extension direction of the installed box culvert T. At the same time, the horizontal part h1 of the box culvert H on the shuttle vehicle 3 is kept facing backward, the arc-shaped bottom h2 is facing forward, and the hoisting side (b) is facing upward. S3, hoisting and assembly of box culverts First, the lifting tool 4 is aligned with the corresponding lifting holes of the horizontal and vertical support parts, respectively. Then, the crane 5 is lifted horizontally and moved forward to the front of the box culvert H to be installed. Second, the front end of the box culvert H is flipped downward with the rear edge of the assembly side a as the reference, so that the horizontal part h1 of the box culvert H faces upward, the arc bottom h2 faces downward, and the assembly side a faces backward. Then, the box culvert H is aligned vertically with the already installed box culvert T. Finally, the box culvert H is spliced ​​by connecting the self-assembly side a with the reference side with the lifting side b of the frontmost installed box culvert T.

[0022] In some specific embodiments, the first component m1 includes an L-shaped steel plate 10 forming the bottom corner of the evacuation hole h30, pre-embedded reinforcing bars 11 and sleeves 12 that penetrate into the vertical support h3 from the horizontal and vertical portions of the L-shaped steel plate 10, respectively; the second component m2 includes an external module 20 having a horizontal base 200 and a vertical base 201, and an external connector 21 that detachably connects the horizontal base 200 and the vertical base 201 to the aligned sleeves 12, wherein a lifting hole K is formed on the external module 20. By aligning and detaching the two components, the two lifting holes are kept relatively aligned, thus facilitating the control of the center of gravity during the lifting process. This not only ensures safety but also guarantees that the load-bearing capacity formed by the pre-embedded components meets the lifting requirements regardless of the angle. Furthermore, the outer surface of the L-shaped steel plate 10 is flush with the inner wall of the evacuation hole h30, and the two end faces of the evacuation hole h30 are flush with the opposite end faces of the L-shaped steel plate 10; the horizontal base 200 and the vertical base 201 are both aligned and fitted with the opposite end faces of the L-shaped steel plate 10. Since the outer surface is flush with the inner wall of the evacuation hole, the L-shaped steel plate and the embedded reinforcement are part of the box culvert, and the box culvert does not need to extend beyond the L-shaped steel plate and the embedded reinforcement after assembly, nor does it affect the performance of the evacuation hole itself. Then, the alignment and fitting of the bases maximizes the contact area with the L-shaped steel plate, which is more conducive to uniform stress distribution; as for the thickness of the external module 20, it is generally around 25mm.

[0023] In this example, steel plate rings 22 are welded to both ends of the lifting hole K. The core purpose of the steel plate rings 22 is to enhance, protect, and improve reliability. For example, they disperse stress concentration, as the edge of the lifting hole is the area of ​​highest stress concentration. By increasing the stress-bearing area, the steel plate rings more evenly transmit the enormous concentrated force to the main structure, effectively preventing the steel at the hole edge from tearing or undergoing plastic deformation due to excessive stress. They also protect the slings and prevent accidents; the steel plate rings form a smooth and robust guide surface, reducing the risk of direct friction and cutting between the slings (wire rope, lifting straps) and the edge of the lifting hole, thus extending the service life of the slings. The thickened edges also greatly improve the resistance to deformation, ensuring that the slings are always in the designed position during hoisting, preventing them from coming off or getting stuck, and improving operational safety. Maintaining the stability of the aperture and controlling the center of gravity, the steel plate ring can effectively resist external forces during hoisting, maintaining the designed shape and size of the hoisting hole. At the same time, based on the alignment and disassembly and control of the center of gravity, it ensures that the hoisting force is always transmitted in the predetermined direction, making the box culvert more stable during hoisting and preventing the center of gravity from shifting due to the deformation of the aperture.

