Marble type prestressed hollow anchor rod and construction method thereof

Abstract

The invention relates to the technical field of prestressed anchor rods, in particular to a marble type prestressed hollow anchor rod and a construction method thereof. Comprising a hollow anchor rod body, an expansion head body, a plurality of expansion pieces and a trigger assembly. A basic force transmission and grouting channel is formed through the expansion head body connected with the hollow anchor rod body in a penetrating mode, the multiple radial through holes are formed in the side wall of the expansion head body, the expansion pieces are slidably inserted into the radial through holes, it is ensured that the expansion pieces are stored in the initial state, the appearance of the expansion head body is smooth, and the expansion head body is not prone to deformation. When being driven by external force, a trigger piece located at the inlet of the cavity enters the cavity and pushes the expansion piece outwards in the radial direction. The uncontrollable anchoring action can be thoroughly separated from the simple and controllable mounting action. The anchoring reliability and anchoring force are improved through spiked club type mechanical built-in formed after the multiple expansion pieces are triggered. And meanwhile, the mounting operation becomes simple and reliable due to the working mode of first in-place and then triggering.

Description

Technical Field

[0001] This invention relates to the field of prestressed anchor technology, specifically to a ball-type prestressed hollow anchor and its construction method. Background Technology

[0002] In geotechnical engineering, mining, slope protection, and tunnel construction, prestressed anchors are crucial components for reinforcing soil and rock masses. One end of the anchor is fixed deep within stable soil or rock, while the other end remains exposed. An anchor plate and nut apply active prestress to the surface of the soil or rock mass, effectively enhancing the integrity and stability of the soil and rock mass and inhibiting deformation and failure. The key to effective support lies in ensuring that the anchor can be tensioned to the designed prestress value after installation, and that this prestress must be reliably maintained.

[0003] Prestressed anchor bolts mainly include catalytic coil prestressed hollow anchor bolts and expansion-shell type prestressed hollow anchor bolts. While both technologies are widely used, their inherent working principles lead to inherent engineering defects. Specifically, the anchoring effectiveness of catalytic coil anchor bolts relies entirely on the chemical bond between the resin cartridge and the borehole wall. This not only places stringent requirements on borehole cleanliness but also carries the risk of bond failure during stress, resulting in the anchor bolt being pulled out entirely. On the other hand, the mechanical anchoring mechanism of expansion-shell type anchor bolts suffers from structural fragility and poor controllability. The expansion shell plates are prone to detachment before installation and often jam prematurely due to accidental rotation before the anchor bolt reaches the designed depth, rendering both the borehole and the anchor bolt unusable, wasting materials and time. Summary of the Invention

[0004] This invention addresses the problems of low reliability and low construction success rate of prestressed anchor bolts by proposing a ball-type prestressed hollow anchor bolt and its construction method.

[0005] To address the above problems, this invention provides a ball-type prestressed hollow anchor bolt, comprising: Hollow anchor rod body; An expansion head body is connected to one end of the hollow anchor rod body. The inner cavity of the hollow anchor rod body communicates with the cavity of the expansion head body to form a grouting channel. The side wall of the expansion head body is provided with a grout outlet hole and multiple radial through holes. Multiple expansion tabs, which are slidably inserted into corresponding radial through holes; The triggering component includes a triggering element disposed within the cavity. The triggering element is used to enter the cavity of the expansion head body when driven by an external force, and to push the expansion piece radially outward, so that the expansion piece extends along the through direction of the radial through hole where it is located, and is anchored to the rock wall of the borehole.

[0006] Preferably, the triggering component further includes an elastic limiting member disposed at the entrance of the cavity of the expansion head body, for limiting the triggering member in the initial state.

[0007] Preferably, the elastic limiting member is an annular retaining plate made of high-strength and tough metal, which is arranged around the inner wall of the entrance of the cavity and narrows towards the bottom of the drill hole to form a blocking part. When the trigger is driven by an external force, it opens the blocking part and enters the cavity corresponding to the expansion piece.

[0008] Preferably, the trigger is a high-strength metal ball, and its diameter is larger than the inner diameter of the hollow anchor rod.

[0009] Preferably, the plurality of expansion tabs are arranged in at least two rows along the axial direction of the expansion head body, and the expansion tabs in adjacent rows are staggered in the circumferential direction of the expansion head body.

