Post-cast strip-free structure suitable for subway air shaft accessory and construction method

Abstract

According to the post-cast strip-free structure suitable for the subway air shaft accessory and the construction method, an air shaft main body and an accessory structure are optimized, on the basis that stress of an accessory supporting structure is guaranteed, an underground diaphragm wall or a fender post at a connecting hole is excavated and broken at the same time, the risk of violation of a post-cast strip structure or construction can be avoided, and the construction efficiency is improved. And by optimizing the corresponding main body and auxiliary construction process, the construction difficulty is reduced, and the construction safety is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of subway engineering construction, and particularly relates to a post-pouring belt-free structure applicable to subway air shaft appendages and a construction method thereof. Background Art

[0002] The connection part between the air shaft appendage structure and the main structure of the subway project is usually wide, and the opening part at the connection needs to break the diaphragm wall or retaining pile of the main structure's retaining structure. In the conventional design, the support of the appendage structure needs to support on the main structure's retaining structure. When constructing the connection part between the two, a post-pouring belt needs to be set in the appendage structure, with cumbersome procedures and a long construction period. In actual construction, in order to avoid leaving a post-pouring belt, the construction unit is prone to illegally break the diaphragm wall or retaining pile of the main structure from bottom to top, resulting in the bottom of the main structure's retaining diaphragm wall or retaining pile and the capping beam being suspended, with extremely high safety risks. Summary of the Invention

[0003] In order to overcome the technical problem that when constructing the connection part between the air shaft appendage structure and the main structure in the prior art, a post-pouring belt needs to be set in the appendage structure, resulting in cumbersome procedures and a long construction period, the invention provides a post-pouring belt-free structure applicable to subway air shaft appendages and a construction method thereof, solving the above technical problems.

[0004] A post-pouring belt-free structure applicable to subway air shaft appendages, when designing the support of the main structure, the appendage capping beam is widened to make it exceed the width of the diaphragm wall by not less than 500 mm, and a concrete pier is set at the top of the main structure to support the capping beam. The concrete pier is connected to the capping beam and the main roof slab, showing a shape, used to support the capping beam structure. After the subsequent diaphragm wall or retaining pile below the capping beam is cut, it can maintain self-stability and participate in the force, so that after the retaining structure at the connection part with the appendage is removed, the capping beam relies on the pier to support on the main structure. The quantity, size, and reinforcement of the concrete pier are determined by calculation. The original first concrete support system of the main structure is retained and participates in the force calculation of the appendage support together with the capping beam.

[0005] When designing the support of the appendage structure, the capping beam of the main structure is incorporated into the force of the appendage support structure, and the appendage capping beam is flush with the capping beam of the main structure. Adjust the position of the second and lower supports of the appendage so that the straight support can support at the position where the main structure slab / frame beam is located. When the position is difficult to adjust, a force transfer pier can be set on the top of the slab and beam, or supported by an inclined support on the non-opening part, so that the support avoids the position where the diaphragm wall at the connection between the appendage and the main structure needs to be opened.

[0006] The second and lower supports of the appendage are set at the positions of the main structure slab and beam, and can be directly supported on the main structure after the diaphragm wall or retaining pile is broken, without affecting the breaking of the diaphragm wall or retaining pile. When designing the appendage structure, only a deformation joint needs to be set at the connection part with the main structure, and there is no need to set a post-pouring belt.

[0007] A construction method for a post - cast - in - place strip - free structure applicable to the subway ventilation shaft annex, the construction method comprising the following steps:

[0008] S1: When constructing the main support structure, PVC pipes are embedded at the position of the concrete piers of the capping beam and steel bars are reserved. After the main construction is completed, concrete piers are constructed on the main roof. The anchorage of the concrete piers with the capping beam and the steel bars of the main roof meets the requirements. By means of the reserved PVC pipes, it is ensured that the concrete at the top of the piers is poured densely. An isolation material shall be set between the concrete piers and the main retaining structure and they shall not be connected;

