A prefabricated middle-side box culvert structure at the bottom of a shield tunnel and its construction method

Abstract

The present invention relates to the field of shield tunnel construction, and more particularly to a prefabricated middle-side box culvert structure and construction method at the bottom of a shield tunnel; the structure comprises a prefabricated middle box culvert, a prefabricated side box culvert, and a corbel base; both ends of the prefabricated middle box culvert are detachably connected to prefabricated side box culverts; the corbel base is disposed below one end of the prefabricated side box culvert away from the prefabricated middle box culvert; the lower ends of the prefabricated middle box culvert and the corbel base are connected to shield segments of the shield tunnel; the top surface of the prefabricated middle box culvert is higher than the top surface of the prefabricated side box culvert; supporting corbels capable of supporting the prefabricated side box culverts are disposed on both sides of the prefabricated middle box culvert; and the prefabricated side box culvert and the prefabricated middle box culvert adopt an assembled structure with wedges. The present invention increases the prefabrication rate of the internal structure of the shield tunnel and improves installation efficiency; the prefabricated middle box culvert and the side box culvert are connected by straight bolts, which saves costs and significantly increases construction speed; and the use of a prefabricated structure with wedges is conducive to solving the problem of large gaps in the assembly of the box culvert structure.

Description

Technical Field

[0001] The present invention relates to the field of shield tunnel construction, and in particular to a prefabricated middle-side box culvert structure at the bottom of a shield tunnel and a construction method. Background Art

[0002] With the development of the transportation industry, shield tunnels are widely used in the construction of tunnels in highway, municipal, and railway sectors. However, due to limitations in prefabricated construction technology, the internal space of shield tunnels, and existing prefabrication and construction capabilities, the prefabrication rate of shield tunnel internal structures remains relatively low. The intermediate and side box culverts at the bottom of shield tunnels, as important components of the internal structure, are crucial for improving the prefabrication rate. Existing intermediate box culverts are essentially fully prefabricated, but due to stress requirements, construction procedures, and workspace, side box culverts are often cast in-situ or laminated (semi-cast in-situ, semi-prefabricated) construction, severely restricting the quality and speed of box culvert construction.

[0003] The main deficiencies are as follows: 1) When the side box culvert adopts the cast-in-place method, it is necessary to pre-embed the connector at the edge of the middle box culvert in advance, which is costly. The space below the side box culvert is relatively narrow, the bottom formwork is not easy to remove, the construction operation is difficult, the steel bars need to be arranged and tied on site, the construction speed is slow, and long-term construction has a greater impact on the pipe segments; 2) When the side box culvert adopts the composite component, an additional cast-in-place construction process is added, and the construction progress is still slow. The top of the side box culvert is still connected to the middle box culvert by pre-embedded connectors. The number of connectors used is large and the cost is high. The side box culvert prefabricated parts are not connected to the middle box culvert during construction. The side box culvert prefabricated panels act on the brackets on both sides. The concrete at the corners of the brackets is easily damaged, which has a certain impact on the overall structural safety of the box culvert; 3) The existing prefabricated box culvert structure does not have a wedge variable. When the tunnel plane turning radius is small, the box culvert assembly effect in the curved section of the shield tunnel is poor. The width of the assembly seam increases with the increase of the curve length, which is not conducive to structural stress and construction. Therefore, there is an urgent need for a prefabricated wedge-shaped middle-side box culvert structure at the bottom of a shield tunnel to solve the above problems. Summary of the Invention

[0004] In order to solve the above problems, on the one hand, the present invention provides a prefabricated middle-side box culvert structure at the bottom of a shield tunnel, which is arranged in the shield segments of the shield tunnel. The box culvert structure includes a prefabricated middle box culvert, a prefabricated side box culvert, and a corbel base. The two ends of the prefabricated middle box culvert are detachably connected to the prefabricated side box culvert. The corbel base is arranged below the end of the prefabricated side box culvert away from the prefabricated middle box culvert. The lower ends of the prefabricated middle box culvert and the corbel base are connected to the shield segments of the shield tunnel. The top surface of the prefabricated middle box culvert is higher than the top surface of the prefabricated side box culvert.

