A station deep foundation pit reinforcement system of underpass tunnel and construction method

Abstract

A station deep foundation pit reinforcing system of underpass tunnel and construction method belong to station foundation pit construction technical field, the station deep foundation pit reinforcing system of underpass tunnel, including existing tunnel enclosure pile and between existing tunnel side wall and existing road structure layer, the bottom of existing tunnel side wall and lower excavation have foundation pit, the bottom of foundation pit is provided with roof support assembly, a plurality of foundation pit stand column are arranged below roof support assembly, the upper end of roof support assembly is connected with existing tunnel side wall through backfill structure, the beneficial effect of the present application is, the present application greatly improves the tunnel below the subway station deep foundation pit overall excavation construction efficiency under the premise of ensuring the safety and stability of the existing road tunnel, has its practical significance in the subway station deep foundation pit construction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of station foundation pit construction, in particular to a station deep foundation pit reinforcement system for a tunnel underneath and a construction method. BACKGROUND

[0002] When a subway station deep foundation pit is excavated and a tunnel underneath needs to be passed through, the cover-dig section support pile and the intermediate support pile need to be cut off, thereby destroying the original stress system of the existing road tunnel. In order to ensure the safety of the existing road tunnel structure, the existing tunnel needs to be structurally modified. Using the conventional cover-dig method for construction, the construction process is complex and the construction progress is slow, which cannot meet the safety requirements of the existing tunnel structure and cannot achieve the purpose of improving the tunnel excavation construction efficiency and realizing safe and rapid construction.

[0003] A traffic relief method for subway construction underneath a tunnel underneath is disclosed in patent No. CN109811605A, which includes the following steps: erecting a protective fence in a pedestrian passage, isolating a temporary pedestrian passage from the main road, and conducting traffic relief for the first stage of subway construction; filling the construction foundation pit dug above and making it level with the main road as a traffic relief passage for the second stage of subway construction; filling the tunnel underneath to make it a traffic relief passage for the third stage of subway construction; setting up protective fences on both sides of the main road for the third stage of subway construction; after the third stage of subway construction is completed, restoring the road in the construction section and making it a traffic relief passage for the restoration of the tunnel underneath; excavating and restoring the tunnel underneath to complete the construction. The traffic relief method provided by the patent has complex construction, complex construction process, slow construction progress, poor safety, and still has the problems existing in the existing foundation pit construction. SUMMARY

[0004] To solve the above technical problems, the present application provides a station deep foundation pit reinforcement system for a tunnel underneath and a construction method, which greatly improves the overall excavation construction efficiency of the subway station deep foundation pit underneath the tunnel under the premise of ensuring the safety and stability of the existing road tunnel, and has practical significance in the construction of the subway station deep foundation pit.

[0005] To achieve the above purpose, the technical solution adopted by the present application to solve its technical problems is: the station deep foundation pit reinforcement system for a tunnel underneath, including the existing tunnel support pile, the existing tunnel side wall between them and the existing road structure layer, the bottom of the existing tunnel side wall and the foundation pit underneath are excavated, the top plate support assembly is arranged at the bottom of the foundation pit, a plurality of foundation pit columns are arranged below the top plate support assembly, and the top plate support assembly is connected with the existing tunnel side wall through the backfill structure at the upper end.

[0006] The foundation pit comprises a main section and a sloping excavation section thereon, the height between the upper end of the sloping excavation section and the surface of the existing road structure layer is 40-60 cm, the bottom end of the sloping excavation section is the bottom end of the existing tunnel side wall, and the bottom end of the existing tunnel side wall is the excavation working face of the main section of the foundation pit.

[0007] A steel sheet pile is vertically inserted below the excavation working face.

[0008] The sloping excavation section and the existing tunnel retaining pile are connected through a plurality of anchor cable structures.

[0009] The foundation pit column is provided as a lattice column pile.

[0010] The roof support assembly comprises a horizontal support plate laid on the bottom end of the foundation pit and a station roof cast on the horizontal support plate, and the horizontal support plate and the station roof abut against one side of the steel sheet pile.

[0011] The horizontal support plate and the station roof are both provided as reinforced concrete plates, and the thickness of the horizontal support plate is 200-300 mm.

