A construction method for a pile structure of a composite foundation

Abstract

This invention belongs to the field of civil engineering technology, specifically providing a precast pile cap, including a pile cap body; a pile cap protrusion at the bottom of the pile cap body; a grouting pipe inside the pile cap body, and the grouting pipe penetrating the pile cap body; a grout flow groove on the bottom surface of the pile cap body; and the grout flow groove communicating with the grouting pipe. This invention also provides a pile structure for composite foundations including this precast pile cap and its construction method. The precast pile cap provided by this invention forms a concave-convex connection with the pile body, resulting in small pile cap eccentricity, good reliability of connection with the pile head, and tight adhesion to the surrounding soil and rock. The construction method is simple and efficient, avoiding the tedious process of pile head leveling, and has advantages such as minimal pile body damage, convenient hoisting, and low economic and time costs.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering technology, specifically relating to a precast pile cap, a pile structure for composite foundations, and its construction method. Background Technology

[0002] CFG pile foundation treatment, as a common composite foundation treatment technology, can fully utilize the bearing capacity of the pile body and make good use of the natural bearing capacity of the soil between the piles. The CFG pile structure mainly consists of the pile body, pile cap, and cushion layer. As a key structure to effectively prevent excessive pile penetration, the pile cap has various structural forms and construction methods, mainly divided into cast-in-place pile cap technology and precast pile cap technology.

[0003] While the construction technology for cast-in-place pile caps has matured, its prefabricated construction level is low, curing time is long, and it is difficult to meet construction requirements under tight schedules. Precast pile caps offer better curing conditions, guaranteed quality, and significantly reduce on-site curing time, thus shortening the construction period. However, existing precast pile caps still have the following problems: 1. Poor reliability of the connection between the precast pile cap and the CFG pile head, lacking an effective connection method or requiring complex snap-fit ​​structures for installation, necessitating high construction precision. This makes them primarily suitable for precast piles, with limited applicability to cast-in-place piles; 2. Uneven pile heads easily lead to problems such as pile cap swaying, shifting, and uneven stress, affecting construction quality; 3. When forming the soil mold for rotary-dug pile caps, excessive rotary-drilling is common due to poor construction precision. After installation, gaps exist between the pile cap and the surrounding soil, which cannot be manually compacted, adversely affecting the pile cap's stress and potentially causing tilting.

[0004] Therefore, it is necessary to study a precast pile cap structure and construction method that features a simple and reliable connection between the pile head and the pile cap, easy leveling of the pile top, and tight adhesion between the pile cap and the surrounding soil. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems in the prior art, such as poor connection reliability between pile head and pile cap, difficulty in tightly adhering to the soil around the pile, and cumbersome leveling process for pile head.

[0006] To address this, the present invention provides a precast pile cap, comprising a pile cap body; a pile cap protrusion is provided at the bottom of the pile cap body; a grouting pipe is provided inside the pile cap body, and the grouting pipe penetrates the pile cap body; a grout flow groove is provided on the bottom surface of the pile cap body; the grout flow groove is connected to the grouting pipe.

[0007] Specifically, the top of the aforementioned pile cap body is equipped with a lifting ring.

[0008] The present invention also provides a pile structure for composite foundations, including a pile body and the aforementioned precast pile cap; a groove matching the protrusion of the pile cap is provided on the top of the pile body; the pile cap body is installed on the pile body, and the protrusion of the pile cap is inserted into the groove; the grouting pipe is connected to the groove.

[0009] Specifically, the aforementioned pile cap protrusion is cylindrical, and the diameter of the groove is larger than the diameter of the pile cap protrusion.

[0010] The present invention also provides a construction method for a pile structure for a composite foundation, comprising the following steps:

[0011] (1) Casting precast pile caps;

[0012] (2) Level and compact the ground to the design elevation of the top surface of the pile cap;

[0013] (3) Drilling and grouting the pile body;

[0014] (4) Level the pile head and create a groove;

[0015] (5) Excavate the soil around the top of the pile to form a space to accommodate the precast pile cap, and clean the slag on the top of the pile.

[0016] (6) Hoist the precast pile cap to the top of the pile so that the pile cap protrudes and inserts into the groove at the top of the pile;

[0017] (7) Grouting is carried out through the grouting pipe on the pile cap body to the connection between the pile cap and the pile body until the grout overflows from all sides of the pile cap. Grouting is then stopped to complete the construction of the pile structure.

