Auxiliary construction device and construction method for cast-in-place pile based on ball hole expansion theory

Abstract

The invention relates to the technical field of cast-in-place piles and discloses a cast-in-place pile auxiliary construction device and method based on the ball hole expansion theory, and the cast-in-place pile auxiliary construction device comprises a supporting steel beam used for supporting a reinforcement cage and a support capable of being supported around a pile casing. According to the auxiliary construction device for the cast-in-place pile based on the ball hole expansion theory and the construction method, a first-section reinforcement cage provided with a grouting capsule is hoisted and put into a hole pile foundation well, the first-section reinforcement cage partially stretches out of a pile casing, a supporting steel beam penetrates through the lower portion of a stirrup of the first-section reinforcement cage and is supported on a cross beam, and the first-section reinforcement cage is located above a pile casing opening; the taking and placing assembly moves the sleeve to a main reinforcement of the first section of reinforcement cage, the extension section of reinforcement cage is hoisted to the position of the main reinforcement of the first section of reinforcement cage, the main reinforcement of the extension section of reinforcement cage is inserted into the sleeve, the sleeve is heated by a welding gun to be welded and fixed, the supporting steel beam is taken down, and the first section of reinforcement cage and the extension section of reinforcement cage which are connected continue to be put down. And the extension section reinforcement cage is continuously mounted, so that the reinforcement cage is convenient to mount.

Description

Technical Field

[0001] The invention relates to the technical field of cast-in-place piles, in particular to an auxiliary construction device and a construction method of cast-in-place piles based on spherical hole expansion theory. Background Art

[0002] The spherical pore expansion theory is mainly used to describe and simulate the expansion process of a spherical pore in soil or rock. The spherical pore expansion theory takes into account the structural properties of the soil, the influence of the internal friction angle, and the strain softening characteristics and shear dilatancy of the soil during the expansion process. These characteristics make the spherical pore expansion theory highly accurate and practical in analyzing the structural damage or degradation, stress changes and stress field around the pore during the expansion process of the soil.

[0003] The bored pile of spherical hole expansion theory is an important foundation form, and its construction quality is directly related to the safety and stability of the whole project. When installing the steel cage, the steel cage needs to be connected with multiple sections to reach the depth of the pile foundation well. The multiple sections of the steel cage are completely welded before being hoisted. The length of the steel cage is too long, and it is difficult to vertically hoist it down to the pile foundation well. In addition, pile bottom sediment and pile side mud skin are easily generated during the construction of the bored pile. The existence of pile bottom sediment and pile side mud skin will reduce the normal stress between the pile and the soil. At the same time, the lubricating effect of the mud skin will reduce the ultimate shear stress between the pile and the soil, thereby reducing the ultimate bearing capacity of the pile, resulting in the need to compensate by increasing the pile length, pile diameter or pile number, which not only increases material consumption, construction difficulty and project cost, but also prolongs the construction period. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides an auxiliary construction device and a construction method for cast-in-place piles based on the spherical hole expansion theory, which solve the problems mentioned in the above background.

[0005] The present invention provides the following technical solutions: an auxiliary construction device for cast-in-place piles based on the spherical hole expansion theory, comprising: a supporting steel beam for supporting a steel cage and a bracket that can be supported around the casing;

[0006] The steel cage includes a first section steel cage and an extension section steel cage, and the first section steel cage is connected to the extension section steel cage and adjacent extension section steel cages through sleeves;

[0007] A cylindrical groove for the steel cage to pass through is arranged at the center of the top of the bracket, and a crossbeam is arranged on the bracket. The supporting steel beam passes under the stirrups of the steel cage and is supported on the crossbeam. A pick-and-place assembly for installing a sleeve is arranged on the bracket, and a welding gun for welding the sleeve to the connection between the main reinforcement of the first section of the steel cage and the main reinforcement of the extended section of the steel cage and the connection between the main reinforcement of the adjacent extended section of the steel cage is arranged on the pick-and-place assembly.

[0008] Preferably, an insert shaft for placing the sleeve is provided on one side of the cylindrical groove on the bracket.