[0012] A waterproof layer is provided between the horizontal support plate, the station roof and the existing tunnel retaining pile, the waterproof layer comprises a waterproof coating applied on the end of the horizontal support plate and a waterproof roll laid on the upper surface of the horizontal support plate, and the waterproof roll covers the edge of the horizontal support plate and abuts against the existing tunnel retaining pile.

[0013] The backfill structure comprises a backfill layer and a road surface layer arranged from bottom to top, and the two sides of the road surface layer are connected with the existing tunnel side wall through steel bar planting.

[0014] A construction method of a station deep foundation pit reinforcement system of a tunnel passing underneath, comprising the following steps:

[0015] Step 1: slope excavation of the foundation pit along the bottom of the existing tunnel side wall to the bottom of the existing tunnel side wall;

[0016] Step 2: setting a plurality of anchor cable structures at the position close to the bottom of the existing tunnel side wall of the existing tunnel retaining pile, and driving a steel sheet pile below the existing tunnel side wall;

[0017] Step 3: continue to excavate the foundation pit to the station roof, and construct a horizontal support plate at the bottom of the foundation pit;

[0018] Step 4: constructing a plurality of foundation pit columns below the horizontal support plate;

[0019] Step 5: casting and constructing a station roof and a waterproof layer on the horizontal support plate;

[0020] Step 6: laying backfill layer and pavement layer on the station roof in turn, and connecting the pavement layer with the existing tunnel side wall through steel bar planting.

[0021] The beneficial effects of the present application are:

[0022] 1. The present application provides a station deep foundation pit reinforcement system and construction method for underpassing a tunnel, the station deep foundation pit reinforcement system and construction method for underpassing a tunnel comprising the following steps: excavating the foundation pit to the bottom of the station roof, then constructing a roof support assembly and a foundation pit column, constructing a backfill structure on the roof support assembly, and connecting the backfill structure with the existing tunnel side wall, thereby reducing the influence of process conversion on the construction period, saving the construction period, and ensuring the safety of the existing tunnel structure.

[0023] 2. The present application sets multiple anchor cable structures for structural reinforcement after excavating the foundation pit to the bottom of the existing tunnel side wall, and simultaneously constructs a steel sheet pile close to the side wall, thereby ensuring the safety of the existing underpass tunnel structure and the safety of the foundation pit excavation through multiple reinforcement and support measures.

[0024] 3. The present application sets a waterproof layer between the horizontal support plate, the station roof, and the existing tunnel enclosure pile, sets a waterproof coating on the end of the horizontal support plate, and pre-lays a waterproof roll on the upper surface of the horizontal support plate, so that the edge of the horizontal support plate coated with the waterproof coating is wrapped and abuts on the existing tunnel enclosure pile, thereby improving the waterproof performance of the station roof structure. BRIEF DESCRIPTION OF DRAWINGS

[0025] The following is a brief description of the content expressed by each figure in the specification of the present application and the marks in the figures:

[0026] Figure 1 It is a structural schematic diagram of the station deep foundation pit reinforcement system for underpassing a tunnel according to the present application;

[0027] Figure 2 It is a structural schematic diagram of the existing underpass tunnel structure reinforcement and support according to the present application;

[0028] Figure 3 It is a structural schematic diagram of laying a horizontal support plate in the foundation pit according to the present application;

[0029] Figure 4 It is a structural schematic diagram of setting a foundation pit column in the foundation pit according to the present application;

[0030] Figure 5 It is a structural schematic diagram of setting a waterproof layer between the horizontal support plate, the station roof, and the existing tunnel enclosure pile according to the present application;

[0031] Figure 6 It is a flowchart of the construction method of the station deep foundation pit reinforcement system for underpassing a tunnel according to the present application;

[0032] The marks in the above figure are: 1. existing tunnel retaining pile, 2. existing tunnel side wall, 3. existing road structure layer, 4. main section of foundation pit, 5. slope excavation section, 6. excavation working face, 7. steel sheet pile, 8. anchor structure, 9. horizontal support plate, 10. foundation pit column, 11. station roof, 12. waterproof layer, 121. waterproof coating, 122. waterproof roll material, 13. backfill layer, 14. pavement layer, 15. steel bar. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments will be described clearly and completely below with reference to the drawings in the embodiments of the present application. The following embodiments are used to illustrate the present application but not to limit the scope of the present application.

