Self-locking hoop multi-stage prefabricated ring combined grouting type existing pile in-situ reinforcing device and construction method

Abstract

The invention discloses a self-locking hoop multi-stage prefabricated ring combined grouting type existing pile in-situ reinforcing device and a construction method. The self-locking hoop multi-stage prefabricated ring combined grouting type existing pile in-situ reinforcing device comprises a self-locking prestressed hoop assembly, a multi-stage sectioning prefabricated ring assembly, a hydraulic press-in device and a combined grouting system. The self-locking type prestressed hoop assembly actively locks and fixes an existing pile through a barb-shaped shear key and constructs a counter-force anchoring point. The multi-stage sectioning prefabricated ring assembly is of a concentric nested assembly structure, and an inner and outer bidirectional grouting channel is integrated in the wall of a ring body. The hoop is used for providing vertical counter-force to be matched with the telescopic graded pressing-in and step combined grouting technology, the problem that settlement is caused by insufficient pressing-in counter-force of the prefabricated ring and construction disturbance in the limited space is solved, and the method is particularly suitable for old building and bridge foundation transformation with the clearance being seriously limited; the method has the characteristics of no need of large machinery, immediate compensation of frictional resistance, remarkable reinforcement and synergy and the like, improves the safety and reliability of in-situ reinforcement of the existing pile, and has wide application value.

Description

Technical Field

[0001] This invention relates to a self-locking clamp multi-stage precast ring combined with grouting type in-situ reinforcement device and construction method for existing piles, belonging to the field of pile foundation engineering technology. Background Technology

[0002] Prefabricated steel structure components and precast ring technology are important means of reinforcement and renovation in the field of pile foundation engineering due to their rapid construction and controllable quality. For clamp components, conventional products are only used for connecting new and old interfaces or for passive constraint, and cannot provide the vertical reaction anchor points required for static pressure construction by actively tightening and locking the pile body. This results in insufficient reaction force, making it impossible to carry out pressing operations in confined spaces. For precast ring components, existing products are mostly single physical protective sleeves, which cannot achieve bonding and solidification between the ring body and the existing pile through grouting, nor can they utilize grout penetration to reinforce the soil around the pile.

[0003] With the advancement of urban renewal, there is an urgent need to improve the bearing capacity of existing pile foundations. Conventional in-situ reinforcement techniques, such as increasing the cross-section and adding accompanying piles, have significant limitations: First, the existing pile cap and upper beams and slabs severely restrict the construction clearance, preventing large machinery from entering the site; second, if static pressure is used, there is a lack of on-site loading conditions, and using old pile caps as reaction supports can easily damage the existing structure; third, traditional excavation and expansion techniques can lead to instantaneous loss of skin friction around the piles, easily triggering settlement in sensitive buildings. In addition, conventional grouting techniques are mostly single bottom sealing grouting after pile completion, lacking a "step-by-step compensation" mechanism that is carried out simultaneously with the construction process, and cannot immediately repair the skin friction loss caused by soil displacement or excavation.

[0004] Therefore, both the devices for pile foundation reinforcement and the construction methods for pile foundation reinforcement urgently need to be developed to overcome the problems that existing devices cannot achieve substantial expansion and efficiency improvement of existing piles, and that existing construction methods are limited by space, large machinery and equipment, and can only passively improve the bearing capacity of existing piles. Summary of the Invention

[0005] The purpose of this invention is to provide a self-locking clamp multi-stage precast ring combined with grouting in-situ reinforcement device and construction method for existing piles, so as to solve the defects of existing reinforcement components in the background art, such as the inability to provide reaction force, the lack of grouting expansion function of precast components, the inability of large equipment to enter the site in confined space, and the tendency of traditional processes to cause settlement. This invention can be implemented in extremely confined space, without the need for large mechanical equipment, can actively improve the bearing capacity of existing piles, and can cleverly solve the problem of pile driving reaction force without damaging the existing pile cap.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In one aspect, a self-locking prestressed hoop multi-stage precast ring combined with grouting type in-situ reinforcement device for existing piles includes: a self-locking prestressed hoop assembly and a multi-stage segmented precast ring assembly.

[0008] The self-locking prestressed clamp assembly includes: a clamp body, on the inner wall of which a locking component is provided.