[0018] Specifically, step (3) above is as follows: drilling, pouring concrete to the design elevation above the pile top, and removing drilling slag; vibrating the concrete, scooping off the surface laitance, and when the concrete surface no longer drops, scooping off the over-poured concrete so that the concrete surface reaches the design elevation of the pile top.

[0019] Specifically, in step (4) above, a pile head leveling and forming box is used to level and open grooves; the pile head leveling and forming box includes a box body; a level is provided on the top surface of the box body; a leveling protrusion is provided on the bottom of the box body; the shape of the leveling protrusion is the same as the shape of the pile cap protrusion, and the volume of the leveling protrusion is greater than the volume of the pile cap protrusion.

[0020] Specifically, the top of the aforementioned box is equipped with a pull ring.

[0021] Specifically, step (4) involves placing the pile head leveling and forming box on the concrete surface at the top of the pile, pressing the pile head leveling and forming box downwards until the top surface of the pile head leveling and forming box is level with the leveled ground, adjusting the pile head leveling and forming box to be horizontal by observing the level bubble, and taking out the pile head leveling and forming box after the concrete strength of the pile body reaches the standard.

[0022] Specifically, the precast pile cap is provided with multiple grouting pipes; in step (7), during the grouting process, one of the grouting pipes serves as an air vent, and after the other grouting pipes are filled, the grouting pipe that serves as the air vent is then filled with grout.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] The precast pile cap provided by this invention, by setting a pile cap protrusion, forms a concave-convex connection between the pile cap and the pile body when constructing pile structures for composite foundations. The concave opening at the pile head is slightly larger than the protruding part of the pile cap, facilitating pile cap installation and preventing excessive pile cap eccentricity. After the precast pile cap is installed, grout is injected into the gap at the concave-convex connection through a pre-reserved grouting pipe, which greatly enhances the reliability of the connection between the pile cap and the pile head. In addition, the grout flow channel connected to the grouting pipe can guide the grout into the gap between the precast pile cap and the surrounding soil, ensuring a tight and compact fit between the precast pile cap and the surrounding soil.

[0025] The construction method for pile structures on composite foundations provided by this invention ensures project quality and meets construction schedule requirements. It features fast construction speed, relatively simple process, easy quality control, and low project cost. The use of a pile head leveling and molding box ensures accurate control of the pile top elevation at the design elevation, and the pile head has high flatness, avoiding the shaking problem of precast pile caps caused by uneven pile heads. It also avoids the need for excavation and backfilling of soil between piles and pile cutting and leveling procedures; leveling can be adjusted by observing a level, making operation simple and greatly improving construction efficiency. Furthermore, it avoids damage to the pile body caused by excavation and backfilling of soil between piles and cutting off the pile head, reducing the amount of over-pouring concrete and demonstrating strong economic efficiency.

[0026] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the single-convex precast pile cap in Embodiment 1 of the present invention.

[0028] Figure 2 This is a top view of the single-convex precast pile cap in Embodiment 1 of the present invention.

[0029] Figure 3 This is a bottom view of the single-convex precast pile cap in Embodiment 1 of the present invention.

[0030] Figure 4 This is a schematic diagram of the pile structure in Embodiment 1 of the present invention.

[0031] Figure 5 This is a schematic diagram of the single-convex pile head leveling and forming box in Embodiment 1 of the present invention.

[0032] Figure 6 This is a top view of the single-convex pile head leveling and forming box in Embodiment 1 of the present invention.

[0033] Figure 7 This is a bottom view of the single-convex pile head leveling and forming box in Embodiment 1 of the present invention.

[0034] Figure 8 This is a schematic diagram of the template for the single-convex precast pile cap in Embodiment 1 of the present invention.

[0035] Figure 9 This is a bottom view of the template for the single-convex precast pile cap in Embodiment 1 of the present invention.

[0036] Figure 10 This is a schematic diagram of the structure of the double-convex precast pile cap in Embodiment 2 of the present invention.

[0037] Figure 11 This is a top view of the double-convex precast pile cap in Embodiment 2 of the present invention.

[0038] Figure 12 This is a bottom view of the double-convex precast pile cap in Embodiment 2 of the present invention.