[0034] In the description of the present application, it should be noted that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0035] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0036] The specific embodiment of the present application is as shown in Figure 1 The existing tunnel structure includes existing tunnel retaining pile 1, existing tunnel side wall 2 and existing road structure layer 3 between them, the bottom of the existing tunnel side wall 2 is provided with the existing road structure layer 3, and the surface of the existing road structure layer 3 is the traffic road surface of the tunnel. The present application provides a station deep foundation pit reinforcement system for underpassing a tunnel, a foundation pit is excavated at the bottom and below the existing tunnel side wall 2, a roof support assembly is arranged at the bottom of the foundation pit, and a plurality of foundation pit columns 10 are arranged below the roof support assembly. The foundation pit columns 10 are arranged as lattice column piles, which ensure the safety of the station foundation pit excavation in the later period, and the upper end of the roof support assembly is connected with the existing tunnel side wall 2 through a backfill structure.

[0037] The present application reduces the influence of process conversion on construction period, saves construction period, guarantees the safety of the existing tunnel structure, and ensures the rapid passage of the existing road tunnel as the top plate structure of the subway station.

[0038] Specifically, as shown in Figure 3 , Figure 4 and Figure 5 , the foundation pit comprises a main foundation pit section 4 and a sloping excavation section 5 thereon, the height between the upper end of the sloping excavation section 5 and the surface of the existing road structure layer 3 is 40-60 cm, preferably 50 cm, and the bottom end of the sloping excavation section 5 is the bottom end of the existing tunnel side wall 2, which is also the excavation working surface 6 of the main foundation pit section 4. By excavating the sloping foundation pit to the bottom of the tunnel side wall, removing the lower section of the existing tunnel side wall 2 on both sides of the underpass tunnel road, and excavating the existing road structure layer 3 to expose the excavation working surface 6, the construction of the reinforcing structure can be carried out.

[0039] Specifically, as shown in Figures 2-5 , a plurality of anchor cable structures 8 are connected between the sloping excavation section 5 and the existing tunnel retaining pile 1, the anchor cable structure 8 is made of steel wire, and the anchor device is a anchor device that meets the technical requirements. Steel sheet piles 7 that meet the mechanical performance and size requirements are vertically driven below the excavation working surface 6 near the tunnel structure side, which can be used as a support structure for deep foundation pit excavation. After excavating the foundation pit to the bottom of the existing tunnel side wall 2, the present application sets up a plurality of anchor cable structures 8 for structural reinforcement, and at the same time, steel sheet piles 7 are installed near the side wall, which ensures the safety of the existing underpass tunnel structure and the safety of the foundation pit excavation through multiple reinforcement and support measures.

[0040] Specifically, as shown in Figure 1 and Figure 5 , the top plate support assembly comprises a horizontal support plate 9 laid at the bottom end of the foundation pit and a station top plate 11 cast on the horizontal support plate 9, wherein the horizontal support plate 9 is made of reinforced concrete plate, the thickness of the horizontal support plate 9 is 200-300 mm, preferably 300 mm, and it can be prepared by on-site casting, the station top plate 11 is also a reinforced concrete plate, and the horizontal support plate 9 is used to set up a support, lay a formwork, and bind steel bars before pouring concrete to form the station top plate 11, the station top plate 11 is formed in sections, the steel reinforcement structures in adjacent two sections are connected by a steel reinforcement adapter, which ensures the stability of the station top plate 11 formation. Moreover, the horizontal support plate 9 and the station top plate 11 abut against one side of the steel sheet pile 7, which ensures the safety of the existing underpass tunnel structure.

[0041] Specifically, as shown in Figure 5As shown, a waterproof layer 12 is provided between the horizontal support plate 9, the station roof slab 11, and the existing tunnel retaining piles 1. The waterproof layer 12 includes a waterproof coating 121 applied to the end of the horizontal support plate 9 and a waterproof membrane 122 laid on the upper surface of the horizontal support plate 9. The waterproof coating 121 can be a polyurethane coating structure, and the waterproof membrane 122 is a self-adhesive polymerized modified bitumen waterproof membrane 122. The waterproof membrane 122 covers the edge of the horizontal support plate 9 and is close to the existing tunnel retaining piles 1, preventing water from entering the gap between the station roof slab 11 and the existing tunnel retaining piles 1, and also preventing water from entering the horizontal support plate 9 and below it from the station roof slab 11, thereby improving the waterproof performance of the subway station roof slab 11 structure.

