Construction method of deep and large foundation pit without support replacement

Abstract

This invention discloses a construction method for deep and large foundation pits without the need for replacement supports, belonging to the field of underground structure sequential construction technology. During the main structure construction, after the previous formwork sidewall is completed, only the next steel support is removed; replacement supports are no longer installed, thus eliminating the need for replacement supports. Only the concrete supports are cut, retaining the lintel beams, which function as part of the sidewall, allowing them to play a role in both the excavation and main structure construction phases. The bottom slab ribs are adjusted from triangular bevels to stepped shapes, allowing the scaffold uprights to act vertically on the ribs, ensuring the overall stability of the scaffold. The increased rib cross-sectional dimensions reduce the impact of lateral deformation of the foundation pit on the sidewalls. This invention shortens the construction process, reduces construction costs, ensures foundation pit safety, and has good economic benefits.

Description

Technical Field

[0001] This invention relates to a non-repair support technology for the construction of the main structure in underground space engineering projects such as deep foundation pits, and belongs to the field of building construction. Background Technology

[0002] With economic development, there is a growing demand for efficient urban space utilization and convenient transportation, making the development of underground space and the improvement of underground transportation facilities particularly important. As more and more deep foundation pit projects are undertaken in complex environments, especially in water-rich, soft-soil areas such as riverside and coastal cities, higher demands are placed on foundation pit safety. This requires not only controlling the deformation of the foundation pit support structure to ensure safety, but also minimizing the construction period and improving efficiency. Therefore, it is essential to conduct research on foundation pit support structures to ensure construction safety and improve efficiency.

[0003] In most deep foundation pit projects, the replacement support method is used to ensure the smooth continuation of construction. This involves constructing the replacement support components first, and then removing the supports once their strength meets design requirements. Replacement support components can be temporary or permanent, with different components selected based on project needs. Currently, some research has been conducted both domestically and internationally on replacement support construction devices, structures, and methods. However, the temporary support components used in the replacement process still need to be removed after the main structure is completed. Therefore, this invention employs a combined temporary and permanent support system, proposing a non-replacement support construction method for deep and large foundation pits. By eliminating the need for replacement supports, the construction period is shortened, ensuring foundation pit safety. Summary of the Invention

[0004] Purpose of the invention: To address the shortcomings of existing technologies, this invention proposes a construction method for deep and large foundation pits without the need for replacement of supports, using a combined permanent and temporary support system. This method effectively shortens the construction cycle of deep and large foundation pit projects, reduces the number of procedures, and ensures the smooth and safe construction of foundation pit projects.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A construction method for deep and large foundation pits without the need for support replacement includes the following steps:

[0007] Step S1: In the foundation pit, construct the foundation pit support system and the internal support system. The foundation pit support system includes several retaining structures. The internal support system includes the capping beam, concrete connecting beam, concrete support, steel waler, steel column, steel support, concrete waler, and bored piles built within the retaining structures. Then, construct the bottom slab.

[0008] Step S2: Remove the first steel support above the base plate;

[0009] Step S3: Construct the first formwork sidewall on the base plate;

[0010] Step S4: Construct a stepped bottom slab rib between the side wall and the bottom slab of the first formwork;

[0011] Step S5: Construct the main structural support system under the height area of ​​the first formwork side wall, including uprights, horizontal bars, and scissor braces;

[0012] Step S6: Continue construction upwards, remove the second steel or concrete support above the base plate, and construct the second formwork side wall on the first formwork side wall;

[0013] Step S7: Construct the main structural support system under the height area of ​​the second formwork side wall, including uprights, horizontal bars, and continuous top-mounted steel pipes;

[0014] Step S8: Continue construction upwards until the top of the internal support system is reached, and finally, construct the top slab.

[0015] As a further preferred option, in step S3, the construction of the first formwork sidewall adopts a large steel formwork with a triangular bracket, and there is no need to erect steel replacement supports after the construction of the first formwork sidewall.

[0016] As a further preferred option, in step S3, during steps S7-S8, when constructing the second and above side walls, a full-span scaffold wooden formwork is used.

[0017] As a further preferred option, in step S6, when the support to be removed is a concrete support, only the concrete support is cut, the concrete waler is retained, and the concrete waler is used as part of the side wall.

[0018] As a further preferred embodiment, in step S5, the uprights and horizontal bars at the bottom rib positions are connected to the stepped horizontal and vertical edges of the bottom rib of the stepped structure.

[0019] As a further preferred option, in steps S7-S8, during the construction of the second formwork side wall and the side walls above it, longitudinal main reinforcement bars are reserved, and a tie rod is connected to the main reinforcement bars at one end. A continuous top steel pipe is constructed on the outside of the second formwork side wall and the side walls above it. The other end of the continuous top steel pipe is connected to the tie rod, and the continuous top steel pipe is connected and fixed to the upright.

