A construction method for supporting structure in cast-in-place reinforced concrete foundation pit

Abstract

A construction method for a cast-in-place reinforced concrete foundation pit support structure, the steps of which include the following: 1) dividing the internal support structure into a number of construction units; 2) batch processing the unit steel bar components required for the construction units; 3) while performing step 2), constructing the cushion layer of the foundation pit support structure; 4) hoisting the unit steel bar components onto the cushion layer, and connecting the two ends of adjacent unit steel bar components together; 5) supporting formwork; 6) pouring concrete; 7) disassembling each unit steel bar component of the poured concrete into independent sections, and then hoisting it out of the foundation pit to complete the demolition. The support structure of the present invention has high rigidity, avoids environmental pollution caused by blasting, rope sawing, and mechanical demolition, and the steel cage and embedded parts connecting plate can be processed into a whole in the factory. At the same time, the segmented construction method is adopted to improve the construction and demolition efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of building engineering construction, and in particular to a construction method for a support structure in a cast-in-place reinforced concrete foundation pit. Background Art

[0002] With the rapid development of my country's economy, the scale of urban construction continues to expand. High-rise and super-high-rise buildings are being built around existing buildings, and the depth of foundation pit excavation is increasing. Therefore, the technical requirements for deep foundation pit excavation are getting higher and higher. The support of deep foundation pits must not only ensure the safety and stability of the slopes during construction, and ensure the safety of surrounding buildings, underground pipelines, surrounding roads, etc., but also meet the normal construction of the projects under construction and the requirements for foundation pit deformation control. It is the focus of research on deep foundation pit support engineering. At present, deep foundation pit support adopts the form of vertical support plus horizontal internal support. There are many horizontal internal support concrete structures and steel structures, all of which are completed through overall construction on site. The on-site workload is large, the rigidity of the concrete internal support structure is large, and the construction period is long. When dismantling, the internal support structure is generally dismantled by blasting, concrete demolition, etc., with low dismantling efficiency and large environmental pollution. To this end, a mechanical connection segmented construction method for cast-in-place reinforced concrete foundation pit internal support is invented to achieve fast dismantling of the foundation pit internal support without environmental pollution. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a mechanical connection segmented construction method for supports in a cast-in-place reinforced concrete foundation pit. By using this construction method, the problems of slow support removal speed and environmental pollution caused by removal construction in the existing concrete support construction methods can be solved.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is a construction method of a cast-in-place reinforced concrete foundation pit support structure, the steps of which include the following: 1) dividing the concrete support structure into several construction units; 2) batch processing the unit steel bar components required for the construction units; 3) while performing step 2), the construction of the cushion layer of the foundation pit support structure is carried out; 4) hoisting the unit steel bar components onto the cushion layer, and arranging them in series along the cushion layer length in sequence; then connecting the two ends of the adjacent unit steel bar components together in a detachable manner to form a steel skeleton of the support structure; 5) supporting the formwork; 6) pouring concrete so that each group of unit steel bar components becomes a reinforced concrete unit, and the detachable connection of the unit steel bar components is located on the outside of the poured concrete; 7) digging away the cushion layer as the foundation pit is excavated, and after the foundation pit excavation is completed and the replacement support construction is completed, the connection of the reinforced concrete unit is removed, so that each reinforced concrete unit becomes an independent section structure, and then each section of the reinforced concrete unit is hoisted out of the foundation pit to complete the removal. The cushion layer is a concrete structure, a rammed earth structure or a brick-concrete structure.

[0005] The unit steel bar assembly includes a steel cage and connecting plates arranged at both ends of the steel cage; the connecting plates include square steel plates, and the steel cage is connected to the square steel plates; a plurality of through holes are opened on the square steel plates located on both sides of the steel cage; the square steel plates of adjacent unit steel bar assemblies are connected by bolts.

[0006] The present invention provides a method for constructing a cast-in-place reinforced concrete support structure in a foundation pit. The concrete support is divided into construction units in advance according to the lifting capacity of the on-site lifting equipment, and the steel bars of the divided construction units are placed in a factory to batch-produce unit steel bar assemblies with connecting plates. During construction, the unit steel bar assemblies only need to be connected together by bolts, and then the concrete is poured to complete the construction of the support structure. When the foundation pit is excavated, the cushion layer is removed. After the foundation pit excavation is completed and the support is replaced, the high-strength bolts at the connecting plates can be removed according to the on-site deployment to achieve the rapid and segmented dismantling of the support structure in the foundation pit. This fundamentally solves the problems of slow support removal and environmental pollution caused by the removal construction in the existing concrete support construction method. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 , schematic diagram of the side view of the supporting structure.

[0008] Figure 2 , schematic diagram of the side view of the supporting structure after the formwork is set up.

[0009] Figure 3 , schematic diagram of the cross-sectional structure of the support structure after pouring concrete. DETAILED DESCRIPTION

[0010] In order to make the content of the present invention more clearly understood, the following is a detailed description of the embodiments of the present invention in conjunction with the accompanying drawings. Figure 1 , the present invention is further described in detail.

[0011] First, according to the size of the foundation pit, the lifting capacity of the lifting equipment, and the size, quantity and weight of the steel bars of the supporting structure in the foundation pit, the internal supporting structure is divided into sections, and the supporting beams or supporting columns are divided into several construction units.