[0009] Preferably, there are multiple insertion shafts and pick-and-place assemblies, and the multiple insertion shafts and pick-and-place assemblies are evenly distributed in a circular array along the circumferential direction of the cylindrical groove, and the positions of the multiple insertion shafts and pick-and-place assemblies correspond to the positions of the main bars of the steel cage.

[0010] Preferably, the pick-and-place assembly includes a longitudinal cylinder, a radial cylinder and a connecting block, the longitudinal cylinder is installed on the top of the bracket, the radial cylinder is installed on the telescopic end of the longitudinal cylinder, the connecting block is installed on the telescopic end of the radial cylinder, and the connecting block is provided with a magnet that can adsorb the sleeve, the surface of the magnet is provided with an arc groove, and the inner wall of the arc groove is adapted to the surface of the sleeve.

[0011] Preferably, a bracket is provided on the top of the connecting block, and the welding gun is installed on the bracket;

[0012] A plurality of annular welding wires are fixed in the sleeve. When the welding gun heats the sleeve, the annular welding wires are thermally melted inside the sleeve.

[0013] A construction method of cast-in-place piles based on spherical hole expansion theory comprises the following steps:

[0014] Step S1, setting out the center of the pile position and vertically sinking the casing;

[0015] Step S2, drilling a pile foundation well along the center of the casing by a drilling rig;

[0016] Step S3, installing a grouting capsule on the steel cage;

[0017] Step S4, installing the steel cage into the pile foundation well so that the grouting capsule is located at the bottom of the pile foundation well;

[0018] Step S5, using a closed grouting method to perform pressure grouting in the grouting capsule, so that it expands into an enlarged head, and the enlarged head is suitable for compacting the soil layer around it;

[0019] Step S6, using the open grouting method to fill the hollow gaps in the pile foundation well.

[0020] Preferably, the step S4 includes the following steps:

[0021] Step S41, installing the grouting capsule and the first section of the steel cage: hoisting the first section of the steel cage with the grouting capsule installed into the pile foundation well, and making the first section of the steel cage partially extend out of the casing;

[0022] Step S42, setting a docking auxiliary construction device around the casing: the supporting steel beam can pass under the stirrups of the first section of the steel cage and be supported on the crossbeam, so that the first section of the steel cage is located above the casing opening;

[0023] Step S43, hoisting the extended steel cage: the pick-and-place assembly moves the sleeve to the main reinforcement of the first steel cage, hoists the extended steel cage to the main reinforcement position of the first steel cage, and inserts the main reinforcement of the extended steel cage into the sleeve, and heats the sleeve with a welding gun to weld and fix it;

[0024] Step S44, releasing the first steel cage section: removing the supporting steel beam, and further lowering the connected first steel cage section and the extended steel cage section, and the extended steel cage section can continue to install another extended steel cage section through the sleeve until the grouting capsule is located at the bottom of the pile foundation well;

[0025] Among them, the extended steel cage is set to multiple sections according to actual construction needs.

[0026] Preferably, in step S5, the grouting capsule is configured to be spherical;

[0027] The grouting capsule comprises a first capsule layer and a second capsule layer, wherein a closed inner cavity is provided in the first capsule layer, an intermediate cavity is formed between the first capsule layer and the second capsule layer, a bottom plate is fixed at the bottom of the first section of the steel cage, and the grouting capsule is fixed on the bottom plate;

[0028] The grouting capsule is provided with a first grouting hose connected to the closed inner cavity and a second grouting hose connected to the middle cavity. The lengths of the first grouting hose and the second grouting hose are greater than the depth of the pile foundation well. After the grouting is completed, the first grouting hose and the second grouting hose are sealed and bent into the interior of the pile foundation well.

[0029] Preferably, in step S5, a plurality of slurry outlet holes connected to the middle cavity are provided on the second capsule layer, and grouting is performed on the middle cavity so that the concrete slurry penetrates into the soil layer around the grouting capsule along the slurry outlet holes in a tree root-like manner.