[0010] Preferably, each of the expansion pieces is provided with a limiting plate relative to the inner sidewall of the expansion head body to prevent the expansion piece from completely detaching from the expansion head body when it is pushed outward from the radial through hole.

[0011] Preferably, the outer surface of each expansion piece is uniformly provided with protrusions for increasing friction.

[0012] Preferably, the device further includes an anchor plate and a hemispherical nut, wherein the anchor plate is sleeved on the hollow anchor rod body, the hemispherical nut is threadedly engaged with the hollow anchor rod body, and its spherical surface abuts against the anchor plate.

[0013] Preferably, the slurry outlet is located at the inlet end of the expansion head body away from the cavity.

[0014] This invention also includes a construction method for a ball-bead type prestressed hollow anchor bolt, comprising the following steps: An enlarged section is formed at the bottom of the borehole, and the expansion head body is connected to the hollow anchor rod body and then sent into the bottom of the borehole; Insert the top rod through the hole of the hollow anchor rod body, push the trigger to make it enter the cavity of the expansion head body, drive the expansion plate to extend along the radial through hole direction and anchor it to the rock wall of the expansion section; The hollow anchor rod is tensioned in a direction away from the borehole to apply prestress; Pressure grouting is performed through the grouting channel, and the grout overflows from the grout outlet and fills the borehole.

[0015] The beneficial effects of this invention are as follows: This invention establishes a basic force transmission and grouting channel through an expansion head body that is connected to the hollow anchor rod. Multiple radial through holes are opened on the side wall of the expansion head body, and an expansion piece can be slidably inserted into each radial through hole. This design ensures that the expansion piece is retracted in its initial state, resulting in a relatively smooth shape for the expansion head body. Most importantly, the introduction of a triggering component is crucial. A trigger located at the cavity entrance only enters the cavity when driven by external force, pushing the expansion piece radially outward. This completely separates the uncontrollable anchoring action from the simple and controllable installation action. Throughout the process of the relatively smooth-shaped expansion head body being sent to the bottom of the borehole, the expansion piece remains in a static contracted state. It is only actively triggered by the construction personnel after it has reached the bottom of the hole, thus fundamentally eliminating the risk of premature jamming.

[0016] Therefore, this application presents a ball-bead type prestressed hollow anchor bolt, in which multiple expansion plates form a mace-like mechanical embedment after triggering, improving the reliability and anchoring force of the anchoring. Simultaneously, the pre-deployment, post-trigger working mode simplifies and ensures reliable installation, effectively avoiding waste of materials and time. Furthermore, the grouting channel ensures that grout can fill the borehole, forming permanent support. This provides an excellent solution for geotechnical anchoring engineering. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the initial state of a ball-type prestressed hollow anchor rod according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a ball-type prestressed hollow anchor rod under force driving state in one embodiment of the present invention; Figure 3 yes Figure 2 A magnified view of a portion of the image.

[0018] Explanation of reference numerals in the attached drawings: 1-Hollow anchor rod body; 2-Expansion head body; 21-Grouting hole; 22-Cavity; 3-Expansion plate; 31-Limiting plate; 41-Trigger element; 42-Elastic limiting element; 5-Drill hole; 51-Enlarged section; 6-Anchor plate; 7-Hemispherical nut. Detailed Implementation

[0019] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0020] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used only to distinguish different devices, modules, or components, and are not intended to limit the order of functions performed by these devices, modules, or components or their interdependencies.

[0021] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0022] To address the problems existing in the aforementioned related technologies, this invention provides a ball-type prestressed hollow anchor rod and its construction method.

[0023] See Figures 1 to 3 On one hand, the present invention provides a ball-type prestressed hollow anchor bolt, comprising a hollow anchor bolt body 1, an expansion head body 2, multiple expansion plates 3, and a triggering assembly. The expansion head body 2 is connected to one end of the hollow anchor bolt body 1, and the inner cavity of the hollow anchor bolt body 1 communicates with the cavity 22 of the expansion head body 2 to form a grouting channel; the side wall of the expansion head body 2 is provided with a grout outlet hole 21 and multiple radial through holes; the expansion plates 3 are slidably inserted into the corresponding radial through holes; the triggering assembly includes a trigger element 41 disposed in the cavity 22, which is used to enter the cavity 22 of the expansion head body 2 when driven by an external force, and to push the expansion plates 3 radially outward, so that the expansion plates 3 extend along the through direction of the radial through holes and are anchored to the rock wall of the borehole 5.