[0024] exist Figure 3 The embedded ribs 11 of the embedded component M have L-shaped, T-shaped, and hook-shaped designs. The rated load of the embedded component M, which is composed of embedded ribs 11, sleeves 12, external modules 20, and external connectors 21 with different shapes, is greater than the bearing stress at any angle during actual hoisting. This not only relatively distributes the stress concentration caused by hoisting, but also makes it more conducive to flipping in confined spaces.

[0025] Combination Figure 4 As shown, the box culvert has a self-weight of 30t and is made of C40 concrete. It has 25mm thick embedded steel plates (L-shaped steel plates 10), and is also equipped with embedded reinforcing bars 11 (20mm diameter) and sleeves 12. It is assembled using corresponding external modules 20 and external connectors 21. Two lifting holes K are formed on each of the two external modules 20. The standard load value of a single lifting hole is 15t. Considering a dynamic load factor of 1.2 and a partial factor of 1.3, the following information is provided. .

[0026] Calculation of lower embedded reinforcement (calculation of horizontal embedded reinforcement of L-shaped structure): When the box culvert is vertically hoisted, three working conditions are calculated: (1) the lower embedded component bears all tensile load; (2) the lower embedded component bears all shear load; (3) the lower embedded component bears all tensile load according to a 45° distribution. The embedded component uses 8 HRB400 steel bars with a diameter of 20mm, of which the middle 4 bars are connected to steel sleeves of corresponding size.

[0027] Calculation under condition (1): The lower embedded component bears the entire tensile load. The steel bar diameter is 20mm, and the embedded plate thickness is 25mm. .

[0028] Calculation for working condition (2): The lower embedded component bears the entire shear load.

[0029] Calculation for working condition (3): The lower embedded components bear all tensile loads at a 45° angle.

[0030] Based on the comprehensive calculation of working conditions (1)-(3), the area of ​​the lower embedded steel bars is 1814 mm². 2 The actual configuration consists of 4 rows with 8 HRB400 steel bars (2 per row) each, each with a diameter of 20mm, resulting in an actual area of ​​2512mm². 2 This meets the load-bearing requirements. Similarly, the side is actually reinforced with 3 rows of 6 (2 per row) HRB400 steel bars with a diameter of 20mm, with an actual reinforcement area of ​​1884mm². 2 It meets the stress requirements.

[0031] The embedded length of the tension reinforcement is as follows: For box culvert concrete of grade C40, the embedded length of the HRB400 reinforcement is:

[0032] With a side width of only 400mm, it adopts a method of welding anchor bars on one side.

[0033] Therefore, the length of the reinforcing steel bars in the lower embedded components is taken as 500mm, and the anchorage length of the side reinforcing steel bars is taken as 300mm.

[0034] Calculation of local punching shear in concrete: 1) Calculation of local punching shear in concrete of the lower embedded component. Therefore, the maximum tensile design value of 234kN is less than the local punching shear load of 1089.3kN on concrete, which meets the requirements.

[0035] 2) Calculation of local punching shear of concrete for side-embedded components. Therefore, the maximum tensile design value of 234kN is less than the local punching shear load of 408.5kN on concrete, which meets the requirements.

[0036] In this example, the transportation process in step S2 includes a forward movement, a transfer process, and a reversal process. During the forward movement, the transport vehicle 1 moves along the middle of the horizontal section of the installed box culvert T, and the length direction of the box culvert is consistent with the forward movement direction while traveling in a straight line. Based on moving forward along the middle alignment, the difference in distance between the box culvert and the left and right tunnel walls is avoided to minimize the movement range of the center of gravity alignment adjustment, making it easier to implement the reversal and forward movement of the box culvert.