[0030] Preferably, in step S6,

[0031] The first hollow gap formed between the grouting capsule and the pile foundation well, and the second hollow gap formed between the steel cage and the pile foundation well are grouted by the open grouting method.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention, by arranging a supporting steel beam, a bracket, a sleeve, a pick-and-place assembly and a welding gun, lifts the first section of the steel cage installed with a grouting capsule into the pile foundation well, partially extends the first section of the steel cage to the casing, the supporting steel beam passes through the bottom of the stirrups of the first section of the steel cage and is supported on the crossbeam, the first section of the steel cage is located above the casing mouth, the pick-and-place assembly moves the sleeve to the main reinforcement of the first section of the steel cage, lifts the extension section of the steel cage to the main reinforcement position of the first section of the steel cage, and inserts the main reinforcement of the extension section of the steel cage into the inside of the sleeve, heats the sleeve with a welding gun to weld and fix it, removes the supporting steel beam, continues to lower the connected first section of the steel cage and the extension section of the steel cage, continues to install the extension section of the steel cage, and is convenient for installing the steel cage.

[0034] 2. The present invention forms an enlarged head by expanding the grouting capsule at the bottom of the pile foundation hole. This process effectively compacts the surrounding soil layer and reduces the influence of the sediment at the bottom of the pile. A plurality of slurry outlet holes connected to the middle cavity are provided on the second capsule layer. The middle cavity is grouted so that the concrete slurry penetrates into the soil layer around the grouting capsule along the slurry outlet holes in the shape of tree roots and is tightly connected with the surrounding soil layer. At the same time, the open grouting method is combined with the open grouting method to fill the hollow gaps in the pile foundation hole, thereby improving the bearing capacity of the pile foundation. There is no need to compensate for the problem of insufficient bearing capacity by increasing the pile length, pile diameter or pile number, which effectively reduces the construction cost and difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the auxiliary construction device of the cast-in-place pile of the present invention;

[0036] Figure 2 For the present invention Figure 1 A schematic diagram of the structure at the center A position is enlarged;

[0037] Figure 3 It is a schematic diagram of the structure of the pile foundation well in the construction method of the cast-in-place pile based on the spherical hole expansion theory of the present invention;

[0038] Figure 4 The present invention is a flow chart of the construction method of cast-in-place piles based on the spherical hole expansion theory;

[0039] Figure 5 The present invention is a flow chart for installing the grouting capsule and the steel cage.

[0040] In the figure: 1. supporting steel beam; 2. bracket; 3. steel cage; 4. sleeve; 5. cylindrical groove; 6. cross beam; 7. pick-and-place assembly; 71. longitudinal cylinder; 72. radial cylinder; 73. connecting block; 74. magnet; 75. arc groove; 8. welding gun; 9. plug-in shaft; 10. bracket; 11. grouting capsule; 111. first capsule layer; 112. second capsule layer; 113. closed inner cavity; 114. middle cavity; 12. bottom plate; 13. first grouting hose; 14. second grouting hose. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] See also Figure 1-2 , an auxiliary construction device for cast-in-place piles based on spherical hole expansion theory, comprising: a supporting steel beam 1 for supporting a steel cage 3 and a bracket 2 that can be supported around the casing;

[0043] The steel cage 3 includes a first section steel cage and an extension section steel cage, and the first section steel cage is connected to the extension section steel cage and the adjacent extension section steel cages through a sleeve 4;

[0044] A cylindrical groove 5 for the steel cage 3 to pass through is provided at the center of the top of the bracket 2, and a crossbeam 6 is provided on the bracket 2. The supporting steel beam 1 passes through the stirrups under the steel cage 3 and is supported on the crossbeam 6. A pick-up and placement assembly 7 for installing the sleeve 4 is provided on the bracket 2. The pick-up and placement assembly 7 is provided with a welding gun 8 for welding the sleeve 4 to the connection between the main reinforcement of the first section steel cage and the main reinforcement of the extended section steel cage and the connection between the main reinforcement of the adjacent extended section steel cage.

[0045] An insertion shaft 9 for placing the sleeve 4 is provided on one side of the cylindrical groove 5 on the bracket 2 .

[0046] There are multiple insertion shafts 9 and pick-and-place components 7, which are evenly distributed in a circular array along the circumferential direction of the cylindrical groove 5, and the positions of the multiple insertion shafts 9 and pick-and-place components 7 correspond to the positions of the main bars of the steel cage 3.