[0020] Beneficial effects:

[0021] 1. During the main structure construction phase, only the concrete supports are cut, while the concrete walers are retained. The concrete walers serve as part of the side walls, enabling them to function during both the excavation and main structure construction phases. This eliminates the need for steel supports, reduces construction steps, and saves construction costs.

[0022] 2. By adjusting the bottom plate ribs to a stepped type, the uprights of the disc-lock scaffold can act vertically on the ribs, ensuring the overall stability of the scaffold. The increased cross-sectional size of the ribs reduces the impact of lateral deformation of the foundation pit on the side walls, ensuring the stability of the side wall structure and the safety of the foundation pit.

[0023] 3. By using a modular scaffolding system to divide the construction into sections, multiple sections can be connected in a continuous construction process, which not only does not affect the safety of the foundation pit, but also improves construction efficiency to a certain extent. Attached Figure Description

[0024] Figure 1 This is an elevation view of the foundation pit support of the present invention;

[0025] Figure 2 This is an elevation view of the foundation pit bottom slab and the first formwork sidewall of the present invention.

[0026] Figure 3 This is an elevation view of the construction of the second formwork sidewall of the foundation pit according to the present invention;

[0027] Figure 4 This is an elevation view of the construction of the side wall of the third formwork of the foundation pit according to the present invention;

[0028] Figure 5 This is an elevation view of the construction of the foundation pit top slab of this invention;

[0029] Figure 6 This is a detailed drawing of the reinforcement structure of the upper formwork at the overlap of the working well diaphragm wall ring beam and the subsequent opening of the present invention;

[0030] Figure 7 This is an elevation view of the foundation pit bottom slab, the first formwork side wall, and the bottom slab ribs of the present invention;

[0031] In the picture:

[0032] 1—Cap beam; 13—Bottom plate rib;

[0033] 2 – Concrete tie beam; 14 – Base slab;

[0034] 3 – Concrete support; 15 – Side wall of the first formwork;

[0035] 4 – Steel walers; 16 – Second formwork sidewalls;

[0036] 5 – Steel column; 17 – Support bolt;

[0037] 6 – Steel support; 18 – Continuous jacking steel pipe;

[0038] 7 – Enclosure structure; 19 – Timber formwork;

[0039] 8 – Concrete waler; 20 – Side wall of the third formwork;

[0040] 9 – Bored piles; 21 – Top plate;

[0041] 10 – Scissors brace; 22 – Main reinforcement bar;

[0042] 11 – Upright pole; 23 – Tie rod;

[0043] 12 - Horizontal bar. Detailed Implementation

[0044] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0045] As attached Figure 1-7 As shown, the present invention provides a method for constructing the main structure without replacement support, including a foundation pit support system, an internal support system, a main structure support system, and a main structure;

[0046] The foundation pit support system includes several retaining structures 7. The foundation pit support system is used to keep the foundation pit stable and control deformation.

[0047] The internal support system includes a cap beam 1, a concrete connecting beam 2, multiple reinforced concrete supports 3, concrete walers 8, steel supports 6, steel walers 4, and steel columns 5. The internal support structure supports the foundation pit support system before the main construction frame structure is completed, and coordinates the stress and deformation state.

[0048] The main structural support system includes multiple disc-locked support uprights 11, horizontal bars 12, scissor braces 10, and continuous top steel pipes 18. The main structural support system is used to control the stress and deformation of the foundation pit after the internal support system is removed, and to create space for the construction of the main structure.

[0049] The main structure, including the base plate 14, the first mold side wall 15, the second mold side wall 16, the third mold side wall 20, and the top plate 21, maintains the integrity, stability, and safety of the main structure system after the internal supports are removed.

[0050] In the above embodiment, the foundation pit support system, internal support system, main structure support system, and main structure are constructed alternately to complete the dismantling and support construction of the foundation pit. When the disc-lock scaffolding conflicts with the concrete support 3, the disc-lock scaffolding avoids the concrete support 3 and uses long steel pipes to reinforce the concrete support 3 on all four sides. The steel pipes are locked to the disc-lock uprights 11 of the main structure. In subsequent construction, the concrete support 3 is dismantled by cutting. The concrete walers 8 are designed as permanent and temporary combined components, and part of the concrete walers 8 is retained as part of the side wall.

[0051] In the above embodiment, at the point where the steel ring beam of the working well entrance coincides with the subsequent opening, there are no support points at the four corners of the retaining structure wall, making it impossible to use continuous steel pipe bracing. Therefore, a tie rod of 23 + a continuous top-mounted steel pipe of 18 horizontal locking rod is used for bracing and reinforcement. The specific reinforcement is shown in the attached figure. Figure 6 Tie rod 23 is welded to the root of the inner vertical main reinforcement 22.

