Forward and reverse combined deep foundation pit integrated material platform construction method

Abstract

The invention provides a forward and reverse combined deep foundation pit integrated material platform construction method, and belongs to the technical field of building construction.The construction method comprises the steps that an integrated material platform is deepened in design, a plain concrete cushion layer is poured after earth excavation, and a material platform plate supporting system is arranged on the surface of the plain concrete cushion layer; a bottom film and a top plate of the integrated platform are poured on the material table plate supporting system; the method comprises the following steps: pre-embedding a pull ring during construction of a top plate ring beam, pre-embedding a lug plate after binding reinforcing steel bars on the plate surface of the integrated platform, pouring material platform concrete of the integrated platform and a main body structural plate of the area together, and maintaining for 28 days; pull rods and protectors are installed and finally put into use; the integrated inner supporting plate and the overhanging structural plate extending from the reverse construction area to the forward construction opening area are fully utilized as the discharging platform and are both of a permanent structure, the bearing capacity is greatly improved compared with a common overhanging steel platform, permanent and temporary combination is achieved, later dismantling is avoided, and resource waste is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of building construction, and particularly relates to a construction method for an integrated material platform for a deep foundation pit with combined forward and reverse construction. Background Art

[0002] A deep foundation pit material platform is a temporary operating platform and operating frame set at the edge of a deep foundation pit, mainly used for material stacking and transfer. During the construction of a deep foundation pit, as the foundation pit is excavated, the site will gradually become narrow, and material transportation and stacking are greatly restricted. The deep foundation pit unloading platform can extend outward from the foundation pit, effectively utilizing the space, providing a temporary stacking and transfer place for materials, and avoiding directly stacking materials in the foundation pit, which affects the construction progress and safety.

[0003] With the development of technology and the acceleration of the urbanization process, the urban space is getting smaller and smaller, and the underground space is being paid more and more attention. People continue to dig downward into the underground space. In order to pursue the floor area ratio and the utilization of underground space, deep foundation pit projects are becoming more and more common in the existing engineering fields. There are various methods for deep foundation pits, and the commonly used one is the forward construction of deep foundation pits. However, it often requires replacement or removal of bracing, resulting in waste of resources. At the same time, the foundation pit has a certain deformation, which has a certain impact on the surrounding environment. Especially in the downtown area, it has certain limitations and is not applicable, which will affect the surrounding residents and cause fear. In the old urban area with complex environments, the reverse construction method for deep and large complex foundation pits has certain advantages, such as the integrated slab can be used as bracing and does not need to be demolished later, the foundation pit has small deformation and higher safety, and it is economical, green and efficient. When constructing complex foundation pits by the reverse construction method in the city center, the above-ground part can be constructed in advance, but it is often restricted by the underground working conditions. The reverse construction method has limited site, and reasonable site layout is often the difficulty and pain point of construction.

[0004] In view of the above deficiencies of forward and reverse construction, the combined forward and reverse construction method is becoming more and more common in urban areas. The combined forward and reverse construction method is beneficial to improving work efficiency. However, combined forward and reverse projects also often have limited sites. During the implementation of the project, it is necessary to consider the excavation, concrete pouring formation route, steel bar processing yard, carpentry processing yard, component stacking yard, waste material pool, secondary structure material site, tower crane and construction elevator layout, as well as the carpentry turnover material site. The site requirements are large. In the reverse construction area of combined forward and reverse projects, the reverse construction monomers often need to be constructed upward, occupying a part of the site. In the combined forward and reverse area, it needs to be constructed forward upward after the bottom slab is sealed. In the early stage, it is in an open state and the site cannot be arranged. The primary structure construction is carried out simultaneously above and below the ground. The amount of turnover materials such as formwork is huge and a large stacking yard is required. Completely stacking on the B0 slab poses a hidden danger to the structural safety and cannot ensure the vehicle passage on the B0 slab. Summary of the Invention

[0005] Objective of the Invention: The objective of the present invention is to provide an integrated construction method for a deep foundation pit material platform with combined forward and reverse construction in view of the deficiencies of the prior art. By making full use of the integrated internal support plate, a cantilever structural slab is extended from the reverse construction area to the forward construction opening area as a unloading platform, both of which are permanent structures. The bearing capacity is greatly improved compared with the ordinary cantilever steel material platform, realizing the combination of permanent and temporary structures, avoiding later demolition, reducing resource waste, saving the investment in measures such as the rental of the unloading platform, and at the same time being beneficial to shortening the construction period, having certain economic benefits and application value.