[0039] Figure 13 This is a schematic diagram of the pile structure in Embodiment 2 of the present invention.

[0040] Figure 14 This is a schematic diagram of the structure of the double-convex pile head leveling and forming box in Embodiment 2 of the present invention.

[0041] Figure 15 This is a top view of the double-convex pile head leveling and forming box in Embodiment 2 of the present invention.

[0042] Figure 16 This is a bottom view of the double-convex pile head leveling and forming box in Embodiment 2 of the present invention.

[0043] Figure 17 This is a schematic diagram of the template for the double-convex precast pile cap in Embodiment 2 of the present invention.

[0044] Figure 18 This is a bottom view of the template for the double-convex precast pile cap in Embodiment 2 of the present invention.

[0045] Figure 19 This is a schematic diagram of the construction method for a pile structure used in a composite foundation according to an embodiment of the present invention.

[0046] Attached reference numerals: 1. Precast pile cap; 101. Pile cap body; 102. Pile cap protrusion; 103. Grouting pipe; 104. Grout flow channel; 105. Lifting ring; 2. Pile body; 201. Groove; 3. Pile head leveling and forming box; 301. Box body; 302. Leveling protrusion; 303. Spirit level; 304. Pull ring; 4. Pile cap template; 401. Outer steel mold; 402. Fixing rod; 403. Embedded grouting pipe; 404. Steel bar; Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Although representative embodiments of the present invention have been described in detail, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be defined by the appended claims and their equivalents.

[0048] This invention provides a precast pile cap, comprising a pile cap body; a pile cap protrusion is provided at the bottom of the pile cap body, preferably connected to the center of the bottom surface, and the diameter of the protrusion is smaller than the pile diameter; a grouting pipe is provided inside the pile cap body, and the grouting pipe penetrates the top and bottom surfaces of the pile cap body; a grout flow groove is provided on the bottom surface of the pile cap body; the grout flow groove is connected to the grouting pipe. The precast pile cap provided by this invention eliminates the need for a groove on the pile cap body for connection with the pile body, does not affect the thickness of the pile cap body itself, and ensures the strength of the precast pile cap.

[0049] Precast pile caps are suitable for common frustum, disc, and square pile caps, and can be made of reinforced concrete or plain concrete. The number of grouting pipes and grout flow channels is determined by construction needs, with each grouting pipe corresponding to one grout flow channel. The grouting pipes are preferably positioned adjacent to the outer edge of the pile cap protrusion, so that the outlet of the grouting pipe on the bottom surface of the pile cap body is located in the gap formed between the pile cap protrusion and the side wall of the pile body groove. Compared to the traditional pile cap-pile connection structure where the grout injection point is located at the junction of the bottom surface of the pile cap and the top surface of the pile body, this reduces grout injection resistance and makes it easier for the grout to be injected into the gaps between the precast pile cap and the pile body, and between the precast pile cap and the foundation. The grout flow channel is preferably connected between the grouting pipe and the edge of the pile cap body to ensure that the grout can fill the space between the precast pile cap and the surrounding soil. The pile cap protrusion can be designed as a multi-layered stepped protrusion structure as needed to increase the connection between the pile cap and the pile head.

[0050] To facilitate the hoisting of the pile cap body during subsequent construction, a hoisting ring is provided on the top of the pile cap body. The hoisting ring is preferably a concave type, symmetrically arranged on the upper surface of the pile cap body, and connected to the internal steel bars of the pile cap body to ensure the stable hoisting of the precast pile cap.

[0051] The present invention also provides a pile structure for composite foundations, including a pile body and the aforementioned precast pile cap; a groove matching the protrusion of the pile cap is provided on the top of the pile body; the pile cap body is installed on the pile body, and the protrusion of the pile cap is inserted into the groove; the grouting pipe is connected to the groove.

[0052] Optionally, the pile cap protrusion is cylindrical, and the diameter of the groove at the top of the pile body is larger than the diameter of the pile cap protrusion, with the difference typically being 1-2 centimeters. Having the pile head groove slightly larger than the pile cap protrusion not only facilitates the installation of the precast pile cap but also prevents excessive eccentricity of the precast pile cap.