[0009] The multi-segment precast ring assembly includes: several segment precast rings with different diameters, and each segment precast ring has grouting channels on its inner and outer walls.

[0010] Optionally, the clamp body is configured as two arc-shaped steel plates, which are connected by clamp fastening bolts, and the inner sidewall of the arc-shaped steel plates is provided with several barbed shear keys.

[0011] Optionally, each segmented precast ring includes: a ring body, the ring body being configured as a cavity structure, a cavity grouting hole being provided at the top of the ring body, a cavity grouting inlet pipe being inserted into the cavity of the ring body through the cavity grouting hole, a grout outlet hole being provided on the surface of the cavity grouting inlet pipe, and an inner wall vertical grouting guide groove being provided on the inner wall of the ring body; an outer wall circumferential grouting pipe being provided on the outer wall circumferential grouting pipe, a plurality of grout outlet holes being provided on the outer wall circumferential grouting pipe, and an outer ring grouting inlet pipe being connected to the outer wall circumferential grouting pipe.

[0012] Optionally, the inner wall of the segmented prefabricated ring is welded with a number of inner wall shear studs.

[0013] Secondly, a self-locking prestressed hoop multi-stage precast ring combined with grouting type in-situ reinforcement system for existing piles includes: a self-locking prestressed hoop assembly, a multi-stage precast ring assembly, a hydraulic pressing device, and a combined grouting system.

[0014] The hydraulic pressing device includes a force transmission beam and a jack. The force transmission beam is mounted below the self-locking prestressed clamp assembly and is used to provide the downward pressure for the multi-stage segmented precast ring assembly to press in stages.

[0015] The combined grouting system includes grouting pipelines and grouting pumps connected to each segmented precast ring, used for independent grouting of the soil outside the segmented precast ring and the gap inside the segmented precast ring.

[0016] Optionally, the force-transmitting beam is closely attached to the bottom surface of the arc-shaped steel plate, and the anchoring force is provided by the barbed shear keys on the arc-shaped steel plate.

[0017] Optionally, the jack is installed between the force transmission beam and the multi-stage segmented precast ring assembly, and is connected to an external pump station via hydraulic oil pipes to drive the segmented precast ring to move downwards.

[0018] Optionally, of the N segmented prefabricated rings, the first-level largest diameter segmented prefabricated ring is located on the outermost layer, and the remaining segmented prefabricated rings are nested inwards sequentially until the Nth-level smallest diameter segmented prefabricated ring is located on the innermost layer, and in the initial state, they are folded and stored under the clamp.

[0019] Optionally, the outer diameter of the first-stage maximum diameter segmented precast ring is 1.5 to 2.5 times the diameter D of the existing pile; the radius difference between two adjacent segmented precast rings, and the gap width between the inner wall of the innermost segmented precast ring and the outer wall of the existing pile are all set to 30 mm to 100 mm; the height of each segmented precast ring should preferably be 0.5 to 1.5 times the diameter D of the existing pile.

[0020] Thirdly, a construction method for in-situ reinforcement of existing piles using a combination of self-locking clamps, multi-stage precast rings, and grouting includes the following steps:

[0021] Step 1: Excavate a working pit below the existing pile cap and clean the existing pile body. Install self-locking prestressed clamp components on the top of the existing piles, and apply prestress in stages to embed the barbed shear keys into the pile body, forming a construction anchorage reaction support.

[0022] Step 2: Under the self-locking prestressed clamp assembly, the multi-stage segmented precast rings are assembled into one piece using a concentric nesting method. The force transmission beam and jacks are installed with the clamp assembly as the reaction force support.

[0023] Step 3: Start the jacks to press the multi-stage segmented precast ring assembly into the soil in a telescopic, tiered manner, and then perform staged combined grouting.

[0024] Step 4: Remove the jacks and crossbeams, and pour high-pressure grout into the working pit at the top of the pile until it completely covers the top of the self-locking prestressed clamp assembly and the multi-stage segmented precast ring assembly.

[0025] Optionally, step 3 specifically includes:

[0026] Step 301: Activate the jacks and, relying on the reaction force provided by the clamping assembly, push the entire nested multi-stage segmented precast ring assembly downwards until the outermost first-stage large-diameter segmented precast ring reaches the designed depth. Connect the outer ring grouting inlet pipe of the first-stage segmented precast ring and inject grout into the outer soil through the outer ring grouting pipe.