[0006] Technical Solution: The present invention relates to an integrated construction method for a deep foundation pit material platform with combined forward and reverse construction. The deep foundation pit integrated material platform includes an integrated platform, which is supported by a group of steel pipe columns with one column and one pile under the integrated platform. The steel pipe columns with one column and one pile are connected to the integrated platform through cantilever beams. It also includes side beams and tie rods, and the following steps are included: Step 1. Deepening the design of the integrated material platform: According to the construction progress of the basement and the structural form of the integrated slab, select a suitable position for the material platform, and design the cantilever size of the integrated material platform according to the load that the material platform needs to bear and the space required for material hoisting; side beams are arranged at the ends of the integrated platform; side beams are arranged at the cantilever end to form a closed stress ring to resist the torque and shear force at the end of the cantilever slab.

[0007] In Step 1, select the position of the material platform in combination with the construction progress of the basement (usually located at the middle 1 / 3 span of the foundation pit), avoiding the post-cast strip and the structural weak area to ensure balanced stress. Calculate the cantilever length of the cantilever beam 3 (≤ 1 / 3 of the beam length) through BIM modeling to control the bending moment at the cantilever end within the structural safety range.

[0008] Step 2. Construction of the integrated material platform structure: After the earthwork excavation, pour the plain concrete cushion. The uniform load of the cushion avoids the reduction of the bearing capacity of the foundation soil after being disturbed; set up a support system for the material platform slab on the surface of the plain concrete cushion, and pour the bottom film and top plate of the integrated platform on the support system of the material platform slab; embed pull rings during the construction of the top plate ring beam, and embed ear plates after the steel bars on the surface of the integrated platform are tied. The material platform concrete of the integrated platform is poured together with the main structure slab in this area and cured for 28 days; then turn to Step 3; Step 3. Installation of tie rods and protection Install tie rods, remove the support system of the material platform slab at the bottom of the integrated platform, and set up edge protection around the integrated platform; Step 4. Use of the integrated material platform: After the construction of the material platform is completed, it is put into use immediately.

[0009] Furthermore, additional support bars are added to the surface of the slab of the integrated platform 1 in Step 1.

[0010] Furthermore, the cantilever length of the cantilever beam designed in Step 1 does not exceed 1 / 3 of the beam length. The limitation of the cantilever length (≤1 / 3 beam length) avoids excessive root moment and reduces the risk of structural cracking.

[0011] Furthermore, the formwork support system for the material platform slab in Step 2 is a disk-locked scaffold, which forms a stable spatial grid through node disks. At the same time, the modular installation speed of the disk-locked scaffold is faster than that of the traditional steel pipe scaffold, shortening the construction period of the support system erection.

[0012] Furthermore, the bottom of the ear plate in Step 2 is anchored at the intersection of the side beam and the cantilever beam.

[0013] Furthermore, in Step 3, one end of the tie rod is connected and tightened with the pull ring, and the other end of the tie rod is tightened with the ear.

[0014] Furthermore, the height range of the edge protection in Step 3 is 1.1 - 1.3 m.

[0015] Furthermore, in Step 2, after the formwork support system for the material platform slab is installed, formwork is installed on the top of the formwork support system. The formwork serves as the bottom formwork of the integrated platform 1 and directly bears the self-weight of the poured concrete and construction loads.

