Foundation pit support system based on suspension truss and construction method thereof

Abstract

The application provides a foundation pit support system based on a suspension truss and a construction method thereof, which combines a traditional concrete support system and a steel structure system according to needs through different combination forms to form a suspension truss horizontal support structure of a suspension main beam + a hanging column web + a combined support + an edge constraint system, and has the characteristics of large overall rigidity, convenient construction and the like, can realize the requirements of continuous and reliable force transmission of the support structure system under the condition of large-span support-free foundation pit support without columns, and is suitable for the selection design requirements of large-span support-free foundation pit support which needs to cross large underground obstacles.

Description

Technical Field

[0001] This invention relates to a foundation pit support system based on a suspended truss and its construction method. Background Technology

[0002] Currently, large-scale underground municipal facilities such as municipal tunnels and underground utility tunnels are densely distributed in the core urban areas. The development of underground space in the core urban areas will increasingly face situations that cross existing and planned underground municipal facilities. The retaining and supporting structure system of the new underground space foundation pit needs to avoid the underground municipal facility structure and its protection range. The support system in the foundation pit often needs to cross a span of 30m or more, making it impossible to set up support columns. Since the stress state of the foundation pit support structure components is that of compression-bending components, the out-of-plane bending moment of the support beam under the action of its own weight will increase sharply when the span increases. The combined effect of its own weight bending moment will greatly reduce the horizontal bearing capacity and stability of the support beam. Due to the slenderness ratio limit and material strength limitation of the existing reinforced concrete support and steel support systems, the cross section of the support beam components will be greatly increased, making it difficult to meet the requirements of crossing underground tunnels and forming a reliable horizontal support system for the foundation pit under the condition of selecting economical and reasonable component cross sections. Summary of the Invention

[0003] The purpose of this invention is to provide a foundation pit support system based on a suspended truss and its construction method.

[0004] To address the above problems, this invention provides a foundation pit support system based on a suspended truss, comprising:

[0005] The suspended support beam is set at the top above the underground municipal facility structure to be crossed and its protected area, serving as the vertical main beam and forming the first horizontal force transmission structure system of the foundation pit.

[0006] The composite support beam, together with the suspended support beam, is set in the same vertical plane to form a horizontal force transmission structure system.

[0007] The top of the suspended column web members is set on the suspension support beam, and the bottom of the suspended column web members is connected to the second to the nth combined support beams of the foundation pit, where n is a positive integer. The combined support beams are suspended below the suspension support beams.

[0008] The connection node is pre-embedded in the second and nth combined support beams of the foundation pit and is used to connect with the web members of the hanging column.

[0009] The edge restraint support frame is set on both sides above the protected area of ​​the underground municipal facility structure to be crossed, serving as the restraint support for the suspended support beam and the combined support beam to cross the two sides of the underground municipal facility structure.

[0010] Furthermore, in the above system, the suspended support beam adopts a reinforced concrete structure, a steel-reinforced concrete composite structure, a steel beam structure, a lattice steel structure, or a steel pipe truss structure; the top of the suspended support beam is provided with a reinforced concrete beam slab or a steel structure beam slab as a trestle deck structure.

[0011] Furthermore, in the above system, the composite support beam adopts a reinforced concrete structure, a steel-reinforced concrete composite structure, a steel beam structure, a lattice steel structure, or a steel pipe truss structure.

[0012] Furthermore, the system also includes: a web member structure system 15 and a main chord beam 14. Any combination of the web member structure system 15 connects the first to the nth adjacent main chord beams 14 in the same vertical plane. The web member structure systems 15 used to connect the first to the nth adjacent main chord beams in the same vertical plane are not continuously arranged, but each main chord beam is connected to any adjacent concrete main chord beam through the web member structure system 15 to form a concrete truss beam system.

[0013] Furthermore, in the above system, the hanging column web members are made of steel sections or lattice steel structures or precast reinforced concrete or precast steel-reinforced concrete components, which are used as composite support beams to vertically hang and support the suspension support beams. The hanging column web members are connected in a continuous or segmented manner.