[0042] Specifically, such as Figure 1 As shown, the backfill structure includes a backfill layer 13 and a road surface layer 14 arranged from bottom to top. The backfill layer 13 uses C20 plain concrete with a thickness of 1-1.5m. The road surface layer 14 includes a newly constructed tunnel floor slab and newly constructed tunnel sidewalls, both using C40 waterproof concrete with a waterproof rating of P8. Both sides of the road surface layer 14 (newly constructed tunnel sidewalls) are connected to the existing tunnel sidewalls 2 via steel reinforcement anchors 15. By anchoring the existing tunnel sidewalls 2 with steel reinforcement, the newly constructed tunnel sidewalls and the existing tunnel sidewalls 2 are integrated, improving the structural stability. Furthermore, a protective layer with a thickness of 40-50mm is installed on the outer side of both the newly constructed tunnel floor slab and the newly constructed tunnel sidewalls, ensuring the service life and smoothness of the tunnel structure.

[0043] The construction method for the deep foundation pit reinforcement system of the aforementioned underpass tunnel station involves excavating a foundation pit before station construction to reinforce the underpass tunnel and construct the station roof slab 11. This ensures rapid passage through the existing road tunnel without affecting station construction. Figure 6 As shown, the specific construction steps are as follows:

[0044] Step 1: Excavate the foundation pit along the bottom slope of the existing tunnel sidewall 2 to the bottom of the existing tunnel sidewall 2.

[0045] Remove the lower section of the existing tunnel sidewall 2 on both sides of the underpass road, with the removal height 40-60cm from the surface of the existing road structure layer 3, and excavate the existing road structure layer 3 to expose the excavation working face 6.

[0046] Step 2: Install multiple anchor cable structures 8 at the bottom of the existing tunnel sidewall 2 near the existing tunnel retaining pile 1, and drive steel sheet piles 7 below the existing tunnel sidewall 2.

[0047] The multiple anchor cable structures 8 are arranged near the bottom of the inner side of the existing tunnel side wall 2, and are made of steel strands, and the anchorage devices are anchorage devices meeting the technical requirements. The steel sheet piles 7 meeting the mechanical performance and size requirements are vertically punched below the excavation working face 6 near the side of the tunnel structure, and can be used as the support structure of the deep foundation pit excavation.

[0048] Step 3: Continue to excavate the foundation pit to the station roof, and construct the horizontal support plate 9 at the bottom of the foundation pit.

[0049] Continue to excavate the foundation pit to the station roof 11 below 200-300 mm, and pour the horizontal support plate 9 of 200-300 mm thick reinforced concrete at the bottom of the foundation pit.

[0050] Step 4: Construct multiple foundation pit columns 10 below the horizontal support plate 9.

[0051] Holes are drilled at intervals on the horizontal support plate 9, and lattice column piles are punched into the corresponding holes and poured with concrete to form the foundation pit columns 10, thereby ensuring the safety of the later foundation pit excavation.

[0052] Step 5: Pour and construct the station roof 11 and the waterproof layer 12 on the horizontal support plate 9.

[0053] 1) The waterproof roll material 122 is laid on the upper surface of the horizontal support plate 9 in advance, so that one end of the waterproof roll material 122 extends out of the horizontal support plate 9 by a distance as a wrapping edge; 2) after the support is erected, the formwork is laid and the reinforcement is bound on the horizontal support plate 9, the concrete is poured and formed, the station roof 11 is formed in sections, and the steel reinforcement structures in the adjacent two sections are connected through the steel reinforcement connectors; 3) a waterproof coating 121 is applied to one side of the formed station roof 11, so that the waterproof roll material 122 wraps the edge of the horizontal support plate 9 and abuts against the existing tunnel support pile 1.

[0054] Step 6: Lay the backfill layer 13 and the pavement layer 14 on the station roof 11 in sequence, so that the pavement layer 14 is connected to the existing tunnel side wall 2 through the steel reinforcement 15.