[0037] During the transfer process, multiple shifting unloading outriggers (transfer devices 2) are simultaneously lifted to unload the box culvert H from the transport vehicle 1; and during the reversing process, multiple shifting unloading outriggers (transfer devices 2) are simultaneously lowered to place the box culvert H onto the bearing platform 30. The purpose of the transfer is not only to realize the transfer between the transport vehicle and the connecting vehicle, but also to more effectively lower the center of gravity of the box culvert so that the box culvert lies flat inside the tunnel, and the center of gravity of the box culvert is relatively close to the center of the tunnel, thereby providing maximum convenience for the reversing of the box culvert and the forward movement of the crane, and avoiding collisions between the box culvert and the tunnel wall during transfer and forward movement.

[0038] The reversal process includes a centering connection process and a rotational alignment process. The centering connection process includes an initialization phase, a sensing phase, a calculation phase, a control phase, and an execution phase. The initialization phase involves presetting the box culvert design parameters and a reference coordinate system, with the box culvert thickness direction as the X-axis, the box culvert width direction as the Y-axis, and the box culvert height direction as the Z-axis. The parameters include length, width, height, material density, and segment weight. The sensing phase involves synchronously collecting real-time distance data between the shuttle vehicle and the left side wall, right side wall, and top of the box culvert using distance measuring sensors. The calculation phase involves obtaining the three-dimensional coordinates of the shuttle vehicle relative to the box culvert and the coordinates of the box culvert's center of gravity. The control phase generates a center of gravity adjustment command for the shuttle vehicle based on the coordinate deviation and dynamically adjusts the centering position. The execution phase, after center of gravity alignment, triggers a mechanical lock to stably lock the shuttle vehicle and the box culvert together. In short, the reversing process is broken down into five distinct stages: initialization, perception, calculation, control, and execution. This division embodies a complete perception-decision-execution closed-loop control concept. Its advantages are: the entire connection process is clearly defined, making it easy to understand, implement, and debug; each stage has independent functions, reducing system complexity and improving maintainability and reliability; from data acquisition and coordinate calculation to dynamic adjustment and final locking, the entire process requires no manual intervention, achieving a high degree of automation; in addition, based on the mechanical locking device, it prevents the shuttle vehicle from tilting or overturning due to inaccurate positioning at the bottom of the box culvert, causing the center of gravity to shift. The distance measuring sensors include a left sensor, a right sensor, and a top sensor. The left sensor is installed in the middle of the left side of the shuttle bus, with the detection direction perpendicular to the left side wall of the box culvert, and collects the lateral distance L1. The right sensor is installed in the middle of the right side of the shuttle bus, with the detection direction perpendicular to the right side wall of the box culvert, and collects the lateral distance L2. The top sensor is installed at the center of the top of the shuttle bus, with the detection direction perpendicular to the top of the box culvert, and collects the vertical distance H. Based on a preset reference coordinate system, the distance data is converted into the three-dimensional coordinates of the shuttle bus through trigonometric function calculations: Y = Y0 + ΔY = Y0 + (L1 - L2) ÷ 2, where Y is the current lateral coordinate of the shuttle bus; Y0 is the lateral reference coordinate of the box culvert centerline; ΔY is the lateral offset of the shuttle bus relative to the centerline; Z = Z0 + ΔZ = Z0 + (H0 - H), where Z is the current vertical coordinate of the shuttle bus; Z0 is the reference coordinate of the top of the box culvert; ΔZ is the vertical offset of the shuttle bus relative to the top of the box culvert; H0 is the design height of the box culvert; and H is the distance from the top surface of the supporting platform to the top of the box culvert. First, the symmetrical arrangement of the three sensors (left, right, and top) enables comprehensive perception of the shuttle bus's position and orientation within the culvert cross-section at minimal cost (using only three data points). Second, the coordinate transformation formula is based on simple geometric relationships, requiring minimal computation, responding quickly, and possessing clear physical meaning, allowing for real-time conversion of raw distance data into spatially meaningful coordinates. Furthermore, the lateral coordinate G of the center of gravity... Y G Y =Y0+[(L1-L2)×α]÷2, where α is the mass distribution coefficient, which can be calibrated; the vertical coordinate of the centroid is G.Z G Z =Z0+(H0-H)×k, where the center of gravity height is estimated using the top distance and calibration coefficient k. That is, the formulas for the lateral coordinates of the center of gravity (introducing an empirical coefficient α) and the vertical coordinates (introducing a calibration coefficient k) avoid complex theoretical calculations and are more practical and operable through engineering calibration. Furthermore, the control phase is based on a dynamic closed-loop control strategy, and the formula is as follows: u(t)=K p e(t)+K i +K d Where u(t) is the control output; e(t) is the deviation between the current coordinate and the centroid coordinate, e = target coordinate - current coordinate; K p ,K i ,K d Here, K represents the proportional, integral, and derivative gain coefficients; t is the time variable; and τ is the integral time variable. The classic PID control algorithm is used to achieve dynamic adjustment. Its advantages are: PID control can immediately generate adjustment commands based on the real-time deviation e(t), ensuring a fast system response; the integral term K... i It can accumulate and eliminate persistent deviations, enabling the shuttle bus to ultimately align precisely with the center of gravity coordinates; the differential term K d t can predict the trend of deviation changes and apply reverse control in advance, making the adjustment process smoother and avoiding oscillations around the target position.

