Prefabricated u-shaped groove structure, roadbed, and construction method

Abstract

Disclosed are a prefabricated U-shaped groove structure, a roadbed, and a construction method. The structure comprises U-shaped grooves of a cutting section and U-shaped grooves of an embankment section, and each U-shaped groove comprises a bottom plate and side walls which are assembled. The bottom plate of each U-shaped groove of the cutting section is in a parallelogram shape, and the two surfaces arranged opposite to each other in the bottom plate in the length direction of the roadbed are vertical planes; the bottom plate of each U-shaped groove of the embankment section is rectangular; and the U-shaped groove of the cutting section is fixed onto a corresponding cast-in-place raft slab between the enclosure piles of the cutting section, and is connected to the enclosure piles, the crown beams provided at the top of the enclosure piles, and the cast-in-place raft slab located between the enclosure piles, and each enclosure pile is of a permanent supporting and retaining structure and forms a whole with the U-shaped groove. The bottom plate of the U-shaped groove of the cutting section is designed to be in a parallelogram shape, so that it is ensured that the junction of the embankment section and the cutting section of the prefabricated structure at a large inclination angle is continuous, and no gap is formed between the sections, thereby facilitating transition between the embankment section and the cutting section.

Description

A prefabricated U-shaped channel structure, roadbed, and construction method Technical Field

[0001] This invention belongs to the field of roadbed foundation construction, specifically relating to a prefabricated U-shaped channel structure, roadbed, and construction method. Background Technology

[0002] U-shaped channels, as a roadbed structure, are widely used in the construction of transportation infrastructure such as railways and highways, serving as crucial transition sections between above-ground and underground sections, and between road cuts and embankments. U-shaped channel construction typically employs an open-cut method combined with cast-in-place construction. The open-cut pit retaining structure serves as temporary support, while the cast-in-place U-shaped channel structure provides permanent support. This leads to problems such as high consumption of construction materials, low mechanization levels, difficulty in quality control, and high carbon emissions. Prefabricated construction offers advantages such as being green, environmentally friendly, and efficient; therefore, exploring prefabricated construction methods for U-shaped channels is of great significance.

[0003] Patent CN202211279882.0 discloses a prefabricated U-shaped channel structure and construction method for open-cut tunnels. This patent proposes a prefabricated construction method for roadbed U-shaped channels, with the structure using two T-shaped prefabricated blocks and one straight prefabricated block, achieving full assembly of the U-shaped structure. However, this structural type has a large self-weight, making hoisting and construction inconvenient. At the same time, the T-shaped structure results in a significantly larger amount of excavation than actually needed, and a large amount of backfilling is required for the T-shaped structure and the sidewalls of the foundation pit, which seriously restricts its economic efficiency.

[0004] In patent CN202310960577.6, a prefabricated concrete U-shaped structure and construction method are disclosed. The permanent design of the foundation pit retaining structure is proposed. The structure uses two L-blocks and one straight block, which reduces the weight of the structure and effectively improves the economy and construction convenience. However, the structure has the problem that the prefabricated blocks are connected by post-casting, and the overall assembly of the structure is not achieved. At the same time, the U-shaped channel, as a connecting section between the above-ground and underground, has the transformation between the embankment and the cutting. The cutting section has a large slope, while the embankment section is horizontal. The two have a certain angle, which restricts the applicability of the U-shaped channel structure. In addition to the above problems, the U-shaped channel also has the following problems when adopting the fully prefabricated type: (1) The problem of the U-shaped structure's anti-buoyancy. Although the patent gives the anti-buoyancy form of setting a cast-in-place bottom plate and connecting it with the anti-uplift pile, the form does not consider the U-shaped channel itself floating. Since the retaining structure (drilled pile) does not have waterproofing ability, groundwater will penetrate into the periphery of the U-shaped channel through the retaining structure, causing the U-shaped structure to float. (2) The U-shaped channel structure has a large number of transition nodes, such as the transition between embankments and road cuts, and the transition between the U-shaped structure and existing underground structures. Ensuring the connection of these transition nodes is a challenge in design and construction. (3) Compared with other underground structures, the U-shaped channel has long cantilevered sidewalls. Ensuring the stability of the assembly is crucial to the success of the assembly. Therefore, it is urgent to develop a new type of fully assembled U-shaped channel structure that can adapt to various node transitions and has strong anti-buoyancy performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a prefabricated U-shaped channel structure based on a combined permanent and temporary design concept. By using the foundation pit retaining structure as both a temporary support structure and a permanent retaining structure, the thickness of the U-shaped channel structure and the weight of the prefabricated structure are greatly reduced, thereby lowering the assembly difficulty.