[0047] The pick-and-place assembly 7 includes a longitudinal cylinder 71, a radial cylinder 72 and a connecting block 73. The longitudinal cylinder 71 is mounted on the top of the bracket 2, the radial cylinder 72 is mounted on the telescopic end of the longitudinal cylinder 71, and the connecting block 73 is mounted on the telescopic end of the radial cylinder 72. A magnet 74 that can adsorb the sleeve 4 is provided on the connecting block 73. An arc groove 75 is provided on the surface of the magnet 74, and the inner wall of the arc groove 75 is adapted to the surface of the sleeve 4. When the sleeve 4 is installed, the telescopic end of the longitudinal cylinder 71 drops, driving the radial cylinder 72 to move. The cylinder 72 descends, and the telescopic end of the radial cylinder 72 extends out, pushing the magnet 74 to move through the connecting block 73. The arc groove 75 of the magnet 74 docks with the sleeve 4, sucking the sleeve 4, driving the telescopic end of the longitudinal cylinder 71 to rise to the top of the main reinforcement of the steel cage 3, and the sleeve 4 is located at the horizontal position of the top of the main reinforcement of the steel cage 3. The telescopic end of the radial cylinder 72 extends out, pushing the sleeve 4 to be located above the main reinforcement of the steel cage 3, driving the telescopic end of the longitudinal cylinder 71 to descend, and driving the sleeve 4 to be sleeved on the main reinforcement of the steel cage 3.

[0048] A bracket 10 is provided on the top of the connecting block 73, and a welding gun 8 is installed on the bracket 10. A plurality of annular welding wires are fixed in the sleeve 4. When the welding gun 8 heats the sleeve 4, the annular welding wires are hot-melted inside the sleeve 4. The welding gun 8 adopts an acetylene gun. When the welding gun 8 heats the sleeve, the annular welding wires are hot-melted and connected between the sleeve and the main bars of the first section of the steel cage and the main bars of the extended section of the steel cage, as well as between the main bars of the extended section of the steel cage.

[0049] See also Figure 3-5 A construction method of cast-in-place piles based on spherical hole expansion theory comprises the following steps:

[0050] Step S1, setting out the center of the pile position and vertically sinking the casing;

[0051] Step S2, drilling a pile foundation well along the center of the casing by a drilling rig;

[0052] Step S3, installing a grouting capsule 11 on the steel cage 3;

[0053] Step S4, installing the steel cage 3 into the pile foundation well so that the grouting capsule 11 is located at the bottom of the pile foundation well;

[0054] Step S5, using a closed grouting method to perform pressure grouting in the grouting capsule 11, so that it expands into an enlarged head, and the enlarged head is suitable for compacting the soil layer around it;

[0055] Step S6, using the open grouting method to fill the hollow gaps in the pile foundation well.

[0056] Step S4 includes the following steps:

[0057] Step S41, installing the grouting capsule 11 and the first section of the steel cage: hoisting the first section of the steel cage with the grouting capsule 11 installed into the pile foundation well, and making the first section of the steel cage partially extend out of the casing;

[0058] Step S42, setting a docking auxiliary construction device around the casing: the supporting steel beam 1 can pass under the stirrups of the first section of the steel cage and be supported on the crossbeam 6, so that the first section of the steel cage is located above the casing opening;

[0059] Step S43, hoisting the extended steel cage: the pick-and-place assembly 7 moves the sleeve 4 to the main reinforcement of the first steel cage, hoists the extended steel cage to the main reinforcement position of the first steel cage, and inserts the main reinforcement of the extended steel cage into the sleeve 4, and the welding gun 8 heats the sleeve 4 for welding and fixing;

[0060] Step S44, releasing the first steel cage section: removing the supporting steel beam 1, and further lowering the connected first steel cage section and the extended steel cage section, and the extended steel cage section can continue to install another extended steel cage section through the sleeve 4, until the grouting capsule 11 is located at the bottom of the pile foundation well;

[0061] Among them, the extended steel cage is set to multiple sections according to actual construction needs.