[0039] In summary, after adopting the transportation and assembly construction process of the three-section precast box culvert adapted to confined spaces, firstly, using the bottom corner of the evacuation opening near the hoisting side as a reference, pre-embedded components are pre-embedded and assembled at the bottom corners of the two vertical supports. Each pre-embedded component includes a first component pre-embedded integrally with the vertical support and a second component that is detached from the first component and forms a hoisting hole. Secondly, the box culvert is horizontally supported on a transport vehicle with the assembly side facing down and the hoisting side facing up, and the transport vehicle moves the flat-lying box culvert forward into the transfer area. Then, based on the transfer equipment in the transfer area, the box culvert is unloaded from the transport vehicle and moved to the bottom of the box culvert using a shuttle vehicle, while the center alignment of the shuttle vehicle's carrying platform and the box culvert is adjusted. The transfer equipment then aligns the box culvert with the supporting platform below it. The platform rotates around its own axis to align the horizontal section of the box culvert with the horizontal section of the already installed box culvert, while maintaining the box culvert on the connecting vehicle lying flat with its horizontal section facing backward, its curved bottom facing forward, and its lifting side facing upward. Next, the lifting equipment is aligned with the corresponding lifting holes on the horizontal and vertical supports. The crane then lifts the box culvert horizontally and moves it forward to the front of the box culvert to be installed. Then, using the rear edge of the assembly side as a reference, the front end of the box culvert is flipped downward so that its horizontal section faces upward, its curved bottom faces downward, and its assembly side faces backward. The box culvert is then aligned vertically with the already installed box culvert. Finally, using the lifting side of the foremost installed box culvert as the reference side, the box culvert is aligned with the reference side from the assembly side. The invention employs a docking and splicing method. Firstly, it increases the number of stress points for hoisting by combining pre-embedded and external components to form pre-embedded components with hoisting holes. This not only facilitates multi-point hoisting of the box culvert but also makes it easier to move the box culvert forward and rotate it during hoisting, reducing safety hazards caused by concentrated stress during the hoisting of three-opening precast box culverts. Secondly, it utilizes the box culvert's horizontal transport, transfer and unloading, centering adjustment of the connecting vehicle, and lowering of the box culvert's center of gravity to enable the box culvert to change direction and move forward during hoisting within the tunnel. Simultaneously, it utilizes the space to be installed to perform in-situ rotation and alignment adjustments of the box culvert, thus adapting to the transportation and assembly of three-opening precast box culverts in confined spaces. Thirdly, it uses the alignment and disassembly of two components to maintain the position of the two hoisting holes. Alignment facilitates center of gravity control during hoisting, ensuring safety and ensuring the load-bearing capacity of the pre-embedded components meets hoisting requirements regardless of angle. Fourthly, the steel plate ring expands the stress-bearing area, distributing the large concentrated force more evenly to the main structure, effectively preventing the steel at the hole edge from tearing or undergoing plastic deformation due to excessive stress. Protecting the slings and preventing accidents, the steel plate ring forms a smooth and robust guide surface, reducing the risk of direct friction and cutting between the slings (wire ropes, hoisting slings) and the edge of the hoisting hole, extending the sling's service life. The thickened edge also significantly improves resistance to deformation, ensuring the slings remain in the designed position during hoisting, preventing them from coming off or getting stuck, and enhancing operational safety.To maintain aperture stability and control the center of gravity, the steel plate ring effectively resists external forces during hoisting, preserving the designed shape and size of the hoisting hole. Simultaneously, based on alignment and disassembly, and center of gravity control, it ensures that the hoisting force is always transmitted in the predetermined direction, making the box culvert more stable during transport and preventing center of gravity shift due to orifice deformation. Fifthly, the rated load of the pre-embedded components—combined with pre-embedded ribs, sleeves, external modules, and external connectors of different shapes—is greater than the bearing stress at any angle during actual hoisting. This not only relatively evenly distributes the stress concentration caused by hoisting but also facilitates rotation within confined spaces. Sixthly, the purpose of transshipment is not only to achieve transportation... The system facilitates the transfer of transport vehicles and connecting vehicles, and more effectively lowers the center of gravity of the box culvert, allowing it to lie flat inside the tunnel with its center of gravity relatively close to the tunnel's center. This maximizes space for reversing the box culvert and moving the crane forward, avoiding collisions with the tunnel walls during box culvert transfer and forward movement. Simultaneously, the transport vehicle moves along the center of the horizontal section of the installed box culvert, ensuring that the length direction of the box culvert aligns with the forward direction during straight-line travel. This alignment along the center avoids excessive differences in distance between the box culvert and the left and right tunnel walls, minimizing the range of motion required for center of gravity alignment adjustment, and facilitating box culvert reversal and forward lifting. Furthermore, the reversal process is broken down into initialization, sensing, and calculation steps. The five clearly defined stages of perception, decision-making, and execution embody a complete closed-loop control concept. Its advantages include: clear steps throughout the entire connection process, facilitating understanding, implementation, and debugging; independent function for each stage, reducing system complexity and improving maintainability and reliability; high automation, requiring no manual intervention throughout the entire process from data acquisition and coordinate calculation to dynamic adjustment and final locking; and a mechanical locking device to prevent the shuttle vehicle from tilting or overturning due to inaccurate positioning at the bottom of the culvert. Furthermore, the symmetrical layout of the left, right, and top sensors minimizes costs (three sensors...). According to the data, the position and posture of the shuttle bus within the culvert section are fully perceived; secondly, the coordinate transformation formula is based on simple geometric relationships, with low computational load, fast response, and clear physical meaning, and can convert the original distance data into coordinates with spatial meaning in real time; the horizontal coordinate formula of the center of gravity (introducing the empirical coefficient α) and the vertical coordinate formula (introducing the calibration coefficient k) avoid complex theoretical calculations and are closer to reality through engineering calibration, making them more operable and practical; seventhly, the classic PID control algorithm is used to achieve dynamic adjustment, the advantage of which is that PID control can immediately generate adjustment commands according to the real-time deviation e(t), ensuring the system's rapid response; integral term K; i It can accumulate and eliminate persistent deviations, enabling the shuttle bus to ultimately align precisely with the center of gravity coordinates; the differential term K d The system can predict the trend of deviation changes and apply reverse control in advance to make the adjustment process smoother and avoid oscillations around the target position. The eighth aspect is the setting of mechanical locking to prevent the shuttle vehicle from tilting or overturning due to inaccurate positioning at the bottom of the box culvert, which would cause the center of gravity to shift. At the same time, there is a linkage between the multiple lifting and lowering displacement unloading outriggers (transfer device 2), that is, they need to maintain synchronous movement. Generally, hydraulic cylinders are used to maintain the stability and safety of construction based on synchronous oil supply and unloading.