[0005] Furthermore, a plurality of first threaded holes are embedded at positions on the prefabricated intermediate box culvert where the prefabricated side box culvert is fixed, a protrusion is provided on one end of the prefabricated side box culvert connected to the prefabricated intermediate box culvert, and a through hole or a second threaded hole corresponding to the first threaded hole is provided on the protrusion.

[0006] Furthermore, a slope chamfer is provided on the side of the prefabricated side box culvert close to the shield segment.

[0007] Furthermore, supporting brackets for supporting the prefabricated side box culverts are provided on both sides of the prefabricated middle box culvert.

[0008] Furthermore, a buffer layer is provided on the upper end surface of the supporting corbel, and the buffer layer is made of plastic material.

[0009] Furthermore, the space between the prefabricated side box culvert, the corbel base and the shield segments is filled with concrete, and the space between the bottom of the prefabricated middle box culvert and the shield segments is filled with concrete.

[0010] Furthermore, the upper end surfaces of the prefabricated middle box culvert and the prefabricated side box culverts at both ends thereof are matching wedge-shaped structures, and the widths of both ends of the prefabricated middle box culvert are the same as the widths of the prefabricated side box culverts at their connected ends.

[0011] On the other hand, the present invention also provides a construction method for a prefabricated middle-side box culvert at the bottom of a shield tunnel, comprising the following steps:

[0012] S1: Prefabricated intermediate box culverts and prefabricated side box culverts are manufactured in a factory and transported to the site. The prefabricated intermediate box culvert is provided with a first threaded hole for connection with the prefabricated side box culvert and a supporting bracket for supporting the prefabricated side box culvert. The prefabricated side box culvert is provided with a through hole or a second threaded hole for connection with the prefabricated intermediate box culvert. The installation position and installation height of the prefabricated intermediate box culvert and the prefabricated side box culvert are set according to the construction situation.

[0013] S2: Cast-in-situ corbel base at the lower end of the precast side box culvert;

[0014] S3: Install the prefabricated middle box culvert, connect the bottom of the prefabricated middle box culvert with the shield segment, assemble the prefabricated side box culvert between the prefabricated middle box culvert and the corbel base, and adjust them to a suitable position;

[0015] S4: Align the through hole or the second threaded hole of the prefabricated side box culvert with the first threaded hole of the prefabricated middle box culvert and fix them with straight bolts;

[0016] S5: Repeat the above operations S1-S4 to assemble the box culvert structure in sequence along the excavation direction;

[0017] S6: After assembling a certain length along the longitudinal direction of the shield tunnel, backfill and cast the cavity between the prefabricated side box culvert, the corbel base and the shield segments to ensure the stability of the lower box culvert structure system.

[0018] Furthermore, in said S1, the upper end surfaces of the prefabricated middle box culvert and the prefabricated side box culverts at both ends of the factory are matching wedge-shaped structures, and the widths of both ends of the prefabricated middle box culvert are the same as the widths of the prefabricated side box culverts at their connected ends.

[0019] Furthermore, in S3, the shield tunnel is a curved section, the width of the prefabricated side box culvert on the inner side is smaller than the width of the prefabricated side box culvert on the outer side, and the shield tunnel is a straight section, and the box culvert structure is alternately arranged left and right along the longitudinal direction of the shield tunnel.

[0020] Due to the adoption of the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0021] 1) The intermediate box culvert and the side box culvert in the present invention are both prefabricated structures, which increases the prefabrication rate of the internal structure of the shield tunnel and improves installation efficiency. The prefabricated intermediate box culvert and the side box culvert are connected by straight bolts, which avoids the need to embed connectors in the prefabricated parts, saving costs. At the same time, it avoids the need to arrange the upper layer of steel bars on site, greatly improving construction speed.

