Manufacturing method of pile cap for pile foundation static load test

Abstract

The invention relates to a method for manufacturing a pile cap for a pile foundation static load test. The method comprises the steps that S1, earth excavation is conducted, specifically, earth excavation is conducted to expose an over-grouting part of a reinforced concrete cast-in-place pile head; s2, base layer cleaning and removing are conducted, specifically, base layer cleaning and surface removing are conducted on the surface of the exposed pile head over-grouting part; s3, selecting and processing carbon fiber cloth: selecting different types of carbon fiber cloth and pasting thicknesses according to the magnitude of the loading load, and pre-cutting the carbon fiber cloth; s4, surface treatment and pasting are conducted, specifically, the carbon fiber cloth cut in the step S3 is coated with an adhesive, and then the carbon fiber cloth is pasted to the surface of the over-filled part of the pile head removed in the step S2; and S5, protection layer arrangement: after the carbon fiber cloth pasted in the step S4 is solidified, a protection layer is pasted on the top of the pile head over-filling part pasted with the carbon fiber cloth, and then pile cap manufacturing is completed. The construction method has the beneficial effects that the construction speed is high, concrete of the over-grouting part is directly utilized, the time for curing the cast-in-place pile cap is not needed, and reservation and machining are not needed.

Description

Technical Field

[0001] The invention relates to the technical field of building construction, in particular to a method for manufacturing a pile cap for a pile foundation static load test. Background Art

[0002] At present, the bearing capacity of pile foundation is generally tested by static loading, but pile caps need to be made before static loading. The loading force is transmitted to the pile body through the pile cap, which makes the static load bearing surface flatter and more uniform on the one hand, and protects the pile from damage on the other hand. There are two common methods for making pile caps, one is reinforced concrete cast-in-place pile caps, and the other is steel pile caps.

[0003] The specific method of cast-in-place pile cap is: first, remove all the over-poured concrete on the pile head, directly anchor the pile head anchor steel bar into the pile cap, then tie the steel bar, support the formwork, pour the concrete, and maintain. Generally, at least one grade higher than the pile is used. After reaching the maintenance strength, a static load test is carried out; after the test is completed, all the reinforced concrete of the pile cap is removed to expose the pile head anchor steel bar for pouring the pedestal. Advantages of cast-in-place pile cap: uniform force and good protection for the pile head; Disadvantages are complex construction procedures, long construction time, large construction workload, and long maintenance cycle. After the static load test is completed, the workload of removing the reinforced concrete pile cap is also very large, which seriously affects the construction period; Because in the foundation construction process, pile cap production-pile foundation static load test is generally a key line, and waiting for the next step of construction due to failure to complete the static load test is a common event.

[0004] The specific method of steel pile cap is: customize the steel pile cap according to the size of the pile diameter. The steel pile cap is generally composed of an upper steel plate and a side steel hoop. The upper steel plate is used to transmit static load pressure, and the side steel hoop is used to constrain concrete deformation (the part of the concrete that is over-filled above the design elevation of the pile top is not equipped with steel bars) and prevent the pile head concrete from being damaged or cracked. Before using the steel pile cap, it is necessary to customize the steel pile cap components in advance according to the pile diameter and static load test pressure. After digging out the over-filled part above the pile head, the loose concrete on the surface needs to be removed; the upper surface should be flattened or cut flat; the side should be removed into a standard arc shape, which must fit closely with the size of the prefabricated steel hoop so that the steel hoop is evenly stressed; then install the steel pile cap components separately and conduct a static load test. The advantage of steel pile caps is that compared with cast-in-place pile caps, they are simple to make and take less time, which can save construction time. The disadvantage is that they need to be customized in advance according to the pile diameter, and the sizes of steel hoops for different pile diameters are also different, so there are more customized specifications and models. In addition, the treatment of the base surface (over-poured concrete) is also required to be high, especially the side, which needs to be cut into standard arc-shaped specifications and dimensions to make it fit closely with the size of the prefabricated steel hoops, which is difficult to handle.

[0005] In summary, a pile cap method that is simple to make, has a short construction period, and can speed up the overall construction progress of the project is a technical problem that needs to be solved urgently. Summary of the invention

[0006] The present invention aims at the technical problems existing in the prior art and provides a method for manufacturing a pile cap for a pile foundation static load test, so as to shorten the pile cap manufacturing cycle, reduce the difficulty of pile cap manufacturing, and thus accelerate the overall construction progress of the foundation project.

