Combined foundation pit supporting system and construction method

Abstract

The invention provides a combined type foundation pit supporting system and a construction method, and belongs to the technical field of foundation pit supporting structures. The combined foundation pit supporting system comprises an enclosure structure and a plurality of supporting structures, wherein each supporting structure comprises an inclined supporting pile and a supporting assembly. The construction method comprises the steps that S1, the foundation pit support structure, the inclined supporting piles and the capping beams are constructed; s2, a first steel enclosing purlin and a first supporting structure are constructed; s3, a second steel enclosing purlin and a second supporting structure are constructed; s4, constructing a foundation slab; and S5-S6, the steel structure is dismantled and recycled. A supporting assembly is arranged on an inclined supporting pile to serve as a fulcrum, so that the inclined supporting pile is changed into a multi-span continuous pressing rod from a single-span pressing rod; the slenderness ratio of the inclined supporting piles and lateral deformation of the foundation pit are reduced, and the application range of a traditional inclined strut is expanded to a deeper foundation pit. The advantage that the middle of an inclined strut system is open is reserved, the multipoint constraint advantage of multiple horizontal supports in the pit is also achieved, deformation of the enclosure wall can be effectively controlled, and efficient and safe construction of the deep foundation pit is achieved.

Description

Technical Field

[0001] This invention belongs to the field of foundation pit support structure technology, and specifically relates to a combined foundation pit support system and construction method. Background Technology

[0002] Foundation pit support engineering refers to temporary (or partially permanent) retaining, reinforcement, and protection measures taken during the construction of underground parts of buildings or structures to ensure the safety of foundation pit excavation and underground structure construction, as well as to protect the surrounding environment (such as adjacent buildings, roads, pipelines, etc.) from damage. In existing foundation pit support engineering, the conventional inclined support pile system inserts the bottom of the inclined pile, which serves as a load-bearing component, into the soil below the foundation pit base, and supports the top of the pile with a reinforced concrete capping beam at the top of the foundation pit. Through the "two-point support" form of elastic constraint at the bottom and simple support (or consolidation) at the top, it serves as the foundation pit support structure to resist the water and soil pressure outside the pit.

[0003] However, because this system has only one support point at the top above the pit bottom, it is prone to excessive deformation under deep soil pressure. Therefore, the span cannot be too large, meaning it can only be used in relatively shallow foundation pits (mostly single-story underground foundation pits with a depth not exceeding 7m). For deep foundation pit projects with two or more underground floors, conventional inclined support piles are unsuitable due to insufficient resistance and excessive deformation. Summary of the Invention

[0004] In order to improve the support strength of foundation pit support, enhance the support effect on foundation pit, and enable the support system to be applicable to deeper foundation pit support, this invention provides a combined foundation pit support system and construction method.

[0005] The technical solution of the present invention is as follows:

[0006] A combined foundation pit support system, comprising:

[0007] The retaining structure is set on the side wall of the foundation pit;

[0008] Several supporting structures are provided at intervals on the side of the retaining structure facing away from the pit sidewall to support the retaining structure.

[0009] The supporting structure includes:

[0010] Inclined support piles are used to extend obliquely downward from the top of the retaining structure into the soil at the bottom of the foundation pit.

[0011] A support assembly is provided between the retaining structure and the inclined support piles to provide a fulcrum for the inclined support piles away from their ends.

[0012] Furthermore, it also includes:

[0013] A capping beam is installed at the top of the retaining structure to fix the top of the inclined support piles;

[0014] A steel waler is used to be installed on the side of the retaining structure facing away from the pit sidewall, and is used to fix the end of the support assembly away from the inclined support pile;

[0015] The foundation plate is used to be set at the bottom of the pit, and its end abuts against the side of the retaining structure facing away from the pit sidewall.