[0006] The technical solution adopted in this invention is as follows:

[0007] In a first aspect, the present invention discloses a prefabricated U-shaped channel structure, including a U-shaped channel for a road cutting section and a U-shaped channel for a road embankment section. Each U-shaped channel includes a bottom plate and side walls spliced ​​together. The bottom plate of the U-shaped channel for the road cutting section is parallelogram-shaped, and two surfaces of the bottom plate arranged opposite each other along the length of the roadbed are vertical planes. The bottom plate of each U-shaped channel in the road embankment section is rectangular. The U-shaped channel for the road cutting section is fixed to a cast-in-place raft slab between the retaining piles of the road cutting section, and is connected to the retaining piles, a capping beam set on the top of the retaining piles, and the cast-in-place raft slab located between the retaining piles. The retaining piles are permanent support structures and form an integral part with the U-shaped channel.

[0008] As a further technical solution, the retaining piles are pre-installed with connecting steel bars, which are connected to the transverse connecting steel bars of the cast-in-place raft slab; the side walls are connected to the steel bars in the pre-embedded sleeves on the cap beam through pre-reserved holes in the side walls using connectors; the cast-in-place raft slab is also pre-embedded with vertical connecting steel bars, which pass through the pre-reserved openings in the precast bottom slab and are connected to the bottom slab of the precast components. These three connections ensure the coordinated stress distribution and anti-buoyancy of the structure.

[0009] As a further technical solution, a sleeve and a rebar connector are pre-embedded on the cap beam, and a reserved hole is set on the side wall. After the side wall is installed in place, the pre-embedded rebar passes through the reserved hole and is connected to the rebar in the pre-embedded sleeve on the cap beam using the rebar connector.

[0010] As a further technical solution, the sidewall and the bottom plate are connected by tenons and connecting steel bars; the connecting steel bars of the U-shaped groove in the cutting section are arranged crosswise; and the connecting steel bars of the U-shaped groove in the embankment section are arranged horizontally.

[0011] As a further technical solution, a waterproof structure is provided at the joint of the bottom plate and the side wall tongue and groove joint. The waterproof structure includes a composite elastic sealing gasket and a water-swellable rubber sealing gasket. The gap between the two sealing gaskets is filled with sealant. An embedded waterproof structure is provided on the outside of the water-swellable rubber sealing gasket.

[0012] As a further technical solution, the embedded waterproof structure includes an isolation sponge, polymer mortar and water-swellable rubber. The polymer mortar is located on the outermost side of the tenon joint, followed by water-swellable rubber and isolation sponge in sequence.

[0013] As a further technical solution, a support device is also installed on the outside of the side wall of the embankment section.

[0014] As a further technical solution, a fine-leveling strip is also provided on the cast-in-place raft slab.

[0015] As a further technical solution, the precision flat strip is set at the bottom of the two side walls and the bottom of the base plate.

[0016] As a further technical solution, the width of the precision strip at the bottom of the side wall is greater than the length of the bottom of the side wall to avoid the side wall block from being eccentric.

[0017] Secondly, the present invention also discloses a roadbed, the roadbed comprising a plurality of prefabricated U-shaped groove structures arranged along the vehicle travel direction, and the plurality of prefabricated U-shaped groove structures being connected by connecting steel bars along the vehicle travel direction.

[0018] As a further technical solution, adjacent base slabs are connected to each other and side walls are connected to each other by reinforcing bars.

[0019] As a further technical solution, the bottom plate of the U-shaped channel in the cutting section and the bottom plate of the U-shaped channel in the embankment section are horizontally connected by steel bars.

[0020] Thirdly, the present invention also discloses a construction method for a prefabricated U-shaped channel structure, as follows:

[0021] Step 1: Excavate the foundation pit and construct retaining piles and capping beams within the pit;

[0022] Step 2: Construct the cast-in-place raft foundation between the retaining piles;

[0023] Step 3: Construct the first ring of prefabricated U-shaped channel for the road cut section on the raft slab, and connect the first ring of prefabricated U-shaped channel to the existing underground structure.