[0022] 2) In the present invention, a protrusion is provided on one end of the prefabricated side box culvert close to the prefabricated middle box culvert, and the top surface elevation of the prefabricated side box culvert is lower than that of the prefabricated middle box culvert. This not only solves the problem of insufficient thickness of the lower lane cushion in the shield tunnel, but also facilitates on-site assembly of straight bolts, speeding up assembly and thereby increasing construction speed.

[0023] 3) The bottom of the prefabricated side box culvert close to the shield segment in the present invention is provided with a sloped chamfer, which is conducive to the dense filling of the corner concrete;

[0024] 4) The prefabricated middle box culvert and prefabricated side box culvert in the present invention adopt a prefabricated structure with a wedge-shaped portion, which is conducive to solving the problem of large gaps in the assembly of the box culvert structure, especially the problem of poor assembly effect in curved sections, reducing assembly errors and improving the assembly quality of the box culvert;

[0025] 5) In the present invention, a buffer layer is provided on the top surface of the supporting corbel of the prefabricated intermediate box culvert, which prevents the prefabricated side box culvert from directly acting on the supporting corbel concrete. It has a certain buffering effect and is beneficial to protecting the integrity and safety of the prefabricated intermediate box culvert supporting corbel. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic structural diagram of the prefabricated middle-side box culvert structure at the bottom of a shield tunnel according to the present invention;

[0027] Figure 2This is a schematic diagram of the partial structure of the prefabricated middle-side box culvert structure at the bottom of the shield tunnel of the present invention;

[0028] Figure 3 This is a structural schematic diagram of a prefabricated middle box culvert in the prefabricated middle-side box culvert structure at the bottom of a shield tunnel according to the present invention;

[0029] Figure 4 It is a structural schematic diagram of the prefabricated side box culvert in the prefabricated middle-side box culvert structure at the bottom of the shield tunnel of the present invention;

[0030] Figure 5 This is a structural schematic diagram of the connection between the prefabricated side box culvert and the prefabricated middle box culvert in the prefabricated middle-side box culvert structure at the bottom of a shield tunnel according to the present invention;

[0031] Figure 6 This is a schematic diagram of the assembly structure of the prefabricated middle-side box culvert structure at the bottom of the shield tunnel of the present invention.

[0032] 1- Prefabricated middle box culvert; 2- Prefabricated side box culvert; 3- Corbel base; 4- Backfill concrete structure; 5- Shield segment; 6- Straight bolt; 7- Support corbel; 8- First threaded hole; 9- Slope chamfer; 10- Connection hole. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. In the accompanying drawings, the sizes and relative sizes of certain parts may be exaggerated for clarity.

[0034] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connection" and "connected" should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In the description of the present invention, terms such as "up", "down", "left", "right", "front", and "back" and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limiting the present invention.

