Hollow pile end rotary grouting device and grouting method

Abstract

The present invention provides a hollow pile end screw-out grouting device and a grouting method, wherein a pile bottom sealing structure is fixedly installed at the bottom of the hollow pile, a hole is axially penetrated through the pile bottom sealing structure, and a screw-out grouting device is threadedly installed in the hole; the top of the screw-out grouting device is used to connect with the grouting pipe in the hollow pile, a grouting channel is provided in the screw-out grouting device, a grouting inlet is provided at the top of the screw-out grouting device for conducting the grouting pipe and the grouting channel, and a grouting hole is provided on the side wall at the bottom of the screw-out grouting device and connected to the grouting channel. The movable grouting pipe is used as a grouting tool and can be reused. At the same time, the movable grouting pipe is also used as a driving component for driving the screw-out grouting device to penetrate into the soil layer. It has multiple uses and does not need to use other tools to move the screw-out grouting device downward, thereby improving the grouting efficiency.

Description

Technical Field

[0001] The invention relates to building pile foundation construction, and in particular to a pile bottom grouting system based on hollow piles and a pile bottom grouting method thereof. Background Art

[0002] Hollow piles are mainly divided into two categories: concrete hollow piles and prefabricated steel piles. Hollow piles can withstand large loads, have reliable pile body quality, fast construction speed, and economical engineering cost. They are one of the widely used pile types in pile foundation engineering. Hollow piles are widely used in engineering due to factors such as small construction impact and mature pile making technology. Commonly used hollow piles are concrete prefabricated pipe piles and steel pipe piles.

[0003] At present, the commonly used hollow piles in China generally do not have pre-buried grouting pipes in the pile body. During the application process, it is often difficult to fully exert the bearing capacity of the pile body due to construction or soil layer reasons, resulting in the phenomenon that the bearing capacity of a single pile is far lower than the bearing capacity of the pile body. The main reason is that the soil layer strength on the pile side and pile end is insufficient and cannot provide sufficient pile side friction resistance and pile end resistance. Therefore, the grouting technology of the pile side and pile end of the hollow pile has gradually begun to develop. However, the current hollow pile post-grouting technology is difficult to promote and apply on a large scale due to the complex design, difficult construction, and high implementation cost.

[0004] Chinese patent application number 201810340103.0 discloses a post-grouting pile head and a post-grouting construction method. Through a mechanical structure, the front end of the pile head is displaced due to the grouting pressure, and cement slurry is injected into the soil through the grouting hole at the pile head, thereby completing the post-grouting construction of the pile end. The shortcomings of this invention are: 1. The structure of the pre-grouting end of this technology is relatively complicated, and it is necessary to open a hole in the pre-grouting end. Conventional processing methods cannot be used for processing, and special processing molds are required. The processing difficulty is relatively high, and the processing accuracy control is difficult; 2. There is no grouting pipe docking device, and the upper grouting pipe must be followed up at the beginning of pile driving. When the pipe pile is connected, the grouting pipe needs to be connected synchronously, which affects the efficiency of pile driving construction and the grouting pipe cannot be recycled, and the use cost is high; 3. The grouting hole lacks a reliable hole blocking protection structure, and hole blocking is very likely to occur during pile driving, resulting in grouting failure.

[0005] Chinese patent application number 200720029134.1 discloses a grouting pile head with a certain distance between the bottom pile head and the pile end. Cement slurry is injected into the soil through the middle grouting pipe to form a grouting body. The shortcomings of this invention are as follows: 1. There is no grouting pipe docking device. The upper grouting pipe must be followed up with the construction at the beginning of pile driving. The grouting pipe needs to be connected synchronously when the pile is connected, which affects the efficiency of pile driving construction and the grouting pipe cannot be recycled; 2. There is no slurry check structure. After the grouting is completed and the grouting plug pressure is released, the injected slurry is easy to flow back from the soil to the inside of the PHC pile, and the grouting reinforcement effect is poor; 3. The grouting outlet is located on the side of the pile end, and it is difficult for the slurry to flow to the pile end, and it is difficult to achieve effective reinforcement of the pile bottom soil.