[0062] In step S5, the grouting capsule 11 is set to be spherical;

[0063] The grouting capsule 11 includes a first capsule layer 111 and a second capsule layer 112. A closed inner cavity 113 is provided in the first capsule layer 111. An intermediate cavity 114 is formed between the first capsule layer 111 and the second capsule layer 112. A bottom plate 12 is fixed to the bottom of the first section of the steel cage 3. The grouting capsule 11 is fixed to the bottom plate 12.

[0064] The grouting capsule 11 is provided with a first grouting hose 13 connected to the closed inner cavity 113 and a second grouting hose 14 connected to the middle cavity 114. The lengths of the first grouting hose 13 and the second grouting hose 14 are greater than the depth of the pile foundation well. After grouting is completed, the first grouting hose 13 and the second grouting hose 14 are sealed and bent into the pile foundation well.

[0065] In step S5, a plurality of grouting holes connected to the middle cavity 114 are provided on the second capsule layer 112, and grouting is performed on the middle cavity 114, so that the concrete slurry penetrates into the soil layer around the grouting capsule 11 along the grouting holes in a tree root-like manner.

[0066] In step S6, the first hollow gap formed between the grouting capsule 11 and the pile foundation hole, and the second hollow gap formed between the steel cage 3 and the pile foundation hole are grouted by the open grouting method.

[0067] The grouting capsule 11 expands at the bottom of the pile foundation hole to form an enlarged head. This process effectively compacts the surrounding soil layer and reduces the influence of the sediment at the bottom of the pile. The second capsule layer 112 is provided with a plurality of grouting holes connected to the middle cavity 114. The middle cavity 114 is grouted, so that the concrete slurry penetrates into the soil layer around the grouting capsule 11 along the grouting holes in the shape of tree roots, and is tightly connected with the surrounding soil layer. At the same time, the open grouting method is combined with the open grouting method to fill the hollow gaps in the pile foundation hole, thereby improving the bearing capacity of the pile foundation. There is no need to compensate for the problem of insufficient bearing capacity by increasing the pile length, pile diameter or pile number, which effectively reduces the construction cost and difficulty.

[0068] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An auxiliary construction device for cast-in-place piles based on the spherical hole expansion theory. It is characterized in that include: A support steel beam (1) for supporting a steel cage (3) and a bracket (2) that can be supported around the casing; The steel cage (3) comprises a first section steel cage and an extension section steel cage, and the first section steel cage and the extension section steel cage as well as adjacent extension section steel cages are connected via sleeves (4); A columnar groove (5) is provided at the center of the top of the support (2) for the steel cage (3) to pass through, a crossbeam (6) is provided on the support (2), the support steel beam (1) passes through the bottom of the stirrups of the steel cage (3) and rests on the crossbeam (6), a pick-up and placement assembly (7) for installing the sleeve (4) is provided on the support (2), and a welding gun (8) is provided on the pick-up and placement assembly (7) for welding the sleeve (4) to the connection between the main reinforcement of the first section steel cage and the main reinforcement of the extended section steel cage and the connection between the main reinforcement of the adjacent extended section steel cage.

2. The auxiliary construction device for cast-in-place piles based on the spherical hole expansion theory according to claim 1, It is characterized in that An insertion shaft (9) for placing the sleeve (4) is provided on one side of the cylindrical groove (5) on the bracket (2).

3. The auxiliary construction device for cast-in-place piles based on the spherical hole expansion theory according to claim 2, It is characterized in that The number of the insertion shafts (9) and the pick-and-place components (7) is multiple, and the multiple insertion shafts (9) and the pick-and-place components (7) are uniformly distributed in a ring array along the circumferential direction of the cylindrical groove (5), and the positions of the multiple insertion shafts (9) and the pick-and-place components (7) correspond to the positions of the main bars of the steel cage (3).

4. The auxiliary construction device for cast-in-place piles based on the spherical hole expansion theory according to claim 3, It is characterized in that The pick-and-place assembly (7) comprises a longitudinal cylinder (71), a radial cylinder (72) and a connecting block (73); the longitudinal cylinder (71) is mounted on the top of the bracket (2); the radial cylinder (72) is mounted on the telescopic end of the longitudinal cylinder (71); the connecting block (73) is mounted on the telescopic end of the radial cylinder (72); a magnet (74) capable of adsorbing the sleeve (4) is provided on the connecting block (73); an arc groove (75) is provided on the surface of the magnet (74); and the inner wall of the arc groove (75) is matched with the surface of the sleeve (4).