[0036] As the instruction manual Figure 1-2 As shown, an embodiment of the present invention provides a prefabricated middle-side box culvert structure at the bottom of a shield tunnel, which is arranged in the shield segment 5 of the shield tunnel and is arranged in sequence along the longitudinal direction of the shield tunnel. The box culvert structure includes a prefabricated middle box culvert 1, a prefabricated side box culvert 2, and a corbel base 3. The two ends of the prefabricated middle box culvert 1 are detachably connected to the prefabricated side box culvert 2. The corbel base 3 is arranged below the end of the side box culvert 2 away from the prefabricated middle box culvert 1. The corbel base 3 can be constructed by cast-in-situ concrete to support the prefabricated side box culvert 2 above it. The two ends of the prefabricated side box culvert 2 are fixed by the prefabricated middle box culvert 1 and the corbel base 3 respectively. The prefabricated side box culvert 2 and the prefabricated middle box culvert 1 are laid horizontally along the shield tunnel. The prefabricated side box culvert 2 and the segments of the shield tunnel A certain gap is left between them, and the stability of the box culvert structure system can be ensured by cast-in-place concrete, that is, a backfill concrete structure 4 is formed between the prefabricated side box culvert 2, the corbel base 3 and the shield segment 5. The lower ends of the prefabricated intermediate box culvert 1 and the corbel base 3 are connected to the shield segment 5 of the shield tunnel. The top surface of the prefabricated intermediate box culvert 1 is higher than the top surface of the prefabricated side box culvert 2. Due to the existence of super-high cross slope, the top cushion layer of the lower side span lane slab in the double-layer tunnel is often too thin. Making the top surface of the prefabricated side box culvert lower than the top surface of the prefabricated intermediate box culvert can solve the problem of insufficient cushion layer thickness of the lower lane in the shield tunnel; at the same time, the prefabricated side box culvert and the prefabricated intermediate box culvert are connected with straight bolts. The top surface of the prefabricated side box culvert is lower than the prefabricated intermediate box culvert, and protrusions can be set to facilitate the tightening construction of the bolts.

[0037] In a specific implementation manner, steel bars are pre-embedded at the position where the corbel base 3 is set on the shield segment 5, and then the corbel base 3 is cast in situ, which can increase the strength of the corbel base 3. The prefabricated intermediate box culvert 1 can be pre-embedded with connectors or connecting parts at the bottom during the prefabrication process. At the same time, structural parts that can be connected to the connectors or connecting parts are also pre-embedded at the corresponding positions of the shield segment 5 to realize the installation of the prefabricated intermediate box culvert 1. After the installation is completed, concrete can be cast in situ at the connection between the bottom of the prefabricated intermediate box culvert 1 and the shield segment 5 for reinforcement.

[0038] As one of the implementation methods, as shown in the attached specification Figure 3 As shown, a plurality of first threaded holes 8 are pre-buried at the position where the prefabricated intermediate box culvert 1 is fixed to the prefabricated side box culvert 2. Specifically, a plurality of threaded sleeves are evenly pre-buried on the side wall where the prefabricated intermediate box culvert 1 is connected to the prefabricated side box culvert 2 to form a first threaded hole 8, which can be threadedly connected with a straight bolt 6. A protrusion is provided on the end of the prefabricated side box culvert 2 connected to the prefabricated intermediate box culvert 1. After the prefabricated side box culvert 2 and the prefabricated intermediate box culvert 1 are spliced, the height of the protrusion is the same as the height of the prefabricated intermediate box culvert 1. A connecting hole 10 corresponding to the first threaded hole 8 is provided on the protrusion. The connecting hole 10 can be a through hole or a second threaded hole. Specifically, as shown in the attached manual Figure 5As shown, a steel pipe or a threaded sleeve is pre-embedded on the protrusion of the prefabricated side box culvert 2 for the straight bolt 6 to pass through or be threadedly connected with the straight bolt 6. The connecting hole 10 is set through the protrusion, and the position of the connecting hole 10 corresponds to the position of the first threaded hole 8. After the positions of the prefabricated side box culvert 2 and the prefabricated intermediate box culvert 1 are adjusted, the straight bolt 6 passes through the connecting hole 10 and is threadedly connected to the first threaded hole 8 to achieve the fixation of the prefabricated intermediate box culvert 1 and the prefabricated side box culvert 2. A groove for accommodating the nut of the straight bolt 6 is also provided at the protrusion. The groove can be made of cast-in-situ concrete on one side of the protrusion after the prefabricated side box culvert 2 and the prefabricated intermediate box culvert 1 are connected. After the prefabricated intermediate box culvert 1 and the prefabricated side box culvert 2 are connected , grouting is injected at its joint to fill the gap; supporting corbels 7 for supporting the prefabricated side box culverts 2 are provided on both sides of the prefabricated intermediate box culvert 1, and the supporting corbels 7 are located below the prefabricated side box culvert 2. During the assembly process, the two ends of the prefabricated side box culvert 2 are respectively arranged on the corbel base 3 and the supporting corbel 7, and then connected by straight bolts 6 to achieve effective connection between the prefabricated intermediate box culvert 1 and the prefabricated side box culvert 2. In order to avoid the prefabricated side box culvert 2 directly acting on the supporting corbel 7, a buffer layer can be provided on the top surface of the supporting corbel 7, which can be made of plastic material, such as EVA plastic sheet, which can reduce the force of the prefabricated side box culvert 2 on the supporting corbel 7, which is beneficial to protecting the integrity and safety of the supporting corbel of the prefabricated intermediate box culvert 1.