[0016] Furthermore, the support component includes a first support structure, the first support structure comprising:

[0017] A first support beam, one end of which is connected to the steel waler, and the other end abutting against the side of the inclined support pile facing the pit sidewall; and / or,

[0018] The first support beam abuts against one end of the inclined support pile, and two sets of connecting components are provided between the inclined support pile and the first support beam.

[0019] Furthermore, the two sets of connecting components are symmetrically arranged on both sides of the inclined support pile with the axis of symmetry as the axis of symmetry, and each set of connecting components includes:

[0020] A corbel plate, wherein the corbel plate is mounted on the inclined support pile;

[0021] A tie rod is provided between the corbel plate and the first support beam.

[0022] Furthermore, the corbel plate is connected to the inclined support pile via a first connecting plate.

[0023] Furthermore, the support component also includes a second support structure, the second support structure comprising:

[0024] Two second support beams are symmetrically arranged on both sides of the inclined support pile with the axis of symmetry as the axis of symmetry.

[0025] Furthermore, one end of each second support beam is connected to the steel waler, and the other end is connected to the inclined support pile via two second connecting plates; and / or,

[0026] The two second connecting plates on each of the second support beams are located at the top and bottom of the second support beam, respectively.

[0027] Furthermore, the second support structure also includes a plurality of lacing strips, which are spaced apart between the two second support beams.

[0028] Furthermore, the inclined support pile has an inclination angle of 30-50° in the direction of gravity; and / or,

[0029] The first and second support beams are arranged in parallel with a spacing of 2.5-3.5m.

[0030] A construction method for a combined foundation pit support system includes the following steps:

[0031] S1, Construction pit retaining structure, inclined support piles, and capping beam;

[0032] S2. Excavate the earthwork to the bottom of the first supporting structure, and construct the first steel waler and the first supporting structure;

[0033] S3. Excavate the earthwork to the bottom of the second support structure, and construct the second steel waler and the second support structure;

[0034] S4. Excavate the earthwork to the bottom of the pit and construct the foundation slab;

[0035] S5. Remove the second supporting structure and the second steel waler, and construct the second underground floor structure;

[0036] S6. Remove the first supporting structure and the first steel waler, and cut off the inclined support piles above the foundation slab to construct the first basement level structure.

[0037] The beneficial effects of this invention are as follows:

[0038] This invention discloses a combined foundation pit support system and construction method. By setting support components on inclined support piles as central fulcrums, and connecting the top of the inclined support piles to a capping beam and inserting the bottom into the foundation to form inclined support, multiple horizontal steel support beams are vertically spaced and reliably connected to the inclined support piles. This transforms the inclined support piles from single-span compression members to multi-span continuous compression members. The vertical multi-span continuous structural system composed of the inclined support piles and support components significantly reduces the slenderness ratio of the inclined support piles and the lateral deformation of the foundation pit, expanding the application range of traditional inclined bracing from shallow foundation pits not exceeding 7m to deeper foundation pits (e.g., 10-15m). This invention retains the advantage of an open central section in the inclined bracing system while also possessing the multi-point constraint advantage of multiple horizontal supports within the pit. It can effectively control the deformation of the retaining wall, improve the support capacity of the support system, and achieve efficient and safe construction of deep foundation pits. Attached Figure Description

[0039] Figure 1 This is a structural schematic diagram of a combined foundation pit support system according to Embodiment 1 of the present invention;

[0040] Figure 2 This is a schematic diagram of the horizontal cross-sectional structure of the first support structure in Embodiment 1 of the present invention;

[0041] Figure 3 This is a schematic diagram of the horizontal cross-sectional structure of the second support structure in Embodiment 1 of the present invention;

[0042] Figure 4 This is a construction diagram of step S1 in embodiment 2 of the present invention;

[0043] Figure 5 This is a construction diagram of step S2 in embodiment 2 of the present invention;

[0044] Figure 6 This is a construction diagram of step S3 in embodiment 2 of the present invention;

[0045] Figure 7 This is a construction diagram of step S4 in embodiment 2 of the present invention;

[0046] Figure 8 This is a construction diagram of the subsequent construction of the underground second-floor structure in Embodiment 2 of the present invention;

[0047] Figure 9 This is a construction diagram of the subsequent construction of the underground floor structure in Embodiment 2 of the present invention.