[0006] In summary, the conventional grouting devices currently have the disadvantages of complex structure, lack of grouting pipe docking device, difficulty in grouting pipe docking, lack of reliable grouting hole protection structure, poor grouting reinforcement effect, high implementation cost, and high requirements for implementation control. The hollow pile grouting pile heads currently used in the market have more or less one or more of these disadvantages. Therefore, there is a lack of a grouting device and method that integrates the advantages of simple processing, convenient docking, convenient construction, fast construction, not easy to block the pipe, not easy to block the slurry outlet hole, and no slurry backflow. Summary of the invention

[0007] The purpose of the present invention is to propose a new hollow pile end screw-out grouting device and pile bottom grouting method based on the deficiencies of the above-mentioned technology. A screw-out grouting device is threadedly connected to the pile bottom sealing structure fixed at the bottom of the hollow pile. After the screw-out grouting device is connected to the grouting pipe in the hollow pile, the screw-out grouting device is driven by the grouting pipe to rotate and penetrate into the soil layer to perform grouting, thereby improving the pile bottom bearing capacity. In order to achieve the above-mentioned technical effects, the technical scheme adopted by the present invention is as follows:

[0008] A hollow pile end rotary grouting device is provided, wherein a pile bottom sealing structure is fixedly installed at the bottom of the hollow pile.

[0009] The pile bottom sealing structure is axially penetrated with a hole, and a screw-out grouting device is threadedly installed in the hole;

[0010] The top end of the swing-out grouting device is used to connect with the grouting pipe in the hollow pile, a grouting channel is arranged in the swing-out grouting device, a grouting inlet is arranged at the top of the swing-out grouting device to connect the grouting pipe and the grouting channel, and a grouting hole is arranged on the bottom side wall of the swing-out grouting device to connect with the grouting channel.

[0011] Furthermore, the grouting pipe is axially lifted and lowered in the hollow pile;

[0012] The bottom of the grouting pipe is detachably connected to the top of the swing-out grouting device.

[0013] Furthermore, the grouting pipe is connected to the top of the swing-out grouting device through a threaded connection or a rotating buckle, and the grouting pipe and the swing-out grouting device are relatively fixed after being connected in place.

[0014] Furthermore, the rotary grouting device comprises a rigid tube, and the internal space of the rigid tube serves as the grouting channel;

[0015] The upper side wall of the rigid tube is provided with an external thread matched with the internal thread of the inner wall of the hole, and the lower side wall of the rigid tube is provided with at least one slurry outlet hole.

[0016] Furthermore, the middle side wall of the rigid tube is provided with a limit baffle protruding outwards;

[0017] The lower end surface of the rigid tube is provided with a protective cover, and the hole is closed by the protective cover during the pile pressing stage.

[0018] Furthermore, the pile bottom sealing structure is one of a pile bottom steel plate and a pile tip, or a combination of the two.

[0019] Furthermore, the pile bottom sealing structure is in the shape of a cone, a cross, a hemisphere or a spindle which is wide at the top and narrow at the bottom.

[0020] Furthermore, a one-way valve is provided in the swing-out grouting device.

[0021] Furthermore, a grouting bag is provided at the bottom of the swing-out grouting device, and the internal cavity of the grouting bag is connected to the grouting hole.

[0022] Furthermore, a protective device is provided on the top of the swing-out grouting device.