[0027] Step 302: The jack continues to push the remaining segmented precast rings downwards, causing the second-stage segmented precast rings to extend from inside the first-stage segmented precast rings and be pressed deeper. After being pressed in place, grout is injected through the grouting inlet pipe of the first-stage segmented precast ring. The grout flows out through the vertical grouting channel on the inner wall, filling the gap between the first-stage segmented precast rings and the existing piles, thus locking the first-stage segmented precast rings to the existing piles. Grouting is then performed on the soil outside the second-stage segmented precast rings through the outer ring grouting inlet pipe.

[0028] Step 303: Repeat step 302 until the innermost Nth-level segmented precast ring is pressed into the design depth. Grout the upper-level segmented precast ring to the existing pile, and grout the outer ring of the Nth-level segmented precast ring to reinforce the soil, and grout the inner cavity to seal the bottom and fill the gaps.

[0029] Beneficial Effects: This invention discloses a self-locking prestressed hoop multi-stage precast ring combined with grouting in-situ reinforcement device and construction method for existing piles, including: a self-locking prestressed hoop assembly, a multi-stage segmented precast ring assembly, a hydraulic pressing device, and a combined grouting system. The self-locking prestressed hoop assembly actively locks the existing pile and constructs reaction anchor points using barbed shear keys; the multi-stage segmented precast ring assembly adopts a concentric nested assembly structure, and the ring body wall integrates internal and external bidirectional grouting channels. This invention solves the problems of insufficient precast ring pressing reaction force and settlement caused by construction disturbance in confined spaces by providing vertical reaction force through the hoop combined with telescopic staged pressing and stepped combined grouting process. It is particularly suitable for the renovation of old building and bridge foundations with severely limited clearance, and has the characteristics of not requiring large machinery, instant frictional resistance compensation, and significant reinforcement efficiency, improving the safety and reliability of in-situ reinforcement of existing piles, and has wide application value. Compared with the prior art, this invention has the following beneficial effects:

[0030] (1) Innovation of the device structure: The present invention realizes active constraint on existing piles through the barbed shear key design of the self-locking prestressed hoop assembly, solving the problem of lack of static pressure construction reaction force under confined space; the multi-level segmented precast ring assembly integrates internal and external bidirectional grouting channels, which not only realizes the reliable connection between the component and the pile body, but also expands the pile diameter and strengthens the soil around the pile through grouting.

[0031] (2) Adaptability of construction technology: The concentric nesting and expansion-expansion stage pressing process is adopted to fold and assemble the multi-level expansion structure, which reduces the requirements for vertical construction clearance and can complete the reinforcement under the existing foundation without the need for large machinery.

[0032] (3) Effectiveness of settlement control: The tiered grouting process establishes an instant compensation mechanism. Grout is injected at the moment the soil is disturbed by the pressing of the outer wall, which effectively offsets the loss of side friction resistance and ensures that the bearing capacity of the existing piles does not decrease throughout the construction process, greatly reducing the settlement risk of the upper sensitive buildings.

[0033] (4) Structural durability: The final overall sealing completely encapsulates metal components such as clamps and bolts in concrete or grout, avoiding corrosion in the underground environment and ensuring the long-term durability of the reinforced structure. Attached Figure Description

[0034] Figure 1 This is a schematic cross-sectional view (front view) of the in-situ reinforcement device in an embodiment of the present invention.

[0035] Figure 2 This is a schematic plan view (top view) of the in-situ reinforcement device in an embodiment of the present invention.

[0036] Figure 3 This is a schematic diagram of the structure of the self-locking prestressed clamp assembly in this invention.

[0037] Figure 4 This is a schematic diagram of the prefabricated ring in this invention.

[0038] Figure 5 This is a schematic diagram illustrating the construction principle of pressing the precast ring in this invention.

[0039] Figure 6 This is a schematic diagram of the construction method of the present invention.