[0024] Step 4: Construct the prefabricated U-shaped channel for the remaining ring of the road cutting section. During construction, after each set number of prefabricated U-shaped channels are constructed, the bottom plate, side walls, retaining piles, cap beams, and cast-in-place raft slab of the assembled U-shaped channel must be connected. After connection, they must be cast into one piece until the construction of all road cutting sections is completed.

[0025] Step 5 involves assembling the prefabricated U-shaped channel of the embankment section. After the prefabricated construction of the cutting section is completed, a precision-rolled threaded steel connector is pre-embedded in its tail section as a force transmission device to provide tensioning conditions for the embankment section and ensure that tensioning of the embankment section will not damage the cutting section components when there is an inclination angle.

[0026] Step 7: All joints between prefabricated structural components are sealed by grouting. All joints in the circumferential and longitudinal directions of the U-shaped groove need to be grouted at an appropriate time after the structure is assembled. Grouting is carried out through the sealed ducts after tensioning is completed.

[0027] The beneficial effects of the above embodiments of the present invention are as follows:

[0028] 1. Permanent design of the retaining structure for the cutting section and lightweight design of the U-shaped channel structure for the cutting section: The pit and the prefabricated U-shaped channel adopt a pile-wall integrated type. The external retaining structure mainly bears the soil pressure, while the internal U-shaped channel structure bears the water pressure, which greatly reduces the thickness of the U-shaped channel structure and the weight of the prefabricated structure, thereby reducing the assembly difficulty. The bottom plate of the U-shaped channel in the cutting section is designed as a parallelogram, and the two opposite sides of the bottom plate along the length of the roadbed are vertical planes to ensure that the prefabricated structure is tightly connected and without gaps at the intersection of the embankment and the cutting section with a large angle of inclination, which facilitates the conversion between the embankment and the cutting section.

[0029] 2. To ensure the integrity of the retaining structure and the U-shaped channel structure in the cutting section and to improve the anti-buoyancy performance of the U-shaped channel in the later stage, the retaining pile structure is connected to the cast-in-place raft slab, the retaining pile structure is connected to the side wall of the U-shaped channel, and the cast-in-place raft slab is connected to the bottom plate of the U-shaped channel. This improves the overall structure and ensures the coordinated stress and anti-buoyancy of the structure.

[0030] 4. Force-transfer embedded parts are installed at the transition between the embankment section and the cutting section to provide tensioning conditions for the embankment section and ensure that tensioning of the embankment section will not damage the components of the cutting section when there is an inclination angle.

[0031] 6. Attitude control measures: The width of the precision leveling strips on both sides of the road cutting section and the embankment section is greater than the bottom length of the L-shaped sidewall to avoid eccentricity; lateral supports are installed in the embankment section to prevent the L-shaped sidewall from overturning. Attached Figure Description

[0032] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0033] Figure 1 is a schematic diagram of the overall structure of the assembled U-shaped channel disclosed in some embodiments of the present invention;

[0034] Figure 2 is a schematic diagram of the foundation pit retaining structure and raft foundation structure disclosed in some embodiments of the present invention;

[0035] Figure 3 is a schematic cross-sectional view of a road cut section disclosed in some embodiments of the present invention;

[0036] Figure 4 is a side view of the bottom plate of the road cut section disclosed in part of the embodiments of the present invention;

[0037] Figure 5 is a side view of the side wall disclosed in a partial embodiment of the present invention;

[0038] Figure 6 is a schematic diagram of the pre-reserved anchorage steel bar holes in the bottom plate disclosed in some embodiments of the present invention;

[0039] Figure 7 is a schematic diagram of the connection between the retaining piles and the side wall disclosed in some embodiments of the present invention;

[0040] Figure 8 is a schematic diagram of the embankment-cut transition section disclosed in part of an embodiment of the present invention;

[0041] Figure 9 is a schematic diagram of the cross-section of the embankment section disclosed in some embodiments of the present invention;

[0042] Figure 10 is a schematic diagram of the waterproof structure at the tenon joint disclosed in part of the embodiments of the present invention;

[0043] Figure 11 is a schematic diagram of the internal caulking waterproof structure disclosed in some embodiments of the present invention;

[0044] Figure 12 is a schematic diagram of the connection section between the existing structure and the prefabricated structure disclosed in some embodiments of the present invention;

[0045] Figure 13 shows the waterproofing structure of the bottom and side walls of the interface between the existing structure and the prefabricated structure disclosed in some embodiments of the present invention.