[0023] A pile bottom grouting method using the above-mentioned hollow pile end rotary grouting device, the pile bottom grouting method is as follows:

[0024] S1, fixing the pile bottom sealing structure with the swing-out grouting device connected thereto on the lower end surface of the hollow pile;

[0025] S2, pressing the hollow pile to a preset depth;

[0026] S3, lowering the grouting pipe through the middle cavity of the hollow pile and docking it with the swing-out grouting device;

[0027] S4, the grouting pipe drives the swing-out grouting device to rotate, so that the swing-out grouting device moves axially downward and penetrates into the soil layer at the pile end;

[0028] S5, the slurry in the grouting pipe is continuously injected into the grouting channel and flows out to the surrounding soil;

[0029] S6, after the pile bottom grouting is completed, the grouting is stopped, and the connection between the grouting pipe and the swing-out grouting device is released;

[0030] S7, taking out the grouting pipe from the middle cavity of the hollow pile, and continuing the grouting construction of the next pile.

[0031] Furthermore, step S2 specifically includes:

[0032] S21, using a mixing pile construction device to perform cement mixing construction to form a mixture of cement slurry and soil at the pile pressing position;

[0033] S22, pressing the hollow pile into the mixture of cement slurry and soil to a designed depth.

[0034] Furthermore, in step S5, when the cement slurry is initially set, the grouting pipe is used to perform grouting at the bottom of the pile to form the grouting body.

[0035] Furthermore, when a grouting bag is installed in the bottom seal of the swing-out grouting device, multiple slow groutings are adopted to control the grouting flow rate to reach the designed control value or the limit saturation value of the grouting bag, and finally form the grouting body.

[0036] Since the present invention adopts the above technical solution, its advantages are:

[0037] 1) Grouting at the bottom of the pile can effectively improve the bearing capacity of the hollow pile, thereby improving the safety of the project and saving materials and project capital investment;

[0038] 2) The rotatable grouting device is pressed into the soil together with the hollow pile. The grouting pipe lowered in the pile is used to drive the rotatable grouting device to rotate and penetrate into the soil layer for grouting. Grouting at the bottom of the pile does not affect the construction of the hollow pile. Grouting can be carried out after the pile pressing construction is completed, thereby improving the efficiency of the hollow pile construction.

[0039] 3) The grouting pipe is a grouting tool that can be reused, saving materials and reducing engineering capital investment. At the same time, the grouting pipe is also used as a driving component for driving the rotatable grouting device to penetrate the soil layer. It has multiple uses and does not require the use of other tools to move the rotatable grouting device downward. At the same time, after the grouting pipe and the rotatable grouting device are assembled in place, continuing to rotate can drive the rotatable grouting device to extend downward, simplifying the process and improving the grouting efficiency.

[0040] 5) A one-way valve can be set in the swivellable grouting device to prevent slurry backflow, improve grouting effect and save grouting materials;

[0041] 6) The structural design is highly reliable and easy to implement, which is conducive to large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0043] Figure 1 This is a schematic diagram of a hollow pile end rotary grouting device provided by the present invention in an initial state in the first embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram after grouting is completed in Embodiment 1 of the present invention;

[0045] Figure 3 This is a structural stereogram of a grouting device that can be rotated out in the first embodiment of the present invention;

[0046] Figure 4 Schematic diagram of a pile bottom sealing structure using a conical hollow conical pile tip in Embodiment 1 of the present invention;

[0047] Figure 5 This is a schematic diagram of a hollow pile end rotary grouting device provided by the present invention in an initial state in the second embodiment of the present invention;

[0048] Figure 6 This is a schematic diagram of a hollow pile end rotary grouting device provided by the present invention in an initial state in Embodiment 3 of the present invention;

[0049] Figure 7 This is a schematic diagram after grouting is completed in Embodiment 3 of the present invention;

[0050] Figure 8 This is a structural stereogram of a grouting device that can be rotated out in Embodiment 3 of the present invention;

[0051] Fig. 9 This is a schematic diagram of a hollow pile end rotary grouting device provided by the present invention in an initial state in a fourth embodiment of the present invention;

[0052] Fig.10 This is a schematic diagram of cement mixing construction at a pile driving position in Embodiment 5 of the present invention;

[0053] Fig.11 This is a schematic diagram of the structure of the pile pressing state in the fifth embodiment of the present invention;

[0054] Fig.12 This is a schematic diagram of a grouting pipe being lowered in a hollow pile in Embodiment 5 of the present invention;

[0055] Fig.13This is a structural schematic diagram of a grouting device in a grouting state in Embodiment 5 of the present invention;

[0056] Fig.14 This is a schematic diagram of the structure after the grouting pipe is recovered in Example 5 of the present invention.

