Front lattice inclined throwing support supporting structure and construction method

Abstract

The invention relates to a front-mounted lattice inclined throwing support supporting structure and a construction method, the front-mounted lattice inclined throwing support supporting structure comprises a first supporting unit and a foundation pit, the first supporting unit is located in a soil body on the inner side edge of the foundation pit, the first supporting unit comprises a second supporting unit located in a soil body at the bottom of the foundation pit, and the second supporting unit is lower than the first supporting unit; and the latticed columns are obliquely arranged between the first supporting unit and the second supporting unit at intervals, penetrate through a bottom plate of the foundation pit and are suitable for being used as a supporting structure of the foundation pit. The method further comprises the following steps that a second supporting unit is constructed in a soil body at the bottom of the foundation pit; the latticed columns are assembled, and water stop plates are installed on the latticed columns; and foundation structure construction is conducted in the foundation pit, and the latticed columns are dismantled after construction is completed. According to the supporting structure, the construction step of installing the lattice inclined throwing support is arranged before the whole foundation pit is excavated, the procedures of reserving back pressure soil, subsequently excavating the back pressure soil and secondarily pouring the bottom plate can be omitted, one-time construction of the foundation pit and the bottom plate is achieved, and the construction period is greatly shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation pit support construction, relates to an oblique brace support system, and in particular to a front-mounted lattice oblique brace support structure and a construction method. Background Art

[0002] At present, the support systems commonly used in foundation pit projects include horizontal support and inclined support. Among them, inclined support is mostly used for foundation pits with a depth of less than 8 meters. It can increase the construction space inside the foundation pit and save a lot of construction costs. During the construction of the traditional inclined support system, it is usually necessary to reserve counter-pressure soil, then construct part of the base plate, set up corbels on the base plate, then construct inclined support, and then excavate the counter-pressure soil, and finally cast the remaining base plate. Not only are the steps cumbersome, but the subsequent excavation of the counter-pressure soil is also difficult. Especially when the foundation pit is adjacent to the original project, resulting in narrow surrounding space, it is difficult to install output equipment on the top of the slope. It is often necessary to reserve an excavation channel in the original project or use a tower crane to remove the counter-pressure soil. The construction steps are cumbersome and the construction period is long, which also increases construction costs and management difficulties. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a front-mounted lattice inclined bracing support structure and a construction method with short construction period and low cost.

[0004] In order to solve the above problems, the technical solution of the present invention is:

[0005] A front-mounted lattice oblique bracing support structure includes a first support unit and a foundation pit, wherein the first support unit is located in the soil on the inner side of the foundation pit and includes:

[0006] The second support unit is located in the soil at the bottom of the foundation pit, and the second support unit is lower than the first support unit;

[0007] A plurality of lattice columns are arranged at intervals and inclined between the first support unit and the second support unit, and penetrate the bottom plate of the foundation pit, suitable for serving as a supporting structure of the foundation pit;

[0008] A plurality of waterstop plates are respectively fixed on a plurality of lattice columns and located inside the base plate.

[0009] In a further embodiment, the first support unit includes a first crown beam and a plurality of first support piles, the plurality of first support piles are arranged at intervals in the soil at the side of the foundation pit, and the first crown beam is commonly arranged at the top ends of the plurality of first support piles.

[0010] In a further embodiment, the second support unit includes a second crown beam and a plurality of second support piles, the plurality of second support piles are arranged at intervals in the soil at the bottom of the foundation pit, and the second crown beam is commonly arranged at the top ends of the plurality of second support piles.

[0011] In a further embodiment, the top end portion of the lattice column is fixedly mounted on the first crown beam, and the bottom end portion of the lattice column is fixedly mounted on the second crown beam.

[0012] In a further embodiment, the lattice column includes four long rods and a plurality of connecting plates. The four long rods form a rectangular structure, and a plurality of connecting plates are fixedly installed at even intervals between two adjacent long rods.