[0039] As the instruction manual Figure 4 As shown, the bottom of the prefabricated side box culvert 2 close to the shield segment 5 is provided with a slope chamfer 9, and its inclination angle and length can be set according to actual needs. The slope chamfer 9 is provided at the lower end of the prefabricated side box culvert 2, which is beneficial to increase the filling density of the corner concrete when backfilling concrete between the prefabricated side box culvert 2, the corbel base 3 and the shield segment 5, thereby increasing the strength of the box culvert system.

[0040] As the instruction manual Figure 6As shown, the upper end faces of the prefabricated middle box culvert 1 and the prefabricated side box culverts 2 at both ends are matching wedge-shaped structures. The widths of the two ends of the prefabricated middle box culvert 1 are the same as the widths of the prefabricated side box culverts 2 at the connected ends. Each set of box culvert structures is composed of a prefabricated middle box culvert 1 and prefabricated side box culverts 2 at both ends, and the box culvert structure is assembled along the excavation direction of the shield tunnel. For curved sections, the shield tunnel has a certain curvature. With one side of the center of the curved section as the inner side, the width of the inner prefabricated side box culvert 2 is smaller than the width of the outer prefabricated side box culvert 2, and the end with the smaller width of the prefabricated middle box culvert 1 is set toward the inside, and the box culvert structure is assembled along the shield tunnel. The tunnel is laid in sequence in the longitudinal direction, and the wedge-shaped amount of the prefabricated intermediate box culvert 1 and the prefabricated side box culvert 2 is set according to actual needs. Specifically, it can be set according to the curvature of the curved section; for straight sections, the upper end faces of the prefabricated intermediate box culvert 1 and the prefabricated side box culvert 2 can be square or wedge-shaped structures. If the prefabricated intermediate box culvert 1 and the prefabricated side box culvert 2 are square, the width of the prefabricated intermediate box culvert 1 and the prefabricated side box culvert 2 are the same, and they can be arranged in sequence along the longitudinal direction of the shield tunnel. If the prefabricated intermediate box culvert 1 and the prefabricated side box culvert 2 are wedge-shaped structures, each group of box culvert structures is alternately arranged left and right along the longitudinal direction of the shield tunnel to reduce the gap in the assembly of the box culvert structure.

[0041] In some embodiments, the prefabricated middle box culvert 1 and the prefabricated side box culvert 2 are made into modular standard parts. The prefabricated side box culvert is a wedge-shaped structure, so two prefabricated side box culvert standard parts of different sizes need to be made, which can save costs, facilitate transportation and spare parts, and grouting can be used to fill the gaps in each set of box culvert structures.

[0042] On the other hand, the present invention also provides a construction method for a prefabricated middle-side box culvert at the bottom of a shield tunnel, comprising the following steps:

[0043] S1: A prefabricated intermediate box culvert 1 and a prefabricated side box culvert 2 are manufactured in the factory and transported to the site. The prefabricated intermediate box culvert 1 is prefabricated with a first threaded hole 8 for connection with the prefabricated side box culvert 2, and a supporting bracket 7 for supporting the prefabricated side box culvert 2. A connector for connection with the shield segment 5 is also pre-buried at the bottom of the prefabricated intermediate box culvert 1. The prefabricated side box culvert 2 is prefabricated with a connecting hole 10 for connection with the prefabricated intermediate box culvert 1, which can be a through hole or a second threaded hole. The installation position and installation height of the prefabricated intermediate box culvert 1 and the prefabricated side box culvert 2 are set according to the construction situation.