[0046] In the diagram: 1. Retaining pile; 101. Crown beam; 102. Reinforcing steel connecting retaining pile and side wall; 102-1. Reinforcing steel connector; 102-2. Embedded sleeve; 102-3. Reserved hole in side wall; 103. Reinforcing steel connecting retaining pile and raft slab; 2. Cast-in-place raft slab; 3. Steel support; 4. Bottom slab; 401. Reserved anchoring steel hole in bottom slab; 401-1. Anchoring steel; 401-2. Grouting hole; 401-3. Reinforcing steel connector; 401-4. Anchoring steel for cast-in-place raft slab; 402-1. Sponge rubber strip; 402 -2- Composite elastic sealing gasket; 402-3- Epoxy resin filling joint; 402-4- Water-swellable rubber sealing gasket; 402-5- Internal caulking waterproofing; 402-6- Polymer mortar filling; 402-7 Water-swellable rubber; 402-8 Isolation sponge; 402-9- Grouting joint; 402- Tongue and groove; 403- Transition section embedded connector; 5 Side wall; 6 Oblique straight bolt; 7 Longitudinal pre-tightening device reserved hole; 8 Circumferential precision rolled threaded steel; 9 Precision flat strip; 12 Lateral support component. Detailed Implementation

[0047] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0048] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0049] For ease of description, the words "up," "down," "left," and "right" appearing in this invention only indicate that they are consistent with the up, down, left, and right directions of the accompanying drawings themselves, and do not limit the structure. They are merely for the purpose of facilitating the description of this invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0050] This embodiment discloses a prefabricated U-shaped channel structure, roadbed, and construction method. Specifically, it includes U-shaped channels for cutting sections and U-shaped channels for embankment sections. Each U-shaped channel in both the cutting and embankment sections includes a bottom plate and side walls spliced ​​together. The difference is that the bottom plate of the cutting section U-shaped channel is parallelogram-shaped, and two faces of the bottom plate arranged opposite each other along the length of the roadbed are vertical planes; the bottom plate of each U-shaped channel in the embankment section is rectangular. The cutting section U-shaped channel is fixed to a cast-in-place raft slab between the retaining piles of the cutting section, and is connected to the retaining piles, a capping beam set on top of the retaining piles, and the cast-in-place raft slab located between the retaining piles. The retaining piles are permanent support structures that form an integral whole with the U-shaped channel. The embankment section U-shaped channel is directly fixed to the roadbed. First, a leveling strip is set on the roadbed, and then the U-shaped channel is placed.

[0051] The installation method of the U-shaped channel in the road cutting section is described below: As shown in Figure 1, the foundation pit retaining structure of the road cutting section includes retaining piles 1, with a capping beam 101 set on top of the retaining piles 1; the raft structure includes a cast-in-place raft slab 2, and the prefabricated U-shaped channel main structure includes two L-shaped side walls 5 and a bottom plate 4; the L-shaped side wall blocks and the bottom plate are aligned by a tongue and groove tenon 402, and inclined tensioning holes are provided at the positions where the L-shaped side wall blocks and the straight block tongue and groove tenon are fitted; after aligning with the reserved tensioning holes, high-strength threaded steel bars are inserted, tensioned to the predetermined value, and then fixed with threaded sleeves and locked with inclined bolts. On the bottom plate 4, longitudinal pre-tensioning device reserved holes 7 are provided along the length direction of the bottom plate 4, and anchoring steel bars 401 are reserved along the height direction of the bottom plate 4.

[0052] In this embodiment, the U-shaped trench adopts open excavation + prefabricated construction. The open excavation pit uses cast-in-place piles + internal supports as the retaining structure. The prefabricated U-shaped trench pit is equipped with a steel support 3 to reduce the lateral displacement of the retaining structure in the early stage of construction. It needs to be removed during the assembly construction process.

[0053] To ensure the stability of the foundation pit after demolition, a cast-in-place raft slab 2 is installed at the bottom of the U-shaped channel, as shown in Figure 2. The bored piles serve as retaining piles during the excavation of the foundation pit and as a support structure for the permanent use stage. The external retaining structure mainly bears the earth pressure, while the internal U-shaped channel structure bears the water pressure. A leveling strip 9 is installed above the cast-in-place raft slab 2. The width of the leveling strip 9 located under the L-side wall block is greater than the length of the bottom of the L-side wall block to prevent the L-side wall block from being eccentric. As shown in Figures 1 and 2, a total of three leveling strips 9 are installed, two of which are located at the bottom of the L-side wall block, specifically at the bottom of the base slab.