[0024] The aforementioned expansion piece 3 is slidably inserted into the corresponding radial through hole. In a preferred embodiment, the expansion piece 3 and the radial through hole are interference-fitted, and initial positioning is achieved by friction.

[0025] To further ensure reliability during handling and drilling, a plastic film can be temporarily wrapped around the exterior of the expansion head body 2. The distal portion of the expansion piece 3 is housed in the radial through hole where it is located. The plastic film covers the outer surface of the expansion head body 2 corresponding to the distal portion of the expansion piece 3, which is used to assist in positioning the expansion piece 3 before installation, preventing it from accidentally protruding due to scraping against the hole wall during the process of the anchor rod entering the borehole 5, thereby avoiding the anchor rod getting stuck before reaching the design depth.

[0026] It should be noted that, because the expansion plates 3 remain in a retracted state throughout the entire process of being inserted into the borehole 5 along with the hollow anchor rod 1, their smooth shape avoids interference with the borehole wall, thus preventing jamming caused by premature component movement and ensuring that the anchor rod can be smoothly and reliably installed to the designed depth. Furthermore, once the hollow anchor rod 1 is in place, through the controllable action of the internal push trigger 41, multiple expansion plates 3 are simultaneously and forcefully pushed radially out, deeply embedding themselves into the rock wall at the bottom of the borehole 5, forming a strong, tooth-like mechanical embedding. The anchoring force provided by this mechanical engagement is far more reliable than the limited and unstable anchoring effect of traditional expansion plates.

[0027] More importantly, the two key steps of installation and anchoring are separated in terms of timing and space, which transforms the construction process from passive and uncontrollable to active and controllable, thereby greatly improving the success rate and efficiency of construction and effectively avoiding the waste of materials and time caused by anchoring failure.

[0028] The through-hole grouting channel ensures that full-length pressure grouting can be carried out after prestressing is applied to form permanent support, thereby integrating timely and reliable end mechanical anchoring with long-term stable full-length bonded support, and realizing a substantial improvement in the comprehensive performance of prestressed anchor bolts.

[0029] The expansion head body 2 and the hollow anchor rod body 1 can be connected by threads. This facilitates assembly and installation, saving construction time.

[0030] In one embodiment of the present invention, the triggering component further includes an elastic limiting member 42, which is disposed at the entrance of the cavity 22 of the expansion head body 2 and is used to limit the triggering member 41 in the initial state. The elastic limiting member 42 is an annular retaining plate made of high-strength and tough metal, which is disposed around the inner wall of the entrance of the cavity 22 and narrows towards the bottom of the drill hole 5 to form a blocking part. When the triggering member 41 is driven by an external force, it opens the blocking part and enters the cavity 22 corresponding to the expansion piece 3.

[0031] It should be noted that the elastic limiting member 42 acts as a safety lock. In the initial state, the inward-curving blocking part formed by the elastic limiting member 42, relying on the elastic tension of the material itself, provides the trigger member 41 with a clear initial position and a pre-tightening force that must be overcome. This design first ensures that during the entire process of transporting, handling, and inserting the anchor rod into the borehole 5, the trigger member 41 will not move accidentally due to vibration or slight collision, thus ensuring the initial stability of the expansion head body 2 and effectively avoiding installation failures caused by loose and easily detached components in traditional expansion-shell anchor rods. More importantly, the anchoring action will not be accidentally initiated due to accidental force during installation. Only when personnel actively apply an external force through the push rod can the trigger member 41 open the blocking part and enter the working position, that is, enter the cavity 22 position corresponding to the expansion plate 3. This triggering mechanism is the fundamental guarantee to prevent the ball-type prestressed hollow anchor rod from jamming prematurely before reaching the bottom of the borehole 5, ensuring the controllability and success rate of installation. Meanwhile, the integrated design of the ring-shaped clamping plate and the constriction opening makes the structure extremely simple and compact, which not only ensures the reliability of the operation, but also reduces the processing difficulty and manufacturing cost of the expansion head body 2.

