A pile head reinforcing structure for hard rock formation construction

Abstract

This utility model provides a pile head reinforcement structure for construction in hard rock formations, including a steel sleeve, a grouting structure disposed between the steel sleeve and the outer surface of the pile head, a shear structure for forming a mechanical interlocking effect between the pile head and the steel sleeve, an anchoring structure for reliable connection with the pile body, a pressure-bearing flange disposed at the bottom of the steel sleeve, and a reinforcing rib structure arranged on the outer wall of the steel sleeve. The steel sleeve is fitted around the periphery of the precast pile head, and the grouting structure fills the space between the inner wall of the steel sleeve and the outer surface of the pile head and is fixed to both. This pile head reinforcement structure for construction in hard rock formations solves the problem that, due to the lack of effective structural reinforcement and circumferential restraint measures for precast pile heads in related technologies, pile heads are prone to spalling, crushing, cracking, and other damage under high loads and impact conditions.

Description

Technical Field

[0001] This utility model belongs to the field of pipe pile technology, and in particular relates to a pile head reinforcement structure for construction in hard rock strata. Background Technology

[0002] When constructing underground engineering projects in hard rock formations, which are characterized by high strength, high integrity, and strong wear resistance, there is a severe challenge that conventional mechanical equipment cannot excavate efficiently. Therefore, the main approach is to rely on drill-and-blast methods to pre-break the rock mass or to use heavy tunnel boring machines (TBMs) for slow cutting. During construction, real-time monitoring and immediate support are highly relied upon to control risks such as rock bursts and spalling, while a powerful ventilation system is used to ensure a safe working environment.

[0003] When constructing pile foundations in such strata, the pile heads often lack targeted reinforcement and restraint structures due to the high stress, concentrated bearing pressure at the pile top, and intense construction disturbances. This makes them prone to failure modes such as concrete spalling, localized crushing, circumferential cracking, and stress concentration under vertical and impact loads, making the pile head the most vulnerable and weakest link in the entire pile foundation system. Furthermore, existing technologies generally lack a systematic structure that coordinates with the external restraint, internal anchoring, and load diffusion of the pile head. This results in insufficient stiffness in the pile head's stress zone and unclear force paths, making it difficult to effectively achieve stable force transmission from the superstructure to the pile body under high-load conditions in hard rock strata, thus compromising bearing capacity and durability.

[0004] Because the precast pile heads in related technologies lack effective structural reinforcement and circumferential restraint measures, the pile heads are prone to spalling, crushing, cracking and other damage under high load and impact conditions, making it impossible to reliably transfer the load of the superstructure and significantly weakening the overall bearing capacity of the pile foundation. Summary of the Invention

[0005] In view of this, the present invention aims to at least partially solve one of the related technical problems.

[0006] To achieve the above objectives, the technical solution of this utility model is implemented as follows:

[0007] A pile head reinforcement structure for construction in hard rock formations includes a steel sleeve, a grouting structure disposed between the steel sleeve and the outer surface of the pile head, a shear structure for forming a mechanical interlocking effect between the pile head and the steel sleeve, an anchoring structure for reliable connection with the pile body, a pressure-bearing flange disposed at the bottom of the steel sleeve, and a reinforcing rib structure arranged on the outer wall of the steel sleeve.

[0008] The steel sleeve is fitted around the outer periphery of the precast pile head, and the grouting structure fills the space between the inner wall of the steel sleeve and the outer surface of the pile head and is solidified between the two.

[0009] The shear structure is installed on the inner wall of the steel sleeve;

[0010] The upper part of the anchoring structure is located in the grouting structure area, and the lower part is embedded in the precast pile.

[0011] The pressure-bearing flange is integrally connected to the bottom of the steel sleeve to expand the pressure-bearing contact area of ​​the pile head and guide the load diffusion;

[0012] The reinforcing rib structure is arranged along the outer wall of the steel sleeve, and its lower end is integrally connected to the pressure-bearing flange.

[0013] Furthermore, the shear structure includes multiple shear keys evenly arranged circumferentially. The shear keys are fixedly installed on the inner wall of the steel sleeve and protrude inward, so that the grouting structure forms a mechanical interlocking structure that resists slippage and pull-out in both the vertical and circumferential directions.