[0044] S2: Determine the installation position of the corbel base 3, pre-embed steel bars on the shield segments 5, and cast the corbel base 3 at the lower end of the prefabricated side box culvert 2 on site;

[0045] S3: Determine the installation position of the intermediate box culvert 1, pre-embed the connectors connected to the prefabricated intermediate box culvert 1 on the shield segments 5 in advance, hoist the prefabricated intermediate box culvert to the target position and install it, connect the bottom of the prefabricated intermediate box culvert 1 with the shield segments 5, assemble the prefabricated side box culvert 2 between the prefabricated intermediate box culvert 1 and the corbel base 3, that is, hoist the prefabricated side box culvert 2 to the corbel base 3 and the supporting corbel 7 of the prefabricated intermediate box culvert 1, and adjust it to a suitable position;

[0046] S4: Align the through hole or the second threaded hole of the prefabricated side box culvert 2 with the first threaded hole 8 of the prefabricated middle box culvert 1 and fix them with straight bolts 6;

[0047] S5: Repeat the above operations S1-S4 to assemble the box culvert structure in sequence along the shield tunneling direction;

[0048] S6: After assembling a certain length along the longitudinal direction of the shield tunnel, backfill and cast the cavity between the prefabricated side box culvert 2, the corbel base 3 and the shield segment 5 to ensure the stability of the lower box culvert structure system, and grouting is performed at each joint to fill the gap.

[0049] The embodiment is detailed. The upper end surfaces of the prefabricated intermediate box culvert 1 and the prefabricated side box culvert 2 are square or matching wedge-shaped structures, and the widths of both ends of the prefabricated intermediate box culvert 1 are the same as the widths of the prefabricated side box culvert 2 at the connected ends. Figure 6 As shown, the shield tunnel is a curved section, the width of the prefabricated side box culvert 2 on the inner side is smaller than the width of the prefabricated side box culvert 2 on the outer side, and the shield tunnel is a straight section. The box culvert structures are alternately arranged left and right along the longitudinal direction of the shield tunnel to reduce the gap between the box culvert structures.

[0050] In summary, the present invention provides a prefabricated middle-side box culvert structure and construction method at the bottom of a shield tunnel. Both the side box culvert and the middle box culvert adopt prefabricated structures, which improves the prefabrication rate of the box culvert structure and improves the installation efficiency. The prefabricated side box culvert and the prefabricated middle box culvert adopt a threaded connection method and are detachably connected by straight bolts, avoiding the need to embed connectors in prefabricated parts, saving costs and greatly improving the construction speed. The prefabricated side box culvert and the prefabricated middle box culvert adopt a wedge structure, which can reduce the gap between the box culvert structures during the splicing process, making it particularly suitable for use in curved sections, reducing assembly errors and improving the assembly quality of the box culvert.