[0032] In one embodiment of the present invention, the trigger 41 is a high-strength metal ball, and its diameter is larger than the inner diameter of the hollow anchor rod body 1.

[0033] It should be noted that the diameter of the trigger element 41 is larger than the inner diameter of the hollow anchor rod body 1. When the hollow anchor rod body 1 and the expansion head body 2 are connected, it prevents the trigger element 41 from falling out through the inner cavity of the hollow anchor rod body 1. The trigger element 41 is a high-strength metal ball. Its spherical shape allows it to efficiently convert axial thrust into uniform radial expansion force when pushed by the top rod. When the metal ball enters the cavity 22, its spherical surface can simultaneously and equally contact and squeeze the inner end faces of multiple expansion pieces 2, thereby driving all expansion pieces 3 to extend synchronously and smoothly along their respective radial through holes. This "ball-like" force transmission method avoids the problem of expansion pieces getting stuck or unfolding sequentially due to uneven force. Moreover, the self-adjusting capability of the trigger element 41 ball reduces the requirements for installation alignment. Even under conditions where the force applied by the top rod is slightly eccentric, the ball can automatically adjust the contact position through slight rolling, ensuring that the expansion force is always transmitted in the design direction. This reduces the requirements for construction operation precision.

[0034] In one embodiment of the present invention, a plurality of expansion plates 3 are arranged in at least two rows along the axial direction of the expansion head body 2, and the expansion plates 3 in adjacent rows are staggered in the circumferential direction of the expansion head body 2.

[0035] It should be noted that the use of at least two rows of expansion plates 3 arranged at axial intervals and staggered in the circumferential direction in a mace-like layout achieves multi-dimensional optimization of anchoring performance through a unique mechanical configuration.

[0036] Specifically, this staggered arrangement significantly optimizes the mechanical interaction mechanism between the expansion head body 2 (anchor head) and the rock wall of the borehole 5. Compared to single-row or aligned expansion plates, the staggered layout allows the distal ends of multiple expansion plates 3 to embed into multiple rings at different depths within the rock wall after radial ejection, thus dispersing the enormous tensile force over a larger rock mass area. This effectively avoids excessive stress concentration on a single rock wall ring, significantly reducing the risk of anchorage failure due to local rock mass crushing and providing greater safety redundancy for the entire support system. Simultaneously, this layout provides more contact support points between the anchor head and the rock wall after anchoring, resulting in a more rational stress state and preventing cascading damage caused by the failure of individual support points, thereby comprehensively improving the reliability and durability of the anchorage. This design, with its simple yet ingenious geometric arrangement, achieves a qualitative leap in anchorage performance.

[0037] In one embodiment of the present invention, each expansion piece 3 is provided with a limiting plate 31 relative to the inner sidewall of the expansion head body 2 to prevent the expansion piece 3 from completely detaching from the expansion head body 2 when it is pushed outward from the radial through hole.

[0038] It should be noted that the limiting plate 31 fundamentally solves the risk of the expansion piece 3 accidentally falling off at maximum stroke, thus achieving absolute controllability and safety redundancy in the anchoring process.

[0039] Specifically, the limiting plate 31 acts as a physical barrier, its core function being to set a clear limit for the radial movement of the expansion piece 3. When the trigger 41 pushes the expansion piece 3 outward, the expansion piece 3 will eventually come into contact with the limiting plate 31. This ensures that even under unfavorable conditions such as abnormally soft rock or slightly out-of-tolerance dimensions of the enlarged section of the borehole 5, the expansion piece 3 will never completely detach from the expansion head body 2 due to overextension. This completely avoids the engineering problems of the entire anchor system failing due to the detachment of core components and the difficulty in recovering components left at the bottom of the hole, greatly improving the reliability of the support operation.

[0040] From a mechanical performance perspective, the presence of the limiting plate 31 ensures that the expansion piece 3 and the expansion head body 2 are always connected as a complete load-bearing unit. When subjected to long-term, significant prestress and complex loads caused by rock deformation, the reaction force from the rock wall experienced by the expansion piece 3 can be effectively transmitted back to the expansion head body 2 and the hollow anchor rod 1 through the limiting plate 31, without creating potential bending or shear weaknesses at the connection between the expansion piece 3 and the expansion head body 2. This force transmission path is more direct and rational, significantly enhancing the integrity and load-bearing durability of the anchor head structure.