[0014] Furthermore, the anchoring structure includes a plurality of anchoring steel bars evenly arranged circumferentially. The tops of the plurality of anchoring steel bars are located within or in direct contact with the grouting structure, and the bottoms are pre-embedded into the interior of the precast pile and integrally fixed with the pile body reinforcement cage / concrete. The anchoring steel bars have a bending structure in the middle.

[0015] Furthermore, the grouting structure includes multiple grouting cavities, which are evenly arranged circumferentially on the inner wall of the steel sleeve. Each grouting cavity is filled with non-shrink high-strength grouting material or structural epoxy grouting material.

[0016] Furthermore, the steel sleeve is a segmented sleeve structure, consisting of two or three arc-shaped steel plates joined together and locked together by connectors, and an upper connecting plate is provided on the upper end face of the steel sleeve.

[0017] Furthermore, it also includes a centering mechanism, which includes an annular sleeve, a positioning ring, and multiple centering bolts. The annular sleeve is disposed on the lower end face of the upper connecting plate, and the multiple centering bolts are evenly arranged on the annular sleeve around its circumference.

[0018] The centering bolt passes through the outer wall of the steel sleeve, and the inner end of the centering bolt contacts the outer side of the pile head through the top positioning ring, so as to realize the fine adjustment and centering of the steel sleeve relative to the axis of the pile head.

[0019] Furthermore, multiple hoisting structures are evenly arranged around the upper end face of the upper connecting plate. The hoisting structure includes a vertical plate, a stiffening plate, and a lifting lug. The lower end face of the vertical plate is fixed to the upper end face of the upper connecting plate through the stiffening plate, and the lifting lug is provided on the outer end face of the vertical plate.

[0020] Furthermore, the number of centering bolts is three.

[0021] Furthermore, the pressure-bearing flange is an annular thick plate structure, fixed to the inner side of the bottom of the steel sleeve, with its inner edge located in the upper part of the pile head.

[0022] Furthermore, the reinforcing rib structure includes multiple outer reinforcing ribs arranged along the axial direction of the steel sleeve. The multiple reinforcing ribs are evenly arranged circumferentially on the outer wall of the steel sleeve, and the bottom end of each reinforcing rib is provided with a bent inclined surface and integrally connected to the pressure-bearing flange.

[0023] Compared with existing technologies, the pile head reinforcement structure for hard rock strata construction described in this utility model has the following advantages:

[0024] 1. A three-dimensional mechanical interlocking system of "surface-key-body" is formed by multiple rows of shear keys between the outer steel sleeve and the inner grouting layer. This allows vertical loads and accidental impacts to be quickly dispersed into multiple shear units along the circumference after entering the pile head, and secondary homogenization is achieved through the circumferential arching effect, thereby significantly reducing the concentration of peak shear stress and tensile stress on a single section. Under the guidance of the pressure-bearing flange, the concentrated pressure at the pile top changes from point-to-surface contact to circumferential diffusion, further suppressing the risk of spalling and crushing of the pile head concrete under eccentric compression and local impact. The integrated connection between the outer reinforcing bars and the flange improves the overall stability of the thin-walled sleeve under the combined action of external pressure and local impact, making it less prone to buckling and yielding, and ensuring that the outer hoop provides reliable restraint throughout its entire lifespan. The internal anchoring steel bars, after being set with a bent structure, exhibit higher hysteretic energy dissipation and pull-out bearing capacity under low-cycle repeated loading. The synergistic bonding with the grouting layer can effectively suppress the initiation of circumferential cracks and delay crack penetration.

