Structural bottom plate and construction method thereof

Abstract

The invention discloses a structural bottom plate and a construction method thereof. The structural bottom plate comprises a plurality of horizontal reinforced concrete beams arranged in the structural bottom plate, and the reinforced concrete beams are arranged in a crisscross mode to form a grid structure. By arranging the net-shaped reinforced concrete beam in the structural bottom plate, strong constraint can be formed in the concrete pouring process of the structural bottom plate, temperature compensation is conducted on the bottom plate, cracks generated in the structural bottom plate are effectively controlled, and even after concrete pouring is completed, the net-shaped reinforced concrete beam can also serve as an internal reinforcing structure of the structural bottom plate; therefore, the overall bearing capacity of the structural bottom plate is improved. And the reinforced concrete beams can serve as horizontal supporting structures of the foundation pit, the clear height between the bottommost horizontal supporting structure and the bottom excavation face is reduced, the deformation can be effectively controlled, and the safety risk of foundation pit construction is reduced. The reinforced concrete beam is poured in the structural bottom plate, one support can be omitted in the back-building process, the construction period is shortened, and the using amount of concrete materials is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of underground construction engineering, and in particular to a structural base plate including a horizontal supporting structure and a construction method thereof. Background Art

[0002] In the construction of underground projects with ultra-thick base plates, the lowest horizontal support structure of the foundation pit is set above the top elevation of the large base plate. Since the large base plate is thick, the cantilever of the ground-connected wall will be too long after the excavation of the large base plate. This may cause a large deformation of the foundation pit between the soil excavation surface and the lowest horizontal support structure, which will increase the construction risk. Summary of the invention

[0003] In view of the problem that the thickness of the large base plate leads to large deformation of the lowest space in the existing underground engineering construction with ultra-thick base plate, the present invention provides a structural base plate and a construction method thereof, which can effectively solve the above problem.

[0004] In order to solve the above technical problems, the present invention includes the following technical solutions: A structural bottom plate, the structural bottom plate comprises a plurality of horizontal reinforced concrete beams arranged inside, the reinforced concrete beams are arranged vertically and horizontally to form a grid structure; during the construction of the structural bottom plate, the grid structure serves as the horizontal support structure of the bottom layer of the foundation pit; when the concrete of the structural bottom plate is poured, the grid structure is poured inside the structural bottom plate; after the construction of the structural bottom plate is completed, the grid structure serves as the internal reinforcement structure of the structural bottom plate; A horizontal flow pipe is arranged in the reinforced concrete beam, and a reinforcing partition is arranged in the flow pipe to form flow holes, which are used to make the concrete flow in different pouring areas after the concrete of the structural bottom plate is poured to the height of the flow pipe.

[0005] Furthermore, the flow pipe is made of steel pipe with a wall thickness of d satisfy: d > D · f c / (2 f y ),in D is the outer diameter of the flow tube, f c is the concrete compressive strength of reinforced concrete beams, f y is the steel strength of the flow tube.

[0006] Furthermore, a reinforcement ring is arranged around the flow hole, and the reinforcement ring includes longitudinal reinforcement and stirrups. The longitudinal reinforcement is consistent with the length direction of the flow tube and is arranged at intervals along the circumferential direction of the flow tube. The stirrups are arranged around the longitudinal reinforcement.

[0007] Furthermore, a bracket is arranged below the flow tube, the bracket comprising a support ring and a connecting piece, the connecting piece is fixed to the longitudinal reinforcement and stirrups of the reinforced concrete beam, the top of the connecting piece is fixed to the support ring, and the support ring supports the flow tube.

[0008] Furthermore, cooling pipes are provided at the top and bottom of the reinforced concrete beam, and the tops of the water inlet and outlet of the cooling pipes are higher than the upper surface of the structural base plate, so as to absorb hydration heat by conducting injected water when pouring concrete of the structural base plate.

[0009] Accordingly, the present invention also provides a construction method of the structural base plate, comprising the following steps: Step 1: Carry out foundation pit construction and complete the construction of the bottom horizontal support structure. The horizontal support structure is a reinforced concrete beam arranged vertically and horizontally. The top elevation of the horizontal support structure is lower than the top elevation of the structural bottom plate, and the bottom elevation of the horizontal support structure is higher than the bottom elevation of the structural bottom plate; Step 2: After the horizontal support structure forms a complete support force system, excavate the soil to the excavation surface, pour the structural bottom plate cushion layer, and pour the concrete of the structural bottom plate. After the concrete of the structural bottom plate is poured to the height of the flow pipe, the concrete flows in different pouring areas through the flow holes; after the concrete pouring of the structural bottom plate is completed, the horizontal support structure forms a mesh support dispersed in the structural bottom plate.