[0048] In the diagram: 1. Enclosure structure; 2. Inclined support piles; 3. Top beam; 4. Steel waler; 5. Foundation slab; 601. First support beam; 602. Corbel plate; 603. Tie rod; 604. First connecting plate; 701. Second support beam; 702. Second connecting plate; 703. Tie strip. Detailed Implementation

[0049] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0050] Example 1:

[0051] refer to Figures 1 to 3 This embodiment provides a combined foundation pit support system, including: a retaining structure 1 and several supporting structures, and may also include a capping beam 3, a steel waler 4 and a foundation slab 5.

[0052] The retaining structure 1 is set on the side wall of the foundation pit. It can be formed by setting up continuous walls or piles around the perimeter of the foundation pit. The height direction of the retaining structure 1 can be consistent with the depth direction of the foundation pit.

[0053] Several supporting structures are spaced apart on the side of the retaining structure 1 facing away from the pit sidewall to support the retaining structure 1. The spacing between the supporting structures can be set at 3-6m according to the depth and size of the pit.

[0054] The support structure includes: inclined support piles 2 and support components.

[0055] Inclined support piles 2 are used in the soil extending obliquely downward from the top of the retaining structure 1 to the bottom of the pit. The inclination angle of the inclined support piles 2 in the direction of gravity can be 30-50°. Specifically, the inclination angle of the inclined support piles 2 can be determined according to the depth of the pit and the cross-sectional dimensions. The inclined support piles 2 can adopt box-shaped or H-shaped steel sections (such as steel square piles), and the cross-sectional height can be 400-900mm. The wall thickness meets the stability requirements of the compression member. The upper end of the inclined support piles 2 can be hinged to the capping beam through ear plates, pins or high-strength bolts, and the lower end is implanted below the bottom of the pit by static pressure or rotary drilling. The inclined support piles 2 are arranged vertically through the entire excavation depth of the pit and also serve as the main vertical load-bearing and horizontal thrust-resistant components.

[0056] The support components are installed between the retaining structure 1 and the inclined support piles 2 to provide a support point away from the end of the inclined support piles 2. On the basis of the inclined support piles 2 (supported by the top capping beam 3 and inserted into the soil at the bottom), multiple support beams are added to form an integrated and coordinated force-bearing system of inclined support piles 2 and horizontal support beams. The horizontal support beams provide a central support point for the inclined support piles 2, transforming the original single-span compression rod structure into a multi-span continuous support system. Preferably, two or three support components can be set along the depth direction of the foundation pit, and the vertical spacing of the support beams in each support component is 2.5-3.5m.

[0057] The capping beam 3 is used to be installed on the top of the retaining structure 1 to fix the top of the inclined support pile 2. Preferably, the cross-sectional shape of the capping beam 3 can be irregular, and the edge is at 90 degrees with the cross section of the inclined support pile 2 to ensure the reliability of force transmission. The upper end of the inclined support pile 2 is inserted into the capping beam 3 at a certain distance (not less than 200mm) to improve the connection stability.

[0058] The steel waler 4 is used to be installed on the side of the retaining structure 1 facing away from the pit sidewall, and is used to fix the end of the support assembly away from the inclined support pile 2.

[0059] The foundation plate 5 is used to be set at the bottom of the pit, and its end abuts against the side of the retaining structure 1 facing away from the pit sidewall.