[0054] The bottom plate of the U-shaped channel in the cutting section is designed as a parallelogram to ensure that the prefabricated structure can be easily spliced ​​in the cutting section with a large angle of inclination, and that the connection between the embankment and the cutting section is tight and without gaps.

[0055] To ensure the integrity of the structure, various structural elements were connected accordingly in the design. Specifically, the retaining pile 1 is connected to the reinforcing bars of the cast-in-place raft slab 2 by the outward extension of the central reinforcing bars of the pile, and the precast side wall 5 is connected to the reserved reinforcing bars of the cap beam through pre-embedded connectors; as shown in Figure 6, the cast-in-place raft slab has pre-embedded anchoring reinforcing bars 401-4; the anchoring reinforcing bars 401-4 pass through the reserved openings in the cast-in-place raft slab and are connected to the anchoring reinforcing bars in the bottom plate of the precast components. These three connections ensure the coordinated stress distribution and anti-buoyancy of the structure.

[0056] Furthermore, as shown in Figure 6, anchoring steel bar holes are reserved on the straight base plate. Anchoring steel bars 401-1 are inserted into the reserved anchoring steel bar holes 401 on the base plate and screwed to the cast-in-place raft slab anchoring steel bars 401-4 through steel bar connectors 401-3. After the connection is completed, the gaps in the holes are sealed by grouting through grouting holes 401-2 to ensure that the precast component base plate and the cast-in-place raft slab are tightly connected and share the load.

[0057] As shown in Figure 7, the L-shaped side wall 5 is connected to the retaining pile cap beam 101 by steel bars. The cap beam 101 has a lateral embedded sleeve 102-2. After the L-shaped side wall 5 is positioned, the connecting steel bar 102 passes through the reserved hole of the side wall 5 and is connected and fixed to the connecting steel bar knob through the steel bar connector 102-1 to ensure that the retaining pile 1 and the side wall 5 are subjected to force together.

[0058] The main structure of the U-shaped channel of the embankment section in this embodiment is shown in Figure 3. It includes two L-shaped sidewall blocks and a base plate. The base plate is a straight block. The L-shaped sidewall blocks and the straight block are aligned by a tenon 402. An inclined tensioning hole is provided at the tenon-and-contact position of the L-shaped sidewall blocks and the straight block. After aligning with the reserved tensioning hole, a high-strength threaded steel bar is inserted, tensioned to a predetermined value, and then fixed with a threaded sleeve and locked with a straight bolt. On the base plate 4, a longitudinal pre-tensioning device reserved hole 7 is provided along the length direction of the base plate 4, and an anchoring steel bar 401 is reserved along the height direction of the base plate 4.

[0059] As shown in Figure 8, in this embodiment, the U-shaped bottom plates of the cutting section and the embankment section have different shapes. The U-shaped bottom plate of the cutting section is a parallelogram design, and the two opposite faces of the bottom plate along the length of the roadbed are vertical planes. This ensures that the prefabricated structure is tightly connected and without gaps at the intersection of the embankment and the cutting section with a large angle of inclination. Connectors are pre-embedded in the cutting section to facilitate tensioning of the embankment section. The transition section where the U-shaped bottom plate of the cutting section connects to the U-shaped bottom plate of the embankment section is connected by pre-embedded connectors 403. The U-shaped bottom plate of the embankment section is rectangular. Although the designs are different, the thickness of the U-shaped bottom plate of the embankment section and the U-shaped bottom plate of the cutting section are the same.

[0060] The connection between the sidewalls and bottom slab of each U-shaped channel in both the cutting section and the embankment section is achieved through tenon and mortise joints and precision-rolled threaded steel bars. The difference lies in the connection method: the bottom slab and sidewalls in the cutting section are connected with diagonal straight bolts, while those in the embankment section are connected with horizontal precision-rolled threaded steel bars. Furthermore, the cutting section also has a connection to the cast-in-place raft slab. As shown in Figure 9, the prefabricated U-shaped channel structure along the road defense line is fixed using a longitudinal pre-tightening device, while the pre-embedded anchor bars in the bottom slab of the embankment section are eliminated, and the circumferential splice joint is replaced with a tenon and mortise joint and precision-rolled threaded steel bar connection.