[0040] In the diagram: 1-Existing pile, 2-Existing pile cap, 3-Arched steel plate, 4-Clamping bolt, 5-Segmented precast ring, 6-Outer ring grouting inlet pipe, 7-Cavity grouting inlet pipe, 8-Grouting outlet hole, 9-Filling binder, 10-Outer wall circumferential grouting pipe, 11-Precast ring connecting bolt, 12-Vertical bolt hole, 13-Barbed shear key, 14-Horizontal bolt hole, 15-Cavity grouting hole, 16-Inner wall shear stud, 17-Inner wall vertical grouting channel, 18-Jack; 19-Force transmission beam; 20-Hydraulic oil pipe. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0042] The present invention will be further described below with reference to specific embodiments.

[0043] Example 1:

[0044] This embodiment introduces a self-locking clamp multi-stage precast ring combined with grouting type in-situ reinforcement device for existing piles, such as... Figure 1-2 As shown in Figure 5, it includes: a self-locking prestressed clamp assembly and a multi-segment precast ring assembly.

[0045] The self-locking prestressed clamp assembly includes: a clamp body, on the inner wall of which a locking component is provided.

[0046] The multi-segment precast ring assembly includes: several segment precast rings with different diameters, and each segment precast ring 5 has grouting channels on its inner and outer walls.

[0047] Furthermore, the clamp body is configured as two arc-shaped steel plates 3, which are connected by clamp fastening bolts 4, and the inner sidewall of the arc-shaped steel plates 3 is provided with several barbed shear keys 13.

[0048] It not only provides active confining pressure constraint, but more importantly, it serves as a vertical reaction anchor point for subsequent pile driving construction, replacing the vulnerable existing pile cap 2 as a load-bearing support.

[0049] Furthermore, the connection of the arc-shaped steel plate 3 is pre-set with horizontal bolt holes 14 for passing through the clamping bolts 4 to apply prestress.

[0050] Furthermore, the top and bottom flanges of the arc-shaped steel plate 3 are pre-set with vertical bolt holes 12 for mechanical splicing and positioning with the force transmission beam 19 below or other components.

[0051] Furthermore, the barbed shear key 13 has a conical protrusion.

[0052] Under the prestress applied by the clamp fastening bolt 4, it can penetrate and embed into the concrete surface of the existing pile 1, forming a high-strength mechanical interlocking force and static friction force, thereby enabling the clamp assembly to withstand vertical reaction force without slippage. This design creates a force support point independent of the existing pile cap 2, avoiding the structural damage risk caused by using the old pile cap as a reaction frame.

[0053] Furthermore, the multi-level segmented precast ring assembly adopts a "concentric nesting and telescopic linkage" structure and is located below the self-locking prestressed clamp assembly. It includes N levels (N≥2) of segmented precast rings 5 ​​assembled in a concentric nesting manner, with the diameter of each level of segmented precast ring 5 decreasing sequentially to expand the body and increase efficiency.

[0054] Furthermore, each segmented precast ring 5 integrates a dual-loop grouting structure, including: a ring body, which is configured as a cavity structure, with a cavity grouting hole 15 at the top of the ring body, a cavity grouting inlet pipe 7 inserted into the cavity of the ring body through the cavity grouting hole 15, and a grout outlet hole 8 on the surface of the cavity grouting inlet pipe 7; an inner wall vertical grouting groove 17 on the inner wall of the ring body for grouting into the inner gap to achieve structural locking; an outer wall circumferential grouting pipe 10 on the outer wall of the ring body, with several grout outlet holes 8 on the outer wall circumferential grouting pipe 10, and an outer ring grouting inlet pipe 6 connected to the outer wall circumferential grouting pipe 10 for immediate grouting into the soil outside the ring to compensate for side friction.

[0055] Furthermore, the inner wall of the segmented precast ring 5 is welded with a number of inner wall shear studs 16 to enhance the bonding performance between the filler adhesive and the precast ring.

[0056] Furthermore, the flange structure of the segmented prefabricated ring 5 is connected by prefabricated ring connecting bolts 11.

[0057] Example 2:

[0058] This embodiment introduces a self-locking clamp multi-stage precast ring combined with grouting in-situ reinforcement system for existing piles, such as... Figure 1 , 5 As shown, it includes: a self-locking prestressed clamp assembly, a multi-segment precast ring assembly, a hydraulic pressing device, and a combined grouting system.