[0025] 2. The use of a segmented sleeve combined with an upper connecting plate and centering mechanism allows for on-site positioning and concentricity fine-tuning without dismantling the original pile or removing a large area of ​​concrete. The assembly process has minimal site restrictions and clear requirements for hoisting equipment. The combination of three-point centering bolts and positioning rings provides a direct and reliable geometric verification method, enabling axial correction before final tightening of the longitudinal joint and maintaining a stable posture during grouting, ensuring subsequent filling and interface quality from the source. The grouting cavity adopts a circumferential multi-cavity and layered interconnected arrangement, which is beneficial for… The design incorporates ventilation and avoids voids, while also facilitating the injection of different grout materials with varying properties to suit complex working conditions, providing a wider construction window. The standardized design of longitudinal joint sealing, grout inlet and outlet joints, and external wall reinforcement makes it easy to verify and accept the sealing and impermeability, with clear quality control points that facilitate the creation of standardized operating instructions. At the same time, the hoisting structure functions as both a tool hanging point and a safety anchor point during construction, reducing the need for temporary component erection, improving construction efficiency, and lowering safety risks. Overall, it demonstrates excellent assembly friendliness, adaptability, and quality control. Attached Figure Description

[0026] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings:

[0027] Figure 1 This is a schematic diagram of a pile head reinforcement structure for construction in hard rock formations, as described in an embodiment of this utility model.

[0028] Figure 2 This is a schematic diagram of the centering mechanism described in an embodiment of the present utility model;

[0029] Figure 3 This is a schematic diagram of the centering bolt described in an embodiment of the present utility model;

[0030] Figure 4 This is a schematic diagram of the combination of anchoring steel bars and grouting cavity as described in an embodiment of this utility model.

[0031] Explanation of reference numerals in the attached figures:

[0032] 100. Steel sleeve; 110. Reinforcing rib structure; 120. Pressure bearing flange; 200. Upper connecting plate; 300. Lifting structure; 310. Vertical plate; 320. Lifting lug; 400. Centering mechanism; 410. Annular sleeve; 420. Centering bolt; 430. Positioning ring; 500. Anchoring structure; 610. Grouting cavity; 620. Shear key. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0034] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0035] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0036] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] This embodiment provides a pile head reinforcement structure for construction in hard rock formations. Its construction and assembly revolve around a collaborative approach of "external circumferential constraint—internal mechanical interlocking—vertical bearing pressure diffusion—construction alignment verification." The structure includes a steel sleeve 100, a grouting structure disposed between the steel sleeve 100 and the outer surface of the precast pile head, a shear structure fixed to the inner wall of the steel sleeve 100 and forming an anti-slip / anti-pull-out interlocking with the grouting structure, an anchoring structure 500 working along the pile direction with the internal reinforcement and concrete to achieve closed-loop force flow, and a steel sleeve 100... The steel sleeve 100 is an integrally installed pressure-bearing flange 120 at the bottom, which is used to expand the bearing contact area of ​​the pile top and guide the spread of load. The steel sleeve 100 is axially distributed along the outer wall of the steel sleeve 100 and integrally connected with the pressure-bearing flange 120 to suppress local buckling of the outer wall. The steel sleeve 100 is preferably a split sleeve structure, which is formed by splicing two or three arc-shaped steel plates to form a complete ring. It is locked at the longitudinal joint by high-strength connectors. The upper end connecting plate 200 is integrally welded on the upper end face, so that the steel sleeve 100 can be used as a load-bearing base for traction and centering during the construction period. To achieve slight concentricity correction of the steel sleeve 100 relative to the pile head axis during the installation phase, a centering mechanism 400 is coaxially arranged on the lower surface of the upper connecting plate 200. The centering mechanism 400 includes an annular sleeve 410, a positioning ring 430, and multiple centering bolts 420 (three in this embodiment, arranged equiangularly around the circumference). The centering bolts 420 pass through the outer wall of the annular sleeve 410 and are threadedly engaged with the annular sleeve 410. The outer wall of the steel sleeve 100 has a pre-set through hole that can mate with the centering bolts 420, and its inner end abuts against the positioning ring. The ring 430 indirectly contacts the outer side of the pile head, and the steel sleeve 100 is precisely aligned with the pile axis by slight tightening. To facilitate on-site hoisting and positioning, multiple hoisting structures 300 are arranged equidistantly on the upper surface of the upper connecting plate 200. The hoisting structure 300 is composed of a vertical plate 310, a stiffening plate, and a lifting lug 320. The lower end of the vertical plate 310 is welded to the upper connecting plate 200 as a whole through the stiffening plate. The lifting lug 320 is exposed to facilitate quick connection with the lifting slings and can be used as a temporary support point or tool hanging point during concrete grouting and curing.