[0057] Description of reference numerals:

[0058] Grouting pipe 1; thread 1.1; hollow pile 2; screw-out grouting device 3; auxiliary docking device 3.1; rigid pipe 3.2; one-way valve 3.3; external thread 3.4; grouting hole 3.5; protective cover 3.6; grouting bag 3.8; auxiliary docking device 3.9; pile bottom sealing structure 4; internal thread 4.1; hole 4.2; grouting body 5; soil body 6; mixing pile 7, mixing body 8. DETAILED DESCRIPTION

[0059] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is apparent to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features well known in the art are not described.

[0060] In order to fully understand the present invention, detailed steps and detailed structures will be proposed in the following description to illustrate the technical solution of the present invention. The preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0061] The present invention provides a hollow pile end screw-out grouting device, wherein a pile bottom sealing structure 4 is fixedly installed at the bottom of the hollow pile 2. A hole 4.2 is axially penetrated through the pile bottom sealing structure 4, and a screw-out grouting device 3 is threadedly installed in the hole 4.2. The top of the screw-out grouting device 3 is used for detachably connecting with a grouting pipe 1 in the hollow pile 2, a grouting channel is provided in the screw-out grouting device 3, a grouting inlet is provided at the top of the screw-out grouting device 3 for conducting the hollow pile 2 and the grouting channel, and a grouting hole is provided on the side wall of the bottom of the screw-out grouting device 3 to connect with the grouting channel.

[0062] In the present invention, the pile bottom sealing structure 4 can be selected as one of the pile bottom steel plate, the pile tip or a combination of the two. In order to reduce the pile pressing resistance, the pile bottom sealing structure 4 is a cone, cross, hemispherical or spindle shape that is wide at the top and narrow at the bottom.

[0063] The advantages of the present invention using a liftable grouting pipe 1 are as follows: since the pile driving construction needs to be implemented in multiple sections, the fixed grouting pipe must be connected when the different sections of the piles are connected, which affects the efficiency of the pile driving construction. The grouting pipe can be lowered from the pile hole for grouting after all the pile driving is completed; (2) the grouting pipe can be reused, and a fixed grouting pipe needs to be installed for each pile, which saves material for the grouting pipe; the grouting pipe can be lowered for grouting after the pile driving construction, avoiding the risk of damaging the grouting pipe during the pile driving construction, and the grouting success rate is more reliable; the grouting pipe is used as a grouting tool on the one hand, and also as a driving component for driving the rotatable grouting device to penetrate the soil layer on the other hand. It has multiple uses and does not need to use other tools to move the rotatable grouting device downward; (5) after the grouting pipe and the rotatable grouting device are assembled in place, they can continue to rotate to drive the rotatable grouting device to extend downward, simplifying the process and improving the grouting efficiency. Embodiment 1

[0064] The embodiment of the present invention specifically relates to a device and a specific grouting method that can be used for grouting at the bottom of a hollow pile, wherein the grouting device includes a threaded grouting pipe 1, a hollow pile 2, a rotary grouting device 3, and a pile bottom sealing structure 4.

[0065] The grouting pipe 1 with tapered threads is docked and fixed with the tapered auxiliary docking device 3.1 at the top of the screw-out grouting device 3 through the threads, and the threaded grouting pipe 1 drives the screw-out grouting device 3 to rotate.

[0066] The external thread 3.4 provided in the middle section of the rigid tube 3.2 in the screw-out grouting device 3 is threadedly connected with the internal thread 4.1 of the hole 4.2 of the pile bottom sealing structure 4. The position of the screw-out grouting device 3 is controlled by rotating the grouting pipe 1 with the bottom thread, so that the screw-out grouting device 3 is screwed out downward.

