Manufacturing method of pile cap for single-pile static load test

Abstract

The invention relates to a manufacturing method of a pile cap for a single-pile static load test, which comprises the following steps: S1, carrying out earth excavation so as to expose concrete of an over-grouting part of a cast-in-place pile or a precast pile head, and removing loose concrete and sharp protrusions on the surface of the cast-in-place pile; s2, a prefabricated restraining piece is arranged outside the exposed over-grouting part concrete or the pile head of the prefabricated pile in the S1 in a sleeving mode, and a gap is formed between the inner wall of the restraining piece and the over-grouting part concrete or the side wall of the pile head of the prefabricated pile; and S3, the gaps in the S2 are filled with high-strength expansion materials. Compared with a cast-in-place pile cap, the expansion constraint method for manufacturing the pile cap has the advantages that the construction procedures of breaking and removing over-grouting part concrete on the upper portion of a pile, binding reinforcing steel bars, erecting formworks and the like are omitted, and the construction speed is higher; compared with a manufacturing method of a steel pile cap, the method has the advantages that the number of machining and manufacturing parts of the restraining part is small, the precision requirement is low, and meanwhile the installation speed is high.

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 single pile static load test. Background Art

[0002] At present, the bearing capacity test of a single pile generally adopts the static load method, but before the static load is performed, a pile cap must be made. The loaded 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 head from damage on the other hand. There are currently two methods for making pile caps, one is a reinforced concrete cast-in-place pile cap, and the other is a steel pile cap.

[0003] Cast-in-place pile cap: First, remove the over-cast concrete at the pile head, and directly anchor the pile head anchoring steel bars into the pile cap. Then tie the steel bars, support the formwork, pour the concrete, and maintain the pile. 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, the reinforced concrete of the pile cap is removed to expose the pile head steel bars for pouring the pedestal. Advantages of cast-in-place pile caps: uniform force and good protection for the pile head; Disadvantages: complex process, long construction time, large construction workload, long maintenance cycle, and large removal workload after the test is completed, which will affect the construction period; Generally, in the foundation construction process, the static load of the pile foundation is a key line, and waiting for the static load due to the production of the pile cap is a common event.

[0004] Steel pile cap: Before using the steel pile cap, it is necessary to customize the steel pile cap components in advance according to the pile diameter and test pressure. 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 the deformation of the pile head concrete (the over-filled part of the pile head is not equipped with steel bars) and prevent the pile head concrete from being damaged or cracked. Before using the steel pile cap, the loose concrete of the pile head needs to be removed after the pile head is dug out. The upper part should be flattened and the side should be cut into an arc shape to ensure that the steel hoop can fit tightly and bear force evenly; then install the side steel hoop and the upper steel plate respectively to conduct a static load test. Advantages of steel pile cap: It can save construction time and is relatively fast, but it needs to be customized in advance, and the steel hoops of different pile diameters are also different. There are many customized specifications and models, and then the processing accuracy of the base surface (over-filled part of concrete) is required to be high.

[0005] Therefore, there is an urgent need for a simple and quick pile cap production method to reduce production processes, shorten production cycles, and reduce production difficulty. 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 single pile static load test, which can reduce the pile cap manufacturing process, shorten the manufacturing cycle and accelerate the 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 making a pile cap for a single pile static load test comprises the following steps: S1. Excavation to expose the overfilled concrete of the cast-in-place pile or the head of the precast pile, and remove the loose concrete and sharp protrusions on the surface; S2, putting the prefabricated restraining member on the exposed part of the over-cast concrete or the precast pile head in S1, and there is a gap between the inner wall of the restraining member and the side wall of the over-cast concrete or the precast pile head; S3, filling the gap of S2 with high-strength expansion material.

[0008] As a further technical solution, in step S2, the vertical distance between the inner wall of the restraining member and the side wall of the over-cast concrete or the precast pile head is greater than or equal to 100 mm and less than 1 / 2 of the diameter of the cast-in-place pile.

[0009] As a further technical solution, the height of the restraining member is the height of the pile cap to be made.

[0010] As a further technical solution, the strength grade of the high-strength expansion material is greater than or equal to the strength grade of the over-poured portion of concrete.

[0011] As a further technical solution, the filling height is not less than the height of the pile cap to be made.

[0012] As a further technical solution, when expansive concrete is selected as the high-strength expansive material, the 14-day limited expansion rate is greater than or equal to 0.03%.

[0013] As a further technical solution, it also includes S4, curing the filled high-strength expansive material so that its strength after solidification is greater than or equal to the strength of the over-filled concrete.

[0014] As a further technical solution, it also includes S5, pasting a pressure-bearing steel plate on the upper surface of the over-filled concrete or the precast pile head.