[0013] In a further embodiment, the installation positions of the several connecting plates on each long rod are consistent, so that the corresponding four connecting plates form a rectangular structure on the outside of the four long rods.

[0014] In a further embodiment, a plurality of waterstop plates are respectively mounted on corresponding long rods, and the plurality of waterstop plates are located on the same horizontal plane.

[0015] In a further embodiment, the water stop plate is a trapezoidal structure.

[0016] A construction method for a front-mounted lattice diagonal brace support, suitable for constructing a lattice diagonal brace support structure, comprises the following steps:

[0017] constructing a second support unit in the soil at the bottom of the foundation pit;

[0018] Assemble lattice columns and install waterstop plates on them;

[0019] The foundation structure is constructed in the foundation pit and the lattice columns are removed after the construction is completed.

[0020] In a further embodiment, the construction of the foundation structure is carried out in the foundation pit, and the lattice columns are removed after the construction is completed, specifically including:

[0021] The lattice columns are removed after the foundation structure reaches the design strength;

[0022] During demolition, the lattice columns are cut along the top surface of the base plate, the lattice columns above the base plate are removed, and the lattice columns below the base plate are retained.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. This support structure uses the support structure of the existing project as the first support unit, and then constructs the second support unit in the soil at the bottom of the foundation pit. A number of lattice columns are fixedly installed at an angle between the top end of the first support unit and the top end of the second support unit to form an inclined support structure for the foundation pit. The construction step of installing the lattice inclined support is moved forward before the overall excavation of the foundation pit, which can save the process of reserving counter-pressure soil and subsequent excavation of counter-pressure soil and secondary pouring of the base plate, thus realizing the one-time construction of the foundation pit and the base plate, greatly shortening the construction period. Compared with the traditional construction method, it can save about 30 days of construction time.

[0025] 2. This support structure reduces costs such as back pressure soil excavation, tower crane usage time, and water and electricity fees. At the same time, by utilizing the support structure of the existing project as the first support unit and the reasonable design of the lattice column support, it reduces material and construction costs. After actual construction verification, it can save costs of approximately 217,200 yuan.

[0026] 3. The construction quality of the second crown beam and the second supporting pile of this support structure is effectively controlled. The concrete strength and pile body integrity meet the design requirements. The connection of the lattice columns is firm, and waterstop plates are fixed on the lattice columns. The waterstop measures are in place, which ensures the stability and waterproof performance of the foundation pit support and improves the quality of the project.

[0027] 4. This support structure has strong applicability and can be used in various complex geological conditions and narrow construction spaces. It has significant advantages, especially in projects with limited space around the foundation pit and high construction period requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a side view of a front-mounted lattice diagonal bracing support structure;

[0029] Figure 2 This is a schematic diagram of a front-mounted lattice inclined bracing support structure;

[0030] Figure 3 for Figure 2 A magnified view of point A in the figure;

[0031] Figure 4 This is a schematic diagram of a waterstop plate of a front-mounted lattice inclined bracing support structure;

[0032] Figure 5 The figure is a flow chart of a construction method of a front-mounted lattice inclined bracing support.

[0033] In the figure: 1. first supporting unit; 11. first crown beam; 12. first supporting pile; 2. lattice column; 21. long rod; 22. connecting plate; 3. water stop plate; 4. second supporting unit; 41. second crown beam; 42. second supporting pile; 5. bottom plate. DETAILED DESCRIPTION

[0034] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate directions or

[0035] The positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0036] During construction, the traditional inclined support system requires reserved counter-pressure soil to ensure the stability of the foundation pit. However, the subsequent excavation of the counter-pressure soil is difficult, especially when the space around the foundation pit is narrow. It is difficult to set up excavation equipment on the top of the slope, and it is often necessary to reserve an excavation channel within the existing project or use a tower crane to remove the counter-pressure soil. Not only that, after the excavation of the counter-pressure soil is completed, the reserved bottom plate needs to be poured a second time, leaving construction joints and adding water-stop steel plates, which increases the risk of water leakage; and the early construction requires the installation of corbels, which need to be chiseled and cleaned in the later stages. This series of processes seriously affects the construction progress, resulting in delays, while also increasing construction costs and management difficulties.