[0059] The hydraulic pressing device includes a force transmission beam 19 and a jack 18. The force transmission beam 19 is mounted below the self-locking prestressed clamp assembly and is used to provide the downward pressure for the multi-stage segmented precast ring assembly to press in stages.

[0060] The combined grouting system includes grouting pipelines and grouting pumps connected to each segmented precast ring, used for independent grouting of the soil outside the segmented precast ring and the gap inside the segmented precast ring.

[0061] Furthermore, the force-transmitting beam 19 is closely attached to the bottom surface of the arc-shaped steel plate 3, and the barbed shear keys 13 on the arc-shaped steel plate 3 provide anchoring force as a reaction force base, so that there is no need to pile loads on the construction site or borrow the weight of the upper structure.

[0062] Furthermore, the jack 18 is installed between the force transmission beam 19 and the multi-stage segmented precast ring assembly, and is connected to an external pump station through a hydraulic oil pipe 20 to drive the segmented precast ring to move downward.

[0063] Furthermore, the outer ring grouting inlet pipe 6 is connected to the outer wall circumferential grouting pipe 10 of the segmented precast ring 5, which is used to inject grout to reinforce the disturbed soil at the moment when each stage of the precast ring is pressed in and generates a soil squeezing effect.

[0064] Furthermore, the cavity grouting inlet pipe 7 is connected to the grout storage cavity inside the segmented precast ring 5 through the cavity grouting hole 15, which is used to fill the gap between the previous and next stages with grout after the next stage precast ring extends into place, so as to achieve integrated connection.

[0065] Furthermore, the N segmented prefabricated rings 5 ​​adopt a diameter gradation design of "larger on the outside and smaller on the inside," with the largest diameter segmented prefabricated ring of the first level located on the outermost layer, and the remaining segmented prefabricated rings nested inwards sequentially until the smallest diameter segmented prefabricated ring of the Nth level is located on the innermost layer. This structure folds and stores under the clamp in its initial state, significantly reducing the device height and effectively solving the problem of severely limited vertical clearance and the inability to install large components during the renovation of existing building foundations.

[0066] Furthermore, the dimensional relationship of the segmented precast rings 5 ​​is configured as follows: the outer diameter of the first-stage segmented precast ring with the largest diameter should be 1.5 to 2.5 times the diameter D of the existing pile to ensure the expansion and efficiency enhancement area; the radius difference between adjacent segments of the precast rings and the gap width between the inner wall of the innermost segmented precast ring and the outer wall of the existing pile should be set to 30 mm to 100 mm to ensure the flow space of the grouting material; the height of each segmented precast ring should be 0.5 to 1.5 times the diameter D of the existing pile to facilitate segmented pressing in a low headroom environment.

[0067] Example 3:

[0068] This embodiment describes a construction method for in-situ reinforcement of existing piles using a combination of self-locking clamps, multi-stage precast rings, and grouting. Figure 6 As shown, it includes the following steps:

[0069] Step 1: Construction of the reaction anchor point. Excavate the soil below the existing pile cap 2 to form a working pit, and clean the existing pile 1. Install a self-locking prestressed clamp assembly on the top of the existing pile, and apply prestress in stages to embed the barbed shear key 13 into the pile body, forming the construction anchor reaction support.

[0070] This is used to actively apply confining pressure to the pile body to create a reaction point, thus avoiding the structural cracking risk that may be caused by directly using the aged and insufficiently strong existing pile cap 2 as a jack support.

[0071] Step Two: Component Assembly and Equipment Placement. Below the clamp assembly, the multi-stage segmented prefabricated rings 5 ​​are assembled into a single unit using a concentric nesting method. Using the clamp assembly as a reaction force support, the force transmission beam 19 and the jacks 18 are installed.

[0072] This method utilizes concentric nesting assembly, allowing multi-level prefabricated rings to be folded and stored in their initial state, significantly reducing construction height and adapting to the low clearance requirements of underground confined spaces.

[0073] Step 3: Telescopic Pressing and Step-by-Step Combined Grouting. Activate jack 18 to telescopically press the multi-stage segmented precast ring assembly into the soil in stages, and then perform step-by-step combined grouting.