[0009] S2: After the construction of the retaining structure of the annex part, the main capping beam and the first - layer concrete support are completed, during the downward excavation process, the 50 - m - long structure of the annex is divided into 2 sections. For each section, the main diaphragm wall of the opening part is broken synchronously with the excavation. For every 1 m - 2 m of excavation, the main diaphragm wall is cut into layers and blocks by a wire saw and transported out;

[0010] S3: For each layer of excavation, construct the second - layer support of the annex. The second - layer support of the annex is directly supported on the position of the partial roof of the main structure or the force - transfer pier on the top of the roof until the excavation of the annex part reaches the bottom;

[0011] S4: When constructing the annex structure, a deformation joint is set as required at the connection between the annex structure and the main structure.

[0012] Generally speaking, compared with the prior art through the above - mentioned technical solutions conceived by the present invention, the following beneficial effects can be achieved: The post - cast - in - place strip - free structure and construction method applicable to the subway ventilation shaft annex of the present invention, by optimizing the main body and annex structure of the ventilation shaft, on the basis of ensuring the force - bearing of the annex support structure, realizes that the diaphragm wall or retaining pile at the connection opening can be broken as it is excavated, which can avoid the risks of post - cast - in - place strip structure or construction violations. By optimizing the corresponding main body and annex construction processes, the construction difficulty is reduced and the construction safety is ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The following further elaborates in detail the specific implementation manners of the present invention in conjunction with the drawings, wherein:

[0014] Figure 1 is the plan view of the main body and annex structure of the ventilation shaft of the post - cast - in - place strip - free structure applicable to the subway ventilation shaft annex of the present invention;

[0015] Figure 2 is the cross - sectional view of the main body and annex structure of the ventilation shaft of the post - cast - in - place strip - free structure applicable to the subway ventilation shaft annex of the present invention;

[0016] In the figure: 1 - main capping beam, 2 - concrete pier, 3 - main diaphragm wall, 4 - PVC pipe, 5 - main concrete straight support, 6 - annex capping beam, 7 - second - layer support of the annex, 8 - deformation joint. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention relates to a post-cast strip-free structure applicable to the subway ventilation shaft annex. When designing the support of the main structure, the main crown beam 1 is widened from 1.4×1.0 m to 2 m×1.0 m, so that it exceeds the width of the main diaphragm wall 3 by 600 mm. Four concrete piers 2 with a size of 0.8 m×1.0 m are arranged at the top of the main structure. The concrete piers 2 are connected to the main crown beam 1 and are in a shape. After the main diaphragm wall 3 at the connection part with the annex is cut off, the main crown beam 1 can rely on the concrete piers 2 to be supported on the main structure. The reinforcement of the concrete piers 2 is determined by calculation. The two main concrete straight braces 5 of the first concrete support of the original main structure are retained and participate in the force calculation of the annex structure support together with the main crown beam 1.

[0018] When designing the support of the annex structure, the main crown beam 1 is incorporated into the force of the annex support structure. The annex crown beam 6 is flush with the main crown beam 1. The position of the second steel support 7 of the annex part is adjusted so that the second steel support 7 can support on the top plate position of the main structure. If the position is difficult to adjust, a force transfer pier is arranged on the top of the main structure top plate, and the pier model is not less than 0.6 m×0.6 m. It can also be supported by an inclined brace on the non-opening part, avoiding the position that needs to be opened at the connection between the annex and the main body, such as Figure 1 and Figure 2 shown, which are the plan view and cross-sectional view of the ventilation shaft main body and the annex structure.

[0019] When designing the annex structure, only a 20-mm deformation joint 8 needs to be set at the connection part with the main structure, and no post-cast strip is required.