[0053] This invention also provides a construction method for pile structures on composite foundations, referring to... Figure 19 This includes the following steps:

[0054] (1) Precast pile caps are cast in batches using pile cap templates;

[0055] (2) Level and compact the ground to the design elevation of the top surface of the pile cap;

[0056] (3) Drilling and grouting the pile body;

[0057] Specifically, pour plain concrete to a height above the design elevation of the pile top, promptly remove drilling slag, vibrate the concrete, skim off the surface laitance, and once the concrete surface stops dropping, skim off any excess concrete to bring the concrete surface to the design elevation of the pile top.

[0058] (4) Level the pile head and create a groove;

[0059] Specifically, a pile head leveling and forming box is used for leveling and creating grooves; the pile head leveling and forming box includes a box body; a level instrument, preferably a bubble level, is provided on the top surface of the box body and is located at the center of the top surface; a leveling protrusion is provided on the bottom of the box body; the shape of the leveling protrusion is the same as that of the pile cap protrusion, and the volume of the leveling protrusion is larger than that of the pile cap protrusion; a pull ring is provided on the top of the pile head leveling and forming box; the pile head leveling is performed simultaneously with the integral forming of the groove on the pile head by the pile head leveling and forming box.

[0060] Place the pile head leveling molding box on the concrete surface of the pile top and press it down until the top surface of the pile head leveling molding box is level with the leveled ground. Adjust the pile head leveling molding box to be horizontal by observing the level bubble. After the concrete strength of the pile body reaches the standard, remove the pile head leveling molding box. If the leveling molding box is tightly bonded to the pile top, it can be removed by pulling the ring.

[0061] (5) Lay a film or wooden board at the top of the pile, remove the soil around the top of the pile, and make the size slightly larger than the precast pile cap to form a space to accommodate the precast pile cap. Clean the slag on the top of the pile.

[0062] (6) Hoist the precast pile cap to the top of the pile so that the pile cap protrudes and inserts into the groove at the top of the pile;

[0063] (7) Grouting is injected into the connection between the pile cap and the pile body through the grouting pipe opened on the pile cap body. The grout first fills the annular gap at the connection between the pile cap and the pile top, and then fills the gap between the pile cap and the surrounding soil along the grout flow channel at the bottom of the precast pile cap until the grout overflows from all sides of the precast pile cap. Grouting is then stopped, and the pile structure construction is completed.

[0064] The effects of the precast pile cap, pile structure for composite foundation, and construction method of the present invention will be studied through specific embodiments below.

[0065] Example 1:

[0066] Reference Figure 1-3 This embodiment provides a single-convex precast pile cap, including a pile cap body; the bottom center of the pile cap body has a downward-facing cylindrical pile cap protrusion; two vertical grouting pipes are provided inside the pile cap body, symmetrically arranged on both sides of the pile cap protrusion, penetrating the top and bottom surfaces of the pile cap body along the thickness direction, and the outlet of the grouting pipe on the bottom surface of the pile cap body is close to the side of the pile cap protrusion; two grout flow channels perpendicular to the direction of the vertical grouting pipes are provided on the bottom surface of the pile cap body, one grout flow channel is connected to one grouting pipe, and the grout flow channel is connected between the outlet of the grouting pipe on the bottom surface of the pile cap body and the edge of the pile cap body. The top surface of the precast pile cap has two symmetrically arranged concave lifting rings.

[0067] The present invention also provides a pile structure for composite foundations, including a pile body and the aforementioned precast pile cap; a groove matching the protrusion of the pile cap is provided on the top of the pile body; the pile cap body is installed on the pile body, and the pile cap protrusion is inserted into the groove; the opening of the grouting pipe on the bottom surface of the pile cap body is located between the side wall of the lower groove and the outer wall of the pile cap protrusion, so that during subsequent grouting, the grout is directly injected into the gap formed between the pile cap protrusion and the side wall of the groove, thereby reducing the grout injection resistance.

[0068] The above-mentioned pile structure is constructed through the following steps:

[0069] (1) Through such Figure 8-9 The above-mentioned single-convex precast pile caps were cast in batches using the pile cap template shown.

