Construction method of post-cast concrete of underground vertical structure column by top-down method

Abstract

The application relates to a post-poured concrete construction method for a column of an underground vertical structure by a reverse construction method, and particularly relates to the following steps: constructing a column head, installing longitudinal steel bars of a column body and a high-pressure grouting pipe; installing other structural steel bars; setting a mortar reverse ridge; installing a column body formwork and a supporting system, setting a vibrating hole and an exhaust hole; installing a concrete discharging pipe, setting a vibrating hole for vibration; after the vibrating hole at the top of the column body is closed, mainly performing concrete vibration through a concrete pouring opening of the last layer and the vibrating hole; performing non-pressure water test on the grouting pipe; curing the concrete, removing the formwork; performing ultrasonic detection on a construction joint interface position; performing high-pressure grouting; performing ultrasonic detection on the construction joint interface again; constructing the column body; closing a floor hole opening by the reverse construction method, and removing temporary supports one by one. The application has the advantages that the concrete is fully vibrated, the vibration efficiency is high, gas in the construction joint position is fully discharged, two construction joints are not generated, the construction cost is low, and the filling material at the construction joint position is safe and reliable.

Description

Technical Field

[0001] This invention relates to the field of civil engineering construction, specifically a reverse construction method for post-cast concrete in underground vertical structural columns. Background Technology

[0002] In reverse construction, the basement floor slab is constructed from top to bottom, requiring openings in the slab for material and machinery access. Basement structural columns cannot be completed in one go during slab construction. When pouring the zero-level slab structure, column reinforcement is pre-reserved, and the column heads of the next floor are poured. Construction then proceeds layer by layer downwards. After the basement raft slab is completed, the column bodies of each floor are constructed from bottom to top. In this reverse construction method, construction joints exist in the vertical load-bearing structural columns—the contact surface between the later-constructed column body and the earlier-constructed column head. Concrete shrinkage causes gaps at this contact surface, and insufficient vibration can easily lead to air bubble accumulation. Therefore, controlling the concrete pouring quality of underground vertical structural columns in reverse construction is crucial, especially at the construction joint where the column head meets the column body. This invention provides a method for post-pouring concrete in underground vertical structural columns in reverse construction, aiming to solve the problem of difficult quality control at the column head location in reverse construction.

[0003] Based on existing construction techniques, the main methods for constructing vertical structural columns using the reverse construction method are: Over-pouring: Concrete is poured using tamping holes or bell-shaped openings, extending the pouring surface beyond the construction joint by a minimum height of 300mm; Grouting: A gap of less than 50mm is left at the interface between the first poured column head and the subsequent poured column body, and then filled and compacted using a high-strength, non-shrink grout of a grade higher than the original structure. These methods have the following problems: ① Although the over-pouring height can meet the requirements, the over-pouring is limited to the pouring hole or vibratory tamping hole, and the pressure generated by the over-pouring concrete is insufficient to expel air bubbles from the construction joint; ② Although the grouting method uses high-strength, non-shrink grout, it artificially transforms one construction joint into two, increasing construction costs. Furthermore, the grout lacks aggregate components, making it difficult to guarantee overall strength, especially for super high-rise buildings with high requirements for vertical structural bearing capacity and deformation, and large component geometric dimensions. Summary of the Invention

[0004] The present invention aims to overcome the defects of the prior art and provide a method for post-cast concrete construction of underground vertical structural columns using the reverse construction method, thereby solving the problem of difficulty in controlling the concrete quality at the column head position of underground vertical structural columns using the reverse construction method.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0006] A method for constructing underground vertical structural columns using a reverse construction approach with post-cast concrete, characterized by comprising the following steps:

[0007] Step 1: When constructing the floor slab at the ground level, construct the column head, and at the same time reserve column body reinforcement bars, pre-embed steel bar sleeves, and pre-embed PVC pipes as concrete pouring holes and vibration holes. Construct each floor slab and the column head of the next floor in sequence from top to bottom.

[0008] Step 2: After the basement raft slab construction is completed, roughen the surface of the column head and column body of the lowest floor of the basement, and remove the PVC pipes and steel bar sleeves of the pre-embedded concrete pouring holes and vibration holes.

[0009] Step 3: Grind the surface of the steel pipe column inside the column. After the steel pipe column is ground, clean the roughened concrete surface.

[0010] Step 4: Install the longitudinal reinforcement bars of the column body; do not install them at the temporary opening locations yet.