[0016] Beneficial effects: Compared with the prior art, the advantages of the present invention are as follows: (1) The traditional construction sequence for the downward construction method is: earth excavation → cushion construction → support erection → structural pouring, which conforms to the conventional "top-down" construction sequence. However, the present invention adopts a combined downward and upward construction method for the deep foundation pit integrated material platform. The downward construction part is: the in-situ construction of the cantilever beam and the integrated platform, which needs to be carried out after the support system is completed. The upward construction part is: the permanent steel pipe columns are pre-constructed before the earth excavation as the vertical support for the later structure, utilizing the concept of "support first and then excavate" in the upward construction method. The structural construction is carried out simultaneously: the concrete of the integrated platform is poured together with the main structure slab to achieve the "upward construction superposition" of the horizontal structure, reducing the usage of temporary supports. (2) The advantages of the coordinated downward and upward construction in the present invention are: by the early load-bearing of the steel pipe columns (upward construction), the cantilever platform (downward construction) is allowed to be constructed synchronously with the basement structure, shortening the construction period. At the same time, as a part of the permanent structure, the integrated platform avoids the occupation of the construction site by the traditional temporary storage yard and solves the problem of "chaotic layout". Description of the Drawings

[0017] Figure 1 It is the plan view of the integrated material platform Figure 2 It is the construction drawing of the formwork support for the integrated material platform Figure 3 It is the reinforcement drawing of the tie rod for the integrated material platform Figure 4 It is the usage drawing of the integrated material platform In the figure: 1. Integrated material platform; 2. Additional reinforcement of the support; 3. Cantilever beam; 4. One-column and one-pile steel pipe column; 5. Side beam; 6. Embedded pull ring; 7. Integrated material platform; 8. Embedded ear plate; 9. Support frame; 10. Pad layer; 11. Finished product reinforcement rod; 12. Edge protection. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the embodiments.

[0019] A forward-backward combined deep foundation pit includes an integrated platform 1, which is supported by a set of steel pipe columns 4 with one column and one pile below. The steel pipe columns 4 are connected to the integrated platform 1 via cantilever beams 3. The method also includes side beams 5 and tie rods 11. The construction method of the forward-backward combined deep foundation pit includes the following steps: Step 1: Deepen the design of integrated material platform: like Figure 1 As shown, based on the basement construction schedule and structural characteristics, the material platform was located in the middle 1 / 3 of the foundation pit span, avoiding post-cast strips and weak structural areas. The cantilever dimensions of the integrated material platform were designed based on the loads it would bear and the space required for material lifting. The cantilever length was verified through BIM modeling (≤ 1 / 3 of the clear span of the side beam), and the load (forklift + material ≤ 8kN / m²) was calculated. Side beams 5 were installed at the ends of integrated platform 1 to ensure its integrity and stability. C12@200 support reinforcement 2 was added to the slab of integrated platform 1, and the cantilever length of the designed cantilever beam was designed to not exceed 1 / 3 of the beam length.

[0020] Step 2: Construction of integrated material platform structure: After excavation, a plain concrete cushion layer 10 was poured. A material platform support system 9, consisting of a hinged frame, was installed on the surface of the plain concrete cushion layer 10. The base membrane and top slab of the integrated platform 1 were cast on top of the material platform support system 9. Once the material platform support system 9 was installed, a formwork was installed on top of the material platform support system 9. This formwork served as the bottom formwork for the integrated platform 1, directly bearing the weight of the poured concrete and construction loads. The formwork was constructed of 15mm plywood. During the construction of the top slab ring beam, a pull ring 6 made of Q235B was embedded. After the reinforcement of the integrated platform 1 was tied, ear plates 8 made of Q235B were embedded. The bottom of the ear plates 8 were anchored at the junction of the edge beam 5 and the cantilever beam 3 to a depth of 20 cm. The concrete for the integrated platform 1's material platform was poured together with the main structural slab in this area and cured for 28 days.