[0052] In the above example, the full-length top steel pipe 18 should be locked with the uprights 11 and horizontal bars 12 of the full-span disc buckle scaffold.

[0053] The function of the supporting bolt 17 is to connect the continuous jacking steel pipe 18 to the main reinforcement 22 through the supporting bolt 17 and tie rod 23 during the construction of the side wall and roof slab, and then connect it to the back rib of the wooden formwork for the side wall (or roof slab) to reinforce the formwork for pouring the side wall and roof slab. After the steel replacement support is removed, the stress deformation of the enclosure structure is controlled in the upper part by the continuous jacking steel pipe 18 and in the lower part by the scissor brace 10 (the main deformation is in the lower part). In the embodiment, the continuous jacking steel pipe 18 is connected to the horizontal bar 12 after verification. If no verification is performed or the verification result is unreasonable, the continuous jacking steel pipe 18 should not be connected to the horizontal bar 12, and the supporting bolt 17 is only connected to the enclosure structure on both sides through the continuous jacking steel pipe 18.

[0054] This embodiment also provides a construction method for a main structure without replacement support technology. Taking a three-form side wall as an example, from bottom to top, the side walls are: the first form side wall 15, the second form side wall 16, and the third form side wall 20. However, it is not limited to a three-form side wall; the number of side walls can be set according to the actual construction situation. The method includes the following steps:

[0055] Step S1, Construction of the foundation pit support system: Before the dismantling and support construction of the foundation pit project, the foundation pit plane is divided into several flow sections, and the dismantling and support construction of each flow section is carried out independently upward.

[0056] In the above steps, the foundation pit can be divided into several flow sections. Earthwork excavation is carried out in each flow section, and the soil layer height difference between adjacent flow sections should meet the design requirements. When excavating to the corresponding position, the capping beam 1, concrete waler 8, reinforced concrete support 3, steel waler 4, and steel support 6 are constructed sequentially until the designed bottom surface of the foundation pit is reached. Then, reinforced concrete is poured for the side walls and bottom slab of the foundation pit. The construction of the foundation pit bottom slab should be carried out separately according to the divided flow sections. Then, the dismantling of supports above 14mm of the foundation pit bottom slab begins, as shown in the attached diagram. Figure 1-2 As shown.

[0057] Step S2: Pour part of the side wall up to the bottom support 6, remove the bottom support 6, and complete the pouring of the first formwork side wall 15;

[0058] In the above construction steps, after the reinforced concrete pouring of part of the side walls and the base slab 14 is completed, and after the concrete strength of the base slab 14 and the side walls reaches the design requirements, the bottom steel support 6 is removed. After removal, the pouring of the first formwork side wall 15 is completed. In this embodiment, a large steel formwork with a triangular bracket is used to construct the first formwork side wall 15. After the concrete strength of the first formwork side wall 15 reaches the design requirements, the base slab rib 13 is poured, and then the support removal construction continues, as shown in the attached figure. Figure 2 As shown.

[0059] Step S3, construction of the bottom slab rib plate 13 and the first main structure support system, erecting full-span disc buckle scaffolding uprights 11, horizontal bars 12, and scissor braces 10;

[0060] In the above construction steps, after the strength of the first formwork side wall 15 reaches the design requirements, the construction of the bottom slab rib 13 is carried out. The bottom slab rib 13, the first formwork side wall 15, and the bottom slab 14 should be poured with the same grade of concrete. In this embodiment, considering the subsequent erection of the full-span scaffolding, the bottom slab rib 13 is adjusted from the triangular shape of the original design to a stepped shape, and the scaffolding base is placed on the stepped plane, which helps to improve the stability of the scaffolding base. (See attached figure) Figure 2 , 7 As shown.

[0061] Step S4, dismantle support 6, and construct the second main structure support system by erecting full-span disc buckle support uprights 11, horizontal bars 12, scissor braces 10, continuous top steel pipes 18 and side wall wooden formwork 19.

[0062] In the above construction steps, after the concrete strength of the foundation pit bottom slab 14, the first formwork side wall 15, and the bottom slab rib 13 reaches the design requirements, and the lower full-span scaffold uprights 11, horizontal bars 12, and scissor braces 10 are erected, the construction of this main structural support system will proceed. It should be noted that this main structural support system differs from the lower one in that it uses continuous top-mounted steel pipes 18 and side wall wooden formwork 19. Since this example uses a no-replacement-support technique, continuous top-mounted steel pipes 18 are needed to control the stress and deformation of the foundation pit. If there is a central partition wall in the foundation pit, the continuous top-mounted steel pipes 18 should be tightly fitted to the central partition wall when installing the second formwork side wall wooden formwork 19. Furthermore, except for the first formwork side wall which is cast using large triangular steel molds, all other formwork side walls are cast using wooden formwork 19.