[0015] As a further technical solution, in step S2, a support plate is added to the bottom of the gap formed by the inner wall of the restraint and the side wall of the over-filled concrete portion, so that the high-strength expansion material in step S3 is located on the upper part of the support plate and does not flow out. The beneficial effects of the present invention are: 1. Fast construction speed and saved process: Compared with cast-in-place pile caps, the expansion constraint method saves construction processes such as breaking the over-cast concrete on the top of the pile, tying steel bars, and supporting formwork, and the construction speed is faster; compared with the method for making steel caps, the constraint parts in the method of the present invention are less processed and manufactured, and the processing and manufacturing precision requirements are not high, and the installation speed is fast; 2. Simple and quick production: directly hoist the restraint parts and fill them with high-strength expansion materials, without complicated processes; 3. Flexible and convenient construction: The method of the present invention is applicable to pile heads of various shapes and is convenient to construct; there are no strict requirements on the shape of the pile head or the over-filled concrete in the method; 4. Economic savings: By over-pouring concrete on the upper part of the pile, the amount of reinforced concrete can be saved. In addition, after the static load test of the pile is completed, the outer restraints can be removed and recycled, which has certain economic advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of preparing a pile cap according to Example 1 of the present invention; Figure 2 This is a schematic diagram of the top view of the pile cap prepared in Example 1 of the present invention.

[0017] In the accompanying drawings, the components represented by the reference numerals are listed as follows: Pile top elevation 1, over-filled concrete 2, high-strength expansion material 3, restraint 4, steel plate 5. DETAILED DESCRIPTION

[0018] 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.

[0019] 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.

[0020] 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.

[0021] Cast-in-place pile caps require the removal of over-cast concrete at the pile head, tying of steel bars, and then cast-in-place concrete to reach the curing strength. There are many processes, which are time-consuming and labor-intensive. Steel pile caps need to be ordered in advance according to the pile diameter, are complex to make, and are difficult to install. To ensure uniform force, the concrete processing accuracy of the pile head is also required to be high. Therefore, the following embodiments are provided to solve the above problems.

[0022] During the construction of cast-in-place piles, the upper concrete of the pile head (above the designed pile top elevation 1) is the over-cast concrete 2, which has no longitudinal reinforcement and stirrups, and only the pile head anchoring steel bars extend into it, so the bearing capacity is limited; the over-cast part must be removed before the foundation cap is constructed, and this part of the over-cast concrete 2 is basically useless. This embodiment makes reasonable use of this part to save costs and shorten construction period.

[0023] This embodiment provides a method for manufacturing a pile cap for a single pile static load test. The overfilled portion mentioned below indicates that the upper concrete of the pile cap (above the designed pile top elevation) is the overfilled portion concrete 2. The manufacturing method comprises the following steps: S1. Excavation to expose the overfilled concrete 2 of the cast-in-place pile or the head of the precast pile, and remove the loose concrete and sharp protrusions on the surface; S2, putting the prefabricated restraining member on the exposed part of the over-cast concrete or the precast pile head in S1, and there is a gap between the inner wall of the restraining member and the side wall of the over-cast concrete or the precast pile head; S3, filling the gap of S2 with high-strength expansion material 3.

[0024] More specifically, in step S1: after the bored pile reaches the curing strength, earth excavation is carried out to excavate the over-cast concrete or the precast pile head, and then the base is cleaned and the loose concrete on the surface is removed; The following is an example of overfilled concrete: In step S2, the prefabricated restraint 4 is used to cover the overcast concrete 2 of the cast-in-place pile. In this process, the inscribed circle diameter of the restraint 4 is larger than the maximum diameter of the overcast concrete 2 column. For example, the vertical distance between the inner wall of the restraint 4 and the side wall of the overcast concrete 2 is greater than or equal to 100 mm and less than 1 / 2 of the diameter of the overcast concrete 2 column, ensuring that the pile head or the overcast concrete 2 on the upper part of the pile can be covered during installation. The height of the restraint 4 is the height of the pile cap to be made, for example, the height is not less than 1m, and the thickness of the restraint is determined according to the bearing capacity required by the static load test.

[0025] For example, the restraint 4 can be made of a steel sleeve, a carbon fiber plate, a steel frame wooden formwork component, a steel pipe support plus a steel formwork, a steel ring plus a wooden formwork composite component or other materials, and the shape can be a hollow cylinder, a square tube or a hollow polygonal column. According to the bearing capacity requirements of the static load test, the corresponding restraint material and thickness are selected to ensure that the expansion of the high-strength expansion material 3 and the deformation under pressure in the static load test can be restrained in the later stage.