[0021] Step 3: Install the pull rod and protection Install the tie rod 11, connect and tighten one end of the tie rod 11 to the pull ring 6, and tighten the other end of the tie rod 11 to the ear plate 8; Remove the platform board support system 9 at the bottom of the integrated platform 1, and set up the edge protection 12 around the integrated platform 1; The height of the edge protection 12 is 1.2m. Step 4: Use of the integrated platform: After the platform construction is completed, it is put into use immediately. The forklift drives onto the platform to transport materials. The platform is cantilevered from the main structure and has a large bearing capacity, solving the problem of chaotic layout caused by excessive stacking yards of turnover materials and the like during the large-area construction of the basement with combined forward and reverse construction.

[0022] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as a limitation of the present invention itself. Various changes can be made in its form and details without departing from the spirit and scope of the present invention defined by the appended claims.

Claims

1. A construction method for an integrated material platform for deep foundation pits with combined forward and reverse directions. The integrated material platform for deep foundation pits includes an integrated platform (1), which is supported by a group of single-column single-pile steel pipe columns (4) below. The single-column single-pile steel pipe columns (4) are connected to the integrated platform (1) through cantilever beams (3), and also include side beams (5) and tie rods (11), and is characterized in that It includes the following steps: Step 1. Deepening the design of the integrated material platform: According to the construction progress of the basement and the structural form of the integrated board, select a suitable position for the material platform, and design the cantilever size of the integrated material platform according to the load that the material platform needs to bear and the space required for material hoisting; a side beam (5) is provided at the end of the integrated platform (1); Step 2. Construction of the integrated material platform structure: After the earthwork is excavated, a plain concrete cushion (10) is poured. A support system (9) for the platform slab is arranged on the surface of the plain concrete cushion (10). The bottom formwork and top slab of the integrated platform (1) are poured on the support system (9) for the platform slab; when the ring beam of the top slab is constructed, a pull ring (6) is embedded. After the steel bars on the surface of the integrated platform (1) are tied, an ear plate (8) is embedded. The platform concrete of the integrated platform (1) is poured together with the main structure slab in this area and cured for 28 days; then turn to Step 3; Step 3. Installation of tie rods and protection Install tie rods (11), remove the support system (9) for the platform slab at the bottom of the integrated platform (1), and set up edge protection (12) around the integrated platform (1); Step 4. Use of the integrated material platform: After the construction of the material platform is completed, it is put into use immediately.

2. The construction method of an integrated material platform for deep foundation pits with combined forward and reverse directions according to claim 1, wherein: In Step 1, additional support bars (2) are added on the surface of the integrated platform (1).

3. The construction method of an integrated material platform for a deep foundation pit with combined forward and reverse directions according to claim 1, characterized in that: In Step 1, the cantilever length of the designed cantilever beam does not exceed 1 / 3 of the beam length.

4. A construction method for an integrated material platform for deep foundation pits with combined forward and reverse operations according to claim 1, characterized in that: In Step 2, the support system (9) for the platform slab is a disc buckle formwork system.

5. A construction method for an integrated material platform in a deep foundation pit with combined forward and reverse directions, characterized in that: In Step 2, the bottom of the ear plate (8) is anchored at the intersection of the side beam (5) and the cantilever beam (3).

6. A construction method for an integrated material platform in a deep foundation pit with combined forward and reverse directions, characterized in that: In Step 3, one end of the tie rod (11) is connected and tightened with the pull ring (6), and the other end of the tie rod (11) is tightened with the ear plate (8).

7. A construction method for an integrated material platform in a deep foundation pit with combined forward and reverse directions according to claim 1, characterized in that: In Step 3, the height range of the edge protection (12) is 1.1 - 1.3 m.

8. A construction method for an integrated material platform in a deep foundation pit with combined forward and reverse directions according to claim 1, characterized in that: In Step 2, after the support system (9) for the platform slab is installed, a formwork is installed on the top of the support system (9) for the platform slab. The formwork serves as the bottom formwork of the integrated platform (1) and directly bears the self-weight of the poured concrete and the construction load.

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