[0020] The construction method of the post-cast strip-free structure applicable to the subway ventilation shaft annex provided by the present invention includes the following steps:

[0021] Step 1: When constructing the main diaphragm wall, the main crown beam 1 pre-buries a φ200-mm PVC pipe 4 and reserves connecting steel bars at the position of the concrete piers 2. After the main construction is completed, the concrete piers 2 are constructed on the main top plate. The reinforcement anchorage of the concrete piers 2 with the main crown beam 1 and the main top plate steel bars meets the requirement of 35d. When pouring the concrete at the top of the pier, it is poured through the reserved PVC pipe 4 to ensure the compactness of the top concrete. A separation material such as felt and geotextile needs to be set between the concrete piers and the main retaining structure, and the two are not connected;

[0022] Step 2: After the construction of the retaining structure, crown beam and the first concrete support of the annex part is completed, during the downward excavation process, the 50-m-long structure of the annex is divided into 2 sections. The main diaphragm wall 3 of the opening part of each section is broken synchronously with the excavation. For every 1 m - 2 m of excavation, the main diaphragm wall 1 is cut into layers and blocks by a wire saw and transported out;

[0023] Step 3: When constructing the support for each excavated layer, the second steel support 7 is directly jacked at the position of the partial top plate of the main structure or at the position of the force transfer pier on the top of the top plate until the excavation of the auxiliary part reaches the bottom;

[0024] Step 4: When constructing the auxiliary structure, a 20-mm deformation joint 8 is arranged as required at the connection between the auxiliary structure and the main structure.

Claims

1. A post - casting belt - free structure applicable to the annex of the subway ventilation shaft, characterized in that, The crown beam (1) of the air shaft main body is widened and concrete piers (2) are provided below. When designing the support of the main structure, the attached crown beam (6) is widened so that the width exceeding the main diaphragm wall (3) is not less than 500 mm. A concrete pier (2) is provided at the top of the main structure to support the capping beam. The concrete pier (2) is connected to the main capping beam (1) and the main roof slab, and is in the shape of When the main capping beam (1) is constructed, a PVC pipe (4) is embedded at the position of the concrete pier (2) and steel bars are reserved. An isolation material is provided between the concrete pier (2) and the main retaining structure, and the two are not interconnected; The second and lower supports of the air shaft attachment (7) are arranged at the position of the beam slab of the air shaft main structure, so that the second and lower supports can be directly supported on the position where the main structure slab or frame beam is located, and the support is avoided from the position where the enclosure structure at the connection between the attachment and the main body needs to be holed. Only deformation joints (8) need to be set at the connection part between the air shaft attachment structure and the main structure, and no post-cast strip is set. During construction, the main enclosure structure of the air shaft is demolished from top to bottom along with the excavation.

2. The post - cast strip - free structure applicable to the subway ventilation shaft annex according to claim 1, wherein, During construction, the main enclosure structure of the air shaft is demolished from top to bottom along with the excavation. The diaphragm wall or retaining pile of the holed part is demolished synchronously in layers and sections along with the excavation, and the excavation depth of each layer is 1 m - 2 m.

3. The construction method of a post - casting belt - free structure applicable to the subway ventilation shaft annex according to claim 1, wherein, This construction method includes the following construction steps: S1: When constructing the main support structure, PVC pipes (4) are embedded at the position of the concrete piers (2) of the main crown beam (1) and steel bars are reserved. After the main construction is completed, concrete piers (2) are constructed on the main roof. The concrete piers (2) are anchored with the main crown beam (1) and the main roof steel bars to meet the design requirements. The top concrete of the concrete piers (2) is ensured to be poured densely through the reserved PVC pipes (4). An isolation material is set between the concrete piers (2) and the main enclosure structure, and the two are not connected. S2: After the enclosure structure of the attached part, the main crown beam (1) and the first concrete support are constructed, during the downward excavation process, the 50 m long structure of the attachment is divided into 2 sections. The main diaphragm wall (3) of the holed part of each section is demolished synchronously along with the excavation. For every 1 m - 2 m of excavation, the main diaphragm wall (3) is cut into layers and blocks by a wire saw and transported out. S3: For every layer of excavation, the second support (7) of the attachment is constructed. The second support (7) of the attachment is directly supported on the position of the partial roof of the main structure or the force transfer pier at the top of the roof until the attached part is excavated to the bottom. S4: When constructing the attached structure, deformation joints (8) are set as required at the connection between the attached structure and the main structure.

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