[0014] Furthermore, in the above system, the connection node is connected to the web member of the hanging column by means of anchor bars, anchor steel frames, high-strength bolts, or welding.

[0015] Furthermore, in the above system, when the hanging column web members adopt a continuous connection, the connection nodes are connected by anchor bars or connecting plates with anchor bars; when the hanging column web members adopt a segmented connection, the connection nodes are connected by anchor bars, anchor steel frames, high-strength bolts, or welding to form a reliable connection with the hanging column web members.

[0016] Furthermore, in the above system, the edge restraint support frame is composed of supporting columns, restraint support beams, and restraint edge trusses.

[0017] The constraint support beam is set on both sides of the underground facility structure to be crossed, and is connected to the suspension support beam and the composite support beam, serving as the constraint support for the suspension support beam and the composite support beam. The constraint support beam adopts a cast-in-place reinforced concrete structure, a cast-in-place steel-reinforced concrete composite structure, a steel structure, or a steel truss structure.

[0018] The supporting column is used to vertically support and constrain the support beam. The supporting column adopts a driven steel pipe pile column structure system, a driven steel pipe concrete pile column structure system, a drilled cast-in-place pile internal steel pipe column structure system, a cement mixing pile internal steel pipe column structure system, or a cement mixing pile internal lattice steel column structure system.

[0019] The constrained side truss is set between the constrained support beam and the vertical retaining structure. The constrained side truss is reliably and rigidly connected to the constrained support beam as a lateral constrained support for the constrained support beam, and as a horizontal force transmission system to transfer the soil pressure of the foundation pit to the suspended support beam and the composite support beam. The constrained side truss adopts a cast-in-place reinforced concrete structure, a cast-in-place steel-reinforced concrete composite structure, a steel structure, or a lattice steel structure.

[0020] According to another aspect of the present invention, a construction method for a foundation pit support system based on a suspension truss is also provided, characterized in that, when the foundation pit support system based on a suspension truss described in any of the above claims is used, and the web members of the suspended columns are in a continuous connection form, the method includes:

[0021] Step S11: After the construction of the vertical retaining structure around the foundation pit, the supporting columns and hanging column web members of the edge restraint support frame structure are completed and reach the design strength, the foundation pit excavation begins. The first excavation reaches the design bottom elevation of the suspended support beam. The suspended support beam and trestle bridge plate structure are constructed, as well as the restraint support beams and restraint side trusses at both ends of the suspended support beam.

[0022] Step S12: After the suspended support beam is completed and reaches the design strength, the second earthwork excavation is carried out to the design bottom elevation of the first composite support beam. The composite support beam is constructed and reliably connected to the web members of the hanging column. The constraint support beams and constraint side truss structures at both ends of the first composite support beam are constructed.

[0023] Step S13: After the structural strength of the first composite support beam reaches the design requirements, the third earthwork excavation is carried out to the design bottom elevation of the second composite support beam. The second composite support beam is constructed, and the composite support beam is reliably connected to the web members of the hanging column. The constraint support beams and constraint side truss structures at both ends of the second composite support beam are constructed.

[0024] Step S14: Repeat step S13 above until the construction of the nth composite support beam and the two end restraint support beams and restraint side trusses required by the foundation pit support design is completed.

[0025] Step S15: Construct the foundation slab of the underground structure, and rebuild the underground structure according to the design requirements of the foundation pit and the underground structure design drawings. Then, dismantle the foundation pit support system based on the suspended truss layer by layer from the nth to the 1st truss.

[0026] Furthermore, in the above method, when the hanging column web members adopt a continuous segmented connection form, the method includes:

[0027] Step S21: After the construction of the vertical retaining structure around the foundation pit and the supporting columns of the edge restraint support frame structure are completed and reach the design strength, the foundation pit excavation begins. The first excavation reaches the design bottom elevation of the suspended support beam. The suspended support beam, connecting nodes, trestle bridge plate structure, and restraint support beams and restraint edge trusses at both ends of the suspended support beam are constructed.

[0028] Step S22: After the suspended support beam is completed and reaches the design strength, the second earthwork excavation is carried out, excavating to the design bottom elevation of the first composite support beam. The first composite support beam, connection nodes, hanging column web members between the first composite support beam and the suspended support beam, constraint support beams at both ends of the first composite support beam, and constraint side trusses are constructed.