[0074] Furthermore, step three specifically includes:

[0075] Step 301: Perform the first stage of pressing and stabilizing the outer side: Activate jack 18, relying on the reaction force provided by the clamp assembly, to push the entire nested multi-stage segmented precast ring assembly downwards until the outermost first-stage large-diameter segmented precast ring reaches the designed depth. At this point, immediately connect the outer ring grouting inlet pipe 6 of the first-stage segmented precast ring, and inject grout into the outer soil through the outer ring grouting pipe 10 to quickly reinforce the disturbed soil. The construction follows a "top-down" pressing sequence, avoiding the problem of excessive initial disturbance of deep soil caused by a "bottom-up" process, thus reducing construction risks.

[0076] Step 302: Perform intermediate-stage extension and stepped alternating grouting: Jack 18 continues to push the remaining internal segmented precast rings downwards, causing the second-stage segmented precast rings to extend from inside the first-stage segmented precast rings and be pressed deeper. After being pressed into place, a two-step grouting process is performed simultaneously: First, "internal locking," which involves grouting through the cavity grouting inlet pipe 7 of the first-stage segmented precast ring. The grout flows out through the vertical guide grouting groove 17 on the inner wall, filling the gap between the first-stage segmented precast ring and the existing pile 1, thus locking the first-stage segmented precast ring and the existing pile 1; Second, "external reinforcement," which involves simultaneously grouting and reinforcing the soil outside the second-stage segmented precast ring through the outer ring grouting inlet pipe 6.

[0077] Step 303: Perform final stage pressing and bottom sealing grouting: Repeat the "extend-press-alternate grouting" steps of step 302 until the innermost Nth-level segmented precast ring is pressed into the designed depth. At this time, perform internal locking grouting on the previous level segmented precast ring, and simultaneously open the outer ring grouting of the Nth-level segmented precast ring to reinforce the soil, and perform inner cavity grouting to achieve bottom sealing and fill the gaps.

[0078] Step 4: Overall sealing. Remove jack 18 and crossbeam 19, and pour high-pressure grout into the excavated working pit at the top of the pile until the top of the self-locking prestressed clamp assembly and the multi-stage segmented precast ring assembly are completely covered.

[0079] Furthermore, the solidified filler cement 9 binds the existing pile 1, the self-locking prestressed clamp assembly, and the multi-stage segmented precast ring assembly into a single unit, forming a permanent anti-corrosion and load-bearing node.

[0080] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A self-locking clamp multi-stage precast ring combined with grouting type in-situ reinforcement device for existing piles, characterized in that, include: Self-locking prestressed clamp assembly, multi-segment precast ring assembly; The self-locking prestressed clamp assembly includes: a clamp body, wherein a locking component is provided on the inner wall of the clamp body; The multi-segment precast ring assembly includes: several segment precast rings with different diameters, and each segment precast ring has grouting channels on its inner and outer walls.

2. The self-locking clamp multi-stage precast ring combined with grouting type in-situ reinforcement device for existing piles according to claim 1, characterized in that, The clamp body is composed of two arc-shaped steel plates, which are connected by clamp fastening bolts. The inner sidewall of the arc-shaped steel plates is provided with several barbed shear keys.

3. The self-locking clamp multi-stage precast ring combined with grouting type in-situ reinforcement device for existing piles according to claim 1, characterized in that, Each segmented precast ring includes: a ring body, the ring body being configured as a cavity structure, a cavity grouting hole being provided at the top of the ring body, a cavity grouting inlet pipe being inserted into the cavity of the ring body through the cavity grouting hole, a grout outlet hole being provided on the surface of the cavity grouting inlet pipe, and an inner wall vertical grouting guide groove being provided on the inner wall of the ring body; an outer wall circumferential grouting pipe being provided on the outer wall circumferential grouting pipe, a plurality of grout outlet holes being provided on the outer wall circumferential grouting pipe, and an outer ring grouting inlet pipe being connected to the outer wall circumferential grouting pipe.

4. The self-locking clamp multi-stage precast ring combined with grouting type in-situ reinforcement device for existing piles according to claim 1, characterized in that, The inner wall of the segmented prefabricated ring is welded with several inner wall shear studs.