[0012] According to the length of the divided construction unit, the overall processing of the unit steel bar assembly consisting of the steel cage 2 and the connecting parts of the construction unit is carried out in batches in the factory. The unit steel bar assembly of each construction unit includes a steel cage 2 and connecting parts located at both ends of the steel cage. The connecting parts include a connecting plate 3 and an anchor steel bar 4. The connecting plate is a square steel plate. Since it needs to have sufficient bending resistance and can transmit axial pressure, a number of reinforcing ribs can be set on the connecting plate to improve its bending strength. The two ends of the steel cage 2 are fixed on the connecting plate. The connecting plates on both sides of the steel cage are provided with connecting holes. The steel cage includes steel bars and stirrups. The steel cage is formed by fixing the two ends of the steel bars of the required size to the steel bar joints on the connecting plate through a connecting device, then tying stirrups on the steel bars, and then tying stirrups on the outside of the steel bars. The steel cage is fixed together with the connecting parts to form a unit steel bar assembly.

[0013] The anchoring steel bars are staggered with the steel bars of the steel cage, and the anchoring steel bars strengthen the combination with the concrete 5. The steel cage and the connecting plate can be connected by welding, or by a detachable method, such as tying or setting a joint on the connecting plate, and then connecting to the steel cage through a sleeve.

[0014] While processing the unit steel bar components, the cushion layer 1 of the internal support structure is constructed. The cushion layer is generally a concrete structure, rammed earth structure, brick-concrete structure or other easily removable structure with a certain width and thickness. The width of the cushion layer structure is greater than or equal to the width of the internal support structure.

[0015] When the cushion layer is completed, it is positioned and laid out, and the unit steel bar assemblies transported to the construction site are hoisted onto the cushion layer, and the unit steel bar assemblies are arranged in series so that the connecting plates at both ends of each unit steel bar assembly are placed close to each other. After the position of the unit steel bar assemblies is fixed, the connecting plates of adjacent unit steel bar assemblies are connected together by high-strength bolts 6 to form a steel bar structure that supports the entire structure. By hoisting, installing and fixing the unit steel bar assemblies that have been processed in batches in the factory on site, the steps of on-site steel bar tying construction are saved, so that the processing of the unit steel bar assemblies can be carried out before or simultaneously with the cushion layer construction, shortening the construction time.

[0016] After the unit steel bar assembly is hoisted and installed, the formwork 7 is supported, and the bolts are located on the outside of the formwork; then concrete 5 is poured, and the unit steel bar assembly becomes a reinforced concrete unit after the concrete is poured, and the bolts at the connecting plate are located on the outside of the reinforced concrete unit. Then the foundation pit is excavated. During the excavation of the foundation pit, the cushion layer is removed along with the excavation of the foundation pit, and only the supporting structure in the foundation pit is left to support the foundation pit. After the excavation of the foundation pit is completed and the replacement of the support construction is completed, the supporting structure is dismantled. During the dismantling, the bolts at the connecting plate of the reinforced concrete unit are first unscrewed. Since there is no concrete at the bolts of the connecting plate, when the bolts are unscrewed, the supporting structure becomes a segmented reinforced concrete unit. Then the segmented reinforced concrete units are hoisted out of the foundation pit one by one by the lifting equipment, that is, the supporting structure is completely dismantled. The supporting structure is designed and constructed in sections, which saves a lot of demolition time and demolition volume compared with the demolition of the overall steel bar binding construction in the past, and protects the environment.

[0017] The invention discloses a mechanical connection segmented construction method for supports in a cast-in-place reinforced concrete foundation pit, which is convenient to construct and has strong feasibility. It solves the problems of slow support removal speed and environmental pollution caused by removal construction in the existing cast-in-place concrete support construction method, and has good prospects for promotion and application.

Claims

1. A construction method for a cast-in-place reinforced concrete foundation pit support structure, the steps comprising: 1) Divide the concrete internal support structure into several construction units; 2) Batch processing of unit steel bar components required for construction units, the unit steel bar components comprising a steel bar cage and connecting plates arranged at both ends of the steel bar cage; the connecting plates comprising square steel plates, the steel bar cage being connected to the square steel plates; a plurality of through holes being opened on the square steel plates located on both sides of the steel bar cage; a steel bar joint being fixedly arranged at the position of the steel bar of the steel bar cage corresponding to the steel bar of the steel bar cage, the steel bar joint being connected to the steel bar cage through a sleeve with a thread; a plurality of anchoring steel bars being fixedly arranged on the square steel plates; 3) While carrying out step 2), the cushion layer of the supporting structure in the foundation pit is constructed; 4) Hoist the unit steel bar assemblies onto the cushion layer and arrange them adjacent to each other in series along the cushion layer length; then connect the square steel plates at both ends of the adjacent unit steel bar assemblies together in a detachable manner by bolts to form a steel bar skeleton of the supporting structure; 5) Setting up formwork; 6) Concrete pouring makes each unit steel bar assembly become a reinforced concrete unit, and the detachable connection of the unit steel bar assembly is located on the outside of the poured concrete; 7) As the foundation pit is excavated, the cushion layer is excavated away. After the foundation pit excavation is completed and the support replacement construction is completed, the connection between the reinforced concrete units is removed to make each reinforced concrete unit an independent section structure. Then each section of the reinforced concrete unit is hoisted out of the foundation pit to complete the removal.

2. The construction method of the cast-in-situ reinforced concrete foundation pit support structure according to claim 1, characterized in that The cushion layer is a concrete structure, a rammed earth structure or a brick-concrete structure.

3. The construction method of the cast-in-situ reinforced concrete foundation pit support structure according to claim 1, characterized in that The cushion layer is a concrete layer, a rammed earth layer or a brick-concrete structure layer.

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