[0055] 1) C20 plain concrete is used to backfill on the station roof 11 to form a backfill layer 13 with a thickness of 1-1.5 m;

[0056] 2) C40 waterproof concrete with a waterproof grade of P8 is used to pour to form a newly built tunnel bottom plate and a newly built tunnel side wall on the backfill layer 13;

[0057] 3) The newly built tunnel side wall is connected to the existing tunnel side wall 2 through the steel reinforcement 15;

[0058] 4) A protective layer with a thickness of 40-50 mm is arranged outside the newly built tunnel bottom plate and the newly built tunnel side wall.

[0059] Through the above construction, the existing tunnel traffic can be recovered, and the construction of the station under the roof structure of the subway station can be carried out under the condition of normal traffic.

[0060] In conclusion, the application greatly improves the overall excavation construction efficiency of the subway station deep foundation pit under the premise of ensuring the safety and stability of the existing road tunnel, and has practical significance in the construction of the subway station deep foundation pit.

[0061] The above is only to illustrate some principles of the application by means of diagrams, and this specification is not intended to limit the application to the specific structures and application ranges shown and described, so all possible corresponding modifications and equivalents belong to the patent application scope of the application.

Claims

1. A deep foundation pit reinforcement system for a station under a tunnel, comprising existing tunnel retaining piles and existing tunnel sidewalls and existing road structure layers between them, characterized in that, The existing tunnel sidewall has a foundation pit excavated at the bottom and below. A top plate support assembly is installed at the bottom of the foundation pit. Multiple foundation pit columns are installed below the top plate support assembly. The upper end of the top plate support assembly is connected to the existing tunnel sidewall through a backfill structure. The lower sections of the existing tunnel sidewalls on both sides of the underpass tunnel are removed, and the existing road structure layer is excavated to expose the excavation face; steel sheet piles are vertically inserted below the excavation face; the backfill structure includes a backfill layer and a pavement layer arranged from bottom to top, and the two sides of the pavement layer are connected to the existing tunnel sidewalls by steel reinforcement. The top plate support assembly includes a horizontal support plate laid at the bottom of the foundation pit and a station top plate cast on it, wherein the horizontal support plate and the station top plate abut against one side of the steel sheet pile; Both the horizontal support plate and the station roof slab are made of reinforced concrete slabs, and the thickness of the horizontal support plate is 200~300mm; A waterproof layer is provided between the horizontal support plate, the station roof slab and the existing tunnel retaining piles. The waterproof layer includes a waterproof coating applied to the end of the horizontal support plate and a waterproof membrane laid on the upper surface of the horizontal support plate. The waterproof membrane covers the edge of the horizontal support plate and is close to the existing tunnel retaining piles.

2. The deep foundation pit reinforcement system for underpass tunnels as described in claim 1, characterized in that: The foundation pit includes a main section of the foundation pit and a sloped excavation section above it. The height between the upper end of the sloped excavation section and the surface of the existing road structure layer is 40-60cm. The bottom end of the sloped excavation section is the bottom end of the existing tunnel sidewall, and the bottom end of the existing tunnel sidewall is the excavation working face of the main section of the foundation pit.

3. The deep foundation pit reinforcement system for underpass tunnels according to claim 2, characterized in that: The slope excavation section is connected to the existing tunnel retaining piles by a multi-anchor cable structure.

4. The deep foundation pit reinforcement system for underpass tunnels as described in claim 1, characterized in that: The foundation pit columns are constructed using a grid-structured pile system.

5. A construction method for a deep foundation pit reinforcement system for an underpass tunnel as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Excavate the foundation pit along the bottom slope of the existing tunnel sidewall down to the bottom of the existing tunnel sidewall; Step 2: Install multiple anchor cable structures near the bottom of the existing tunnel sidewalls of the existing tunnel retaining piles, and drive steel sheet piles under the existing tunnel sidewalls. Step 3: Continue excavating the foundation pit to the top of the station, and construct horizontal support slabs at the bottom of the foundation pit; Step 4: Construct multiple foundation pit columns below the horizontal support plate; Step 5: Pour the construction station roof slab and waterproof layer onto the horizontal support plate; Step 6: Lay backfill layer and road surface layer in sequence on the station roof slab, and connect the road surface layer to the existing tunnel sidewall through steel reinforcement.

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