[0070] The pile cap template consists of an outer steel mold, fixing rods, embedded grouting pipes, and steel bars. The outer steel mold has the same shape as the outer surface of the precast pile cap, and steel bars are welded inside its bottom surface to form grout flow channels on the bottom surface of the precast pile cap. The fixing rods are positioned in the same place as the vertical grouting pipes in the precast pile cap, perpendicular to the bottom surface of the outer steel mold and welded to it. The grouting pipes are fitted over the fixing rods and are integrated with the reinforced concrete pouring, becoming part of the precast pile cap and providing a channel for subsequent grouting. The inner diameter of the embedded grouting pipes is the same as the diameter of the grouting pipes, slightly larger than the diameter of the fixing rods, and the length is equal to the length of the grouting pipes. Before pouring concrete, a thin layer of grease is applied to the inner surface of the outer steel mold and the outer surface of the fixing rods to ensure smooth demolding of the precast pile cap.

[0071] (2) Level and compact the ground to the design elevation of the top surface of the pile cap.

[0072] (3) Drill holes and pour plain concrete to 30cm above the design elevation of the pile top. Remove the drilling slag in time. Vibrate the concrete within 3m below the concrete surface and remove the surface laitance. When the concrete surface no longer drops, remove the over-poured concrete so that the concrete surface reaches the design elevation of the pile top.

[0073] (4) Use a pile head leveling molding box to level and open grooves.

[0074] The pile head leveling and forming box, as shown Figure 5-7 As shown, it includes a box body; the bottom and top surfaces of the box body are parallel and are both horizontal. A spirit level is embedded in the center of the top surface, and a cylindrical leveling protrusion is provided in the center of the bottom surface. The diameter of the leveling protrusion is 1cm larger than the diameter of the pile cap protrusion, and the height is equal to that of the pile cap protrusion, ensuring that the groove formed on the pile body can accommodate the pile cap protrusion. Two pull rings are symmetrically provided on the top of the box body.

[0075] Place the pile head leveling molding box on the concrete surface at the top of the pile. Press the box downwards from directly above until the top surface of the box is level with the leveled ground. Adjust the top surface of the box to be horizontal by observing the spirit level. Once the concrete strength of the pile body reaches the standard, remove the box to complete the leveling of the top of the pile body and create a groove. If the leveling molding box is tightly bonded to the pile top, it can be removed using the pull ring.

[0076] (5) Lay a film or wooden board at the top of the pile, remove the soil around the top of the pile, and make the size slightly larger than the precast pile cap to form a space to accommodate the precast pile cap. Clean the slag on the top of the pile.

[0077] (6) Hoist the precast pile cap to the top of the pile so that the pile cap protrudes and inserts into the groove at the top of the pile;

[0078] (7) Grout is injected into the connection between the pile cap and the pile body through the grouting pipe opened on the pile cap body. The grout first fills the annular gap at the connection between the pile cap and the pile top, and then fills the gap between the pile cap and the surrounding soil along the grout flow channel at the bottom of the precast pile cap until the grout overflows from all sides of the precast pile cap. Grouting is then stopped, and the process is completed. Figure 4 Construction of the pile structure shown.

[0079] The single-concave-convex connection provided in this embodiment significantly enhances the reliability of the connection between the pile cap and the pile head by filling the gap at the convex-concave joint with grout. During grouting, the grout fills the gap between the precast pile cap and the surrounding soil, ensuring a tight and compact fit between the precast pile cap and the surrounding soil. The use of the pile head leveling and forming box ensures that the pile top elevation is accurately controlled at the design elevation, and the pile head has high flatness. It avoids the need for excavation and backfilling of soil between piles and the pile cutting and leveling process. Leveling can be adjusted by observing the level bubble, making the operation simple and greatly improving construction efficiency. It also avoids damage to the pile body caused by excavation and backfilling of soil between piles and cutting off the pile head, reducing the amount of over-pouring concrete and making it highly economical.

[0080] Example 2:

[0081] Reference Figure 10-12 This embodiment provides a double-convex precast pile cap, including a pile cap body. The bottom center of the pile cap body has a downward-facing double-layered stepped pile cap protrusion, which includes a first cylinder and a second cylinder. The diameter of the first cylinder is larger than that of the second cylinder. The top surface of the first cylinder is connected to the bottom surface of the pile cap body, and the bottom surface is connected to the top surface of the second cylinder. The center of the bottom surface of the pile cap body, the center of the first cylinder, and the center of the second cylinder are on a straight line. Two grouting pipes are provided inside the pile cap body, symmetrically arranged on both sides of the pile cap protrusion, and penetrate the pile cap body and the first cylinder along the thickness direction. The circular cross-section of the outlet is tangent to the bottom surface of the second cylinder. The precast pile cap has two grout flow channels, each consisting of a first transverse channel on the bottom surface of the pile cap, a longitudinal pipe penetrating the first cylinder, and a second transverse channel on the bottom surface of the first cylinder. The first transverse channel connects the upper end of the longitudinal pipe to the edge of the pile cap body. The lower outlet of the longitudinal pipe connects to the outlet of the grouting pipe on the bottom surface of the first cylinder through the second transverse channel, facilitating the flow of grout into the grout flow channels. The top surface of the precast pile cap has two symmetrically arranged concave lifting rings.

[0082] The present invention also provides a pile structure for composite foundations, including a pile body and the aforementioned precast pile cap; the top of the pile body is provided with a double-layer groove that matches the protrusion of the pile cap; the pile cap body is installed on the pile body, and the protrusion of the pile cap is inserted into the groove; the outlet of the grouting pipe formed on the bottom surface of the first cylinder is located between the side wall of the groove and the outer wall of the second cylinder, so that during subsequent grouting, the grout is directly injected into the gap formed between the protrusion of the pile cap and the side wall of the groove, thereby reducing the grout injection resistance.

[0083] The above-mentioned pile structure is constructed through the following steps:

[0084] (1) Through such Figure 17-18 The above-mentioned single-convex precast pile caps were cast in batches using the pile cap template shown.

[0085] The pile cap formwork consists of an outer steel mold, fixing rods, embedded grouting pipes, and steel bars. The outer steel mold has the same shape as the outer surface of the precast pile cap, and steel bars are welded inside its bottom surface to form grout flow channels on the bottom surface of the precast pile cap. The fixing rods are positioned in the same location as the vertical grouting pipes, perpendicular to the bottom surface of the outer steel mold and welded to it. The grouting pipes are fitted over the fixing rods and are integrated with the reinforced concrete pouring, becoming part of the precast pile cap and providing a channel for subsequent grouting. The inner diameter of the embedded grouting pipes is the same as the diameter of the grouting pipes, slightly larger than the diameter of the fixing rods, and the length is equal to the length of the grouting pipes. Before pouring concrete, a thin layer of grease is applied to the inner surface of the outer steel mold and the outer surface of the fixing rods to ensure smooth demolding of the precast pile cap.

[0086] (2) Level and compact the ground to the design elevation of the top surface of the pile cap.

[0087] (3) Drill holes and pour plain concrete to 30cm above the design elevation of the pile top. Remove the drilling slag in time. Vibrate the concrete within 3m below the concrete surface and remove the surface laitance. When the concrete surface no longer drops, remove the over-poured concrete so that the concrete surface reaches the design elevation of the pile top.

[0088] (4) Use a pile head leveling molding box to level and open grooves.

[0089] The pile head leveling and forming box, as shown Figure 14-16 As shown, it includes a box body; the bottom and top surfaces of the box body are parallel and are both horizontal. A spirit level is embedded in the center of the top surface, and a leveling protrusion consisting of two layers of cylinders with the same shape as the pile cap protrusion is provided in the center of the bottom surface; the diameter of the two cylinders of the leveling protrusion is 2cm larger than that of the pile cap protrusion, and the height is equal to that of the pile cap protrusion, ensuring that the groove formed on the pile body can accommodate the pile cap protrusion; two pull rings are symmetrically provided on the top of the box body.

[0090] Place the pile head leveling molding box on the concrete surface at the top of the pile. Press the box downwards from directly above until the top surface of the box is level with the leveled ground. Adjust the top surface of the box to be horizontal by observing the spirit level. Once the concrete strength of the pile body reaches the standard, remove the box to complete the leveling of the top of the pile body and create a groove. If the leveling molding box is tightly bonded to the pile top, it can be removed using the pull ring.

[0091] (5) Lay a film or wooden board at the top of the pile, remove the soil around the top of the pile, and make the size slightly larger than the precast pile cap to form a space to accommodate the precast pile cap. Clean the slag on the top of the pile.