[0067] The pile bottom sealing structure 4 adopts a conical pile tip, and a hole 4.2 with a diameter slightly larger than that of the rotary grouting device 3 is opened at the lower end.

[0068] A one-way valve 3.3 is provided inside the rotary grouting device 3 to ensure that the slurry can only flow from the grouting pipe to the slurry outlet hole 3.5 and cannot flow in the opposite direction. The protective cover 3.6 at the bottom of the rotary grouting device 3 is conical, and the outer edge can cover the hole 4.2 provided in the pile bottom sealing structure 4 to ensure the sealing effect of the pile bottom sealing structure 4 during the pile pressing process and prevent soil from entering.

[0069] The specific implementation method of the grouting method of the present invention is as follows:

[0070] S1, connect and assemble the screw-out grouting device 3 and the pile bottom sealing structure 4. Screw the screw-out grouting device 3 into the hole 4.2 of the pile bottom sealing structure 4, so that the protective cover 3.6 contacts the pile bottom sealing structure 4, and forms a pile tip grouting structure, such as Figure 1 shown.

[0071] S2. Connect the hollow threaded pile tip to the bottom of the hollow pile 2 by welding, and perform conventional pile driving operations. After the pile foundation is constructed to the designed depth, lower the threaded grouting pipe 1 from the middle cavity of the hollow pile 2. The threaded grouting pipe 1 contacts the screw-out grouting device 3 through the tapered thread 1.1. Rotate the grouting pipe 1 to make it tightly connected with the auxiliary docking device 3.1 on the top of the screw-out grouting device 3.

[0072] S3, continue to rotate the grouting pipe 1, drive the swing-out grouting device 3 to be pushed out, and the grouting device protection cover 3.6 penetrates into the soil at the pile end and exposes the hole 4.2.

[0073] S4, connect the grouting pipe 1 to the grouting equipment to perform grouting operation until the grouting is completed, and the slurry flows out from the slurry outlet hole 3.5 to form a grouting body 5, such as Figure 2 shown.

[0074] S5. After the grouting operation is completed, the grouting pipe 1 is rotated in the reverse direction to disengage it from the swing-out grouting device 3, and the grouting pipe 1 is recovered to complete the grouting work. After the grouting is completed, a large volume of grouting body 5 is formed at the bottom of the swing-out grouting device 3. When the grouting pipe 1 is rotated, since the grouting body 5 is closely matched with the soil, when the grouting pipe 1 is rotated in the reverse direction, the grouting body 5 provides a reaction force to prevent the swing-out grouting device 3 from rotating with the grouting pipe 1 and being unable to be unlocked. Embodiment 2

[0075] The second embodiment is similar to the first embodiment, and the main difference is that:

[0076] The cross-sectional structure of the pile bottom sealing structure 4 has undergone certain changes, wherein certain grooves are opened in the internal holes of the pile body. Since the grouting pipe is connected to the top of the grouting device with threads, and it is necessary to prevent the grouting pipe from rotating, the outer diameter of the grouting pipe is larger than the screw-out grouting device. After the internal holes of the pile body are grooved, the length of the screw-out grouting pipe can be reduced, making it easier to press the grouting pipe down a longer distance, thereby improving the grouting effect.

[0077] (2) The pile bottom sealing structure 4 is changed from the original pointed cone to the current spindle shape to adapt to different pile foundation construction stratum conditions. When the pile tip is a flat-head pile tip, the grouting device end protection cover 3.6 at the front end of the rotary grouting device 3 is changed from the original cone to a horizontal baffle.

[0078] This embodiment is mainly to enrich the application scenarios of this patent and to meet the construction scenarios of different types of grouting pipes. Embodiment 3

[0079] The third embodiment is similar to the first embodiment, and the main difference is that:

[0080] The tapered thread 1.1 at the bottom of the grooved grouting pipe 1 is changed from the original internal thread type to an external thread setting, and the auxiliary docking device 3.1 at the top of the lower screw-out grouting device 3 is changed from the original external thread to an internal thread device, which is convenient for docking with the upper grouting pipe 1.