[0040] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A transportation and assembly construction process for a three-section precast box culvert adapted to confined spaces, wherein the box culvert forms an assembly side and a hoisting side from both sides along its thickness direction, and the box culvert includes a horizontal section, an arc-shaped bottom, and a vertical support section, wherein the vertical support section has evacuation holes, characterized in that, The process includes the following steps: S1, Prefabrication of box culverts Using the bottom corner of the evacuation hole near the hoisting side as a reference, pre-embedded and assembled pre-embedded components are formed at the bottom corners of the two vertical support parts respectively. Each pre-embedded component includes a first part pre-embedded and formed integrally with the vertical support part, and a second part that is detached from the first part and has a hoisting hole. S2, Box Culvert Transportation First, the box culvert is placed horizontally on a transport vehicle with the self-assembly side facing down and the hoisting side facing up, and the transport vehicle then moves the flat box culvert forward into the transfer area. Secondly, the transfer equipment in the transfer area unloads the box culvert from the transport vehicle and moves it to the bottom of the box culvert using a shuttle vehicle. At the same time, the center alignment adjustment of the shuttle vehicle's carrying platform and the box culvert is carried out. Finally, the transfer equipment aligns the box culvert and lowers it onto the carrying platform below. The center of gravity of the box culvert is close to the center of the tunnel. The carrying platform rotates around its own axis to make the horizontal part of the box culvert consistent with the horizontal extension direction of the installed box culvert. At the same time, the box culvert on the shuttle vehicle is kept lying flat with the horizontal part facing backward, the arc bottom facing forward, and the hoisting side facing upward. S3, hoisting and assembly of box culverts First, align the lifting tools with the corresponding lifting holes on the horizontal and vertical support sections, then lift the culvert horizontally and move it forward to the front of the box culvert to be installed. Second, using the rear edge of the assembly side as a reference, flip the front end of the box culvert downwards so that the horizontal part of the box culvert faces upwards, the curved bottom faces downwards, and the assembly side faces backwards. Then align the box culvert vertically with the already installed box culvert. Finally, using the lifting side of the frontmost installed box culvert as the reference side, connect and splice the box culvert from the assembly side to the reference side.