[0011] Step 5: Install the high-pressure grouting pipe;

[0012] Step Six: Install other structural reinforcement bars and longitudinal reinforcement bars at temporary openings in the column;

[0013] Step 7: Use a high-pressure water gun again to clean the roughened surface inside the column;

[0014] Step 8: Install a mortar curb at the column base;

[0015] Step 9: Install column formwork and support system. Before installing the formwork, vibration holes should be set in the middle and top of the column, and venting holes should be set at the top of the column.

[0016] Step 10: Install the special concrete discharge pipe at the discharge hole position of the upper layer. The length of the discharge pipe is determined according to the floor height to ensure that the free fall height of the concrete does not exceed 1500mm. Place the square discharge hopper at the discharge hole position. When pouring through other discharge holes, move the discharge hopper into position in advance.

[0017] Step 11: During the concrete pouring process, in addition to vibrating the concrete through the vibration holes of the upper layer, it is also necessary to vibrate it through the vibration holes set at the column formwork position. At the same time, when using one pouring port for concrete pouring, other pouring ports can also be used as vibration holes.

[0018] Step 12: After the concrete vibration hole at the top of the column is sealed, the concrete is mainly vibrated through the concrete pouring port and vibration hole of the next layer. It is necessary to see concrete slurry overflowing from the vent hole of the column. Continue to pour concrete until the pouring hole and vibration hole are sealed tightly.

[0019] Step 13: Immediately after the concrete pouring is completed, conduct a pressureless water flow test on the grouting pipe to check for blockages. If any blockages are found, they should be cleared promptly.

[0020] Step Fourteen: Cur the concrete as required and remove the formwork at the specified time;

[0021] Step 15: Perform ultrasonic testing on the construction joint interface before high-pressure grouting and record the data;

[0022] Step 16: 14 days after the concrete pouring is completed, high-pressure grouting begins;

[0023] Step 17: After grouting is completed, use ultrasound to inspect the construction joint interface again. Compare the inspection data with the data before grouting to check whether the grouting is sufficient.

[0024] Step 18: Only after the test is passed can the construction of the column body of the next floor at the same location be carried out. Then repeat the above construction and testing process until all vertical structural columns are completed.

[0025] Step 19: Only after all the columns constructed in the reverse construction method have been completed, passed the tests, reached the standard strength, and the openings in the floor slabs constructed in the reverse construction method have been sealed can the temporary supports set up during the reverse construction method be removed one by one.

[0026] The method for constructing underground vertical structural columns using the reverse construction method is characterized in that: in step four, the longitudinal reinforcement of the column body is installed, but the longitudinal reinforcement at the temporary opening inside the column body is not installed temporarily. The opening is used to install a high-pressure grouting pipe and structural reinforcement.

[0027] The aforementioned method for constructing underground vertical structural columns using the reverse construction method is characterized by the following: In step five, a high-pressure grouting pipe is used. The grouting pipe has an outer diameter of 6mm, a wall thickness of 1.2mm, a spacing of 320mm between pipes, a spacing of 150mm between grouting holes on the pipe, and a hole diameter of 2mm. The grouting holes are sealed with a polyvinyl chloride film. The grouting pipe is fixed to the column head surface at the specified spacing. Fixing the grouting pipe to the column head surface prevents displacement of the grouting pipe during concrete pouring and vibration, thus affecting the grouting effect. The film sealing of the grouting holes prevents concrete slurry from clogging the grouting pipe and does not affect the high-pressure grouting.

[0028] The method for constructing underground vertical structural columns using the reverse construction method is characterized in that: in step sixteen, epoxy resin is used as the grouting material, the strength of the grouting material needs to be one grade higher than the strength of the column, the grouting pressure is 2 MPa, the grouting sequence is from one side to the other side, and epoxy resin flows out fully from the other end of each pipe. The other end of the grouting pipe is first sealed by electric welding, and then the grouting machine is removed from the grouting head position. A check device is installed inside the grouting head to ensure that the epoxy resin does not flow back.