[0061] Furthermore, since the cantilever portion of the "L"-shaped sidewall is large and there is no support on the outside of the sidewall of the embankment section, the prefabricated U-shaped channel components are prone to instability. Therefore, lateral support members 12 are added to the sidewall of the embankment section to prevent the sidewall block from overturning. The upper part of the lateral support member is fixed to the outside of the sidewall of the L block, and the lower end is supported on the ground.

[0062] In this embodiment, the assembled structure of the tenon and mortise joint adopts a self-waterproof structure and joint waterproofing, namely a "two pads, one injection and one embedding" waterproofing structure, forming a multi-layer waterproofing system. As shown in Figures 10 and 11, "two pads" refers to two waterproof sealing pads that are pasted on before the components are assembled, such as the composite elastic sealing pad 402-2 and the water-swellable rubber sealing pad 402-4 shown in Figure 10. The composite elastic sealing pad 402-2 and the water-swellable rubber sealing pad 402-4 are placed at both ends of the gap formed by the tenon and mortise, and a grouting gap is formed between them. "One grouting" refers to the grouting of the joint groove between the waterproof sealing pads, see the epoxy resin filling joint 402-3 in Figure 10. "One embedding" refers to the waterproofing of the joint between the tenons and mortise of the components, see the internal waterproofing joint 402-5 in Figure 10. The internal waterproofing joint 402-5 shown in Figure 11 includes the polymer mortar filling 402-6; the water-swellable rubber 402-7; the isolation sponge 402-8; and the grouting joint 402-9. The polymer mortar is located on the outermost side of the tenon and mortise joint, and then the water-swellable rubber and the isolation sponge are placed in sequence inward.

[0063] It should be noted that the self-waterproofing and joint waterproofing of the tongue and groove parts mentioned here include the waterproofing of the part where the side wall and the bottom plate are connected by the tongue and groove in each U-shaped groove.

[0064] This embodiment also provides a roadbed, which includes the prefabricated U-shaped channel structure described above; and along the vehicle travel direction, several of the prefabricated U-shaped channel structures are connected by connecting steel bars. The bottom slabs of the cut section and the embankment section are connected to each other, and the side walls are connected to each other by horizontally arranged connecting steel bars.

[0065] The specific construction process for the aforementioned U-shaped trough structure of the roadbed is as follows:

[0066] After the foundation pit and cast-in-place base slab are completed, the prefabricated structure is assembled. The assembly process is as follows: fine leveling strip construction, assembly of the first ring bottom slab and side wall blocks. After the first ring is assembled, the subsequent prefabricated components are assembled, and the base slab and side wall trenches are grouted.

[0067] 1. Excavation of the foundation pit

[0068] The open-cut foundation pit uses cast-in-place piles and internal bracing as the retaining structure. The cast-in-place piles have a diameter of 1.25m and a pile spacing of 1.5m. A steel support is installed at the top of the cast-in-place piles at the capping beam position, which needs to be removed during the assembly construction process.

[0069] 2. Cast-in-place raft foundation construction

[0070] After excavation, the surface of the jet grouting piles on the pit sidewalls was roughened. After excavation to the bottom, the raft foundation was poured. Reinforcing bars were installed at the raft foundation locations, and the connection points with the raft foundation were roughened before binding the reinforcing bars. Once the cast-in-place raft foundation reached its design strength, the steel supports at the capping beam location were removed. Due to the steep road surface, to ensure smooth construction of the prefabricated U-shaped channel, leveling strips were installed above the raft foundation to maintain longitudinal linearity control of the upper components. The width of the leveling strips on both sides was greater than the bottom length of the L-shaped sidewall to prevent eccentricity of the L-shaped sidewall blocks.

[0071] 3. Construction of the connection between the first ring of the prefabricated U-shaped channel and the existing underground structure in the road cutting section.

[0072] The existing underground structure is a cast-in-place structure, and its transition section with the precast section is connected by a hidden column structure formed by cast-in-place reinforced concrete to ensure that the two are subjected to the same stress. The bottom connection section between the existing underground structure and the first ring prefabricated U-shaped channel structure is shown in Figure 12. The waterproof material layer 17 of the connection section, from top to bottom, consists of the precast component top plate, 1.55mm thick double-sided butyl rubber roll, bottom slab waterproof layer, backfill micro-expansion concrete, and cushion concrete.