[0010] Furthermore, the flow pipe is made of steel pipe with a wall thickness of d satisfy: d > D · f c / (2 f y ),in D is the outer diameter of the flow tube, f c is the concrete compressive strength of reinforced concrete beams, f y is the steel strength of the flow tube.

[0011] Furthermore, cooling pipes are provided at the top and bottom of the reinforced concrete beam, and the tops of the water inlets and outlets of the cooling pipes are higher than the upper surface of the structural bottom plate; In step 2, after the concrete pouring of the structural bottom plate is completed, the water inlet and outlet of the cooling pipe extend out of the structural bottom plate, and water is injected into the cooling water pipe, thereby effectively conducting and absorbing the hydration heat and controlling the occurrence of cracks in the structural bottom plate.

[0012] Due to the adoption of the above technical scheme, the present invention has the following advantages and positive effects compared with the prior art: the meshed reinforced concrete beams provided in the structural bottom plate provided in this embodiment can form strong constraints during the concrete pouring process of the structural bottom plate, effectively control the cracks in the structural bottom plate, and even after the concrete pouring is completed, the meshed reinforced concrete beams can also serve as the internal reinforcement structure of the structural bottom plate, thereby improving the overall bearing capacity of the structural bottom plate. Moreover, during the construction of the structural bottom plate, the reinforced concrete beams can provide horizontal support force as the horizontal support structure of the foundation pit, and the reinforced concrete beams are arranged within the height range of the structural bottom plate, which reduces the net height between the bottom horizontal support structure and the bottom excavation surface, reduces the cantilever height of the ground-connected wall, can effectively control the deformation, and reduce the safety risk of foundation pit construction. In addition, a horizontal flow pipe is arranged on the reinforced concrete beam, so that the concrete of the structural bottom plate can flow in different pouring areas through the flow hole during pouring, so that the structural bottom plate can be poured synchronously, and the quality of the structural bottom plate is improved. In addition, cooling pipes are installed in the reinforced concrete beams, which can effectively conduct and absorb hydration heat during the construction of ultra-thick structural bottom plates, control the occurrence of cracks in the structural bottom plates, and significantly improve the construction quality of the structural bottom plates. In addition, by pouring reinforced concrete beams in the structural bottom plates, one less support can be removed during the backbuilding process, further saving construction time and improving the overall progress of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of a longitudinal slope surface of a structural bottom plate in one embodiment of the present invention; Figure 2 It is a schematic diagram of the longitudinal slope of a reinforced concrete beam in one embodiment of the present invention.

[0014] The numbers in the figure are as follows: 1-ground-connected wall; 2-horizontal supporting structure; 3-reinforced concrete beam; 4-structural bottom plate; 5-flow pipe; 6-reinforced partition; 7-flow hole; 8-reinforcement ring; 9-horizontal reinforcement rib; 10-support ring; 11-connector; 12-cooling pipe. DETAILED DESCRIPTION

[0015] The following is a further detailed description of a structural base plate and a construction method thereof provided by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer in conjunction with the following description. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0016] Embodiment 1

[0017] Combination Figure 1As shown, the structural base plate 4 provided in this embodiment includes a plurality of horizontal reinforced concrete beams 3 arranged inside, and the reinforced concrete beams 4 are arranged vertically and horizontally in a cross-arranged manner to form a grid structure. In the earthwork construction of the structural base plate, the grid structure serves as a horizontal support structure for the foundation pit. Of course, the structural base plate also includes conventional structures such as concrete covering the reinforced concrete beams and a cushion layer at the bottom. The difference between the structural base plate in this embodiment and the conventional base plate is that when setting the horizontal support of the foundation pit, the lowest level support is set at a position inside the structural base plate, thereby reducing the net height between the lowest level support and the excavation surface of the soil of the structural base plate, thereby reducing the deformation of the ground-connected wall. After the structural base plate is cast, the internal mesh-like reinforced concrete beams will serve as the internal reinforcement structure of the structural base plate, thereby improving the overall bearing capacity of the structural base plate.

[0018] like Figure 1 As shown, the thickness of the structural bottom plate 4 is 5.7m, and the height of the reinforced concrete beam 3 reaches 1m. When the concrete of the structural bottom plate is poured to the bottom of the reinforced concrete beam, the cross-shaped reinforced concrete beam 3 divides the pouring area into multiple pouring bins, so that the concrete between different pouring bins cannot flow to each other, which will affect the integral pouring of the structural bottom plate concrete. Based on this, Figure 2 As shown, a horizontal flow tube 5 is provided on the reinforced concrete beam 3, and a reinforcing partition 6 is provided inside the flow tube 5 to form a flow hole 7. After the concrete of the structural base plate is poured to the height of the flow tube, the concrete flows in different casting bins through the flow holes, thereby solving the problem caused by the inability of concrete between casting bins to flow mutually.