[0060] The foundation pit support system of this embodiment uses support components set on inclined support piles 2 as central fulcrums. Based on the connection between the top of the inclined support piles 2 and the capping beam 3, and the insertion of the bottom end into the foundation at the bottom of the pit to form inclined support, multiple horizontal steel support beams are set vertically at intervals and reliably connected to the inclined support piles 2. This transforms the inclined support piles 2 from single-span compression members to multi-span continuous compression members. The vertical multi-span continuous structural system composed of the inclined support piles 2 and the support components significantly reduces the slenderness ratio of the inclined support piles 2 and the lateral deformation of the foundation pit, expanding the applicable range of traditional inclined bracing from shallow foundation pits not exceeding 7m to deeper foundation pits (such as 10-15m). This invention retains the advantage of an open central section in the inclined bracing system while also possessing the multi-point constraint advantage of multiple horizontal supports within the pit. It can effectively control the deformation of the retaining wall, improve the support capacity of the support system, and achieve efficient and safe construction of deep foundation pits.

[0061] In a preferred embodiment, the support assembly includes a first support structure and a second support structure, wherein the first support structure includes a first support beam 601.

[0062] One end of the first support beam 601 is connected to the steel waler 4. The first support beam 601 can be connected to the steel waler 4 by welding or high-strength bolts. The other end abuts against the side of the inclined support pile 2 facing the sidewall of the foundation pit.

[0063] The first support beam 601 abuts against one end of the inclined support pile 2, and two sets of connecting components can be provided between the inclined support pile 2 and the first support beam 601.

[0064] refer to Figure 2 Two sets of connecting components are symmetrically arranged on both sides of the inclined support pile 2 with the axis of symmetry as the axis of symmetry. Each set of connecting components includes: bracket plate 602 and tie rod 603. The series of combinations of inclined support pile 2-horizontal support beam-tie rod 603-bracket plate ensures that the axial force of the first support beam 601 is reliably transmitted, the lateral displacement of the inclined support pile 2 at this elevation is limited, and stress concentration is avoided.

[0065] The corbel plate 602 is installed on the inclined support pile 2. The corbel plate 602 is connected to the inclined support pile 2 through the first connecting plate 604. The first connecting plate 604 can be "L" shaped. The corbel plate 602 can also be connected to the inclined support pile 2 by welding. The first connecting plate 604 can be connected to the web plate or stiffening rib of the inclined support pile 2 by high-strength bolts to form a rigid node. The horizontal support beam can not only withstand the lateral water and soil pressure transmitted from the retaining structure 1, but also provide a continuous support point for the inclined support pile 2, transforming the inclined support pile 2 from a single-span compression member into a three-span or four-span continuous compression member, preventing the inclined support pile 2 from deforming and improving the support capacity.

[0066] The tie rod 603 is installed between the corbel plate 602 and the first support beam 601.

[0067] The second support structure includes two second support beams 701 and may also include several tie bars 703. When the foundation pit is excavated to the elevation of the second support beams 701, the increase in excavation depth increases the retaining pressure, so a "double-bar horizontal support beam" arrangement can be adopted.

[0068] Two second support beams 701 are symmetrically arranged on both sides of the inclined support pile 2 with the axis of symmetry as the axis of symmetry.

[0069] One end of each second support beam 701 is connected to the steel waler 4, which can be achieved by welding or high-strength bolts. The other end is connected to the inclined support pile 2 via two second connecting plates 702, which can be L-shaped. The two second connecting plates 702 on each second support beam 701 are located at the top and bottom of the beam, respectively, and can be connected to the inclined support pile 2 via high-strength bolts.

[0070] Several tie bars 703 are spaced apart between the two second support beams 701 to ensure that the two second support beams 701 share the load. This "double-bar horizontal support beam" connection node forms a spatial box-shaped rigid zone, which significantly enhances the bending stiffness and overall stability of the inclined support pile 2 in the deeper excavation stage.

[0071] The first support beam 601 and the second support beam 701 are arranged in parallel, and the spacing can be 2.5-3.5m. The first support beam 601 and the second support beam 701 can be arranged horizontally, and H-shaped steel or box-shaped steel are used. The span is equal to the horizontal spacing between adjacent inclined support piles 2.