[0073] Water-swellable sealant 16, grouting pipe and special-shaped waterstop 19 are installed on the connection end face. Water-swellable sealant 16 is installed inside the sealing gasket of the precast component. The waterstop and grouting pipe are closer to the water-facing side. The existing structure and the precast section are connected in a ring with special-shaped waterstop 19, which is directly facing the sealing gasket on the back side and transitions with the waterproof layer of the existing structure.

[0074] The first ring base plate was hoisted onto the leveling strip, and its anchoring reinforcement was connected to the cast-in-place raft slab through pre-drilled holes in the base plate. Then, the two side walls of the first ring prefabricated U-shaped channel were hoisted onto their corresponding leveling strips. The side walls were then pressed tightly against the pit sidewalls using thin-walled jacks behind them, and the side walls and base plate were locked together with diagonal bolts. The longitudinal pre-tensioning device was then tightened, and the ducts were sealed with grout after tensioning. Waterproofing construction was carried out simultaneously with assembly.

[0075] 4. Assembly and construction of the remaining prefabricated U-shaped channels in the road cutting section.

[0076] The second ring base plate is hoisted onto the leveling strip, and its anchoring reinforcement is connected to the cast-in-place raft slab through pre-drilled holes in the base plate. Then, the two side walls of the second ring prefabricated U-shaped channel are hoisted onto their corresponding leveling strips. The side walls are then pressed tightly against the pit sidewalls using thin-walled jacks behind them, and the side walls and base plate are locked together with diagonal bolts. The longitudinal pre-tensioning device is then tightened, and the ducts are sealed with grout after tensioning. Waterproofing construction is carried out simultaneously with assembly.

[0077] The sidewalls and bottom slab are continuously assembled in at least four rings. The foundation is backfilled with grout through pre-embedded pipes, and plain concrete is backfilled behind the "L"-shaped components of the sidewalls. Reinforcing bars are passed through pre-drilled holes in the "L"-shaped components of the sidewalls and connected to the anchoring reinforcing bars in the pre-embedded sleeves of the capping beam via rebar connectors. For the bottom slab's straight blocks, precision-rolled threaded steel bars are inserted through pre-drilled anchoring holes in the bottom slab and connected to the raft foundation anchoring reinforcing bars via rebar connectors. After connection, grouting is used to seal the connection, completing the connection between the bottom slab's straight blocks and the cast-in-place raft foundation.

[0078] 5. Prefabricated U-shaped channel assembly construction for embankment sections

[0079] After the prefabricated construction of the cutting section is completed, a precision-rolled threaded steel connector is pre-embedded in its tail ring as a force transmission device to provide tensioning conditions for the embankment section and ensure that tensioning of the embankment section will not damage the components of the cutting section when there is an inclination angle.

[0080] After the first ring of the embankment section is assembled, the second ring is assembled in the same way. After the assembly is completed, the route direction is connected and fixed by a longitudinal pre-tightening device.

[0081] Because the cantilever portion of the "L"-shaped sidewall is relatively large, a support is fixed on the outside of the sidewall in the embankment section. The upper end of the support is fixed to the sidewall, and the lower end supports the ground to prevent the sidewall block from overturning.

[0082] 6. Grouting at joints, bottom, and sidewalls.

[0083] All joints between prefabricated structural components are sealed with grout. Grouting is required at an appropriate time after structural assembly for all circumferential and longitudinal joints, and after tensioning, grouting is performed through sealed ducts. Since the base slab separates from the foundation concrete during assembly, backfilling and grouting are required every 10-20 rings during construction. After grouting, the base slab, side walls, and foundation concrete are in close contact.

[0084] 7. Construction completed;

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A prefabricated U-shaped channel structure, comprising a U-shaped channel for a road cutting section and a U-shaped channel for a road embankment section, each U-shaped channel comprising a bottom plate and side walls spliced ​​together, characterized in that, The bottom plate of the U-shaped channel in the cutting section is parallelogram-shaped, and two opposite faces of the bottom plate along the length of the roadbed are vertical planes; the bottom plate of each U-shaped channel in the embankment section is rectangular; and the U-shaped channel in the cutting section is fixed on the cast-in-place raft slab between the retaining piles of the cutting section, and is connected to the retaining piles, the capping beam on the top of the retaining piles, and the cast-in-place raft slab located between the retaining piles. The retaining piles are permanent support structures and form an integral whole with the U-shaped channel.