[0063] Step S5: Pour the second formwork side wall 16 and continue to erect the full-span scaffolding upwards;

[0064] In the above construction steps, based on the completed main structural support system and the side wall wooden formwork 19, the second formwork side wall 16 is poured. It should be noted that the currently dismantled supports are all steel supports 6; the concrete supports 3 have not been dismantled. At locations where the disc-lock scaffolding conflicts with the concrete supports 3, the disc-lock scaffolding avoids the concrete supports 3, using long steel pipes tightly secured to the concrete supports 3 on all four sides. The steel pipes are locked to the main structural disc-lock uprights 11. After the second formwork side wall is poured, the disc-lock scaffolding continues to be erected upwards. (See attached...) Figure 3 As shown.

[0065] Step S6: Remove other steel supports 6, construct the main structural support system and main structure, and remove the steel supports 6 from bottom to top, repeating the above steps S4-S5.

[0066] In the above construction steps, the construction sequence is as follows: first, dismantle the supports 6; then, erect the full-span scaffolding uprights 11, horizontal bars 12, scissor braces 10, continuous top-mounted steel pipes 18, and side wall wooden formwork 19; finally, pour the side wall concrete. It should be noted that all dismantled supports are steel supports 6, and the concrete supports 3 are all reinforced with long steel pipes tightened on all four sides. (See attached...) Figure 4 As shown.

[0067] After removing all supports (such as concrete support 3 and steel support 6) and constructing the side walls (first formwork side wall 15, second formwork side wall 16, third formwork side wall 20 and more side walls), there is no need to erect steel replacement supports.

[0068] Step S7: After the side wall concrete reaches the design strength requirement, remove the steel column 5, pour the top slab 21, and remove the concrete support 3.

[0069] In the above construction steps, after the concrete strength of each formwork sidewall reaches the design strength requirement, the steel columns 5 are cut in sections from top to bottom. According to the design requirements, the top slab 21 is poured with concrete of the same grade as the sidewalls and bottom slab 14, and the top slab is also poured using wooden formwork. In addition, the concrete supports 3 are removed by cutting, and the concrete walers 8 are designed as permanent and temporary combined components, with part of the concrete walers 8 being retained as part of the sidewalls.

[0070] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A construction method for deep and large foundation pits without the need for support replacement, characterized in that, Includes the following steps: Step S1: In the foundation pit, construct the foundation pit support system and the internal support system. The foundation pit support system includes several retaining structures (7). The internal support system includes the cap beam (1), concrete connecting beam (2), concrete support (3), steel waler (4), steel column (5), steel support (6), concrete waler (8), and bored pile (9) built in the retaining structure (7). Then construct the bottom slab (14). Step S2, remove the first steel support (6) above the base plate (14); Step S3: Construct the first formwork sidewall (15) on the base plate (14); Step S4: Construct a stepped bottom slab rib (13) between the first formwork side wall (15) and the bottom slab (14); Step S5: Construct the main structural support system under the height area of ​​the first formwork side wall (15), including uprights (11), horizontal bars (12), scissor braces (10), uprights (11) and horizontal bars (12) at the position of the bottom plate rib (13), which are connected to the step horizontal and vertical edges of the bottom plate rib (13) of the stepped structure. Step S6, continue construction upwards, remove the second steel support (6) or concrete support (3) above the base plate (14), and construct the second formwork side wall (16) on the first formwork side wall (15). When the support to be removed is a concrete support (3), only the concrete support (3) is cut, the concrete waler (8) is retained, and the concrete waler (8) is used as part of the side wall. Step S7: Construct the main structural support system under the height area of ​​the second formwork side wall (16), including uprights (11), horizontal bars (12), and continuous top steel pipes (18). Step S8, continue construction upwards until the top of the internal support system is reached, and finally construct the top slab (21); In steps S7-S8, during the construction of the second formwork side wall (16) and above, longitudinal main reinforcement bars (22) are reserved, and a tie rod (23) is connected to the main reinforcement bars (22) at one end. A continuous top steel pipe (18) is constructed outside the second formwork side wall (16) and above. The continuous top steel pipe (18) is connected to the other end of the tie rod (23), and the continuous top steel pipe (18) is connected and fixed to the upright (11).

2. The construction method for deep and large foundation pits without support replacement as described in claim 1, characterized in that: In step S3, the construction of the first mold side wall (15) adopts a large steel mold with a triangular support.

3. The construction method for deep and large foundation pits without support replacement as described in claim 1, characterized in that: In step S3, and in steps S7-S8, when constructing the second formwork side wall (16) and above, a full-span scaffold wooden formwork is used.

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