[0029] Step S23: After the structural strength of the first composite support beam reaches the design requirements, the third earthwork excavation is carried out to the design bottom elevation of the second composite support beam. The second composite support beam, connection nodes, hanging column web members between the second and first composite support beams, constraint support beams at both ends of the second composite support beam, and constraint side trusses are constructed.

[0030] Step S24: Repeat step S23 above until the construction of the foundation pit support design requirements, including the nth composite support beam, connection node, hanging column web between the nth and n-1th composite support beams, constraint support beams at both ends of the nth composite support beam, and constraint side truss, is completed.

[0031] Step S25: Construct the foundation slab of the underground structure, and rebuild the underground structure according to the design requirements of the foundation pit and the underground structure design drawings. Then, dismantle the foundation pit support system based on the suspended truss layer by layer from the nth to the 1st truss.

[0032] Compared with existing technologies, this invention combines traditional concrete support systems and steel structure systems in different combinations as needed to form a suspended truss horizontal support structure consisting of a suspended main beam, suspended column web members, combined support, and edge restraint system. It features high overall rigidity and convenient construction, and can meet the requirements of continuous and reliable force transmission of the support structure system under the condition of large-span foundation pit support without column support. It is suitable for the selection and design of large-span unsupported foundation pit support that needs to cross large underground obstacles. Attached Figure Description

[0033] Figure 1 This is a cross-sectional view of a suspended truss large-span unsupported foundation pit support system according to an embodiment of the present invention;

[0034] Figure 2This is a plan view of a large-span, unsupported foundation pit support system for a suspended truss according to an embodiment of the present invention.

[0035] Figure 3 This is a cross-sectional design drawing of an embodiment of the edge constraint support frame of the present invention;

[0036] Figure 4 This is a detailed drawing of the continuous hanging column web members and connecting nodes of the present invention;

[0037] Figure 5-1 , 5-2 This is a detailed drawing of the segmented hanging column web members and connection nodes of the present invention;

[0038] Figures 6-1 to 6-5 This is a general construction flowchart of the large-span unsupported foundation pit support system of the suspended truss of the present invention, which adopts a continuous hanging column web member connection form;

[0039] Figures 7-1 to 7-5 This is a general construction flowchart of the suspended truss large-span unsupported foundation pit support system of the present invention, which adopts a segmented hanging column web member connection form;

[0040] The numbers in the diagram are as follows:

[0041] 11. Suspended support beam; 12. Composite support beam; 13. Suspended column web member; 14. Main chord beam; 15. Web member structural system; 16. Support column; 17. Restrained support beam; 18. Restrained side truss;

[0042] 21. Connecting plate; 22. Steel bracket; 23. Embedded part. Detailed Implementation

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Figure 1 This is a cross-sectional view of a suspended truss large-span unsupported foundation pit support system according to an embodiment of the present invention; Figure 2 This is a plan view of a large-span, unsupported foundation pit support system for a suspended truss according to an embodiment of the present invention. Figure 3 This is a cross-sectional design drawing of an embodiment of the edge constraint support frame of the present invention; Figure 4 This is a detailed drawing of the continuous hanging column web members and connecting nodes of the present invention; Figure 5-1 , 5-2 This is a detailed drawing of the segmented suspended column web members and connection nodes of the present invention. It includes: a suspension support beam 11; a combined support beam 12; suspended column web members 13; a main chord beam 14; a web member structural system 15; a supporting column 16; a restraint support beam 17; and a restraint side truss 18.

[0045] 21. Connecting plate; 22. Steel bracket; 23. Embedded part

[0046] like Figures 1 to 5-1 As shown in Figure 5-2, the present invention provides a foundation pit support system based on a suspended truss, comprising:

[0047] Suspension support beam 11 is set at the top above the underground municipal facility structure to be crossed and its protected area, serving as the vertical main beam and forming the first horizontal force transmission structure system of the foundation pit;

[0048] The composite support beam 12 is set in the same vertical plane as the suspension support beam, serving as a horizontal force transmission structure system;

[0049] The top of the suspended column web member 13 is set on the suspension support beam 11, and the bottom of the suspended column web member is connected to the second to the nth combined support beam 12 of the foundation pit, where n is a positive integer. The combined support beam 12 is suspended below the suspension support beam 11.