[0038] To form a reliable circumferential constraint and vertical pressure channel, the pressure flange 120 adopts an annular thick plate structure and is fixed to the inner side of the bottom of the steel sleeve 100. Its inner edge is located in the upper part of the pile head to avoid interference with the pile body's edges and facilitate the connection of the grout. There is no abrupt change between the lower surface of the pressure flange 120 and the inner wall of the steel sleeve 100. The transition part adopts rounded corners or chamfers to reduce secondary stress concentration and guide the pressure to diffuse in the circumferential direction. The reinforcing rib structure 110 is composed of multiple outer reinforcing ribs, arranged along the axial direction of the steel sleeve 100 and equidistant in the circumferential direction. The bottom end of each outer reinforcing rib is provided with a bent inclined surface and is integrally connected to the pressure flange 120. This suppresses the buckling instability of the outer wall of the steel sleeve when vertical pressure and lateral impact work together, and smoothly transmits the concentrated stress to the pressure flange 120 to complete the diffusion. The shear structure employs multiple shear keys 620, which are fixed to the inner wall of the steel sleeve 100 and protrude inward, arranged equidistantly along the circumference. Preferably, adjacent shear keys are staggered vertically at a certain distance to form a "plum blossom" three-dimensional interlocking sequence. The height and spacing are matched with the target aggregate particle size, the roughness of the pile head outer wall, and the compressive strength of the grout, thereby simultaneously forming a mechanical interlocking interface that resists slippage and pull-out in both the vertical and circumferential directions, improving the shear bearing capacity and energy dissipation capacity of the pile head-grout-steel sleeve composite interface.

[0039] The grouting structure employs multiple grouting cavities 610 set within the inner wall of the steel sleeve 100 to achieve rapid filling and uniform pressure distribution. These cavities 610 are equidistantly arranged circumferentially and communicate with each other or with different sections within the sleeve's inner cavity. Each grouting cavity 610 is filled with non-shrink high-strength grouting material or structural epoxy grouting material, preferably a formula with rapid early strength development and good interfacial bonding performance with both concrete and steel. To reduce leakage risk and improve filling quality, the inlet and outlet ports of the grouting cavities 610 can be positioned at different elevations with pre-reserved venting channels. The inner wall of the cavity is roughened or has fine toothed protrusions to increase the interfacial bonding area. Tongue-and-groove joints or rubber / butyl seals are added at the longitudinal joints of the segmented sleeve, and bolt pre-tightening torque is controlled to ensure sealing during the grouting pressure stage. The anchorage structure 500 includes multiple anchorage steel bars evenly arranged circumferentially, preferably HRB400 or equivalent grade steel bars. The upper end of the steel bar is located within the grouting structure area and is directly wrapped and consolidated with the grout. The lower end is pre-embedded into the precast pile along its length and forms an anchorage section with the pile body reinforcement cage / concrete. To improve the pull-out bearing capacity and ductility under low-cycle repeated loading, the anchorage steel bars are provided with a bending structure (such as U-shaped or zigzag shape) in the middle. The radius of the rounded corner and the inner lining sleeve at the bend can be configured to be 3-5 times the diameter of the steel bar to reduce stress concentration. Limiting pads are arranged on the outside of the bend area to ensure the spatial position and protective layer thickness during the construction stage and prevent the anchorage steel bars from shifting during grouting compaction or load impact.

[0040] To improve assembly efficiency, the inner wall of the steel sleeve 100 can be roughened by sandblasting to Sa2.5 grade and coated with a compatible primer before leaving the factory to inhibit corrosion. The shear key 620, the outer reinforcing rib, and the pressure flange 120 are all beveled and fully penetrated welded and subjected to ultrasonic / magnetic particle testing to ensure that the weld quality meets the load-bearing requirements. The upper connecting plate 200 can be configured with a thickened area and pre-drilled elongated holes according to the construction lifting capacity to accommodate different specifications of lifting tools. In the centering mechanism 400, it is recommended to use fine-thread high-strength bolts for the centering bolts 420 and to use spring washers / nylon locking parts to prevent loosening. A stiffening ring is added at the weld between the annular sleeve 410 and the upper connecting plate 200 to improve local bending stiffness. When there is local honeycomb pitting or eccentric tilt on the outer surface of the pile head, a removable pressure-resistant shim can be placed between the positioning ring 430 and the pile head for fine adjustment to keep the steel sleeve 100 concentric and create uniform boundary conditions for subsequent load transfer.