[0029] The beneficial effects of this invention are as follows: As can be seen from the above technical solution, this application provides a method for post-cast concrete construction of underground vertical structural columns using the reverse construction method. This invention mainly addresses issues related to whether concrete vibration is sufficient, vibration efficiency, whether air bubbles are expelled at the construction location, the number of construction joints, construction cost, the safety and reliability of the filling material at the construction joints, the bearing capacity and deformation requirements of the vertical structure, the size of the vertical load-bearing components, and the quality inspection of construction joints. This invention ensures sufficient concrete vibration, high vibration efficiency, and complete expulsion of air from the construction joints, preventing the formation of two construction joints. It also results in low construction cost, safe and reliable filling materials at the construction joints, and ensures the quality of the construction joints through experimental testing. This provides an effective connection for the vertical load-bearing components in the reverse construction method and is suitable for reverse construction projects with high requirements for the bearing capacity and deformation of the vertical structure and large component geometric dimensions. Attached Figure Description

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0031] Figure 1 This is an overall schematic diagram;

[0032] Figure 2 Axial view Figure 1 ;

[0033] Figure 3 This is a top-down view diagram;

[0034] Figure 4 This is a schematic diagram of the pouring process;

[0035] Figure 5 Axial view Figure 2 . Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection claimed in this application.

[0037] like Figure 1-5 As shown: A reverse construction method for post-cast concrete in underground vertical structural columns, the specific steps are as follows:

[0038] 1) When constructing the ground floor slab, construct 100mm column heads, and simultaneously reserve column reinforcement bars, embed steel sleeves, and embed PVC pipes of specific dimensions as concrete pouring holes and vibration holes. Construct each floor slab and the column heads of the next floor sequentially from top to bottom. Using PVC pipes as embedded parts makes removal easier.

[0039] 2) After the basement raft slab construction is completed, the surface of the column heads and the raft slab at the lowest level of the basement should be roughened, and the PVC pipes and steel bar sleeves of the pre-embedded concrete pouring holes and vibration holes should be removed. Roughening the concrete surface can remove the laitance on the concrete surface, making the concrete at the junction of the old and new concrete dense and firmly bonded.

[0040] 3) Grind the surface of the internal steel pipe column. After grinding, clean the roughened concrete surface. Grinding the steel pipe column removes rust and slag, allowing for better bonding with the concrete.

[0041] 4) Install the longitudinal reinforcement bars of the column body. Do not install the longitudinal reinforcement bars at the temporary openings inside the column body for the time being. These openings are more convenient for the installation of high-pressure grouting pipes and structural reinforcement bars.

[0042] 5) Install high-pressure grouting pipes. The outer diameter of the grouting pipe is 6mm, the wall thickness is 1.2mm, the spacing between grouting pipes is 320mm, the spacing between grouting holes on the grouting pipe is 150mm, and the diameter of the grouting holes is 2mm. The grouting holes must be sealed with a polyvinyl chloride film. Fix the grouting pipes to the column head surface according to the specified spacing. Fixing the grouting pipes to the column head surface can prevent the grouting pipes from shifting during concrete pouring and vibration, which would affect the grouting effect. The film sealing of the grouting holes can prevent concrete slurry from clogging the grouting pipes, while not affecting high-pressure grouting.

[0043] 6) Install other structural reinforcement bars and longitudinal reinforcement bars at temporary openings in the column body;

[0044] 7) Clean the roughened surface inside the column again with a high-pressure water gun. This final high-pressure water cleaning ensures effective bonding between the old and new concrete surfaces.

[0045] 8) Install mortar curbs at the column base to prevent concrete slurry from flowing out during concrete vibration. This can prevent column base rot.

[0046] 9) Install column formwork and support system. Before installing the formwork, vibratory holes with dimensions of 150mm*250mm should be set in the middle and top of the column, with a spacing of no more than 900mm. Vent holes should be set at the top of the column. Setting vibratory holes at the middle and top of the column can significantly improve the vibration efficiency and quality of concrete, ensuring the quality of the column concrete, especially for large and tall columns.

[0047] 10) Install the specially designed concrete discharge pipe at the discharge hole position of the previous layer. The length of the discharge pipe is determined according to the floor height to ensure that the free fall height of the concrete does not exceed 1500mm. Place the square discharge hopper at the discharge hole position. When pouring through other discharge holes, move the discharge hopper into position in advance. The discharge pipe can prevent segregation caused by high drop during concrete pouring, and the movable square discharge hopper can improve concrete delivery.

[0048] 11) During concrete pouring, in addition to vibration through the upper-layer vibration holes, vibration is also required through the vibration holes set at the column formwork locations. Furthermore, when using one pouring port, the other pouring ports can also serve as vibration holes. When the concrete is about to reach the vibration hole, the vibration hole is sealed in advance using a tongue-and-groove formwork and secured with nails. Finally, it is reinforced with independent diagonal braces before continuing concrete pouring.

[0049] 12) After the concrete vibration holes at the top of the column are sealed, concrete vibration is mainly carried out through the concrete pouring port and vibration holes of the previous layer. Concrete slurry should be observed overflowing from the column's vent holes. Continue pouring concrete until the pouring holes and vibration holes are completely sealed. Sealing the concrete pouring holes primarily improves the concrete quality of the construction joint section through this over-pouring method.