2. The assembled U-shaped groove structure as described in claim 1, characterized in that, The retaining piles are pre-installed with connecting steel bars, which are connected to the transverse connecting steel bars of the cast-in-place raft slab; the side walls are connected to the steel bars in the pre-embedded sleeves on the cap beam by inserting steel bars through the pre-reserved holes in the side walls and using connectors; the cast-in-place raft slab is also pre-embedded with vertical connecting steel bars, which pass through the pre-reserved openings in the precast bottom slab and are connected to the bottom slab of the precast components.

3. The assembled U-shaped groove structure as described in claim 1, characterized in that, A sleeve is pre-embedded in the cap beam, and a reserved hole is set in the side wall. After the side wall is installed in place, the pre-embedded steel bars pass through the reserved hole and are connected to the steel bars in the pre-embedded sleeve of the cap beam using a steel bar connector.

4. The assembled U-shaped groove structure as described in claim 1, characterized in that, The sidewalls and the bottom plate are connected by tenons and connecting steel bars; the connecting steel bars of the U-shaped groove in the cutting section are arranged crosswise; the connecting steel bars of the U-shaped groove in the embankment section are arranged horizontally.

5. The assembled U-shaped groove structure as described in claim 1, characterized in that, A waterproof structure is provided at the joint of the base plate and the side wall tongue and groove joints. The waterproof structure includes a composite elastic sealing gasket and a water-swellable rubber sealing gasket. The gap between the two sealing gaskets is filled with sealant. An embedded waterproof structure is provided on the outside of the water-swellable rubber sealing gasket.

6. The assembled U-shaped groove structure as described in claim 5, characterized in that, The embedded waterproof structure includes an insulating sponge, polymer mortar, and water-swellable rubber. The polymer mortar is located on the outermost side of the tongue and groove joint, followed by water-swellable rubber and insulating sponge in sequence.

7. The assembled U-shaped groove structure as described in claim 4, characterized in that, Support devices are also installed on the outside of the side walls of the embankment section.

8. The assembled U-shaped groove structure as described in claim 1, characterized in that, The cast-in-place raft slab is also provided with precision leveling strips.

9. The assembled U-shaped groove structure as described in claim 1, characterized in that, The precision leveling strip is set at the bottom of the two side walls and the bottom of the base plate; the precision leveling strip at the bottom of the side walls has a width greater than the length of the bottom of the side walls.

10. A roadbed, characterized in that, The invention includes several prefabricated U-shaped channel structures as described in any one of claims 1-9, arranged along the vehicle's direction of travel, and the several prefabricated U-shaped channel structures are connected by connecting steel bars along the vehicle's direction of travel.

11. A roadbed as described in claim 10, characterized in that, Adjacent base slabs are connected to each other, and side walls are connected to each other by reinforcing bars.

12. A roadbed as described in claim 10, characterized in that, The bottom slab of the U-shaped channel in the cutting section is horizontally connected to the bottom slab of the U-shaped channel in the embankment section by steel bars.

13. A method for constructing a roadbed with a prefabricated U-shaped channel structure, characterized in that, as follows: Step 1: Excavate the foundation pit and construct retaining piles and capping beams within the pit; Step 2: Construct the cast-in-place raft foundation between the retaining piles; Step 3: Construct the first ring U-shaped channel of the road cut section on the raft slab and connect the first ring U-shaped channel to the existing underground structure. Step 4: Construct the prefabricated U-shaped channel for the remaining ring of the road cutting section. During construction, after each set number of prefabricated U-shaped channels are constructed, the bottom plate, side walls, retaining piles, cap beams, and cast-in-place raft slab of the assembled U-shaped channel must be connected. After connection, they must be cast into one piece until the construction of all road cutting sections is completed. Step 5 involves assembling the prefabricated U-shaped channel of the embankment section. After the prefabricated construction of the cutting section is completed, a precision-rolled threaded steel connector is pre-embedded in its tail section as a force transmission device to provide tensioning conditions for the embankment section and ensure that tensioning of the embankment section will not damage the cutting section components when there is an inclination angle. Step 7: All joints between prefabricated structural components are sealed by grouting. All joints in the circumferential and longitudinal directions of the U-shaped groove need to be grouted at an appropriate time after the structure is assembled. Grouting is carried out through the sealed ducts after tensioning is completed.

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