[0007] The technical solution of the present invention to solve the above technical problem is as follows: A method for manufacturing a pile cap for a pile foundation static load test comprises the following steps: S1. Earth excavation: Earth excavation should be done to expose the overfilled part of the reinforced concrete pile head; S2. Base cleaning and removal: Clean the base and remove the surface of the exposed pile head over-irrigation part; S3. Selection and processing of carbon fiber cloth: Select different types of carbon fiber cloth and pasting thickness according to the load size, and cut the carbon fiber cloth in advance.

[0008] S4, surface treatment and pasting: after the surface is removed in step S2, the surface of the pile head overfilled part is coated with adhesive, and then the carbon fiber cloth cut in step S3 is pasted; S5, setting of protective layer: after the carbon fiber cloth pasted in step S4 is cured, the top of the overfilled part of the pile head with the carbon fiber cloth is pasted, and the pile cap is made.

[0009] As a further technical solution, step S2 includes the following steps: S21. Clean the soil on the surface of the exposed pile head overfilled part; S22. Remove the loose concrete on the top and sides of the over-filled part of the pile head, and the top must be flattened or cut into a horizontal surface, and the sides must be rounded without sharp protrusions or bulges.

[0010] As a further technical solution, in step S3, the type and amount of the required carbon fiber cloth are calculated according to the specific shape of the over-filled part of the pile head and the reinforcement requirements, and then the carbon fiber cloth of the required shape is cut.

[0011] As a further technical solution, in step S4, the top of the pile head super-filled part is first pasted, and then the side of the pile head super-filled part is pasted by overlapping the upper and lower parts of the circumferential bundle.

[0012] As a further technical solution, the edge of the carbon fiber cloth pasted on the top of the pile head super-irrigation part is pasted on the side of the pile head super-irrigation part and overlapped with the inner body of the carbon fiber cloth on the side of the pile head super-irrigation part.

[0013] As a further technical solution, in step S5, the protective layer is a pressure-bearing steel plate, and the size of the pressure-bearing steel plate is not less than the size of the top surface of the over-filled part of the pile head.

[0014] As a further technical solution, in step S1, earth excavation is carried out after the strength of the bored pile reaches the requirement, and the over-cast part of the pile head exposed by excavation is the part above the designed elevation of the bored pile top.

[0015] As a further technical solution, it also includes S6, static load test and removal: the prepared pile cap is subjected to a pile foundation static load test, and then the protective layer, carbon fiber cloth, and part of the over-filled concrete at the pile head are removed in turn.

[0016] The beneficial effects of the present invention are: 1. Fast construction speed: The carbon fiber reinforcement method is much faster than the cast-in-place pile cap construction speed, and the over-cast concrete is directly used without waiting for the curing time of the cast-in-place pile cap; compared with the steel pile cap, there is no need to book and process it; 2. Simple production, no need for large equipment and complex processes; carbon fiber reinforcement technology is mature, simple to operate, widely used, safe and reliable.

[0017] 3. In addition, the present invention directly utilizes the over-cast concrete on the upper part of the pile, without the need for additional pouring of reinforced concrete or additional removal, thereby saving materials and construction procedures; the carbon fiber cloth removed after the static load of the pile foundation is completed can be recycled; therefore, the present invention has an overall economic advantage. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of the carbon fiber reinforced pile cap in Example 1.

[0019] In the accompanying drawings, the components represented by the reference numerals are listed as follows: Over-cast part of pile head 1, carbon fiber cloth 2, protective layer 3, design elevation of cast-in-place pile top 4, reinforced concrete cast-in-place pile head 5, steel bars 6, pile head anchor bars 7, natural ground 8. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0021] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0022] In the description of the present application, the term "for example" is used to mean "used as an example, illustration or description". Any embodiment described as "for example" in the present application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is given to enable any technician in the field to implement and use the present invention. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present invention can be implemented without using these specific details. In other examples, well-known structures and processes will not be elaborated in detail to avoid unnecessary details to obscure the description of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in the present application.

[0023] This embodiment solves the shortcomings of the complicated production and long production cycle of the pile cap before the static load test of the bored pile foundation. When the pile cap is cast in place, it needs to reach the curing strength for 28 days, which is very time-consuming. It also needs to be broken after the static load test is completed, and the workload is also large. When the steel pile cap is used, it needs to be pre-ordered according to the pile diameter. It is complicated to make and has certain installation difficulties. The force is uneven and sometimes the pile head is crushed.