[0051] Those skilled in the art will appreciate that the present invention can be implemented in many other specific forms without departing from the spirit and scope of the present invention. Although embodiments of the present invention have been described, it should be understood that the present invention should not be limited to these embodiments, and those skilled in the art can make changes and modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A prefabricated middle-side box culvert structure at the bottom of a shield tunnel, which is arranged in a shield segment of a shield tunnel, characterized in that: The box culvert structure includes a prefabricated middle box culvert, a prefabricated side box culvert, and a corbel base, wherein both ends of the prefabricated middle box culvert are detachably connected to the prefabricated side box culvert, the corbel base is arranged below one end of the prefabricated side box culvert away from the prefabricated middle box culvert, the lower ends of the prefabricated middle box culvert and the corbel base are connected to the shield segments of the shield tunnel, the top surface of the prefabricated middle box culvert is higher than the top surface of the prefabricated side box culvert; a plurality of first threaded holes are pre-embedded at the position where the prefabricated side box culvert is fixed to the prefabricated side box culvert, a protrusion is provided on the end of the prefabricated side box culvert connected to the prefabricated middle box culvert, a through hole or a second threaded hole corresponding to the first threaded hole is provided on the protrusion, and a slope chamfer is provided on the side of the prefabricated side box culvert close to the shield segment, the upper end faces of the prefabricated middle box culvert and the prefabricated side box culverts at both ends thereof are matching wedge structures, and the widths of the two ends of the prefabricated middle box culvert are the same as the widths of the prefabricated side box culverts at the ends connected thereto.

2. The prefabricated middle-side box culvert structure at the bottom of a shield tunnel according to claim 1, characterized in that: Supporting brackets for supporting the prefabricated side box culverts are provided on both sides of the prefabricated middle box culvert.

3. The prefabricated middle-side box culvert structure at the bottom of a shield tunnel according to claim 2, characterized in that: A buffer layer is provided on the upper end surface of the supporting corbel, and the buffer layer is made of plastic material.

4. The prefabricated middle-side box culvert structure at the bottom of a shield tunnel according to claim 1, characterized in that: The space between the prefabricated side box culvert, the corbel base and the shield segments is filled with concrete, and the space between the bottom of the prefabricated middle box culvert and the shield segments is filled with concrete.

5. A construction method for prefabricated middle-side box culvert at the bottom of a shield tunnel, characterized in that: The prefabricated middle-side box culvert structure at the bottom of a shield tunnel according to any one of claims 1 to 4 is used, comprising the following steps: S1: Prefabricated intermediate box culverts and prefabricated side box culverts are manufactured in a factory and transported to the site. The prefabricated intermediate box culvert is provided with a first threaded hole for connection with the prefabricated side box culvert and a supporting bracket for supporting the prefabricated side box culvert. The prefabricated side box culvert is provided with a through hole or a second threaded hole for connection with the prefabricated intermediate box culvert. The installation position and installation height of the prefabricated intermediate box culvert and the prefabricated side box culvert are set according to the construction situation. S2: Cast-in-situ corbel base at the lower end of the precast side box culvert; S3: Install the prefabricated middle box culvert, connect the bottom of the prefabricated middle box culvert with the shield segment, assemble the prefabricated side box culvert between the prefabricated middle box culvert and the corbel base, and adjust them to a suitable position; S4: Align the through hole or the second threaded hole of the prefabricated side box culvert with the first threaded hole of the prefabricated middle box culvert and fix them with straight bolts; S5: Repeat the above operations S1-S4 to assemble the box culvert structure in sequence along the excavation direction; S6: After assembling a certain length along the longitudinal direction of the shield tunnel, backfill and cast the cavity between the prefabricated side box culvert, the corbel base and the shield segments to ensure the stability of the box culvert structure system.

6. The construction method of prefabricated middle-side box culvert at the bottom of a shield tunnel according to claim 5, characterized in that: In S1, the upper end surfaces of the prefabricated middle box culvert and the prefabricated side box culverts at both ends of the prefabricated middle box culvert are matched wedge-shaped structures, and the widths of both ends of the prefabricated middle box culvert are the same as the widths of the prefabricated side box culverts at the ends connected thereto.

7. The construction method of prefabricated middle-side box culvert at the bottom of a shield tunnel according to claim 6, characterized in that: In the above-mentioned S3, the shield tunnel is a curved section, with one side of the center of the curved section as the inner side, and the width of the prefabricated side box culvert on the inner side is smaller than the width of the prefabricated side box culvert on the outer side.

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