[0041] In one embodiment of the present invention, the outer surface of each expansion piece 3 is provided with protrusions or patterns for increasing friction.

[0042] Specifically, when the protrusions or patterns on the expansion plate 3 are radially pushed out and pressed into the rock wall of the borehole 5, they can efficiently break down the loose debris and dust layer on the surface of the rock wall, allowing the expansion plate 3 to make direct contact with the solid rock surface. Under high pressure, these microstructures will generate a unique mechanical interlocking effect, and their circumferential and axial vertical surfaces can effectively resist the shear deformation of the rock mass, just like countless tiny anchors that tightly anchor the expansion plate to the rock mass.

[0043] In one embodiment of the present invention, an anchor plate 6 and a hemispherical nut 7 are also included. The anchor plate 6 is sleeved on the hollow anchor rod body 1, and the hemispherical nut 7 is threadedly engaged with the hollow anchor rod body 1, with its spherical surface abutting against the anchor plate 6.

[0044] Furthermore, an external torque can be applied to the hemispherical nut 7, causing it to move towards the bottom of the borehole 5. The rotational torque applied to the hemispherical nut 7 is converted into an axial tensile force tightly adhering to the axis of the hollow anchor rod 1. The linear movement of the hemispherical nut 7 transmits the force evenly to the anchor plate 6 through its spherical contact with the anchor plate 6. The anchor plate 6 then applies this force as a concentrated pressure to the borehole wall of the borehole 5. At this time, since the expansion plate 3 of the expansion head body 2 has formed a mechanical self-locking with the bottom rock wall of the borehole 5, when the borehole wall applies a reverse support force to the hollow anchor rod 1 through the anchor plate 6, the hollow anchor rod 1 is tensioned, generating the prestress required by the design. This process cleverly utilizes simple mechanical principles to convert easily applied rotational torque into precise axial prestress, ensuring the reliability of the support effect.

[0045] In one embodiment of the present invention, the slurry outlet 21 is opened at the inlet end of the expansion head body 2 away from the cavity 22.

[0046] It should be noted that after the grout is injected through the hollow anchor rod 1, it is guided to the deepest part of the expansion head body 2 and forced to overflow from the single grout outlet at the bottom. This grout filling mode can most effectively remove air and water from the borehole 5 completely from the borehole opening, thereby forming a dense, void-free, full-length bond between the rod and the borehole wall, ensuring the integrity of the permanent support.

[0047] On the other hand, the present invention also includes a construction method for a ball-bead type prestressed hollow anchor bolt, comprising the following steps: S1: An enlarged section 51 is formed at the bottom of the borehole 5. The expansion head body 2 is connected to the hollow anchor rod body 1 and then sent into the bottom of the borehole 5. S2: Insert the top rod into the hole of the hollow anchor rod body 1, push the trigger 41 to make it enter the cavity 22 of the expansion head body 2, drive the expansion plate 3 to extend along the radial through hole and anchor it to the rock wall of the expansion section 51. S3: Tension the hollow anchor rod 1 in a direction away from borehole 5 to apply prestress; S4: Pressure grouting is performed through the grouting channel, and the grout overflows from the grout outlet 21 and fills the borehole 5.

[0048] In step S1, when the assembled anchor rod is inserted into the bottom of the borehole, the expansion plate 3 does not initially extend out of its radial through hole. Crucially, the trigger element 41 is located at the entrance of the cavity 22 and is not driven by external force, ensuring the entire anchor rod head maintains a smooth and streamlined shape. This ensures that the anchor rod will not experience the premature jamming phenomenon common in traditional expansion-shell anchor rods during insertion, allowing for seamless installation to the designated position in one go, laying the foundation for a high construction success rate.

[0049] Step S2 is the core step in activating the anchoring function. By inserting a push rod into the borehole, the trigger 41 is actively pushed, and the controllable action completely hands over the initiative of anchoring to the construction personnel. The trigger 41 drives multiple expansion plates 3 to extend radially and fully embed into the rock wall of the enlarged section 51 at the bottom of the borehole 5 pre-formed in step S1. This allows the anchor head, i.e., the expansion head body 2, to have a larger mechanical engagement area with the borehole wall, increasing its friction with the borehole wall. This step provides a fundamental guarantee for subsequent tensioning.