[0024] In order to solve the above shortcomings of pile cap production, this embodiment proposes a simple pile cap production method to shorten the pile cap production cycle and reduce the difficulty of pile cap production, thereby accelerating the overall construction progress of the foundation project. The specific method includes the following steps: S1. Earth excavation: Earth excavation is to expose the overfilled part of the pile head of the reinforced concrete cast-in-place pile 1; S2. Base cleaning and removal: Clean the base and remove the surface of the exposed over-filled part of the pile head.

[0025] S3. Selection and processing of carbon fiber cloth: Select different types of carbon fiber cloth and pasting thickness according to the load size, and cut the carbon fiber cloth in advance.

[0026] S4, surface treatment and pasting: after the surface is removed in step S2, the surface of the pile head overfilling part 1 is coated with an adhesive, and then the carbon fiber cloth 2 cut in step S3 is pasted; S5, setting of protective layer: after the carbon fiber cloth pasted in step S4 is cured, a protective layer 3 is pasted on the top of the pile head super-pouring part 1 pasted with the carbon fiber cloth 2, and the pile cap is manufactured.

[0027] For example, in step S1, earthwork excavation is carried out after the strength of the bored pile reaches the requirement, and the pile head over-filled part 1 exposed by the excavation is the part above the designed elevation 4 of the bored pile top. Because during the construction of the bored pile, the upper concrete of the reinforced concrete bored pile pile head 5 (i.e., the part above the designed pile top elevation 4) is the pile head over-filled part 1, and the strength of this part of the concrete is the same as the strength of the pile, but there is no steel bar (only the pile head anchor bar 7 extends into it), so the bearing capacity is limited and it cannot be used as a static load pile cap. In general, the height of the over-filled part in actual construction is not less than 1m, and some can even reach 2-3m, and the diameter of the over-filled part is not less than the pile diameter, so it can meet the size and strength requirements of the pile cap, while the conventional cast-in-place pile cap will break the over-filled concrete of this part, and then cast the concrete again after tying the steel bars. The over-filled part should also be removed before the foundation cap is constructed, and this over-filled part is basically useless. In this embodiment, the over-filled concrete on the pile head 5 (i.e., the pile head over-filled portion 1) is utilized, which does not add additional construction steps and economic costs during the pile foundation static load test, and effectively saves construction time.

[0028] In this process, earthwork excavation starts from the natural ground 8 to the designed elevation 4 of the top of the cast-in-place pile, and the overcast part 1 of the pile head is avoided from being damaged during excavation. (See Figure 1 ) For example, step S2 includes the following steps: S21, first clean the soil on the surface of the exposed pile head overfilling part 1; S22. Remove the loose concrete on the top and sides of the over-filled part 1 of the pile head, and the top needs to be flattened or cut into a horizontal plane, and the sides are rounded without sharp protrusions; to ensure the necessary pile cap height and the flatness of the upper surface, the top is 0.6 meters to 1.5 meters from the pile top elevation 4 (that is, the proposed pile cap height, selected according to the pile diameter and loading pressure), and the excess is cut off; the sides of the over-filled part 1 of the pile head are required to be clean, tidy, rounded, without protrusions, loose holes, etc., to facilitate the use of carbon fiber cloth for reinforcement in the later stage to improve the reinforcement strength.

[0029] For example, in step S3, the type and amount of the required carbon fiber cloth are calculated according to the specific shape of the pile head super-pouring part 1 and the reinforcement requirements, and then the carbon fiber cloth of the required shape is cut; in more detail, the shape, size and reinforcement requirements of the top and side of the pile head super-pouring part 1 are measured, and then the appropriate type of carbon fiber cloth is selected according to these requirements and cut into the required shape and size for use; and the width of the cut carbon fiber cloth strip is not more than 300 mm and not less than 150 mm; it is selected specifically according to the size of the pile cap.

[0030] For example, in step S4, the top of the pile head super-irrigation part 1 is first pasted, and then the side of the pile head super-irrigation part 1 is pasted by overlapping the upper and lower parts of the pile head using a circumferential binding.

[0031] In more detail, the edge of the carbon fiber cloth pasted on the top of the pile head super-irrigation part 1 is pasted on the side of the pile head super-irrigation part 1 and overlapped in the carbon fiber cloth on the side of the pile head super-irrigation part 1, so that the carbon fiber cloth pasted on the entire pile head super-irrigation part 1 is a whole.