[0026] If the high-strength expansion material 3 used has high fluidity, or the bottom is not directly in contact with the ground but suspended, in order to prevent leakage, in step S2, a support plate is added to the bottom of the gap formed by the inner wall of the constraint member 4 and the side wall of the over-filled concrete 2, so that the high-strength expansion material 3 in step S3 is located on the upper part of the support plate; for example, the constraint member 4 can be installed after the support plate is placed, but in the later stage, after the high-strength expansion material 3 is filled and cured, the support plate needs to be removed.

[0027] In step S3, the strength grade of the high-strength expansive material 3 is not less than the strength grade of the over-cast concrete 2, and the high-strength expansive material 3 should fill the entire gap, and the filling height is not less than the pile cap height. In this process, the high-strength expansive material 3 is circumferentially constrained by the outer constraint 4, so the expansion of the high-strength expansive material 3 also forms a circumferential constraint on the over-cast concrete 2, generating lateral compressive stress toward the pile axis, thereby improving the bearing capacity of the over-cast concrete 2 of the cast-in-place pile. For example, the high-strength expansive material 3 uses expansive concrete, high-strength expansive foam, etc., and early-strength materials can be selected to save maintenance time. When the high-strength expansive material 3 uses expansive concrete, its composition should not conflict with the cast-in-place pile concrete; the expansion rate is determined according to the gap size between the constraint 4 and the over-cast concrete 2, combined with the static load force requirements, and its 14-day limited expansion rate should be not less than 0.03%; in order to speed up the construction speed, early-strength expansive concrete can also be used.

[0028] The process also includes S4, curing the filled high-strength expansion material 3 so that its strength after curing is greater than or equal to the strength of the over-cast concrete 2. When the high-strength expansion material 3 is cured, it can form a pile cap together with the peripheral restraint member 4 and the over-cast concrete 2 of the cast-in-place pile.

[0029] In the specific implementation process, in order to increase the integrity of the pile cap, it also includes S5, pasting a pressure-bearing steel plate 5 on the upper surface of the over-filled concrete 2, and the steel plate 5 also covers the upper surface of the high-strength expansion material as a force transmission mechanism for the static load test.

[0030] After the pile cap is completed (such as Figure 1 , Figure 2 ), that is, a static load test can be carried out. After the test is completed, the restraining member 4, the high-strength expansion material 3 and the over-filled concrete 2 are removed, and the restraining member 4 can be recycled and reused.

[0031] This embodiment solves the shortcomings of complex pile cap production and long production cycle before a single pile static load test, thereby shortening the pile cap production cycle and reducing the production difficulty, thereby accelerating the progress of foundation engineering construction.

[0032] 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.

[0033] 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.

[0034] 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 single pile static load test, characterized in that: The steps include: S1. Excavation to expose the overfilled concrete of the cast-in-place pile or the head of the precast pile, and remove the loose concrete and sharp protrusions on the surface; S2, putting the prefabricated restraining member (4) on the exposed part of the over-cast concrete or the prefabricated pile head in S1, and there is a gap between the inner wall of the restraining member (4) and the side wall of the over-cast concrete or the prefabricated pile head; S3, filling the gap of S2 with high-strength expansion material (3).

2. The method according to claim 1, characterized in that: In step S2, the vertical distance between the inner wall of the restraining member (4) and the side wall of the over-cast concrete or the precast pile head is greater than or equal to 100 mm and less than 1 / 2 of the diameter of the over-cast concrete.

3. The method according to claim 2, characterized in that: The height of the restraining member (4) is the height of the pile cap to be manufactured.

4. The method according to claim 1, characterized in that: The strength grade of the high-strength expansion material (3) is greater than or equal to the strength grade of the concrete in the over-cast portion.

5. The method according to claim 1, characterized in that: The filling height of the high-strength expansion material (3) is not less than the height of the pile cap to be made.

6. The method according to claim 1, characterized in that: When expansive concrete is selected as the high-strength expansive material (3), the 14-day limited expansion rate is greater than or equal to 0.03%.

7. The manufacturing method according to claim 1, characterized in that: The method further includes S4, curing the filled high-strength expansion material (3) so that its strength after solidification is greater than or equal to the strength of the over-filled concrete.

8. The method according to claim 7, characterized in that: The method further comprises S5, wherein a pressure-bearing steel plate is pasted on the upper surface of the over-filled concrete portion or the precast pile head.

9. The manufacturing method according to claim 1, characterized in that: In step S2, a support plate is added to the bottom of the gap formed by the inner wall of the restraining member and the side wall of the overfilling portion, so that the high-strength expansion material in step S3 is located on the upper part of the support plate.

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