[0019] Due to the provision of the flow tube 5, the reinforced concrete beam 3 may have a weak stress point at the flow tube, which is not conducive to the stability of the reinforced concrete beam as a horizontal supporting structure of the foundation pit. Based on this, in this embodiment, a reinforcing ring 8 is provided around the flow tube. The reinforcing ring 8 includes longitudinal bars and stirrups. The longitudinal bars are consistent with the length direction of the flow tube and are arranged at intervals along the circumferential direction of the flow tube. The stirrups are arranged around the longitudinal bars. Preferably, horizontal reinforcing ribs 9 are provided on both the upper and lower sides of the flow ring to further enhance the bending resistance of the reinforced concrete beam at the flow tube. More preferably, the flow tube is made of steel pipe with a wall thickness of d satisfy: d > D · f c / (2 f y ),in D is the outer diameter of the flow tube, f c is the concrete compressive strength of reinforced concrete beams, f y is the steel strength of the flow tube.

[0020] When the steel bars of the reinforced concrete beam are tied, the flow pipe is fixed together. In order to facilitate the fixing of the flow pipe, a bracket is arranged below the flow pipe. For example, the bracket includes a support ring 10 and a connector 11. The support ring can be an arc-shaped steel bar or an arc-shaped plate. The connector can be a connecting steel bar or a connecting rod. The connector can be fixed to the longitudinal bars and stirrups of the reinforced concrete beam. The top of the connector is fixed to the support ring, and the support ring supports the flow pipe. When pouring concrete of the reinforced concrete beam, the flow pipe and the bracket are poured into the concrete together.

[0021] In a specific embodiment, cooling pipes 12 are also provided at the top and bottom of the reinforced concrete beam. The cooling pipes can be made of FRP fiber pipes or steel pipes, which can ensure strength and avoid being damaged during the concrete pouring process, and at the same time can improve the tensile strength of the reinforced concrete beam. The main function of the cooling pipe is that when pouring the concrete of the structural bottom plate, cold water can be injected into the cooling pipe to cool the structural bottom plate. Since the thickness of the structural bottom plate reaches 5.7 meters, by providing two cooling pipes in the reinforced concrete beam, the effect of cooling the structural bottom plate can be achieved, thereby controlling the temperature difference between the inside and the outside.

[0022] As an example, in the construction of a certain project, the basement is 28.7 meters deep and designed for four floors. The structural bottom plate 4 adopts a pile foundation-raft structure. The structural bottom plate of the tower is 5500 mm thick (6000-6300 mm in the giant column area and 8700 mm at the deepest point), and the podium bottom plate is 1300 mm thick. The cushion layer is 200 mm C20 concrete, and the structural bottom plate is high-strength C50 concrete. A total of 6 horizontal support structures 2 are set. The 6th horizontal support structure is also called the lowest horizontal support structure, also called reinforced concrete beam. The horizontal support structure is connected to the purlin to provide support for the ground-connected wall 1. The height range of the lowest horizontal support structure is set within the height range of the structural bottom plate. During the excavation of the soil under the lowest horizontal support structure and the concrete pouring of the structural bottom plate, the lowest horizontal support structure provides horizontal support force. When pouring concrete for the structural slab, the lowest level support structure is poured into the structural slab as part of the structural slab, forming a mesh reinforcement structure in the structural slab to improve the overall performance of the slab and reduce the amount of concrete poured in the structural slab. At the location where the podium is set, a podium slab is set. The podium slab can be constructed first, and the lowest level support structure can be transmitted through the podium slab before the structural slab is constructed.

[0023] Embodiment 2

[0024] This embodiment provides a construction method of the structural base plate described in Embodiment 1, comprising the following steps: Step 1: Carry out foundation pit construction and complete the construction of the bottom horizontal support structure, which is a reinforced concrete beam 3 arranged vertically and horizontally, and the top elevation of the horizontal support structure is lower than the top elevation of the structural bottom plate, and the bottom elevation of the horizontal support structure is higher than the bottom elevation of the structural bottom plate; Step 2: After the horizontal support structure forms a complete support force system, excavate the soil to the excavation surface, pour the structural bottom plate cushion layer, and pour the concrete of the structural bottom plate to cover the horizontal support structure. After the concrete of the structural bottom plate is poured, the horizontal support structure forms a mesh support dispersed in the structural bottom plate, which can effectively reduce the deformation and temperature cracks of the bottom plate and ensure the long-term stability and safety of the structure.