[0032] The specific operation is: prepare the matching impregnating resin glue as the adhesive, select the appropriate impregnating resin before pasting and evenly apply it to the part to be pasted (i.e. the over-filled part of the pile head 1), and apply it twice; there should be no gaps and cracks during the application process; the amount of glue applied should be sufficient, full and even, preferably 2~5mm thick; then lightly press the carbon fiber cloth to the position to be pasted.

[0033] Among them, it is first pasted on the top of the pile head super-irrigation part 1, and the edge of the top carbon fiber cloth extends out of the top surface and vertically overlaps the side of the pile head super-irrigation part 1, and the overlap length is not less than 1 / 2 of the pile cap height; the top carbon fiber is pasted in two layers, and the pasting directions of the two layers are perpendicular to each other; Then, the entire side of the pile head overfilling part 1 is pasted in a circumferential manner. When pasting the side, each carbon fiber cloth is pasted to form a protective enclosure. The lap length of the closed end is not less than 1.5 times the width of the carbon fiber cloth strip, and the closing areas of the upper and lower adjacent carbon fiber cloth strips should be staggered (i.e., the vertical lap seams are staggered); each carbon fiber cloth is pasted from top to bottom in sequence until the bottom of the pile cap, and the lap width of the upper and lower adjacent carbon fiber cloth strips is not less than 50mm (the lap seam is horizontal). According to the above construction method, 2 to 3 layers of carbon fiber are pasted as a whole on the side within the height range of the proposed pile cap (determined according to the size of the static load), one layer is pasted clockwise, and one layer is pasted counterclockwise, and they are switched in sequence. Vertical pasting is not allowed; the horizontal lap seams of the upper and lower layers should be staggered.

[0034] When pasting carbon fiber cloth, paste along the direction of the carbon fiber cloth, and use a roller to roll the pasted carbon fiber cloth several times along the fiber direction to squeeze out bubbles and make the impregnation resin fully saturate the carbon fiber cloth; for the cloth that has just been pasted, use a scraper to scrape from the middle to the edge to remove micro bubbles. Then repeat the glue coating process again to ensure that the carbon fiber cloth is completely soaked in the resin. When the surface of the upper carbon fiber cloth is dry to the touch, immediately paste the next layer.

[0035] Finally, after pasting, apply glue evenly on the surface of the carbon fiber cloth again, and you can use a squeegee to apply it to ensure that the surface is flat and even. Then carry out curing and curing for no less than 24 hours. During this period, avoid external impact and disturbance, avoid high temperature, water and direct sunlight to ensure the bonding strength.

[0036] It should be noted that: when the carbon fiber cloth is pasted on the side of the pile head super-pouring part 1, the pasting surface of each cloth is closely attached to the side of the pile head super-pouring part 1 in a horizontal circumferential direction (clockwise or counterclockwise), and the end is closed to form a closed constraint ring on the side of the pile head super-pouring part 1 as a whole; 2 or more carbon fiber cloths shall not be used in an overlapping manner to form a closed constraint ring in the circumferential direction of a horizontal plane (that is, when pasting horizontally in the circumferential direction of the pile head super-pouring part 1, the length of the pasted carbon fiber cloth at this time is equal to the circumferential length of the horizontal circumferential part of the super-pouring concrete at this time plus the lap length of the end); the pasting direction of the cloth strips shall not be vertical or oblique. After each cloth strip is pasted, the next one is pasted, and a continuous closed constraint ring is formed on the side of the pile head super-pouring part from top to bottom, similar to the stirrups of the column, to improve the bearing capacity and the static load stability in the later stage.

[0037] It should be noted that the thickness and number of layers of the carbon fiber cloth are determined according to the type of pile required for the pile cap and the size of the load to be loaded, so that the prepared pile cap can meet the static load requirements.

[0038] For example, in step S5, after the carbon fiber cloth is pasted, a layer of epoxy resin is rolled on the surface of the pasted carbon fiber cloth to ensure that it can fully cover the surface of the carbon fiber cloth, and then ensure that it fully soaks the pasted carbon fiber cloth. When it is dry to the touch (generally between 3h-24h, specifically determined according to the temperature change during construction; the construction temperature is not lower than -10°C, and the curing temperature is not lower than -5°C), the curing time of the last coat of glue after pasting is completed must be no less than 24h.

[0039] For example, in step S5, the protective layer 3 is a pressure-bearing steel plate, and the size of the pressure-bearing steel plate is not less than the size of the top surface of the pile head overfilling part, which serves as a force transmission mechanism during the static load test. The size and thickness of the pressure-bearing steel plate are determined according to the force transmission size and strength during the static load test, and must be able to meet the force requirements and deformation control requirements. Among them, the upper surface area of ​​the pressure-bearing steel plate is larger than the area of ​​the top of the pile head overfilling part.