[0050] 13) Immediately after the concrete pouring is completed, conduct a pressureless water flow test on the grouting pipe to check for blockages. If any blockages are found, they should be cleared promptly.

[0051] 14) Perform concrete curing as required and remove the formwork at the specified time. Effective concrete curing ensures normal hardening and strength development of the concrete;

[0052] 15) Before high-pressure grouting, perform ultrasonic testing on the interface of the construction joint and record the data. This data will serve as the theoretical basis for checking whether the joint filling is adequate.

[0053] 16) Fourteen days after concrete pouring, high-pressure grouting begins. The grouting material used is epoxy resin (Sikadur 52TH). The strength of the grout needs to be one grade higher than the column strength. The grouting pressure is 2 MPa. The grouting sequence proceeds from one side to the other. Each pipe is grouted until epoxy resin flows fully out at the other end. The other end of the grouting pipe is first sealed by electric welding. Then, the grouting machine is removed from the grouting head. The grouting head is equipped with a check valve to ensure that the epoxy resin does not flow back. The epoxy resin's strength is one grade higher than the column body, allowing for better effective connection to the column. The sealing of the grouting pipes ensures better filling effect of the epoxy resin.

[0054] 17) After grouting is completed, use ultrasonic testing to inspect the construction joint interface again. Compare the test data with the data before grouting to check whether the grouting is sufficient.

[0055] 18) Only after the test is passed can the construction of the column body of the next floor at the same location be carried out. Then repeat the above construction and test process until all vertical component columns are completed.

[0056] 19) Only after all the columns constructed in the reverse construction method have been completed, passed the tests, reached the standard strength, and the openings in the floor slabs constructed in the reverse construction method have been closed can the temporary supports set up in the reverse construction method be removed one by one.

[0057] Compared to the over-pouring method, this invention firstly sets up multiple pouring holes and vibration holes based on the column size, and also sets multiple vibration holes in the middle and top of the column to ensure that the concrete is fully vibrated, especially at the construction joint where the first-poured column head meets the subsequent-poured column body, which greatly improves vibration efficiency. Secondly, vent holes are set at the top formwork of the column body to allow air at the construction joint to be expelled as much as possible during the over-pouring process in the pouring and vibration holes. Compared to the grouting method, even if the grouting method leaves a gap of less than 50mm for secondary grouting, the lack of vibration holes on the side of the column during the first concrete pouring, relying solely on the limited pouring and vibration holes set in the upper layer, makes it difficult to fully vibrate the concrete, especially at the top of the column. In addition, the grouting method artificially turns one construction joint into two construction joints, greatly increasing the difficulty of concrete quality control and construction costs at the construction joint location. In addition, high-flowability, non-shrink grouting materials contain no aggregate components and lack extensive application experiments, making them unsuitable for super high-rise projects with high requirements for vertical structural bearing capacity and deformation, and large component geometric dimensions. Compared with the super-grouting method and the grouting method, this invention pre-embeds grouting pipes at the construction joint location and performs high-pressure grouting 14 days after the concrete pouring is completed. During the high-pressure grouting process, the gas at the construction joint location is discharged through the grouting pipes and filled with epoxy resin of a higher strength grade. The quality of the construction joint is then ensured through ultrasonic testing.

[0058] Compared to existing construction technologies, this invention primarily addresses issues related to the adequacy of concrete vibration, vibration efficiency, air bubble removal at construction sites, the number of construction joints, construction costs, the safety and reliability of the filling material at construction joints, the load-bearing capacity and deformation requirements of the vertical structure, the size of the vertical load-bearing components, and the quality inspection of construction joints. This invention ensures thorough concrete vibration, high vibration efficiency, and complete air removal at construction joints, eliminating the need for double construction joints. It also results in low construction costs, safe and reliable filling materials at construction joints, and ensures the quality of construction joints through experimental testing. This provides an effective connection for vertical load-bearing components in reverse construction methods and is suitable for reverse construction projects with high requirements for vertical structural load-bearing capacity and deformation, and large component geometric dimensions.