[0041] How this example works

[0042] Step 1: Remeasure the outer diameter and verify the axial eccentricity of the precast pile head; clean the loose layer on the outer surface of the pile head and mechanically grind it until the solid aggregate is exposed; control the moisture content within a suitable range; check the weld quality of the steel sleeve 100, pressure flange 120, shear key 620 and outer reinforcing rib and complete the anti-rust treatment; verify the load-bearing capacity markings of the upper connecting plate 200 and the hoisting structure 300.

[0043] Step 2: Using the lifting lug 320, lift each arc plate of the segmented steel sleeve 100 to the outer periphery of the pile head in sequence. Tighten the connecting parts of the longitudinal joint to the specified pre-tightening force percentage so that the sleeve forms a continuous ring but still retains a small adjustment margin. At this time, the inner edge of the pressure flange 120 should be relatively flush with the upper part of the pile head without interference.

[0044] Step 3: Activate the centering mechanism 400 and slowly and evenly tighten the three centering bolts 420 so that the positioning ring 430 contacts the outer side of the pile head and achieves fine adjustment of the concentricity of the sleeve relative to the pile axis; check the levelness and concentricity of the upper connecting plate 200 with a theodolite or laser plumb line. After meeting the requirements, tighten the longitudinal splice connector to the specified torque and perform a second inspection.

[0045] Step 4: Arrange anchoring structures 500mm apart circumferentially according to the design, with the upper end located within the future grouting layer and the lower end pre-embedded into the pile body and reliably tied to the reinforcing cage or chemically anchored with rebar. Set limiters and protective sleeves at the bending structures and check the thickness of the protective layer.

[0046] Step 5: Apply sealing tape to the longitudinal joint of the steel sleeve 100 and install the grout inlet and outlet joints of the grouting cavity 610. Close the exhaust valve and conduct a low-pressure water test (or air test) to check for leaks. If necessary, reinforce the seal until the pressure holding time requirement is met.

[0047] Step Six: Select non-shrink high-strength grouting material or structural epoxy grouting material, and follow the process of starting from the farthest point and moving to the nearth, starting from the bottom and moving to the top, and continuously layering the grouting material. During this process, you can gently tap the outer wall of the sleeve and use short-term low-frequency vibration to help the grout fill the periphery of the shear key 620 and the inner corner of the grouting cavity 610. When thick grout is seen at the vent and there are no obvious air bubbles, close the vent and complete the grouting.

[0048] Step 7: After grouting is completed, maintain wet curing or perform thermal insulation curing according to the material technical conditions. After the specified early strength is reached, remove the temporary fixtures, re-measure the concentricity of the sleeve and the levelness of the upper connecting plate 200, and complete the appearance and dimensional acceptance. If necessary, conduct a trial load to confirm that there is no abnormal deformation of the pressure flange 120 and the reinforcing rib structure 110.

[0049] Step 8: The load of the superstructure is transmitted to the vicinity of the upper connecting plate through the pressure-bearing components and diffused to the circumferential and vertical channels by the pressure-bearing flange 120. Through the mechanical interlocking of the grouting layer and shear key, as well as the joint action of the anchoring steel bars and the pile body, the load is stably transmitted to the precast pile and then to the pile-soil system.