2. The transportation and assembly construction technology for the three-section prefabricated box culvert adapted to confined spaces according to claim 1, characterized in that, In step S1, the first component includes an L-shaped steel plate forming the bottom corner of the evacuation hole, pre-embedded ribs and sleeves that pass through the horizontal and vertical portions of the L-shaped steel plate into the interior of the vertical support portion; the second component includes an external module with a horizontal base and a vertical base, and an external connector that detaches and connects the horizontal base and the vertical base to the aligned sleeve, wherein the lifting hole is formed on the external module.

3. The transportation and assembly construction technology of the three-section precast box culvert adapted to confined spaces according to claim 2, characterized in that, Steel plate rings are welded to both ends of the lifting hole; and / or the shapes of the embedded ribs include straight rod type, I type, L type, T type and hook type.

4. The transportation and assembly construction technology of the three-section precast box culvert adapted to confined spaces according to claim 2, characterized in that, The outer side of the L-shaped steel plate is flush with the inner wall of the evacuation hole, and the two end faces of the evacuation hole are flush with the opposite end faces of the L-shaped steel plate; the horizontal and vertical feet are aligned and fitted with the opposite end faces of the L-shaped steel plate.

5. The transportation and assembly construction technology for the three-section precast box culvert adapted to confined spaces according to claim 1, characterized in that, The transportation process in step S2 includes a forward movement, a transfer process, and a reversal process. During the transfer process, multiple shifting unloading outriggers are simultaneously lifted to unload the box culvert from the transport vehicle. Furthermore, during the reversing process, multiple shifting unloading outriggers descend synchronously to place the box culvert onto the bearing platform.