[0025] In a specific embodiment, a horizontal flow tube is provided on the reinforced concrete beam, and a reinforcing partition is provided inside the flow tube to form a flow hole. In step 2, after the concrete of the structural bottom plate is poured to the height of the flow tube, the concrete flows through the flow hole in different pouring bins, thereby solving the problem caused by the concrete between the pouring bins not being able to flow to each other.

[0026] In a specific embodiment, cooling pipes are also provided at the top and bottom of the reinforced concrete beam. In step 2, after the concrete of the structural bottom plate is poured, the water inlet and outlet of the cooling pipe extend out of the structural bottom plate, and water is injected into the cooling water pipe, thereby effectively conducting and absorbing the hydration heat, controlling the generation of cracks in the structural bottom plate, and significantly improving the construction quality of the structural bottom plate.

[0027] In a specific embodiment, in order to improve the stress-bearing performance of the structural base plate, the surface of the bottom horizontal support structure is roughened and reinforced, and key connections and other pre-embedded methods are used at key locations to enhance the structural synergy effect.

[0028] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0029] The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A structural base plate, characterized in that: The structural bottom plate includes a plurality of horizontal reinforced concrete beams arranged inside, and the reinforced concrete beams are arranged vertically and horizontally to form a grid structure; during the construction of the structural bottom plate, the grid structure serves as the horizontal support structure of the bottom layer of the foundation pit; when the concrete of the structural bottom plate is poured, the grid structure is poured inside the structural bottom plate; after the construction of the structural bottom plate is completed, the grid structure serves as the internal reinforcement structure of the structural bottom plate; A horizontal flow pipe is arranged in the reinforced concrete beam, and a reinforcing partition is arranged in the flow pipe to form flow holes, which are used to make the concrete flow in different pouring areas after the concrete of the structural bottom plate is poured to the height of the flow pipe.

2. The structural base plate according to claim 1, characterized in that: The flow tube is made of steel pipe with a wall thickness of d satisfy: d > D · f c / (2 f y ),in D is the outer diameter of the flow tube, f c is the concrete compressive strength of reinforced concrete beams, f y is the steel strength of the flow tube.

3. The structural base plate according to claim 1, characterized in that: A reinforcement ring is arranged around the flow hole, and the reinforcement ring includes longitudinal reinforcement and stirrups. The longitudinal reinforcement is consistent with the length direction of the flow tube and is arranged at intervals along the circumferential direction of the flow tube. The stirrups are arranged around the longitudinal reinforcement.

4. The structural base plate according to claim 1, characterized in that: A bracket is arranged below the flow pipe, and the bracket comprises a support ring and a connecting piece, the connecting piece is fixed to the longitudinal reinforcement and stirrups of the reinforced concrete beam, the top of the connecting piece is fixed to the support ring, and the support ring supports the flow pipe.

5. The structural base plate according to claim 1, characterized in that: Cooling pipes are also provided at the top and bottom of the reinforced concrete beam. The tops of the water inlet and outlet of the cooling pipes are higher than the upper surface of the structural base plate, so as to absorb hydration heat by conducting injected water when pouring concrete of the structural base plate.

6. The construction method of the structural base plate according to claim 1, characterized in that: The steps include: Step 1: Carry out foundation pit construction and complete the construction of the bottom horizontal support structure. The horizontal support structure is a reinforced concrete beam arranged vertically and horizontally. The top elevation of the horizontal support structure is lower than the top elevation of the structural bottom plate, and the bottom elevation of the horizontal support structure is higher than the bottom elevation of the structural bottom plate; Step 2: After the horizontal support structure forms a complete support force system, excavate the soil to the excavation surface, pour the structure bottom plate cushion layer, and pour the concrete of the structure bottom plate. After the concrete of the structure bottom plate is poured to the height of the flow pipe, the concrete flows in different pouring areas through the flow holes; After the concrete pouring of the structural base plate is completed, the horizontal support structure forms a mesh support dispersed in the structural base plate.

7. The construction method of the structural bottom plate according to claim 6, characterized in that: The flow tube is made of steel pipe with a wall thickness of d satisfy: d > D · f c / (2 f y ),in D is the outer diameter of the flow tube, f c is the concrete compressive strength of reinforced concrete beams, f y is the steel strength of the flow tube.

8. The construction method of the structural bottom plate according to claim 6, characterized in that: Cooling pipes are also provided at the top and bottom of the reinforced concrete beam, and the tops of the water inlets and outlets of the cooling pipes are higher than the upper surface of the structural bottom plate; In step 2, after the concrete pouring of the structural bottom plate is completed, the water inlet and outlet of the cooling pipe extend out of the structural bottom plate, and water is injected into the cooling water pipe, thereby effectively conducting and absorbing the hydration heat and controlling the occurrence of cracks in the structural bottom plate.

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