[0050] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A pile head reinforcement structure for use in hard rock formation construction, characterised in that: It includes a steel sleeve (100), a grouting structure disposed between the steel sleeve (100) and the outer surface of the pile head, a shear structure for forming a mechanical interlocking effect between the pile head and the steel sleeve (100), an anchoring structure (500) for reliable connection with the pile body, a pressure-bearing flange (120) disposed at the bottom of the steel sleeve (100), and a reinforcing rib structure (110) arranged on the outer wall of the steel sleeve (100); The steel sleeve (100) is fitted around the outer periphery of the precast pile head, and the grouting structure fills the space between the inner wall of the steel sleeve (100) and the outer surface of the pile head and is solidified between the two. The shear structure is installed on the inner wall of the steel sleeve (100); The upper part of the anchoring structure (500) is located in the grouting structure area, and the lower part is embedded in the precast pile; The pressure-bearing flange (120) is integrally connected to the bottom of the steel sleeve (100) to expand the pressure-bearing contact area of ​​the pile head and guide the load diffusion; The reinforcing rib structure (110) is arranged along the outer wall of the steel sleeve (100), and its lower end is integrally connected to the pressure flange (120).

2. The pile head reinforcement structure for hard rock strata construction according to claim 1, characterized in that: The shear structure includes multiple shear keys (620) evenly arranged circumferentially. The shear keys (620) are fixedly installed on the inner wall of the steel sleeve (100) and protrude inward, so that the grouting structure forms a mechanical interlocking that is resistant to slippage and pull-out in both the vertical and circumferential directions.

3. A pile head reinforcement structure for construction in hard rock formations according to claim 1 or 2, characterized in that: The anchoring structure (500) includes a plurality of anchoring steel bars evenly arranged in the circumferential direction. The top of the plurality of anchoring steel bars is located in or in direct contact with the grouting structure, and the bottom is pre-embedded into the interior of the precast pile and integrally fixed with the pile body steel cage / concrete. The anchoring steel bars are provided with a bending structure in the middle.

4. A pile head reinforcement structure for construction in hard rock formations according to claim 3, characterized in that: The grouting structure includes multiple grouting cavities (610), which are evenly arranged circumferentially on the inner wall of the steel sleeve (100). Each grouting cavity (610) is filled with non-shrink high-strength grouting material or structural epoxy grouting material.

5. A pile head reinforcement structure for construction in hard rock formations according to claim 3, characterized in that: The steel sleeve (100) is a split sleeve structure, consisting of two or three arc-shaped steel plates joined together and locked together by connectors. An upper connecting plate (200) is provided on the upper end face of the steel sleeve (100).

6. A pile head reinforcement structure for construction in hard rock formations according to claim 5, characterized in that: It also includes a centering mechanism (400), which includes an annular sleeve (410), a positioning ring (430) and a plurality of centering bolts (420). The annular sleeve (410) is disposed on the lower end face of the upper connecting plate (200), and the plurality of centering bolts (420) are evenly disposed on the annular sleeve (410) around its circumference. The centering bolt (420) passes through the outer wall of the steel sleeve (100), and the inner end of the centering bolt (420) contacts the outer side of the pile head through the top positioning ring (430), so as to realize the fine adjustment and centering of the steel sleeve (100) relative to the axis of the pile head.

7. A pile head reinforcement structure for construction in hard rock formations according to claim 6, characterized in that: The upper end connecting plate (200) has multiple hoisting structures (300) evenly arranged around its upper end surface. The hoisting structure (300) includes a vertical plate (310), stiffening plates, and lifting lugs (320). The lower end surface of the vertical plate (310) is fixed to the upper end surface of the upper end connecting plate (200) through the stiffening plates. The lifting lugs (320) are located on the outer end surface of the vertical plate (310).

8. A pile head reinforcement structure for construction in hard rock formations according to claim 6, characterized in that: The number of centering bolts (420) is 3.

9. A pile head reinforcement structure for construction in hard rock formations according to claim 1, characterized in that: The pressure-bearing flange (120) is an annular thick plate structure, fixed to the inner side of the bottom of the steel sleeve (100), with its inner edge located in the upper part of the pile head.

10. A pile head reinforcement structure for construction in hard rock formations according to claim 1, characterized in that: The reinforcing rib structure (110) includes a plurality of outer reinforcing ribs arranged along the axial direction of the steel sleeve (100). The plurality of reinforcing ribs are evenly arranged circumferentially on the outer wall of the steel sleeve (100). The bottom end of each reinforcing rib is provided with a bent inclined surface and is integrally connected to the pressure-bearing flange (120).

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