[0081] When the swing-out grouting device 3 is long, a limit baffle 3.7 is provided to prevent the swing-out grouting device 3 from being swung out and causing the swing-out grouting device 3 to be unable to be recovered after being emptied.

[0082] A grouting bag 3.8 is added to the end of the rotary grouting device 3. After the rotary grouting device 3 is pressed into the soil, grouting is performed by grouting into the grouting bag 3.8. Grouting is completed after the designed grouting volume is reached.

[0083] This embodiment is mainly to increase the application scenarios of actual on-site construction, increase the bearing capacity of the pile end after grouting, and meet the construction scenarios of different types of grouting pipes. Embodiment 4

[0084] The fourth embodiment is similar to the first embodiment, and the main difference from the first embodiment is that:

[0085] No separate pile tip structure is provided, and all grouting devices are arranged in the cavity of the hollow pile 2, thereby reducing costs.

[0086] (2) An auxiliary docking device 3.9 is provided at the upper end of the swing-out grouting device to improve the success rate and efficiency of the connection between the grouting pipe and the grouting device.

[0087] This embodiment is mainly to increase the application scenarios of actual on-site construction, to meet the construction scenarios of different types of grouting pipes, to reduce costs, and to improve the success rate of grouting construction.

[0088] Attached Fig. 9 This is a schematic diagram of the initial state of Example 4. Embodiment 5

[0089] The implementation method of this embodiment is quite different from that of the first embodiment, mainly considering that the method of inserting hollow piles with mixing piles is often used for construction on site.

[0090] The main implementation method of this embodiment is:

[0091] S1, first use the mixing pile 7 to mix cement on the foundation to be reinforced, and form a mixing body 8 of cement slurry and soil in the soil body 6, such as Fig.10 shown.

[0092] S2, using a crane or a static press to sink the hollow pile 2 equipped with a rotary grouting device 3 into the mixing body 8, as shown in FIG. Fig.11 shown.

[0093] S3, when the hollow pile 2 is sunk to the designed depth, the grouting pipe 1 is lowered to the height of the screw-out grouting device 3, and the threaded grouting pipe 1 is lowered from the middle cavity of the hollow pile 2. The threaded grouting pipe 1 contacts the screw-out grouting device 3 through the tapered thread 1.1, and the grouting pipe 1 is continuously rotated to be tightly connected with the auxiliary docking device 3.1 at the top of the screw-out grouting device 3, as shown in FIG. Fig.12 shown.

[0094] S4, when the cement slurry in the hollow pile 2 is initially set, secondary grouting is performed at the bottom of the pile to form a grouting body 5, such as Fig.14 shown.

[0095] S5, reversely rotate the grouting pipe 1 so that the grouting pipe 1 is disconnected from the rotary grouting device 3, and then the grouting pipe 1 is recovered, while the rotary grouting device 3 remains in the soil layer, as shown in FIG. Fig.14 shown.

[0096] The above describes the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and the devices and structures that are not described in detail should be understood to be implemented in a common manner in the art; any technician familiar with the art can use the above-disclosed methods and technical contents to make many possible changes and modifications to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, or modify them into equivalent embodiments of equivalent changes, which does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention are still within the scope of protection of the technical solutions of the present invention.