5. The auxiliary construction device for cast-in-place piles based on the spherical hole expansion theory according to claim 4, It is characterized in that A bracket (10) is provided on the top of the connecting block (73), and the welding gun (8) is mounted on the bracket (10); A plurality of annular welding wires are fixed inside the sleeve (4); when the welding gun (8) heats the sleeve (4), the annular welding wires are thermally melted inside the sleeve (4).

6. A construction method of cast-in-place piles based on spherical hole expansion theory, It is characterized in that The steps include: Step S1, setting out the center of the pile position and vertically sinking the casing; Step S2, drilling a pile foundation well along the center of the casing by a drilling rig; Step S3, installing a grouting capsule (11) on the steel cage (3); Step S4, installing the steel cage (3) into the pile foundation well so that the grouting capsule (11) is located at the bottom of the pile foundation well; Step S5, using a closed grouting method to perform pressure grouting in the grouting capsule (11), so that the capsule expands into an enlarged head, and the enlarged head is suitable for compacting the soil layer around it; Step S6, using the open grouting method to fill the hollow gaps in the pile foundation well.

7. A construction method of cast-in-place piles based on spherical hole expansion theory according to claim 6, It is characterized in that The step S4 includes the following steps: Step S41, installing the grouting capsule (11) and the first section of the steel cage: hoisting the first section of the steel cage installed with the grouting capsule (11) and placing it into the pile foundation well, and making the first section of the steel cage partially extend out of the casing; Step S42, setting a docking auxiliary construction device around the casing: the supporting steel beam (1) can pass under the stirrups of the first section of the steel cage and be supported on the crossbeam (6), so that the first section of the steel cage is located above the casing opening; Step S43, hoisting the extended steel cage: the pick-up and placement assembly (7) moves the sleeve (4) to the main reinforcement of the first steel cage, hoists the extended steel cage to the main reinforcement position of the first steel cage, and inserts the main reinforcement of the extended steel cage into the sleeve (4), and the welding gun (8) heats the sleeve (4) to weld and fix it; Step S44, releasing the first steel cage section: removing the supporting steel beam (1), and further lowering the connected first steel cage section and the extended steel cage section, and the extended steel cage section can continue to install another extended steel cage section through the sleeve (4), until the grouting capsule (11) is located at the bottom of the pile foundation well; Among them, the extended steel cage is set to multiple sections according to actual construction needs.

8. A construction method of cast-in-place piles based on spherical hole expansion theory according to claim 7, It is characterized in that In the step S5, the grouting capsule (11) is configured to be spherical; The grouting capsule (11) comprises a first capsule layer (111) and a second capsule layer (112); a sealed inner cavity (113) is provided in the first capsule layer (111); an intermediate cavity (114) is formed between the first capsule layer (111) and the second capsule layer (112); a bottom plate (12) is fixed to the bottom of the first section of the steel cage (3); and the grouting capsule (11) is fixed on the bottom plate (12); The grouting capsule (11) is provided with a first grouting hose (13) connected to the closed inner cavity (113) and a second grouting hose (14) connected to the middle cavity (114); the lengths of the first grouting hose (13) and the second grouting hose (14) are greater than the depth of the pile foundation well; after grouting is completed, the first grouting hose (13) and the second grouting hose (14) are sealed and bent into the interior of the pile foundation well.

9. A construction method of cast-in-place piles based on spherical hole expansion theory according to claim 8, It is characterized in that In step S5, a plurality of grouting holes connected to the middle cavity (114) are provided on the second capsule layer (112), and grouting is performed on the middle cavity (114), so that the concrete slurry penetrates into the soil layer around the grouting capsule (11) along the grouting holes in a tree root-like manner.

10. A construction method of cast-in-place piles based on spherical hole expansion theory according to claim 9, It is characterized in that In step S6, A first hollow gap formed between the grouting capsule (11) and the pile foundation hole, and a second hollow gap formed between the steel cage (3) and the pile foundation hole are grouted by using an open grouting method.

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