6. The transportation and assembly construction technology for the three-section precast box culvert adapted to confined spaces according to claim 5, characterized in that, During the forward movement, the transport vehicle moves along the middle of the horizontal section of the installed box culvert, and when traveling in a straight line, the length direction of the box culvert is consistent with the forward direction.

7. The transportation and assembly construction technology for the three-section precast box culvert adapted to confined spaces according to claim 5, characterized in that, The reversal process includes a centering connection process and a rotational alignment process. The centering connection process includes an initialization phase, a sensing phase, a calculation phase, a control phase, and an execution phase. The initialization phase involves presetting the box culvert design parameters and a reference coordinate system, with the box culvert thickness direction as the X-axis, the box culvert width direction as the Y-axis, and the box culvert height direction as the Z-axis. The parameters include length, width, height, material density, and segment weight. The sensing phase involves synchronously collecting real-time distance data between the shuttle vehicle and the left side wall, right side wall, and top of the box culvert using distance measuring sensors. The calculation phase involves obtaining the three-dimensional coordinates of the shuttle vehicle relative to the box culvert and the coordinates of the box culvert's center of gravity. The control phase generates a center of gravity adjustment command for the shuttle vehicle based on the coordinate deviation and dynamically adjusts the centering position. The execution phase, after center of gravity alignment, triggers a mechanical lock to stably lock the shuttle vehicle and the box culvert together.

8. The transportation and assembly construction technology of the three-section precast box culvert adapted to confined spaces according to claim 7, characterized in that, The ranging sensor includes a left sensor, a right sensor, and a top sensor. The left sensor is installed in the middle of the left side of the shuttle vehicle, with the detection direction perpendicular to the left side wall of the box culvert, and collects the lateral distance L1. The right sensor is installed in the middle of the right side of the shuttle vehicle, with the detection direction perpendicular to the right side wall of the box culvert, and collects the lateral distance L2. The top sensor is installed at the center of the top of the shuttle vehicle, with the detection direction perpendicular to the top of the box culvert, and collects the vertical distance H. Based on the preset reference coordinate system, the distance data is converted into the three-dimensional coordinates of the shuttle vehicle through trigonometric function calculations. Y = Y0 + ΔY = Y0 + (L1 - L2) ÷ 2, where Y is the current lateral coordinate of the shuttle vehicle; Y0 is the lateral reference coordinate of the box culvert centerline; and ΔY is the lateral offset of the shuttle vehicle relative to the centerline. Z = Z0 + ΔZ = Z0 + (H0 - H), where Z is the current vertical coordinate of the shuttle vehicle; Z0 is the reference coordinate of the top of the box culvert; ΔZ is the vertical offset of the shuttle vehicle relative to the top of the box culvert; H0 is the design height of the box culvert; and H is the distance from the top surface of the bearing platform to the top of the box culvert.

9. The transportation and assembly construction technology for the three-section precast box culvert adapted to confined spaces according to claim 8, characterized in that, Lateral coordinate of the centroid G Y G Y =Y0+[(L1-L2)×α]÷2, where α is the mass distribution coefficient, which can be calibrated; the vertical coordinate of the centroid is G. Z G Z =Z0+(H0-H)×k, where the height of the center of gravity is estimated by the top distance and the calibration coefficient k.

10. The transportation and assembly construction technology for the three-section precast box culvert adapted to confined spaces according to claim 9, characterized in that, During the control phase, a dynamic closed-loop control strategy is used, and the formula is as follows: u(t) = K p e(t)+K i +K d Where u(t) is the control output; e(t) is the deviation between the current coordinate and the centroid coordinate, e = target coordinate - current coordinate; K p ,K i ,K d τ represents the proportional, integral, and differential gain coefficients; t represents the time variable; and τ represents the integral time variable.

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