[0040] During the specific implementation process, after the pile cap is completed and before the static load test, a quality inspection is carried out: the total effective bonding area should not be less than 95% by using the hammer method or the pressure method. When the hollow area of ​​the carbon fiber cloth is less than 10cm 2 When the hollow area is larger than 10cm 2 When repairing the hollow part, it is advisable to cut off the carbon fiber cloth at the hollow part and re-overlap the carbon fiber cloth. The overlapping length should be no less than 2 times the long side of the hollow. If the hollow is on the side of the over-filled part 1 of the pile head, the re-pasted carbon fiber cloth should form a closed loop on the side of the over-filled part 1 of the pile head (re-pasting is required).

[0041] This embodiment also includes S6, static load test and removal: using the manufactured pile cap to perform a pile foundation static load test, after the test is completed, the protective layer, the carbon fiber cloth, and the concrete of the pile head overfilling part 1 are removed in sequence, and then subsequent foundation construction is carried out.

[0042] The embodiment of the present invention forms a pile cap by reinforcing the over-filled part 1 of the pile head with carbon fiber cloth, and the construction is flexible and simple. Compared with a steel pile cap, the method of the present invention does not need to be prefabricated in advance according to the pile diameter, and does not need to be cut into a standard arc shape according to the size of the prefabricated steel cap. The method can be used to make pile caps of different pile diameters. Compared with a cast-in-place pile cap, the method of the present invention does not need to remove the concrete of the over-filled part 1 of the pile head and then tie the steel bars and pour the concrete, and does not need to wait for the curing time required for the cast-in-place pile cap, which saves time and construction materials and construction procedures. That is, the method of the present invention has the advantages of fast and flexible construction speed, simple production, and economic savings.

[0043] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and for parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0044] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0045] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for manufacturing a pile cap for a pile foundation static load test, characterized in that: The steps include: S1. Earthwork excavation: Earthwork excavation is to expose the overfilled part of the reinforced concrete pile head; S2. Base cleaning and removal: Clean the base and remove the surface of the exposed pile head over-irrigation part; S3. Selection and processing of carbon fiber cloth: select different types of carbon fiber cloth and pasting thickness according to the load size, and cut the carbon fiber cloth in advance; S4, surface treatment and pasting: after the surface is removed in step S2, the surface of the pile head overfilled part is coated with adhesive, and then the carbon fiber cloth cut in step S3 is pasted; S5, setting of protective layer: after the carbon fiber cloth pasted in step S4 is cured, a protective layer is pasted on the top of the overfilled part of the pile head pasted with the carbon fiber cloth, and the pile cap is manufactured.

2. The method according to claim 1, characterized in that Step S2 includes the following steps: S21. Clean the soil on the surface of the exposed pile head overfilled part; S22. Remove the loose concrete on the top and sides of the over-filled part of the pile head, and the top must be flattened or cut into a horizontal surface, and the sides must be rounded without protrusions.

3. The method according to claim 1, characterized in that In step S3, the type and amount of the required carbon fiber cloth are calculated according to the specific shape of the over-filled part of the pile head and the reinforcement requirements, and then the carbon fiber cloth of the required shape is cut.

4. The method according to claim 1, characterized in that In step S4, the top of the pile head overfilled portion is first pasted, and then the side of the pile head overfilled portion is pasted by overlapping the upper and lower parts of the pile head using a circumferential bundle.

5. The method according to claim 4, characterized in that The edge of the carbon fiber cloth pasted on the top of the pile head super-irrigation part is pasted on the side of the pile head super-irrigation part and overlapped inside the carbon fiber cloth on the side of the pile head super-irrigation part.

6. The method according to claim 1, characterized in that In step S5, the protective layer is a pressure-bearing steel plate, and the size of the pressure-bearing steel plate is not less than the size of the top surface of the over-filled portion of the pile head.

7. The method according to claim 1, characterized in that In step S1, earth excavation is carried out after the strength of the bored pile reaches the requirement, and the over-cast part of the pile head exposed by excavation is the part above the designed elevation of the bored pile top.

8. The method according to claim 1, characterized in that It also includes S6, static load test and removal: the prepared pile cap is subjected to a pile foundation static load test, and then the protective layer, carbon fiber cloth, and part of the over-filled concrete at the pile head are removed in sequence.

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