[0037] To this end, we proposed a front-mounted lattice inclined bracing support structure and construction method to solve the above problems.

[0038] Example 1:

[0039] A front-mounted lattice inclined bracing support structure, such as Figures 1 to 4 As shown, the structure includes a foundation pit, which is located on the side of an existing project, such as a basement. The existing project includes a first support unit 1, which serves as a supporting structure for the existing project and is located within the soil at the side of the foundation pit. A second support unit 4 is installed within the soil at the bottom of the foundation pit. Several inclined lattice columns 2 are fixedly installed between the top ends of the second support units 4 and the top ends of the first support units 1, forming an oblique support structure for the foundation pit.

[0040] like Figure 1 、 Figure 2As shown, the first support unit 1 includes a first crown beam 11 and several first support piles 12. The first support piles 12 are spaced apart within the soil of the foundation pit sidewalls, and are located between the existing project and the foundation pit. The top ends of the first support piles 12 are collectively provided with the first crown beam 11, and the side end surfaces of the first crown beam 11 can be pre-embedded with several steel plates for connecting to the lattice columns 2. The second support unit 4 includes a second crown beam 41 and several second support piles 42. The second support piles 42 are spaced apart within the soil at the bottom of the foundation pit, and the top ends of the second support piles 42 are collectively provided with the second crown beam 41. The side end surfaces of the second crown beam 41 can be pre-embedded with several steel plates for connecting to the lattice columns 2.

[0041] like Figures 1 to 3 As shown, the top end of the lattice column 2 is fixedly mounted on the side end face of the first crown beam 11, and the bottom end of the lattice column 2 is fixedly mounted on the side end face of the second crown beam 41. The lattice column 2 includes four long rods 21 and a plurality of connecting plates 22. The four long rods 21 form a rectangular structure, and the four long rods 21 are respectively located at the four corners of the rectangle. The long rods 21 can be made of angle steel. A plurality of connecting plates 22 are fixedly mounted at even intervals between two adjacent long rods 21. The plurality of connecting plates 22 on each long rod 21 are installed in the same position, so that the corresponding four connecting plates 22 form a rectangular structure on the outside of the long rods 21. The four connecting plates 22 are respectively located at the four sides of the rectangle, suitable for connecting the four long rods 21 into a whole.

[0042] like Figure 4 As shown, a number of waterstop plates 3 are fixedly installed at the lower end of the lattice column 2. The waterstop plates 3 are located on the same horizontal plane, and all of the waterstop plates 3 are located inside the bottom plate 5 of the foundation pit. There are four waterstop plates 3 in total, and four long rods 21 are respectively installed in the middle of the four waterstop plates 3. The long rods 21 are fully welded to the inner and outer sides of the waterstop plates 3 to ensure the connection and water-stopping quality. The waterstop plates 3 are trapezoidal in structure, and the oblique sides of the four waterstop plates 3 are all located on the inner side, so that the outer sides of the four waterstop plates 3 form a rectangular structure, and the inner sides of the four waterstop plates 3 form a diamond structure. Preferably, the waterstop plates 3 are made of steel plates.

[0043] Example 2:

[0044] A construction method for front-mounted lattice inclined bracing support, such as Figure 5 As shown, the following steps are included:

[0045] S101. Construct the second support unit 4 in the soil at the bottom of the foundation pit:

[0046] A dual-purpose pile design was employed, utilizing the existing first support pile 12 as a side support pile for the foundation pit. A second support unit 4, comprising several second support piles 42, was then constructed within the soil at the bottom end of the foundation pit. A drilling rig was used to construct the second support piles 42. Prior to construction, planning and positioning of the piles were performed, and casings were driven into the designated locations of the second support piles 42. During the construction of the second support piles 42, the deviation between the drill bit center and the top center of the casing was ensured to be less than or equal to 50 mm when the drill rig was in place, and the drill rig chassis was leveled to maintain stability.