[0050] The connection node is pre-embedded in the combined support beam 12 of the second and nth layers of the foundation pit, and is used to connect with the web member 13 of the hanging column.

[0051] The edge restraint support frame is set on both sides above the protected area of ​​the underground municipal facility structure to be crossed, serving as the restraint support for the suspended support beam 11 and the combined support beam 12 to cross the two sides of the underground municipal facility structure.

[0052] This invention provides a suspended truss large-span unsupported foundation pit support system. It combines a traditional concrete support system with a steel structure system in different combinations as needed to form a suspended truss horizontal support structure consisting of a suspended main beam, suspended column web members, combined support, and edge restraint system. It features high overall stiffness and convenient construction, and can meet the requirements of continuous and reliable force transmission of the support structure system under the condition of large-span unsupported foundation pit support. It is suitable for the selection and design of large-span unsupported foundation pit support that needs to cross large underground obstacles.

[0053] In one embodiment of the foundation pit support system based on a suspended truss of the present invention, the suspended support beam 11 can be, but is not limited to, a reinforced concrete structure, a steel-reinforced concrete composite structure, a steel beam structure, a lattice steel structure, or a steel pipe truss structure. Its structural form and cross-sectional dimensions are calculated and determined according to the horizontal earth pressure resistance requirements of the foundation pit and the number of support channels required to be set below it in the same vertical plane. The top of the suspended support beam 11 can be provided with a reinforced concrete beam slab or a steel structure beam slab as a trestle slab structure to improve its horizontal stiffness and serve as a passage for foundation pit construction vehicles and an operation platform.

[0054] In one embodiment of the foundation pit support system based on suspension trusses of the present invention, the composite support beam 12 may be, but is not limited to, reinforced concrete structure, steel-reinforced concrete composite structure, steel beam structure, lattice steel structure or steel pipe truss structure, etc. The number of beams, structural form and cross-sectional dimensions required in the vertical plane are calculated and determined according to the foundation pit excavation depth and the horizontal earth pressure resistance requirements of the foundation pit.

[0055] In one embodiment of the foundation pit support system based on suspension trusses of the present invention, the suspended column web members 13 can be made of steel profiles, lattice steel structures, precast reinforced concrete, or precast steel-reinforced concrete components, and are vertically suspended and connected to the suspension support beam as a composite support beam. The component cross-section and number of components are determined according to the required number of composite support beams and the strength of the selected materials, based on the design calculation results. It can adopt two different connection forms: continuous connection and segmented connection.

[0056] In one embodiment of the foundation pit support system based on suspension trusses of the present invention, the web member structure system 15 can be connected in pairs to the first to nth adjacent main chord beams 14 in the same vertical plane according to the different vertical design loads of the first main chord beam 14. The web member structure system 15 used to connect the first to nth adjacent main chord beams in the same vertical plane can be discontinuous, but it must be ensured that each main chord beam is connected to any adjacent concrete main chord beam through the web member structure system 15 to form a concrete truss beam system.

[0057] In one embodiment of the foundation pit support system based on the suspended truss of the present invention, the connection node can be constructed using a steel bar anchor plate type connection node or a steel frame anchor plate type connection node, depending on the required node strength. It can be connected to the web member of the suspended column by means of anchor bars, anchor steel frames, high-strength bolts or welding, so as to form a reliable connection with the web member of the suspended column.

[0058] In one embodiment of the foundation pit support system based on the suspended truss of the present invention, when the web members of the suspended column adopt a continuous connection, the connection nodes can be connected by anchor bars or by anchor bars on connecting plates; when the web members of the suspended column adopt a segmented connection, the connection nodes can be connected by anchor bars, anchor steel frames, high-strength bolts or welding to form a reliable connection with the web members of the suspended column.

[0059] In one embodiment of the foundation pit support system based on suspension trusses of the present invention, the edge constraint support frame is composed of support columns 16, constraint support beams 17 and constraint edge trusses 18.