[0072] By adding multiple support structures as fulcrums to the inclined support pile 2, the load-sharing effect of the support structure is significantly reduced, the slenderness ratio effect of the inclined support pile 2 is reduced, and the lateral deformation of the foundation pit is reduced. This allows the applicable foundation pit depth to be expanded from no more than 7m to a deeper excavation depth (such as 10-15m). This breaks through the limitation that conventional inclined support pile 2 can only be used for shallow foundation pits with one underground floor, and meets the construction needs of deep foundation pits with two or three underground floors.

[0073] In this embodiment, the first and second support structures can be selected based on the stress calculation of the foundation pit in actual application. For example, the first support structure can be used for the two-point structure of the first inclined support pile, while the second support structure can be used if the calculated internal force is large.

[0074] The layout of the inclined support piles 2 combined with the multi-support structure provides an unobstructed large excavation working face in the middle of the foundation pit. It has the advantages of conventional inclined support piles 2 (the inclined support can provide an open excavation space for the foundation pit, avoiding the problem of small excavation space and low construction efficiency when a large area of ​​horizontal support is set in the foundation pit), and the stress-bearing advantages of conventional multi-support structure in the pit (multiple horizontal supports in deep foundation pits can provide multiple points of support for the retaining structure 1, effectively controlling the deformation of the foundation pit during excavation).

[0075] All components in this embodiment can be made of steel. The modular combination of components and connectors enables a rapid assembly process of "static pressure of inclined support piles 2-layer hoisting of horizontal support beams", which speeds up the construction period of the support system. In addition, the components of the support structure are connected by high-strength bolts or welding. After the underground structure construction is completed and the support system is dismantled, the steel structure can be recycled and reused, reducing carbon emissions. The provided open excavation space can ensure that large machinery can move freely in the middle of the foundation pit, which speeds up the excavation efficiency.

[0076] Example 2:

[0077] refer to Figures 4 to 9 The construction method of a combined foundation pit support system provided in this embodiment includes the following steps: S1-S6.

[0078] S1, Construction pit retaining structure 1, inclined support piles 2, and capping beam 3.

[0079] S2. Excavate the earthwork to the bottom of the first supporting structure, and construct the first steel waler 4 and the first supporting structure.

[0080] S3. Excavate the earthwork to the bottom of the second support structure, and construct the second steel waler 4 and the second support structure.

[0081] S4. Excavate the earthwork to the bottom of the pit and construct the foundation slab 5.

[0082] S5. Dismantle the second support structure and the second steel waler 4, and construct the second basement level structure (leave a hole where the inclined support pile 2 penetrates the first basement floor slab, and fill it later). Figure 8 .

[0083] S6. Demolish the first supporting structure and the first steel waler 4, and cut off the inclined support piles 2 above the foundation slab 5, then construct the first basement level structure, such as... Figure 9 The first and second support structures, as well as the steel waler 4, can all be recycled and reused after dismantling, which helps reduce carbon emissions.

[0084] During construction, auxiliary components can be used to assist in construction and improve construction safety. For example, after each support structure is installed, a pre-jacking force can be applied to the support beam using hydraulic jacks to offset some of the displacement of the retaining wall in advance. Monitors such as strain gauges, inclinometers, and displacement gauges can also be placed in the middle of the inclined support pile 2 (where it connects to the support beam), at the mid-span of the support beam, and at the top of the retaining structure 1 to collect the internal forces of the support system and the deformation of the foundation pit in real time. This allows for real-time monitoring of the support capacity of the support system during the excavation of the foundation pit, thereby improving construction safety.

[0085] The support system constructed according to this embodiment consists of four main parts: inclined support piles 2, horizontal support beams, node connectors, and construction auxiliary components. Combined with the retaining structure 1 around the foundation pit, it forms a spatial frame system of "outer retaining structure - inner inclined support piles 2 - layered horizontal support beams", which has strong support capacity.