[0092] (6) Hoist the precast pile cap to the top of the pile so that the pile cap protrudes and inserts into the groove at the top of the pile;

[0093] (7) Grout is injected into the connection between the pile cap and the pile body through the grouting pipe opened on the pile cap body. The grout first fills the annular gap at the connection between the pile cap and the pile top, and then fills the gap between the pile cap and the surrounding soil along the grout flow channel at the bottom of the precast pile cap until the grout overflows from all sides of the precast pile cap. Grouting is then stopped, and the process is completed. Figure 13 Construction of the pile structure shown.

[0094] The double-convex-concave connection provided in this embodiment is more complex than the single-convex-concave connection, but it greatly improves the connection between the pile cap and the pile body. Grouting fills the gaps at the convex-concave connection, significantly enhancing the reliability of the connection between the pile cap and the pile head. During grouting, the grout fills the gaps between the precast pile cap and the surrounding soil, ensuring a tight and compact fit between the precast pile cap and the surrounding soil. The use of a pile head leveling and molding box ensures accurate control of the pile top elevation at the design elevation, and high pile head flatness. It avoids the need for excavation and backfilling between piles and the pile cutting and leveling process; leveling can be adjusted by observing the level bubble, simplifying operation and greatly improving construction efficiency. Furthermore, it avoids damage to the pile body caused by excavation and backfilling between piles and pile head cutting, reducing over-pouring of concrete and demonstrating strong economic efficiency.

[0095] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A construction method for a pile structure used in composite foundations, characterized in that, The pile structure for composite foundations includes a pile body and a precast pile cap; the precast pile cap includes a pile cap body; the bottom of the pile cap body has a pile cap protrusion; a grouting pipe is formed inside the pile cap body, and the grouting pipe penetrates the pile cap body; a grout flow groove is formed on the bottom surface of the pile cap body; the grout flow groove is connected to the grouting pipe; a groove matching the pile cap protrusion is formed on the top of the pile body; the pile cap body is installed on the pile body, and the pile cap protrusion is inserted into the groove, and the grouting pipe is connected to the groove; the construction method includes the following steps: (1) Casting precast pile caps; (2) Level and compact the ground to the design elevation of the top surface of the pile cap; (3) Drilling and grouting the pile body; (4) Use a pile head leveling molding box to level and open grooves; the pile head leveling molding box includes a box body; the top surface of the box body is equipped with a level instrument; the bottom of the box body is equipped with a leveling protrusion; the shape of the leveling protrusion is the same as the shape of the pile cap protrusion, and the volume of the leveling protrusion is greater than the volume of the pile cap protrusion; place the pile head leveling molding box on the concrete surface of the pile top, and press the pile head leveling molding box downward until the top surface of the pile head leveling molding box is level with the leveled ground. Adjust the pile head leveling molding box to be horizontal by observing the level bubble. After the concrete strength of the pile body reaches the standard, take out the pile head leveling molding box. (5) Remove the soil around the top of the pile to form a space to accommodate the precast pile cap, and clean the slag on the top of the pile; (6) Hoist the precast pile cap to the top of the pile so that the pile cap protrudes into the groove at the top of the pile; (7) Grouting is carried out at the connection between the precast pile cap and the pile body through the grouting pipe on the pile cap body until the grout overflows from the periphery of the precast pile cap, and the grouting is stopped to complete the construction of the pile structure.

2. The construction method for pile structures used in composite foundations as described in claim 1, characterized in that: The top of the pile cap body is equipped with a lifting ring.

3. The construction method for pile structures used in composite foundations as described in claim 1, characterized in that: The pile cap protrusion is cylindrical, and the diameter of the groove is larger than the diameter of the pile cap protrusion.

4. The construction method for pile structures used in composite foundations as described in claim 1, characterized in that: The specific steps (3) are as follows: drilling, pouring concrete to the design elevation above the pile top, removing drilling slag; vibrating the concrete, scooping off the surface laitance, and scooping off the excess concrete so that the concrete surface reaches the design elevation of the pile top when the concrete surface no longer drops.

5. The construction method for pile structures for composite foundations as described in claim 1, characterized in that: The top of the box is equipped with a pull ring.

6. The construction method for pile structures for composite foundations as described in claim 1, characterized in that: The precast pile cap is provided with multiple grouting pipes; in step (7), during the grouting process, one of the grouting pipes serves as an air vent. After the other grouting pipes are filled, the grouting pipe that serves as the air vent is then filled with grout.

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