[0050] Therefore, in step S3, when the hollow anchor rod 1 is tensioned in a direction away from the borehole 5, the tension force can be effectively applied and transmitted to the depth of the rock mass due to the strong and reliable end mechanical anchoring established in step S2, making it easier for the anchor rod to reach or even exceed the design tension strength.

[0051] Finally, the pressure grouting in step S4 completed the formation of permanent support. The entire construction method was logically rigorous and interconnected. Through a series of controllable and orderly operations, the technological advantages brought by the product structure innovation were fully transformed into high efficiency, high reliability, and high quality in on-site construction.

[0052] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A ball-type prestressed hollow anchor bolt, characterized in that, include: Hollow anchor rod body (1); The expansion head body (2) is connected to one end of the hollow anchor rod body (1). The inner cavity of the hollow anchor rod body (1) and the cavity (22) of the expansion head body (2) are connected to form a grouting channel. The side wall of the expansion head body (2) is provided with a grout outlet hole (21) and multiple radial through holes. Multiple expansion tabs (3) are slidably inserted into the corresponding radial through holes; The triggering component includes a triggering element (41) disposed in the cavity (22). The triggering element (41) is used to push the expansion piece (3) radially outward when driven by an external force, so that the expansion piece (3) extends along the through direction of the radial through hole and is anchored to the rock wall of the borehole (5).

2. The ball-type prestressed hollow anchor bolt according to claim 1, characterized in that, The triggering component further includes an elastic limiting member (42), which is disposed at the entrance of the cavity (22) of the expansion head body (2) and is used to limit the triggering member (41) in the initial state.

3. The ball-type prestressed hollow anchor bolt according to claim 2, characterized in that, The elastic limiting member (42) is an annular plate made of high-strength and tough metal. It is arranged around the inner wall of the entrance of the cavity (22) and narrows towards the bottom of the drill hole (5) to form a blocking part. When the trigger member (41) is driven by an external force, it opens the blocking part and enters the cavity (22) corresponding to the expansion piece (3).

4. The ball-type prestressed hollow anchor bolt according to claim 3, characterized in that, The trigger element (41) is a high-strength metal ball, and its diameter is larger than the inner diameter of the hollow anchor rod (1).

5. The ball-type prestressed hollow anchor bolt according to claim 3, characterized in that, The expansion pieces (3) are arranged in at least two rows along the axial direction of the expansion head body (2), and the expansion pieces (3) in adjacent rows are staggered in the circumferential direction of the expansion head body (2).

6. The ball-type prestressed hollow anchor bolt according to claim 5, characterized in that, Each of the expansion pieces (3) is provided with a limiting plate (31) relative to the inner wall of the expansion head body (2) to prevent the expansion piece (3) from completely detaching from the expansion head body (2) when it is pushed outward from the radial through hole.

7. The ball-type prestressed hollow anchor bolt according to claim 6, characterized in that, Each of the expansion pieces (3) has protrusions or patterns on its outer surface to increase friction.

8. The ball-type prestressed hollow anchor bolt according to claim 1, characterized in that, It also includes an anchor plate (6) and a hemispherical nut (7), the anchor plate (6) being sleeved on the hollow anchor rod body (1), the hemispherical nut (7) being threadedly engaged with the hollow anchor rod body (1), and its spherical surface abutting against the anchor plate (6).

9. The ball-type prestressed hollow anchor bolt according to claim 2, characterized in that, The slurry outlet (21) is located at the inlet end of the expansion head body (2) away from the cavity (22).

10. A construction method based on the ball-type prestressed hollow anchor bolt according to any one of claims 1 to 9, characterized in that, Includes the following steps: An enlarged section (51) is formed at the bottom of the borehole (5). The expansion head body (2) is connected to the hollow anchor rod body (1) and then sent into the bottom of the borehole (5). Insert the top rod into the hole of the hollow anchor rod body (1), push the trigger (41) to make it enter the cavity (22) of the expansion head body (2), drive the expansion plate (3) to extend along the radial through hole and anchor it to the rock wall of the expansion section (51); The hollow anchor rod (1) is tensioned in a direction away from the borehole (5) to apply prestress; Pressure grouting is performed through the grouting channel, and the grout overflows from the grout outlet (21) and fills the borehole (5).

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