[0047] The second support piles 42 are numbered, and a skip-driving construction method with two piles spaced apart is adopted to avoid mutual influence of strength between adjacent second support piles 42 and ensure the construction quality of the second support piles 42. During the drilling process, mud wall protection is used to form holes, and the mud surface is guaranteed to be no less than 50 cm below the bottom of the casing to prevent collapse and shrinkage. After the drilling reaches the design elevation, the hole depth, hole diameter and hole shape are checked, and the hole is cleaned after confirming that they meet the requirements. Before construction, the steel cage is processed in the steel processing area in advance. After the hole is cleaned, the steel cage is lowered, and the thickness of the protective layer and the lowering depth are controlled. Finally, concrete is poured to ensure that the concrete strength reaches 100% of the design strength, and the concrete strength of the first batch of second support piles 42 reaches more than 90%, completing the construction of the second support piles 42.

[0048] The second crown beam 41 was constructed beneath the base plate 5. First, a trench was excavated at the construction location for the second crown beam 41 according to the design requirements. The inferior concrete on top of the second support pile 42 was chiseled out, and the top surface of the second support pile 42 was roughened and the scum on top of the pile was removed. The soil between the piles was leveled and compacted to serve as the bottom formwork. The second crown beam 41, with dimensions of 1200mm x 700mm, was constructed according to the design requirements. The steel bars of the second crown beam 41 were placed outside the main bars of the second support pile 42. The intersections of the main bars of the second support pile 42 and the stirrups of the second crown beam 41 were securely connected using plum blossom tying or spot welding. The second crown beam 41 was constructed using double-sided formwork, with a concrete strength of C40. The total time for concrete transportation, pouring, and rest periods did not exceed the initial setting time of the concrete. Concrete was poured continuously in sections within the same construction section, with each section being 30m to 40m long. This ensured that the strength of the second crown beam 41 reached 100% of the design strength, completing the construction of the second support unit 4.

[0049] S102: Assemble the lattice column 2 and install the water stop plate 3 on the lattice column 2.

[0050] The lattice columns 2 were fabricated on-site. Each lattice column 2 was spliced ​​using four L140×10 steel angles, with connecting plates 22 spaced 700 mm apart. The connecting plates 22 measured 400 mm × 300 mm × 10 mm. After the second support unit 4 was completed within the foundation pit, the location for the lattice columns 2 was partially excavated and hoisted using an on-site tower crane. The lattice columns 2 were then temporarily secured. The steel plates on the side end surfaces of the lattice columns 2, the first crown beam 11, and the second crown beam 41 were fully welded to ensure a secure connection.

[0051] S103. Carry out foundation structure construction in the foundation pit. After completion of the construction, remove the lattice column 2:

[0052] After the lattice columns 2 are installed, the foundation pit is excavated as a whole, with the over-excavated areas compacted and backfilled. Waterstop plates 3 are then installed where the lattice columns 2 penetrate the base plate 5. The connection between the waterstop plates 3 and the lattice columns 2 is fully welded inside and outside to prevent potential leakage later. After construction is complete, the dimensions of the lattice columns 2, the spacing between the connecting plates 22, and the welding quality are inspected to ensure a 100% pass rate. Deformation of the support structure after the foundation pit construction is completed is also monitored to ensure that the deformation value is less than the design warning value of 30 mm.