Claims

1. A hollow pile end screw-out grouting device, wherein a pile bottom sealing structure (4) is fixedly installed at the bottom of the hollow pile (2), characterized in that: The pile bottom sealing structure (4) is axially penetrated by a hole (4.2), and a screw-out grouting device (3) is installed in the inner thread of the hole (4.2); The top end of the rotary grouting device (3) is used to connect with the grouting pipe (1) in the hollow pile (2); a grouting channel is provided in the rotary grouting device (3); a grouting inlet is provided at the top of the rotary grouting device (3) for connecting the grouting pipe (1) and the grouting channel; a grouting hole (3.5) is provided on the side wall of the bottom of the rotary grouting device (3) and is connected to the grouting channel; The grouting pipe (1) is axially lifted and lowered in the hollow pile (2), and the bottom of the grouting pipe (1) is detachably connected to the top of the swing-out grouting device (3); The rotary grouting device (3) comprises a rigid tube (3.2), the internal space of the rigid tube (3.2) serving as the grouting channel; the upper side wall of the rigid tube (3.2) is provided with an external thread (3.4) which matches with the internal thread (4.1) of the inner wall of the hole (4.2), and the lower side wall of the rigid tube (3.2) is provided with at least one grouting hole (3.5); The lower end surface of the rigid tube (3.2) is provided with a protective cover (3.6), and the hole (4.2) is closed by the protective cover (3.6) during the pile pressing stage.

2. The hollow pile end rotary grouting device according to claim 1, characterized in that: The grouting pipe (1) is connected to the top end of the swing-out grouting device (3) via a threaded connection or a rotating buckle.

3. The hollow pile end rotary grouting device according to claim 1, characterized in that: The middle side wall of the rigid tube (3.2) is provided with a limit baffle (3.7) protruding outwards.

4. The hollow pile end rotary grouting device according to claim 1, characterized in that: The pile bottom sealing structure (4) is one of a pile bottom steel plate and a pile tip, or a combination of the two.

5. The hollow pile end rotary grouting device according to claim 4, characterized in that: The pile bottom sealing structure (4) is in the shape of a cone, a cross, a hemisphere or a spindle that is wide at the top and narrow at the bottom.

6. The hollow pile end rotary grouting device according to claim 1, characterized in that: A one-way valve (3.3) is provided inside the swing-out grouting device (3).

7. The hollow pile end rotary grouting device according to claim 1, characterized in that: A grouting bag (3.8) is sealed and installed at the bottom of the rotary grouting device (3), and the internal cavity of the grouting bag (3.8) is connected to the grouting hole (3.5).

8. A pile bottom grouting method using the pile end rotary grouting device of the hollow pile according to any one of claims 1 to 7, characterized in that: The pile bottom grouting method is as follows: S1, fixing the pile bottom sealing structure (4) connected to the swing-out grouting device (3) on the lower end surface of the hollow pile (2); S2, pressing the hollow pile (2) to a preset depth; S3, lowering the grouting pipe (1) through the middle cavity of the hollow pile (2) and docking it with the swing-out grouting device (3); S4, the grouting pipe (1) drives the swing-out grouting device (3) to rotate, so that the swing-out grouting device (3) moves axially downward and penetrates into the soil layer at the pile end; S5, the slurry in the grouting pipe (1) is continuously injected into the grouting channel and flows out to the surrounding soil to form a grouting body (5); S6, after the pile bottom grouting is completed, the grouting is stopped, and the connection between the grouting pipe and the swing-out grouting device (3) is released; S7, taking out the grouting pipe (1) from the middle cavity of the hollow pile (2), and continuing the grouting construction of the next pile.

9. The grouting method according to claim 8, characterized in that: Step S2 specifically includes: S21, using a mixing pile construction device to perform cement mixing construction to form a mixture of cement slurry and soil at the pile pressing position; S22, pressing the hollow pile (2) into the mixture of cement slurry and soil to a designed depth.

10. The grouting method according to claim 8, characterized in that: In step S5, when the cement slurry is initially set, the grouting pipe (1) is used to perform grouting at the bottom of the pile to form the grouting body (5).

11. The grouting method according to claim 8, characterized in that: When a grouting bag (3.8) is sealed and installed at the bottom of the swing-out grouting device (3), multiple slow groutings are performed to control the grouting flow rate to reach a designed control value or a limit saturation value of the grouting bag, thereby finally forming the grouting body (5).

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