[0060] In one embodiment of the foundation pit support system based on a suspended truss of the present invention, the constraint support beam 17 is disposed on both sides of the underground facility structure to be crossed, and is connected to the suspended support beam 11 and the composite support beam 12, serving as a constraint support for the suspended support beam and the composite support beam. Depending on the constraint load requirements, it can be, but is not limited to, cast-in-place reinforced concrete structures, cast-in-place steel-reinforced concrete composite structures, steel profile structures, steel truss structures, etc.

[0061] In one embodiment of the foundation pit support system based on the suspension truss of the present invention, the supporting column 16 is used to vertically support the restraint beam, and can be, but is not limited to, a driven steel pipe pile structure system, a driven steel pipe concrete pile structure system, a drilled cast-in-place pile steel pipe column structure system, a cement mixing pile steel pipe column structure system, or a cement mixing pile lattice steel column structure system, etc. The cross section of the restraint column component is determined according to the load design calculation of the edge restraint support structure system.

[0062] In one embodiment of the foundation pit support system based on a suspended truss of the present invention, the constrained side truss 18 is disposed between the constrained support beam and the vertical retaining structure, and is reliably and rigidly connected to the constrained support beam as a lateral constrained support for the constrained support beam and as a horizontal force transmission system to transmit the soil pressure of the foundation pit to the suspended support beam and the composite support beam. It can be, but is not limited to, cast-in-place reinforced concrete structures, cast-in-place steel-reinforced concrete composite structures, steel profile structures, lattice steel structures, etc.

[0063] The general construction process for the continuous connection of the hanging column web members is as follows:

[0064] like Figure 6-1 As shown, in step S11, after the construction of the vertical retaining structure around the foundation pit, the supporting columns 16 of the edge restraint support frame structure, and the hanging column web members 13 are completed and reach the design strength, the foundation pit excavation begins. The first excavation reaches the design bottom elevation of the suspended support beam 11. The suspended support beam 11 and the trestle bridge plate structure are constructed, as well as the restraint support beams 17 and restraint side trusses 18 at both ends of the suspended support beam 11.

[0065] like Figure 6-2 As shown, in step S12, after the suspended support beam is completed and reaches the design strength, the second earthwork excavation is carried out, excavating to the design bottom elevation of the first composite support beam, constructing the composite support beam, and reliably connecting the composite support beam 12 with the hanging column web member 13, and constructing the constraint support beams and constraint side truss structure at both ends of the first composite support beam.

[0066] like Figure 6-3As shown, in step S13, after the structural strength of the first composite support beam reaches the design requirements, the third earthwork excavation is carried out to the design bottom elevation of the second composite support beam, the second composite support beam is constructed, and the composite support beam is reliably connected to the web members of the hanging column. The constraint support beams and constraint side truss structures at both ends of the second composite support beam are constructed.

[0067] like Figure 6-4 As shown, in step S14, repeat step S13 until the construction of the nth composite support beam and the two-end constraint support beam 17 and constraint side truss 18 required by the foundation pit support design is completed.

[0068] like Figure 6-5 As shown, in step S15, the foundation slab of the underground structure is constructed, and the underground structure is rebuilt according to the design requirements of the foundation pit and the design drawings of the underground structure. The foundation pit support system based on the suspension truss is dismantled layer by layer from the nth to the 1st.

[0069] The general construction process for the suspended column web members using a continuous segmented connection method is as follows:

[0070] like Figure 7-1 As shown, in step S21, after the construction of the vertical retaining structure around the foundation pit and the supporting columns of the edge restraint support frame structure are completed and reach the design strength, the foundation pit excavation begins. The first excavation reaches the design bottom elevation of the suspended support beam. The suspended support beam 11, connecting nodes, trestle bridge plate structure, and the restraint support beams 17 and restraint side trusses 18 at both ends of the suspended support beam 11 are constructed.