5. A self-locking clamp multi-stage precast ring combined with grouting in-situ reinforcement system for existing piles, characterized in that, include: The self-locking prestressed clamp assembly, the multi-segment precast ring assembly, and the hydraulic pressing device and the combined grouting system as described in any one of claims 1-4; The hydraulic pressing device includes a force transmission beam and a jack. The force transmission beam is mounted below the self-locking prestressed clamp assembly and is used to provide the downward pressure for the multi-stage segmented precast ring assembly to press in stages. The combined grouting system includes grouting pipelines and grouting pumps connected to each segmented precast ring, used for independent grouting of the soil outside the segmented precast ring and the gap inside the segmented precast ring.

6. The self-locking clamp multi-stage precast ring combined with grouting type existing pile in-situ reinforcement system according to claim 5, characterized in that, The force transmission beam is closely attached to the bottom surface of the arc-shaped steel plate, and the barbed shear keys on the arc-shaped steel plate provide anchoring force; the jack is installed between the force transmission beam and the multi-stage segmented precast ring assembly, and is connected to an external pump station through hydraulic oil pipes to drive the segmented precast ring to move downward.

7. The self-locking clamp multi-stage precast ring combined with grouting in-situ reinforcement system for existing piles according to claim 5, characterized in that, Of the N segmented prefabricated rings, the first-level largest diameter segmented prefabricated ring is located on the outermost layer, and the remaining segmented prefabricated rings are nested inwards sequentially until the Nth-level smallest diameter segmented prefabricated ring is located on the innermost layer. In the initial state, they are folded and stored under the clamp.

8. The self-locking clamp multi-stage precast ring combined with grouting in-situ reinforcement system for existing piles according to claim 5, characterized in that, The outer diameter of the first-stage precast ring with the largest diameter segment is 1.5 to 2.5 times the diameter D of the existing pile; the radius difference between two adjacent precast rings and the gap width between the inner wall of the innermost precast ring and the outer wall of the existing pile are all set to 30 mm to 100 mm; the height of each precast ring should be 0.5 to 1.5 times the diameter D of the existing pile.

9. A construction method for a self-locking clamp multi-stage precast ring combined with grouting in-situ reinforcement system for existing piles, characterized in that, The construction steps include the following: Step 1: Excavate a working pit under the existing pile cap and clean the existing pile body; install self-locking prestressed clamp components on the top of the existing pile, apply prestress in stages to embed the barbed shear keys into the pile body, and form a construction anchoring reaction support. Step 2: Under the self-locking prestressed clamp assembly, the multi-stage segmented precast rings are assembled into one piece using a concentric nesting method. The force transmission beam and jacks are installed with the clamp assembly as the reaction force support. Step 3: Start the jacks to press the multi-stage segmented precast ring assembly into the soil in a telescopic, staged manner, and perform staged combined grouting; Step 4: Remove the jacks and crossbeams, and pour high-pressure grout into the working pit at the top of the pile until it completely covers the top of the self-locking prestressed clamp assembly and the multi-stage segmented precast ring assembly.

10. The construction method according to claim 10, characterized in that, Step 3 specifically includes: Step 301: Start the jack and use the reaction force provided by the clamp assembly to push the entire nested multi-stage segmented precast ring assembly downwards until the outermost first-stage large-diameter segmented precast ring reaches the design depth; connect the outer ring grouting inlet pipe of the first-stage segmented precast ring and grout into the outer soil through the outer ring grouting pipe. Step 302: The jack continues to push the remaining segmented precast rings downwards, causing the second-stage segmented precast rings to extend from inside the first-stage segmented precast rings and be pressed deeper. After being pressed into place, grout is injected through the grouting inlet pipe of the cavity of the first-stage segmented precast rings. The grout flows out through the vertical grouting channel on the inner wall, filling the gap between the first-stage segmented precast rings and the existing piles, thus locking the first-stage segmented precast rings to the existing piles. Grouting is then performed on the soil outside the second-stage segmented precast rings through the outer ring grouting inlet pipe. Step 303: Repeat step 302 until the innermost Nth-level segmented precast ring is pressed into the design depth; perform locking grouting on the previous level segmented precast ring and the existing pile, and perform grouting on the outer ring of the Nth-level segmented precast ring to reinforce the soil, and grouting on the inner cavity to seal the bottom and fill the gap.

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