[0059] The above are merely embodiments provided in this application and are not intended to limit this application. Although this application has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A construction method of post-cast concrete of a vertical structure column in a top-down method, characterized in that It comprises the following steps: Step one: when the construction of the zero floor slab is in progress, the column head is constructed, and the column body insert bar, embedded steel sleeve, and PVC pipe as a concrete pouring hole and vibrating hole are reserved. The floor slabs of each floor and the column head of the next floor are constructed from top to bottom; Step two: after the construction of the basement raft slab is completed, the surface of the column head of the lowest layer of the basement and the surface of the raft slab at the column body position are chiseled, and the PVC pipe and steel sleeve protective sleeve of the embedded concrete pouring hole and vibrating hole are removed; Step three: the surface of the steel pipe column inside the column body is polished, and the concrete chiseled surface is cleaned after the polishing of the steel pipe column is completed; Step four: install the longitudinal steel bars of the column body, and do not install the temporary hole position first; Step five: install the high-pressure grouting pipe; Step six: install other structural steel bars and longitudinal steel bars at the temporary hole position of the column body; Step seven: clean the chiseled surface inside the column again using a high-pressure water gun; Step eight: set the mortar reverse ridge at the column root position; Step nine: install the column body formwork and support system. The formwork needs to be installed in advance at the vibrating hole position in the middle and top of the column body, and an exhaust hole is set at the column head position at the top of the column body; Step ten: install the specially designed concrete feeding pipe at the feeding hole position of the previous layer. The length of the feeding pipe is determined according to the floor height to ensure that the free falling height of the concrete does not exceed 1500mm. Place the square feeding hopper at the feeding hole position. When pouring through other feeding holes, move the feeding hopper in place in advance; Step eleven: during the concrete pouring process, in addition to vibrating the concrete through the vibrating hole of the previous layer, the vibrating hole set at the position of the column body formwork also needs to be vibrated. At the same time, when using one pouring hole to pour concrete, the other pouring holes are used as vibrating holes; Step twelve: after the concrete vibrating hole at the top of the column body is closed, the concrete is vibrated mainly through the concrete pouring hole and vibrating hole of the previous layer. It is necessary to see the overflow of concrete slurry from the exhaust hole of the column body. Continue to pour concrete until the pouring hole and vibrating hole are closed and compacted; Step thirteen: immediately after the completion of concrete pouring, test the non-pressure water flow of the grouting pipe to detect whether the grouting pipe is blocked. If there is a blockage, it needs to be unblocked in time; Step fourteen: perform concrete curing according to the requirements and remove the formwork at the specified time; Step fifteen: perform ultrasonic detection on the construction joint interface position before high-pressure grouting and keep the data; Step sixteen: 14 days after the completion of concrete pouring, start high-pressure grouting; Step seventeen: after grouting is completed, use ultrasonic waves to detect the construction joint interface again. Compare the test data with the data before grouting to check whether the grouting is sufficient; Step eighteen: after the experimental detection is passed, the column body of the same position of the previous layer is constructed, and then the above construction and experimental procedures are repeated until all vertical components, i.e. columns, are completed; Step nineteen: when all the columns constructed by the reverse construction method are completed, the detection is passed, the column body reaches the standard strength, and the reverse construction method floor hole is closed, the temporary supports set during the reverse construction method process can be removed one by one.

2. The post-cast concrete construction method of a reverse construction underground vertical structure column according to claim 1, characterized in that: In step four, the longitudinal steel bars of the column body are installed. The longitudinal steel bars in the temporary hole position inside the column body are not installed temporarily. The high-pressure grouting pipe and structural steel bars are installed at this hole.

3. The post-cast concrete construction method of a reverse construction underground vertical structure column according to claim 1, characterized in that: In step five, high pressure grouting pipe, grouting pipe outer diameter is 6mm, wall thickness is 1.2mm, grouting pipe spacing is 320mm, grouting hole spacing on grouting pipe is 150mm, grouting hole diameter is 2mm, grouting hole needs to use polyvinyl chloride film to be closed, according to the specified spacing, grouting pipe is fixed on the column head surface, grouting pipe is fixed on the column head surface, can prevent concrete pouring and vibrating process, grouting pipe displacement, influence grouting effect, grouting hole film closure can prevent concrete paste from blocking grouting pipe, simultaneously do not affect high pressure grouting.

4. The post-cast concrete construction method of a reverse construction underground vertical structure column according to claim 1, characterized in that: In step sixteen, grouting material adopts epoxy resin, grouting material strength needs to be higher than column strength by one grade, grouting pressure is 2Mpa, grouting sequence is from one side to the other side, every pipe grouting to the other end has epoxy resin to flow out fully, through electric welding mode, the other end of grouting pipe is closed first, then grouting machine is removed from grouting head position, grouting head is internally provided with non-return device, can ensure that epoxy resin does not backflow.

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