[0071] like Figure 7-2 As shown, in step S22, after the suspended support beam is completed and reaches the design strength, the second earthwork excavation is carried out, excavating to the design bottom elevation of the first composite support beam, and constructing the first composite support beam 12, the connecting node, the hanging column web member 13 between the first composite support beam 12 and the suspended support beam 11, the constraint support beams 17 at both ends of the first composite support beam, and the constraint side truss 18.

[0072] like Figure 7-3 As shown, in step S23, after the structural strength of the first composite support beam reaches the design requirements, the third earthwork excavation is carried out to the design bottom elevation of the second composite support beam, and the second composite support beam 12, the connecting node, the hanging column web member 13 between the second composite support beam 12 and the first composite support beam, the restraint support beams 17 at both ends of the second composite support beam and the restraint side truss 18 are constructed.

[0073] like Figure 7-4As shown, in step S24, repeat step S23 until the construction of the foundation pit support design requirements, including the nth composite support beam, connection node, hanging column web members between the nth and (n-1)th composite support beams, constraint support beams at both ends of the nth composite support beam, and constraint side truss, is completed.

[0074] like Figure 7-5 As shown, in step S25, the foundation slab of the underground structure is constructed, and the underground structure is rebuilt according to the design requirements of the foundation pit and the design drawings of the underground structure. The foundation pit support system based on the suspension truss is dismantled layer by layer from the nth to the 1st.

[0075] In summary, this invention provides a suspended truss large-span unsupported foundation pit support system. It combines traditional concrete support systems and steel structure systems in different combinations as needed to form a suspended truss horizontal support structure consisting of a suspended main beam, suspended columns, combined supports, and edge restraints. This system features high overall stiffness and convenient construction, and can meet the requirements of continuous and reliable force transmission of the support structure system under the condition of large-span unsupported foundation pit support. It is suitable for the selection and design needs of large-span unsupported foundation pit support that needs to cross large underground obstacles.

[0076] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0077] Obviously, those skilled in the art can make various modifications and variations to the invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of the invention and their equivalents, the invention is also intended to include these modifications and variations.

Claims

1. A foundation pit support system based on a suspended truss, characterized in that, include: The suspended support beam is set at the top above the underground municipal facility structure to be crossed and its protected area, serving as the vertical main beam and forming the first horizontal force transmission structure system of the foundation pit. The composite support beam, together with the suspended support beam, is set in the same vertical plane to form a horizontal force transmission structure system. The top of the suspended column web members is set on the suspension support beam, and the bottom of the suspended column web members is connected to the second to the nth combined support beams of the foundation pit, where n is a positive integer. The combined support beams are suspended below the suspension support beams. The connection node is pre-embedded in the second and nth combined support beams of the foundation pit and is used to connect with the web members of the hanging column. The edge restraint support frame is set on both sides above the protected area of ​​the underground municipal facility structure to be crossed, and serves as the restraint support for the suspended support beam and the combined support beam to cross the two sides of the underground municipal facility structure. The suspended support beam adopts a reinforced concrete structure, a steel-reinforced concrete composite structure, a steel beam structure, a lattice steel structure, or a steel pipe truss structure; the top of the suspended support beam is provided with a reinforced concrete beam slab or a steel structure beam slab as a trestle slab structure. The composite support beam adopts a reinforced concrete structure, a steel-reinforced concrete composite structure, a steel beam structure, a lattice steel structure, or a steel pipe truss structure. The hanging column web members are made of steel sections, lattice steel structures, precast reinforced concrete, or precast steel-reinforced concrete components, and are vertically suspended and connected to the suspension support beam as a composite support beam. The hanging column web members are either continuous or segmented. The connection node is connected to the web member of the hanging column by means of anchor bars, anchor steel frames, high-strength bolts or welding. When the hanging column web members are connected in a continuous manner, the connection nodes are connected by anchor bars or connecting plates with anchor bars; when the hanging column web members are connected in a segmented manner, the connection nodes are connected by anchor bars, anchor steel frames, high-strength bolts or welding to form a reliable connection with the hanging column web members. The edge restraint support frame is composed of supporting columns, restraint support beams and restraint edge trusses. The constraint support beam is set on both sides of the underground facility structure to be crossed, and is connected to the suspension support beam and the composite support beam, serving as the constraint support for the suspension support beam and the composite support beam. The constraint support beam adopts a cast-in-place reinforced concrete structure, a cast-in-place steel-reinforced concrete composite structure, a steel structure, or a steel truss structure. The supporting column is used to vertically support and constrain the support beam. The supporting column adopts a driven steel pipe pile column structure system, a driven steel pipe concrete pile column structure system, a drilled cast-in-place pile internal steel pipe column structure system, a cement mixing pile internal steel pipe column structure system, or a cement mixing pile internal lattice steel column structure system. The constrained side truss is set between the constrained support beam and the vertical retaining structure. The constrained side truss is reliably and rigidly connected to the constrained support beam as a lateral constrained support for the constrained support beam, and as a horizontal force transmission system to transfer the soil pressure of the foundation pit to the suspended support beam and the composite support beam. The constrained side truss adopts a cast-in-place reinforced concrete structure, a cast-in-place steel-reinforced concrete composite structure, a steel structure, or a lattice steel structure.