[0086] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A combined foundation pit support system, characterized in that, include: Enclosure structure (1) is set on the side wall of the foundation pit; Several supporting structures are provided at intervals on one side of the enclosure structure (1) facing away from the pit sidewall, for supporting the enclosure structure (1); The supporting structure includes: Inclined support piles (2), which are used to extend obliquely downward from the top of the retaining structure (1) to the bottom of the pit in the soil; A support assembly is provided between the enclosure structure (1) and the inclined support pile (2) to provide a fulcrum away from the end of the inclined support pile (2).

2. The combined foundation pit support system as described in claim 1, characterized in that, Also includes: A top beam (3) is used to be installed on the top of the enclosure structure (1) to fix the top of the inclined support pile (2); Steel waler (4) is used to be installed on the side of the retaining structure (1) facing away from the pit sidewall, and is used to fix the end of the support assembly away from the inclined support pile (2); The foundation plate (5) is used to be set at the bottom of the pit, and its end abuts against the side of the retaining structure (1) facing away from the pit sidewall.

3. The combined foundation pit support system as described in claim 2, characterized in that, The support component includes a first support structure, the first support structure comprising: A first support beam (601), one end of which is connected to the steel waler (4), and the other end abutting against the side of the inclined support pile (2) facing the pit sidewall; and / or, The first support beam (601) abuts against one end of the inclined support pile (2) and is provided with two sets of connecting components between the inclined support pile (2).

4. The combined foundation pit support system as described in claim 3, characterized in that, The two sets of connecting components are symmetrically arranged on both sides of the inclined support pile (2) with the axis of symmetry as the axis of symmetry. Each set of connecting components includes: Bracket plate (602), said bracket plate (602) is installed on the inclined support pile (2); Tie rod (603) is disposed between the corbel plate (602) and the first support beam (601).

5. The combined foundation pit support system as described in claim 4, characterized in that, The corbel plate (602) is connected to the inclined support pile (2) through the first connecting plate (604).

6. The combined foundation pit support system as described in claim 3, characterized in that, The support component further includes a second support structure, the second support structure comprising: Two second support beams (701) are symmetrically arranged on both sides of the inclined support pile (2) with the axis of symmetry as the axis of symmetry.

7. The combined foundation pit support system as described in claim 6, characterized in that, One end of each of the second support beams (701) is connected to the steel waler (4), and the other end is connected to the inclined support pile (2) via two second connecting plates (702); and / or, Two second connecting plates (702) on each of the second support beams (701) are located at the top and bottom of the second support beam (701), respectively.

8. The combined foundation pit support system as described in claim 6, characterized in that, The second support structure also includes a plurality of lacing strips (703), which are spaced apart between the two second support beams (701).

9. The combined foundation pit support system as described in claim 6, characterized in that, The inclined support pile (2) has an inclination angle of 30-50° in the direction of gravity; and / or, The first support beam (601) and the second support beam (701) are arranged in parallel.

10. A construction method for a combined foundation pit support system as described in any one of claims 1-9, characterized in that, Includes the following steps: S1, construction pit retaining structure (1), inclined support piles (2), and capping beam (3) as described in claim 2; S2. Excavate the earthwork to the bottom of the first support structure as described in claim 3, and construct the first steel waler (4) as described in claim 2 and the first support structure as described in claim 3; S3. Excavate the earthwork to the bottom of the second support structure as described in claim 6, and construct the second steel waler (4) as described in claim 2 and the second support structure as described in claim 6; S4. Excavate the earthwork to the bottom of the pit and construct the foundation slab (5) as described in claim 2; S5. Demolish the second support structure as described in claim 6 and the second steel waler (4) as described in claim 2, and construct the underground second-floor structure; S6. Demolish the first support structure as described in claim 3 and the first steel waler (4) as described in claim 2, and cut off the inclined support piles (2) above the foundation plate (5) as described in claim 2, and construct the first basement structure.

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