[0053] After the waterstop 3 is installed, the remaining foundation structures within the foundation pit, such as the base plate 5 and the replacement bracing structure, are constructed. Rebar is tied and concrete is poured. During the casting of the base plate 5, some lattice columns 2 within the base plate 5 are cast integrally, connecting the base plate 5 and the lattice columns 2 as a single unit. Once the replacement bracing structure reaches its designed strength, the lattice columns 2 are removed. During removal, the lattice columns 2 are cut along the top surface of the base plate 5, and the portion of lattice columns 2 above the base plate 5 is removed, while the portion of lattice columns 2 within and below the base plate 5 remains.

[0054] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A front-mounted lattice inclined bracing support structure, comprising a first support unit (1) and a foundation pit, wherein the first support unit (1) is located in the soil on the inner side of the foundation pit, and is characterized in that: include: A second support unit (4) is located in the soil at the bottom of the foundation pit, and the second support unit (4) is lower than the first support unit (1); A plurality of lattice columns (2) are arranged at intervals and tilted between the first support unit (1) and the second support unit (4), and penetrate the bottom plate (5) of the foundation pit, and are suitable for serving as a supporting structure of the foundation pit; A plurality of water stop plates (3) are respectively fixed on the plurality of lattice columns (2) and are located inside the base plate (5).

2. The front-mounted lattice oblique bracing support structure according to claim 1 is characterized in that: The first support unit (1) comprises a first crown beam (11) and a plurality of first support piles (12); the plurality of first support piles (12) are arranged at intervals in the soil at the side of the foundation pit; and the first crown beam (11) is commonly arranged at the top ends of the plurality of first support piles (12).

3. The front-mounted lattice oblique bracing support structure according to claim 2 is characterized in that: The second support unit (4) comprises a second crown beam (41) and a plurality of second support piles (42), wherein the plurality of second support piles (42) are arranged at intervals in the soil at the bottom of the foundation pit, and the second crown beam (41) is commonly arranged at the top ends of the plurality of second support piles (42).

4. The front-mounted lattice oblique bracing support structure according to claim 3 is characterized in that: The top end of the lattice column (2) is fixed on the first crown beam (11), and the bottom end of the lattice column (2) is fixed on the second crown beam (41).

5. The front-mounted lattice oblique bracing support structure according to any one of claims 1 to 4, characterized in that: The lattice column (2) comprises four long rods (21) and a plurality of connecting plates (22). The four long rods (21) form a rectangular structure, and a plurality of connecting plates (22) are fixedly installed at even intervals between two adjacent long rods (21).

6. The front-mounted lattice oblique bracing support structure according to claim 5 is characterized in that: The installation positions of the plurality of connecting plates (22) on each of the long rods (21) are consistent, and are suitable for the corresponding four connecting plates (22) to form a rectangular structure outside the four long rods (21).

7. The front-mounted lattice oblique bracing support structure according to claim 6 is characterized in that: The plurality of water stop plates (3) are respectively sleeved on the corresponding long rods (21), and the plurality of water stop plates (3) are located on the same horizontal plane.

8. The front-mounted lattice oblique bracing support structure according to claim 7 is characterized in that: The water stop plate (3) is a trapezoidal structure.

9. A construction method for front-mounted lattice inclined bracing support, characterized in that: Suitable for constructing a lattice oblique bracing support structure according to any one of claims 1 to 8, comprising the following steps: constructing the second support unit (4) in the soil at the bottom of the foundation pit; Assembling the lattice columns (2), and installing the water stop plates (3) on the lattice columns (2); The foundation structure is constructed in the foundation pit, and the lattice columns (2) are removed after the construction is completed.

10. The construction method of front-mounted lattice oblique bracing support according to claim 9, characterized in that: Carrying out foundation structure construction in the foundation pit and removing the lattice column (2) after the construction is completed, specifically includes: After the foundation structure reaches the designed strength, the lattice columns (2) are removed; During removal, the lattice columns (2) are cut along the top surface of the bottom plate (5), the lattice columns (2) above the bottom plate (5) are removed, and the lattice columns (2) below the bottom plate (5) are retained.

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