2. A construction method for a foundation pit support system based on a suspended truss, characterized in that, When using the foundation pit support system based on a suspended truss as described in claim 1, and the suspended column web members are connected in a continuous manner, the method includes: Step S11: After the construction of the vertical retaining structure around the foundation pit, the supporting columns and hanging column web members of the edge restraint support frame structure are completed and reach the design strength, the foundation pit excavation begins. The first excavation reaches the design bottom elevation of the suspended support beam. The suspended support beam and trestle bridge plate structure are constructed, as well as the restraint support beams and restraint side trusses at both ends of the suspended support beam. Step S12: After the suspended support beam is completed and reaches the design strength, the second earthwork excavation is carried out to the design bottom elevation of the first composite support beam. The composite support beam is constructed and reliably connected to the web members of the hanging column. The constraint support beams and constraint side truss structures at both ends of the first composite support beam are constructed. Step S13: After the structural strength of the first composite support beam reaches the design requirements, the third earthwork excavation is carried out to the design bottom elevation of the second composite support beam. The second composite support beam is constructed, and the composite support beam is reliably connected to the web members of the hanging column. The constraint support beams and constraint side truss structures at both ends of the second composite support beam are constructed. Step S14: Repeat step S13 above until the construction of the nth composite support beam and the two end restraint support beams and restraint side trusses required by the foundation pit support design is completed. Step S15: Construct the foundation slab of the underground structure, and rebuild the underground structure according to the design requirements of the foundation pit and the design drawings of the underground structure. Then, dismantle the foundation pit support system based on the suspension truss layer by layer from the nth to the 1st. When the web members of the suspended column are connected in a continuous segmented manner, the method includes: Step S21: After the construction of the vertical retaining structure around the foundation pit and the supporting columns of the edge restraint support frame structure are completed and reach the design strength, the foundation pit excavation begins. The first excavation reaches the design bottom elevation of the suspended support beam. The suspended support beam, connecting nodes, trestle bridge plate structure, and restraint support beams and restraint edge trusses at both ends of the suspended support beam are constructed. Step S22: After the suspended support beam is completed and reaches the design strength, the second earthwork excavation is carried out, excavating to the design bottom elevation of the first composite support beam. The first composite support beam, connection nodes, hanging column web members between the first composite support beam and the suspended support beam, constraint support beams at both ends of the first composite support beam, and constraint side trusses are constructed. Step S23: After the structural strength of the first composite support beam reaches the design requirements, the third earthwork excavation is carried out to the design bottom elevation of the second composite support beam. The second composite support beam, connection nodes, hanging column web members between the second and first composite support beams, constraint support beams at both ends of the second composite support beam, and constraint side trusses are constructed. Step S24: Repeat step S23 above until the construction of the foundation pit support design requirements, including the nth composite support beam, connection node, hanging column web between the nth and n-1th composite support beams, constraint support beams at both ends of the nth composite support beam, and constraint side truss, is completed. Step S25: Construct the foundation slab of the underground structure, and rebuild the underground structure according to the design requirements of the foundation pit and the underground structure design drawings. Then, dismantle the foundation pit support system based on the suspended truss layer by layer from the nth to the 1st truss.

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